Posted on May 15, 2018




 Compression systems must have a compressor, condenser, expansion  device, and evaporator

 Other components enhance system operation

 Controls can be electrical, mechanical, or electromechanical devices

 Mechanical controls start, stop or modulate fluid flow to increase system






 Two-temperature operation is utilized when there are multiple evaporators in the system

 These evaporators typically operate at different temperatures

 The pressures in these evaporators are therefore different

 Two-temperature operation is normally accomplished with mechanical






 Evaporator pressure regulator (EPR)

 Prevents the pressure in an evaporator from dropping below a predetermined pressure

 Two pressures control the valve – Spring pressure – pushes to close the valve – Evaporator pressure – pushes to open the valve

 Evaporator superheat may be high when the EPR is closed




 An EPR is needed in the suction line of each evaporator except the lowest temperature coil

 EPR valves are equipped with Schrader valves to read evaporator pressure

 Multiple EPRs can be set at different pressures so each evaporator can be maintained at a different temperature






 Provide more accurate control

 Located at the evaporator outlet

 Used on single or multiple evaporator systems

 Microprocessor senses case discharge air temperature

 Designed to maintain discharge air temperature in there frigerated case

 Controlled by a bipolar step motor





 Located close to the compressor

 Prevents compressor from overloading on start-up

 Provides a limit to the pressure that can enter the compressor

 Referred to as a close on rise of outlet (CRO) valve

 Resembles an EPR valve





 Valve is best adjusted under a high load condition

 An ammeter should be used when setting the valve

 Excessive amperage indicates that too much refrigerant is entering thecompressor

 Turning the adjusting screw into the valve reduces the refrigerant pressure returning to the compressor

 Turning the screw out of the valve increases the refrigerant pressure returning to the compressor




 Release refrigerant from a system when a high-pressure condition exists

 Spring-loaded type– Located in the vapor space – Resets after opening

 One-time type– Fittings filled with low-temperature solder – Usually located in the suction line near the compressor







 Used on refrigeration systems that are operated year round to maintain head pressure

 Fan cycling, fan speed control, air volume control, condenser flooding

 Intended to simulate design operating conditions

 Help to keep the system’s operating pressures within desired ranges





Device opens on a drop in head pressure, turning condenser fan off

 Device closes on a rise in head pressure, turning condenser fan on

 Fan cycling causes large variances in the head pressure

 Best used on systems with multiple fans





 As the outside temperature drops, the fan slows down to reduce the amount of airflow through the condenser coil

 As the outside temperature rises, the fan speeds up to increase airflow through the condenser

 Some controls monitor the refrigerant’s condensing temperature





 Utilizes piston-controlled shutters and/or dampers

 As the head pressure drops, the shutters close, reducing airflow through the condenser

 Reduced airflow causes the head pressure to rise

 During periods of warm ambient temperatures, the dampers are fully

open to maximize airflow through the condenser coil





 Flooding valves cause liquid refrigerant to move from the receiver to the condenser, reducing its effective surface area, in cold weather

 Systems with flooding valves have oversized receivers to hold excess refrigerant charge in warm weather

 The valve is closed when outdoor temperature is high (all refrigerant is directed to the condenser)




 Used to start or stop refrigerant flow

 Normally open (NO) or normally closed (NC)

 Snap-acting valves (open or closed)

 Valves must be installed with the arrow pointing in the direction of flow

 Often used in conjunction with automatic pump down cycles

 Valve position controlled by a solenoid coil




 Start and stop current flow to components

 Low pressure switch – Closes on a rise in pressure

 High pressure switch – Opens on a rise in pressure

 Low ambient control – Closes on a rise in pressure

 Oil safety switch – Opens on a rise in pressure




 Can be used as low-charge protection and space temperature control

 Low-charge protection – Cut-out pressure set well below normal operating pressure – Cut out pressure should be set above atmospheric pressure to prevent atmosphere from being pulled into the system – Prevents system from operating in a vacuum – Control is normally reset automatically





 Control will cut off the compressor when the pressure equals the system pressure that corresponds to a temperature about 15° cooler than desired box temperature

Control is rated by pressure range and current draw of the contacts





Control will cut off the compressor when the pressure equals the system pressure that corresponds to a temperature about 15° cooler than desired box temperature

