Heating and Air System Questions

1. Why does my indoor fan run continuously and never cycle off?

  Check your thermostat setting and make sure that the fan is set in the "Auto" position and not in the "On" position. This will cause your indoor fan to come on only when called by the thermostat for cooling or heating. Sometimes the setting gets bumped accidentally into the "On" position. If this is not the case, then you should call for service.

2. Why doesn't the fan on my outside unit come on?

 

You should first make sure that there is power to the outside unit. When your thermostat is set and the unit