 Control is rated by pressure range and current draw of the contacts





 When the box temperature rises, the thermostat closes

 The liquid-line solenoid is energized

 Refrigerant flows to the evaporator

 The compressor is still off

 When the low-side pressure increases, the low-pressure control closes

 The compressor is once again energized




 Prevents compressor from operating at high head pressures

 Control opens on a rise in pressure

 Can be automatically or manually reset

 Should be set at a pressure higher than the normal operating head pressure

 Manual reset controls provide better equipment protection




 Starts and stops the condenser fan motor in response to head pressure

 Starts the condenser fan motor when the head pressure rises

 This setting should be lower than the set point on the highpressure control





 Larger compressors are equipped with oil pumps

 Oil pump is connected to the compressor crankshaft

 Oil is forced through holes in the crankshaft

 Measures net oil pressure

 Net oil pressure = pump outlet pressure – suction pressure

 Control uses a double bellows

 Has a time delay built into the control to allow oil pressure to build up





 Typical box temperature ranges from 34°F to 45°F

 Coil temperatures are normally 10° to 15°F cooler than the box

 Coil will be operating below 32°F but box will be above 32°F

Air in box is used to defrost the coil in the off cycle





 Coil defrosts using box temperature air compressor cycles off on the thermostat

 Evaporator fan will continue to run while the compressor is off

 Air in box defrost coil

 Coil defrosts whenever compressor cycles off




 Defrost is controlled by a timer

 System goes into defrost at predetermined times

 Defrost cycle is initiated during low load periods

 Systems in retail establishments often go into defrost when the store is closed





 Box and coil temperatures are both below 32°F

 Coil is defrosted using internal or external heat

 Air in the box cannot be used to defrost the evaporator coil

 Internal heat – Hot gas from the compressor

 External heat – Electric strip heaters





 Uses hot gas from the compressor’s discharge

 Discharge gas is directed into the evaporator

 Utilizes a hot gas solenoid defrost is initiated by a timer

 Defrost is terminated by either time or coil temperature

 Evaporator fan is de-energized during defrost

 Compressor runs during defrost

 Refrigerant condenses in the evaporator





 Usually accomplished with electric heaters mounted to the evaporator coil

 Defrost is initiated by a timer

 Defrost is terminated by either time or coil temperature

 Evaporator fan is de-energized during defrost

 Compressor is de-energized during defrost





 Single pole, double throw switch

 Terminates defrost when frost has all been removed

 Delays evaporator fan start until coil temperature drops

 When ice has been removed, the evaporator surface temperature increases

 The control senses this increase in temperature and the system is putback into refrigeration mode mechanically

 When the coil temperature drops to the set point temperature, the fan is energized






Single pole, double throw switch




 Located in the liquid line

 The device stores liquid refrigerant

 Refrigerant leaves the receiver as 100% liquid

 A dip tube is used to remove the liquid from the bottom

 Must be used on systems with condenser flooding valves

 Found on systems with automatic or thermostatic expansion valves

 Not found on critically charged (capillary tube) systems




 Located in the liquid line between the receiver and expansion device

 Under normal operating conditions, the valve is back seated

 Valve can be front seated in order to pump system down

 Has a service port to enable the technician to take pressure readings

 Valve must be cracked off the back seat to take pressure readings



Backseated Position

 Service port is sealed, line port is open to the device port

 Normal operating position



Cracked off the Backseat Position

 Service port is open to the line port and device port

 Position used for taking system pressure readings

 Position used for adding or removing system refrigerant



Midseated Position

 Service port is open to the line port and device port

 Position used for system evacuation and leak checking


 Service port is open to the device port

 Position used for pumping the system down

 Line port is sealed off



 Located in the liquid line

 Removes dirt, moisture, and acid from the refrigeration system

 Desiccant – Activated alumina, molecular sieve, silica gel

 Can be permanent or replaceable core type

 Connected to system with either solder joints or flare connections





 Allows refrigerant to flow in only one direction

 Can be either the ball type or magnetic type

 Must be installed with the arrow pointing in the direction of refrigerant flow

 Installed at the outlet of the lowest temperature coil on multievaporator systems




 Installed in the liquid line

 Enables the technician to determine if a solid column of liquid is reaching the expansion device

 Can also be supplied with a moisture indicator

 Usually installed after the filter drier





 Used on multi-circuit evaporators

 Located at the outlet of the expansion device

 Designed to allow equal refrigerant flow to all evaporator circuits

 Some distributors are made with side inlets used for hot gas defrost




 In the suction line leaving the evaporator

 Suction and liquid lines are connected to allow heat to transfer between them

 Increases the amount of subcooling in the liquid entering the expansion device

 Prevents liquid from moving through the suction line into the compressor




 Located in the suction line, close to the compressor

 Prevents liquid refrigerant from entering the compressor

 Gives liquid a place to boil off before entering compressor

 Sometimes, the liquid line is routed through the accumulator to help boil away any liquid and also increase liquid subcooling




 Improper TXV setting

 Oversized TXV

 Loose TXV thermal bulb

 System overcharge

 Reduced airflow through evaporator coil

 Low system load

 Defrost problems




 Located in the suction line

 Good compressor protection

 Must be installed when system has become contaminated

 Usually have two pressure ports to read the pressure drop across the device





 Normally attached to the compressor• Valve positions – Back seated – Normal operating    position – Front seated – used for pump down and service

 Mid seated – Used for system evacuation

 Cracked off the back seat – Used for taking pressure readings, charging refrigerant into the   system, or removing refrigerant from the system





 Located in the discharge line

 Normally attached to the compressor

 Used as a gage port and to valve off the compressor for service

 Same positions as the suction service valve

 This valve should not be front seated when the compressor is running except during closed-loop capacity tests




 Installed in the discharge line

 Separates oil from the refrigerant and returns the oil to the compressor

 Oil drops fall to the bottom of the separator

 Oil level raises a float and opens a valve

 Difference between high- and low-side pressures push oil back to the compressor

 Device needs to be kept warm




 Installed to take pressure readings at various points in the system

 Line piercing valves can be installed while the system is running

 Can be saddle type or solder type

 Can either have a Schrader pin or a small valve




 Prevents refrigerant from migrating to the oil in the off cycle

 Prevents oil from foaming and being pumped out of the compressor

 External type heaters

 Insertion type

 Crankcase heat is needed during the off cycle and is sometimes controlled by a set of normally closed contacts that open when the compressor is energized



1 Additional components enhance system operation

2 The EPR is used on multiple evaporator systems to maintain different pressures in each evaporator

3 EPR valves are located in all evaporators except the lowest pressure evaporator

4 The CPR provides a limit to the pressure that can enter the compressor

5 Relief valves release refrigerant from a system when a high-pressure condition exists

 6 Low ambient controls are used on refrigeration systems that operate year round

 7 Common low ambient controls include fan cycling, shutters, dampers and condenser flooding

 8 Solenoid valves are used to start and stop the flow of refrigerant (Snapacting valve)

 9 Liquid line solenoids are used as part of the automatic pump down cycle

 10 Pressure witches open and close in response to sensed pressures

 11 Pressure switches can be operational or safety devices The oil pressure safety control ensures that compressors operate with sufficient oil pressure

 12 Defrosting medium temperature refrigeration systems can be accomplished with planned, random or off-cycle defrost

13  Defrosting low temperature refrigeration systems is accomplished with hot discharge gas (internal) or electric strip heaters (external) Receivers are refrigerant storage tanks located at the outlet of the condenser

14  Receivers are equipped with service valves that can be beackseated, cracked off the backseat, midseated or frontseated

 15 Filter driers remove dirt, moisture, and acid from the refrigeration system

16  Check valves ensure that refrigerant flows through the circuit in only one direction

17  Refrigerant distributor allow equal amounts of refrigerant flow to all evaporator circuits Suction line/liquid line heat exchangers increase subcooling and help ensure that 100% vapor enters the compressor

18  Accumulators help liquid refrigerant boil before it enters the compressor

 19 Oil separators help remove oil from the hot vapor that is discharged from the compressor

 20 Crankcase heat helps boil refrigerant from the oil in the compressor crankcase




The job of your home air conditioner is move heat from inside your home to the outside, thereby cooling you and your home. Air conditioners blow cool air into your home by pulling the heat out of that air. The air is cooled by blowing it over a set of cold pipes called an evaporator coil. This works just like the cooling that happens when water evaporates from your skin. The evaporator coil is filled with a special liquid called a refrigerant, which changes from a liquid to a gas as it absorbs heat from the air. The refrigerant is pumped outside the house to another coil where it gives up its heat and changes back into a liquid. This outside coil is called the condenser because the refrigerant is condensing from a gas back to a fluid just like moisture on a cold window. A pump, called a compressor, is used to move the refrigerant between the two coils and to change the pressure of the refrigerant so that all the refrigerant evaporates or condenses in the appropriate coils.

The energy to do all of this is used by the motor that runs the compressor. The entire system will normally give about three times the cooling energy that the compressor uses. This odd fact happens because the changing of refrigerant from a liquid to a gas and back again lets the system move much more energy than the compressor uses.





Before refrigeration air conditioning was invented, cooling was done by saving big blocks of ice. When cooling machines started to get used, they rated their capacity by the equivalent amount of ice melted in a day, which is where the term “ton” came from sizing air conditioning.

A ton of cooling is now defined as delivering 12,000 BTU/hour of cooling. BTU is short for British Thermal Unit (and is a unit that the British do not use) The BTU is a unit of heating - or in this case, cooling - energy. It’s more important, however, to keep in perspective that a window air conditioner is usually less than one ton. A small home central air conditioner would be about two tons and a large one about five tons.





Unlike most furnaces, air conditioners are complex mechanical systems that depend on a wide variety of conditions to work correctly. They are sized to meet a certain “load” on the house. They are designed to have certain amount of refrigerant, known as the “charge”. They are designed to have a certain amount of air flow across the coils. When any of these things changes, the system will have problems.

If you produce more heat indoors either from having more people or appliances or because of changes in the house, the air conditioning may not be able to keep up.

If the refrigerant charge on the system leaks out, it lowers the capacity of the system. You will simply get less cooling and system will not be able to keep up when the load gets high.

If airflow across the outdoor (condenser) coil is reduced, the ability to reject heat outdoors is reduced and the again the capacity of the system may go down, especially at higher outdoor temperatures.<

In dry climates such as the Southwest United States, the same issues happen with regard to the indoor (evaporator) coil: higher airflow helps, lower airflow hurts. In humid climates, the situation is more complex. At higher airflows, there will be less dehumidification, leading to high indoor humidities. If the airflow gets too low, however, the evaporator coil may freeze. This makes performance worse and can damage the compressor until it fails - leaving you with an expensive repair bill and no cooling!





Almost every air conditioning system has a filter upstream of the evaporator coil. This can be in the return grille or in special slots in the duct system and can be a fuzzy-looking or a folded paper filter. This filter removes particles from the air stream to both keep the air conditioning system clean and to remove particles from the air.

As the filter does its job, it gets loaded with more and more particles. This actually has the effect of making it more efficient, but it also increases resistance and reducing airflow. When this happens, it is time to change the filter. How long it will take to happen depends on how dirty the air is and how big the filter is.

If you don’t change the filter, the air flow will go down, and the system will not perform well. Not only that, but if the filter is too dirty, it starts to become a source or air pollution itself.

If you take the filter out completely, you would solve the low air flow problem, but this victory would be short lived. The particles that the filter would have taken out will now build up on your evaporator coil and eventually cause it to fail. A new filter is a lot cheaper.

When you do buy a new filter, ASHRAE recommends getting one with a Minimum Efficiency Rating Value of MERV 6 or higher.





Routine maintenance such as changing filters can be handled by most consumers, but others require professional service.

It’s a good idea to brush dirt and obstructions from the coils and the drains at the start of each cooling season. Depending on the system and the consumer, this may require a service call from a professional.

If the system is not producing as much cold air as is normal, it could also be an indication of a refrigerant charge or airflow problems. These problems may require servicing.





Another reason systems may appear not to be producing enough cold air is because of duct leakage. Duct leakage can sap 20 to 40% of the energy out of even a well-operating air conditioner, if the ducts pass outside the cooled space (this includes attics, crawlspaces and garages). Ducts outside need to be well insulated. Various products exist specifically for insulating ducts that can be installed by a keen home owner or a professional contractor.

You might be able to get an extra half ton of air conditioner capacity for free, if you seal your leaky ducts. If the ducts are accessible, handy consumers can seal ducts with mastic—that white sticky stuff you can paint on the ducts. Otherwise you would need a professional to seal the ducts.





Sealing leaky ducts may be the biggest single thing you can do to improve efficiency, but a lot of the issues mentioned about will help as well: replace dirty filters, keep the right charge and airflow, clean the coils.

Another thing to do is to make sure the outdoor (condenser) unit is not so hidden from sight that its air flow is blocked or that leaves or other matter are not clogging it.

If you are replacing the air conditioner, look to buy high efficiency equipment. The most generally known efficiency rating is Seasonal Energy Efficiency Rating (SEER). SEER 13 is the minimum efficiency you should consider, but higher efficiencies are likely to be quite cost effective.

Depending on your climate, you may wish to consider other efficiency numbers as well. For example, in hot, dry climates you should look at the Energy Efficiency Rating (EER) which says how well the system will work at peak conditions. If you live in a hot, humid climate you need to consider how well the unit can dehumidify.




You can make your air conditioner work better by reducing the size of the job it has to do. You can do this by improving the building or reducing the internally generated loads that your air conditioner must deal with.

Improving the building “envelope” includes things such increasing insulation levels or shading windows or reducing air leakage. Such improvements will reduce energy spent on heating and cooling, but may require substantial time or investment. When putting in a new roof or new windows, it is usually cost effective to use high-efficiency products. “Cool” roofing, for example, can save half a ton of cooling and a lot of energy over the year.

Reducing internal loads can be simpler. Shut off unneeded electrical appliances, lights and equipment. Shift appliance use (such as washers and dryers) to cooler times of the day. Use local exhaust fans to remove heat and humidity from kitchens and baths. Buying Energy Star or similarly efficiency appliances helps as well.

In some climates other techniques can be used to reduce the load on the air conditioner. In dry climates evaporative air conditions (the modern version of what used to be called “swamp coolers”) can provide substantial cooling. In climates with large temperature swings, such as the hot, dry climates, you can reduce the load by bringing in large amounts of cool outdoor air. Such systems can be called “night cooling” “ventilative cooling” or “residential economizers”.





The previous points have focused on cooling, but the original definition of air conditioning contains more than that; an ideal air conditioner should heat, cool, clean, ventilate, humidify and dehumidify as needed to provide health and comfort. In fact the second most important objective of the original definition is to provide ventilation. Whether or not the piece of equipment we call an air conditioner provides it, ventilation is needed.

Without adequate ventilation, contaminants generated indoors will can lead to significant health and comfort problems. ASHRAE recommends that there be at least enough ventilation to exchange the air inside house once every four hours, depending on house design.

Older homes tend to have leakier walls and leakier ducts and mostly get sufficient ventilation through such leakage. Such leakage and infiltration may not be the most energy efficient approach to ventilation and is an opportunity for savings.

Most new homes and some existing homes are relatively tight and thus require mechanical ventilation to meet minimum ventilation requirements.




Humidity control was the problem that originally spurred the need for air conditioning. Lack of humidity control in hot, humid climates, in particular, can lead to mold growth and other moisture-related problems. High indoor humidities can lead to health and comfort problems.

Modern air conditioners dehumidify as they cool; you can see that by the water that drains away, but this dehumidification is incidental to their main job of controlling temperature. They cannot independently control both temperature and humidity.


In hot, humid climates the incidental dehumidification that occurs may not always be enough to keep the indoor humidity conditions acceptable. (ASHRAE recommends roughly a 60% relative humidity maximum at 78F.) The maximum dehumidification happens not at the hot times of the year—when the air conditioner is running a lot—but at mild times of the year when the air conditioner runs very little.


Although there are some leading edge air conditioning systems that promise to independently control humidity, conventional systems may not be able to sufficiently control the problem and can cause comfort or mold problems in certain situations. Some current high-end systems have enhanced dehumidification, but when the existing system cannot sufficiently dehumidify, it may be necessary to buy a stand-alone dehumidifier.



There are things that consumers can do to lessen the need for dehumidification:


Do not set your thermostat to the “fan on” position. In this position the fan blows air all the time whether your cooling system is running or not and one key impact is that a lot of the moisture your system just took out of the air, will be blown back into the house before it can drain way.

Use exhaust fans during moisture-producing activities. Cooking, bathing, washing, and similar activities produce a lot of moisture inside the home. Exhaust that moisture directly outdoors using a fan. Similarly, avoid drying clothes indoors except with a clothes dryer that is exhausted directly outdoors.


things  you should do


Air conditioning is a specialty area of service and therefore is something that

most people know nothing about, but when summer hits it is important to be

knowledgable. You also want to feel confident that your money is being spent wisely and

that the work you’re receiving is needed. Well, the best way to feel more confident about

these things is to educate yourself. Here are 10 things you should know about the heating

and cooling system in your home:


1. It requires regular maintenance. Service calls are most often related to lack of

maintenance. The good part about the maintenance is a lot of it can be done yourself.


2. An air conditioning system is a sealed system that is to be extensively leak checked

upon installation. Once your HVAC system has been checked, it should not leak unless

something has impacted the unit. This means the thought that an air conditioning system

just needs recharged every so often is a myth.


3. The pressure and temperature relationship of an air conditioning system is very touchy.

Slight adjustments to either of these two factors can result in problems with the system.


4. Air conditioning repairs are often electrical. Three very common problems are: (1) blown

fuses in the service panel located outside near the condensing unit, (2) tripped breakers at

the main electrical panel and (3) blown capacitors.


5. Air conditioning will usually let you know something is wrong before there is a shut

down that is not electrically related. Routinely check the copper lines in your system for

frost or ice.


6. The condenser coil is where the process of the refrigerant returning from a gas to a

liquid begins. There is no mechanical function here. It is simple, the coils either contain

refrigerant or they don’t. If they don’t, you have a problem on your hands.


7. You may have noticed that lately, the air conditioners that people are having installed

are much larger than those they replaced. This is largely related to the fact that energy

regulations have commanded that the minimum SEER rating (efficiency rating) be

increased over the last few years.


8. It’s a good idea to brush dirt and obstructions from the coils and the drains of your

HVAC system at the start of each cooling season.


9. You can use ductless systems to create temperature zones in your home. A room­by-

room ductless system – sometimes called a multi split, with multiple inside air handlers –

allows you to fit your heating and cooling to your specific needs.


10. Changing your air filter regularly is important. If you don’t change the filter, the air flow

will go down, and the system will not perform well. Not only that, but if the filter is too dirty,

it starts to pollute your home’s air.



radiant heaters


1 An electric radiant heater is more energy-efficient as a result of all the heat being focused on heating up the surface, which, in turn, reflects heat back. With a gas heater, some of the energy is used to heat up the surrounding air, and this energy just disappears.

2 An electric radiant heater is safer to run than a gas heater. This is because there is no handling of flammable gas bottles, which always involves some risk. There is also no open flame as in a gas heater.

3 The burning gas in a gas heater is also sensitive to draughts. Unlike an electric radiant heater, which can be installed even where it is exposed to wind and weather.

4 An electric radiant heater requires minimal maintenance, unlike gas heaters, where the gas supply runs out and must be replaced from time to time. Hoses and valves must also be cleaned regularly to ensure that the apparatus functions properly. This is not necessary with an electric radiant heater.

5 An electric radiant heater begins heating as soon as you press the button. You don’t have to wait for the bottled gas to heat up the system before you feel the result.

6 In some locations, such as glazed-in terraces and balconies, the oxygen supply may be too limited to allow use of a gas heater. As gas burns, it consumes oxygen to keep the fire going.

7 Burning bottled gas gives off carbon dioxide and contributes to the greenhouse effect. You avoid this with an electrically-powered radiant heater.

8 Modern electric radiant heaters are very efficient, even small ones. This makes positioning easy, and they won’t restrict space on the terrace.

9 There are also electric radiant heaters that can be sited directly under an awning or a parasol. This is impossible with a gas heater, as the open flame is hazardous in the vicinity of textiles or other flammable material.

10 Operating costs are also more favourable with electric radiant heaters. A standard-size gas bottle will generally be sufficient for up to half a day and must then be replaced. This can be compared with energy-efficient electric radiant heaters, which use minimal electricity in proportion to the heat given off.



 Chimney Liners



Chimney liners provide a barrier between the components of your chimney and the surrounding wood or other building materials. This may seem like an extra layer of protection that isn’t really necessary, but it turns out that having a lining adds more than reassurance. There are some solid reasons you should seriously consider installing a chimney liner if you don’t have one already.


10 Things You Should Know About Chimney Liners

Acidic flue gasses can shorten the life of your chimney by eroding it from the inside out. Installing a liner can extend the life of your chimney while making it safer to use.

Chimney liners also protect the masonry materials in many chimneys, making your chimney a more reliable confinement area for heat and sparks.

Liners help maintain good air flow in the chimney, resulting in a more efficient fire. This will maximize the usefulness of your fuel and save you money.

Aluminum or stainless steel chimney liners in particular wear well, last a long time, and are safe to use.

Chimney liners discourage the back flow of gasses, like carbon monoxide, into your rooms.

Since chimney liners keep sooty air from seeping back into your rooms, your walls, carpeting and furniture will stay cleaner.

A chimney liner can reduce the presence of a smoky or sooty smell in your rooms, making your indoor environment healthier and more pleasant.

Chimney liners make maintenance easier because they naturally reduce creosote buildup. Less creosote means less maintenance and fewer costs for you.

Less creosote also means a furnace or fireplace that runs safer and more efficiently, with a reduced risk of fire.

Chimney liners can be made from many materials, like tile, aluminum, or concrete, making them an investment that can be retrofitted to your existing setup at a number of practical price points.

Chimney liners can enhance the safe operation of your furnace or fireplace, but only if you keep your furnace clean and have it inspected regularly. There’s no magic bullet that will allow you to avoid regular maintenance and periodic inspection of your chimneys, furnaces and fireplaces. To stay safe, schedule yearly inspections of all your chimneys, follow the safety directions on your appliances and equipment, and never leave an open flame unattended.



humidifier  does

Adding a humidifier to your home   especially during the dry winter months   offers a host of benefits. When you live in a dry climate or have a cold and dry winter, you and the things in your home can suffer various ill effects from the dry air. Indoor air, especially in winter, can have humidity levels at around 10 percent, but the ideal humidity level for your home is about 30-40 percent. Here are the top ten benefits to humidified air:


Prevent Illness

Humidity allows tiny hairs in the nose to move and do their job of filtering out bacteria and viruses to prevent colds and flu. Added humidity can also help prevent bloody noses. 


Treat Illness

Air moistened with a humidifier can help soothe some symptoms of colds or flu, including irritation of nasal passages, the throat and bronchial tubes, helping you breath and sleep easier.


Protect Furnishings

Wood furniture and flooring responds negatively to too much or too little moisture in the air. Too little moisture can cause wood to split and crack. Adding a humidifier to any room with wood furniture can help preserve the integrity of the wood.


Preserve Your Voice

Vocal cords need to be supple and well lubricated in order to vibrate and produce the best sounds. Dehydration, viruses and sometimes eating the wrong thing can cause you to lose your singing, and even your speaking, voice. Keeping the air moist, especially while you sleep, can help you get it back.


Moisturize Your Skin

The heat blasting through your home during the winter months can leave skin tight, dry and itchy, especially skin on your hands, which has fewer oil glands. Lips also seem to chap more often and more easily in winter. A humidifier can help keep them moist.


Create Warmth

A humidifier will not only fight the dry skin that usually accompanies winter, it will also make your home feel warmer. The more moisture that is in the air, the warmer it will feel. Air with a temperature of 70 degrees Fahrenheit and 10 percent humidity will feel like 67 degrees, but with 50 percent humidity, it will feel like it is 69 degrees.


Reduce Snoring

Low moisture levels in your nose and soft palate can increase snoring, so staying hydrated can be a big help. That includes drinking plenty of water, of course, but adding moisture to the air with a humidifier can also fight off dryness that can lead to snoring.


Control Static Electricity

One sure sign of winter is the first time you pet the cat and get a jarring jolt of static electricity, or when you find the latest missing sock stuck to someone's shirt or pants. Dealing with an entirely different hairstyle also is no picnic. A humidifier can lessen the potential for static electricity during the winter months.


Lessen Electronics Shock

Added static electricity in your home is annoying, and a little comical, but the very real danger to electronic equipment, including your computer, is decidedly unfunny. The chance of significant damage is minimal, unless you happen to have your computer open at the time   to add RAM, a sound card, or any similar task. The risk is considerable in that case. You could end up with a dead board or other less obvious damage.


Hydrate Plant Life

Many species of indoor plants originally came from tropical climates with high humidity. Indoor air in many climates, especially in winter, does not offer adequate humidity for the plants to thrive. This will become apparent when leaves get brown at the tips or when they die altogether. Adding a humidifier to a room will make a difference for many plants.



Adding humidity to your home can have many positive impacts. It is a balancing act though. Too much moisture in the air can encourage the growth of organisms, including dust mites. Monitoring moisture levels and regular maintenance of your humidifier can ensure you get all of the benefits of moistened air without the risks.




During the winter months, as outside temperatures drop, so does the relative humidity (rh) inside a home. This “thirsty air” begins to absorb moisture from everything it touches, such as woodwork, furniture, paintings, wooden musical instruments, carpet, wood molding, kitchen cabinets, doors, and floors. Moisture is then pulled and absorbed from these hygroscopic, or moisture-retaining, materials, and damage can occur.


For example, cracks will appear in wood floors, leaving a dull finish. Furniture may warp and become loose at the joints. Rare paintings can be destroyed in only a few years as paint cracks and flakes from the canvas. Carpets can deteriorate quickly, and doors will seem to warp before the homeowner’s eyes. Contractors need to keep in mind the symptoms and dangers of poorly controlled humidity levels of indoor air for homes during the winter months.


10 basic things about humidification:


1 To foster healthy indoor living, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommends keeping indoor humidity levels between 40 and 60 percent rh. Relative humidity is the ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air can hold at that temperature, expressed as a percentage.


- 2 - Humidity levels that are too low can aggravate symptoms of asthma, rhinitis, and respiratory infections.


- 3 - Proper humidity control can improve the health and comfort of people living in the home.


- 4 - Proper humidity levels decrease static electricity in the home, eliminating static shock and protecting valuable electronics.


- 5 - Bacteria, viruses, mites, and fungi are virtually inhabitable when a home maintains healthy indoor rh.


- 6 - Mold growth indoors is a serious issue for homes today. Molds are incapable of obtaining moisture directly from the air. Molds thrive indoors when the rh range is consistently from 60 to 99 percent at surface substrates.


This is why properly insulated walls and surfaces of a home are crucial to preventing high temperature differentials between the ambient air and an outer wall. The temperature of a surface at or below its dew point can cause water condensation on a given surface, allowing germination and mold growth regardless of ambient humidity.


- 7 - Proper humidity control can be significant to reducing energy consumption.


- 8 - Proper humidification will make one feel warmer and more comfortable.


A properly controlled whole-house humidifier is designed to decrease the rate of evaporation of moisture from the human body, leaving one feeling warmer at lower temperature settings, thus saving energy costs.


- 9 - Humidity levels that are too low will cause the air to become “thirsty.” This extremely dry air can warp furniture and door frames. Woodwork, paintings, and other valuables can be vulnerable to a low indoor moisture level as well, sometimes causing irreparable damage.


- 10 - Carpeting can also deteriorate quickly in a low-humidity home.




By stabilizing the humidity level indoors, hygroscopic materials - woodwork, furniture, and paintings, for example - will not absorb or give off moisture, protecting them and other valuables from irreparable damage.


When faced with a low-humidity situation, contractors need to understand the cause and possible solutions. One such solution is whole-house humidifiers, which connect directly to a furnace and work with the heating system to distribute moisture throughout the home. These humidifier types rely on furnace heating cycle temperatures to deliver the rated humidity capacity output.


An effective whole-house humidifier injects steam into the airstream with a specifically designed nozzle that allows the vapor gas to be efficiently absorbed at temperature as low as 70°. This type of humidifier is not dependent on the heating cycle to deliver humidity capacity, but only needs airflow as low as 800 cfm at 70°.


Both contractors and homeowners often misunderstand steam humidifiers. The common misperception is that steam humidifiers put water droplets into the air distribution system and cause unwanted pools of stagnant water and damage. This is not true.


Actually, steam humidifiers that use electrode technology to boil water in a renewable steam-generating cylinder are designed to inject pure, sterile steam vapor into the duct airstream, where it is designed to be completely absorbed quickly and efficiently. Meanwhile, electrode steam humidifiers are designed to deliver greater capacity outputs on demand to meet challenging humidity loads to maintain designed rh set points.


Controlling humidity can be a challenge for today’s heating contractor, especially during the winter months. By understanding humidity symptoms, problems, and possible solutions, contractors can better meet the needs of their homeowner customers.


types of air filters

There are many types of air filters on the market these days, but which one is best?  We are often asked the question, do electrostatic air filters work?  The real answer is, it depends.  Electrostatic air filters are washable furnace filters that can be very useful for certain uses, but whether or not they should be used in your house is a much broader question.  If someone in your home suffers from asthma or severe allergies then the answer will likely change.  As a general rule, electrostatic air filters cannot even come close to the filtration power of a high quality anti-allergen filter from 3M or Honeywell, but that doesn’t mean you should rule them out altogether.  Those of you who read our articles regularly, know that we are a small, U.S. Veteran-Owned HVAC company in Southern California, and pride ourselves in giving people honest, straight answers to their questions.  In this article, we will discuss what an electrostatic air filter is, how it works, the pros and cons of using one and whether or not washable furnace filters would work for your home.



What is an Electrostatic Air Filter and How Does It Work?


Electrostatic air filters are washable air filters that theoretically never need to be replaced.  I say ‘theoretically’ because I have a hard time believing that something that is subjected to dirt and debris regularly will work indefinitely, but that is the standard claim.  The idea is that instead of replacing your electrostatic air filter at regular intervals like you would a conventional air filter, you take them out back and wash them off with a hose about once a month.  This is a handy trick if you are sick of spending money on conventional air filters, but do electrostatic air filters work?  They do work, but the question is do they work as well as a conventional air filter?For more information on conventional air filters and how often you should change them, take a look at: Air Conditioning Filter Change – How Often Should I Do It?


How Do Electrostatic Air Filters Work?


These washable furnace filters work by having multiple layers of vented metal which the air passes through.  As the air passes through the first layer of filtration, the air molecules are positively charged by the friction between the air and the filter.  The now positively charged air molecules attach themselves to the next few layers as they pass through the rest of the filter.  Think about it as working kind of like walking across the carpet with your socks on and then touching a door knob – the process of walking across the carpet charges you with static electricity which is then released when you touch a grounded surface like a door knob.  Only instead of your socks scooting across a carpet, it is the air scooting across your air filter that creates a charge and traps dust particles in the air filter.  For more information on electrostatics, try this short vintage physics video – it’s worth a look: Electrostatics – How Electrostatic Air Filters Filter Air.


The Pros of Electrostatic Air Filters


One of the most attractive parts of washable air filters is the fact that you never have to buy a new one.  This is definitely a plus, I mean who wants to buy a new air filter every few months?  Even if you opt for the cheaper air filters that run you 50 cents each (which I do not recommend), you still have to go through the hassle of buying them and replacing them on a regular basis and who wants to deal with that?

The other appealing part about using electrostatic air filters is the price.  If you are buying high quality air filters then you may be spending $15 every few months which adds up to around $60 each and every year.  Now even though this might not break the bank, it can add up over time.  Washable furnace filters cost around $50 to $60 each but never have to be replaced, meaning that they pay for themselves in the first year of their use.  You can’t argue with the cost of these filters, so it may be an option to keep in mind.



The Cons of Electrostatic Air Filters


I have to say that the cons of an electrostatic air filter far outweigh the pros, in my opinion.  There are several problems with a washable air filter, ranging from how effectively they filter your air to how often they have to be washed.  Some of these problems are a matter of preference, but some can’t be argued with and should be kept in mind before making your decision:

Electrostatic air filters can only filter so much.  One of the problems with electrostatic filtration is that it relies on static electricity to operate.  What I mean by this is that static electricity is powerful enough to filter small, lighter dust particles out of the air but what about larger dust and dirt particles?  Or mold spores?  Unfortunately, this is one of the areas that electrostatic filtration falls short in.  An electrostatic air filter will never be able to filter as well as a high quality HEPA filter or even a moderate 1200 MPR filter (micro particle performance rating).  These filters are designed to filter out everything down to a certain specification size and are good at what they do.  If you have someone in your house who suffers from asthma or bad allergies, then I’d definitely recommend you avoid washable furnace filters and instead opt for a high-filtration replaceable filter with at least a 1400 MPR.  For more information on this, take a look at: How to Reduce Asthma Symptoms and How Your Air Conditioner Can Help.



Other problems with electrostatic air filters include:


An additional problem that you run into with inadequately filtered air is that your air conditioning coils get caked with any dust and debris that is not filtered out.  Aside from this stuff polluting your air, it provides an organic substrate for mold and mildew to grow in over time.  If enough of it collects, then you have a perfect recipe for what is called Dirty Sock Syndrome, a situation where your air conditioner starts to make your house smell like a gym or locker room.  It isn’t pleasant.

do electrostatic air filters work - new filterWashable air filters also take time to clean.  Unfortunately, it isn’t just a matter of spraying them down with the hose as they’d like you to believe.  That would make the outside layer clean, but these filters have between eight and ten layers to them.  You actually have to disassemble them and clean each layer separately to properly use them.  This takes about 20 minutes every month or so to do, depending on how much dust is in your area.

Electrostatic air filters also block air flow more than conventional air filters.  Although this may not seem like a big deal, it is to your HVAC system.  If air flow is restricted by 50%, then your air conditioner has to work twice as hard to do the same amount of cooling.  It is true that all air filters restrict air flow to some extent, but electrostatic air filters block more than any other type of air filter.  In fact, we often get maintenance calls for units that use them.  If your air conditioner is running twice as much, its components will wear out quicker.

Because this type of air filter uses static electricity to operate, any particles that make it through the filter are now likely to stick to the inside of your duct work which can promote mold growth and possibly force you to have your air ducts cleaned.  What you will also notice with time is that black dust will start to accumulate around the walls of your house – this dust is difficult to clean sometimes because it is ionically charged and wants to stick to a surface (which is how an electrostatic air filter works).

Just food for thought before investing in a washable air filter.  For information on how to prevent mold and whether or not you need to have your air ducts cleaned, take a look at these helpful articles:


Should I Have My Air Ducts Cleaned?

How Do You Prevent Mold?

Do Electrostatic Air Filters Work?


It depends on what you mean by ‘work.’  They do remove some dust particles from your air, but overall I do not recommend electrostatic air filters for home use.  Electrostatic air filters are an interesting technology but they just won’t work as well as a 3M 1600 MPR and they never will.  The nasty stuff that is in your air needs to be removed for the health of you, your family and your air conditioner.  A disposable filter allows you to do this, then throw this nastiness into the garbage where it belongs.  In the end, although they are a great idea in principle they just won’t filter your air as well as a conventional air filter will.  If you add in the hassle of having to spend 20 minutes a month washing it, then you just aren’t coming out ahead in the long run,



Take a deep breath—if you can. Many of the things we do to keep energy costs down, such as fixing drafty doors and leaky windows, can also seal in pesky pollutants and irritants. Most people who buy air purifiers do so in hopes of easing asthma or allergies. But despite product claims, there's little definitive medical evidence that air purifiers help to relieve respiratory symptoms.


Improving indoor air quality starts with minimizing pollutant sources such as cigarette smoke or dust and pet hair. We test how well a room air purifier removes dust and smoke from an enclosed space, how it performs at high and low speeds, and how quiet it is. For whole-house filters, we test air-flow resistance, which measures how freely air flows through the filter.


The very best portable models we tested were effective at cleaning the air of dust, smoke, and pollen at their highest or lowest speed. For whole-house filters, our recommended models did best at filtering dust and pollen without impeding the airflow of forced-air heating and cooling systems. The worst models weren't terribly effective at any speed.



1 Breathe Easier

Before you resort to buying an air purifier, try some simple steps to reduce indoor air irritants, including:


Vacuum often and thoroughly with a vacuum with HEPA filtration.


Ban smoking indoors.


Maintain your heating equipment and change filters regularly.


Minimize use of candles and wood fires.


Use exhaust fans in kitchen, bath, and laundry areas.


Don't store chemicals, solvents, glues, or pesticides near your living quarters.


If pollen or related allergies keep you from opening windows, run your air conditioner or forced-air cooling system with a clean filter.



2 Types of Air Purifiers

The top selling air purifiers are portables; whole-home systems are the other option. We tested portable room models and filters for homes with forced-air heating and cooling systems.


Room Air Purifiers

These are an option for homes without forced-air heating or cooling.


They’re portable—most room air purifiers weigh from 10 to 20 pounds, have a handle, and stand on the floor or on a table, while heavier models might have wheels.


Some have a high-efficiency particulate air (HEPA) filter, which can capture ultrafine particles. Keep in mind: Most HEPA filters need to be replaced annually, an expense that might approach the cost of the air cleaner, but some models are now available with cleanable HEPA filters.



Room models that use either electrostatic-precipitator or ionizer technology could produce some ozone, a lung irritant.


Dedicated ozone generators, a subcategory of room models, produce large amounts of ozone by design. According to manufacturers, that is to reduce allergens such as dust, smoke, pollen, germs, and mold. Ozone, however, is a serious health concern, prompting the State of California to ban the sale of ozone generators (and other air purifiers that emit more than 50 parts per billion of ozone) from the general market.


Prices: Range from $50 to $850



Whole-House Air Filters

If you already have forced-air heating and cooling, popping in a specialized filter is an inexpensive alternative to a built-in home unit. Basically, it acts as a furnace or central A/C filter that you replace regularly.


It’s easy. You slip out the old filter and slide in the replacement. Some are conventional fiberglass filters; others are pleated or electrically charged to pick up particles. (Note that the electrically-charged versions are not actually electrically powered, even when they have names like Electroclean, and they don't produce ozone.)


Whole-house air filters generally include a range of standard sizes, with some that adapt to fit different-size filter-box or return-air openings.



For thicker filters to fit, you may possibly need to have your ductwork modified by a professional.


The filters must be replaced every one to three months.


Prices: From $20 to $80 per filter

Which air filters scored best in our Ratings?


3 Things to Consider



Operating Costs

Many portable (aka room) models have annual operating costs of $150 to $200 for filter replacement and electricity (with the majority of that cost being for filters). Filter prices can range from around $10 each up to about $100 (with some priced well into the hundreds). Some units use a pre-filter to capture large airborne particles before they reach the HEPA filter, possibly extending its life and can range from around $10 to $35.


Depending on usage, you typically need to replace filters every 3 months. To cut costs, look for room models that are Energy Star qualified, meaning they are relatively energy-efficient compared to standard models. Some models have washable filters that can be reused. For whole-house filters, annual replacement costs are typically under $100.

Keep it Clean

Any type of air purifier won’t work well if the filter is clogged and dusty, and, if filter is full, it may stop working or even release dirt back into the air.


Quietness Counts

Noise level is important, especially if you run an air purifier in a room where you sleep or work. For the sake of efficiency (and quietness), we recommend picking a larger unit and running it on a lower speed, rather than cranking up a small one.


4  Room Air Purifier Features


Fan: Most room air cleaners use a fan to suck in air for filtration. Those without a fan (the air circulates naturally throughout your home) run more quietly, but those we tested without fans worked poorly.

Servicing indicator: A clogged air cleaner works inefficiently. This feature lets you know when the unit needs to be cleaned or the filter replaced.

Programmable timer: These controls allow you to set the purifier to run a few hours before you’ll be using a room, or turn it off automatically.


Carrying handle: Makes it easy to move unit from room to room.


Number of speeds: The unit adjusts to your air-cleaning needs—lower when you are sleeping or working and need quiet, higher when it’s prime pollen time.


Ionizer: If a unit has an ionizer (which attracts particles via an effect like static electricity), it’s important that it not produce ozone (it may say on the box or in an operation manual; you can also check our Ratings), a possible lung irritant.

Remote control: Lets you easily adjust settings from across the room.


Dirt sensor: In some room models, the unit automatically adjusts fan speed to the level of dirt or dust in the air.


Washable pre-filter: A washable—and re-usable—pre- filter collects large particles; if it’s washable, it can help cut overall costs. However, many of our higher-rated models did not have this option.


5  Clearing the Air


What They Do Well

The better air purifiers are especially good at filtering pollutant particles such as dust, smoke from candles or fireplaces, and pollen.


What’s Not So Great

Volatile organic compounds (VOCs) from adhesives, paints, and cleaning products, and other types of gaseous pollutants, however, are another matter. Some portable models with carbon pre-filters are claimed to filter VOCs, but the Environmental Protection Agency warns that such filters are specific to certain gaseous pollutants, not for others, and that no air purifier is expected to remove all gaseous pollutants found in the typical home. Carbon filters also must be replaced often, typically every 3 to 6 months, or they stop working.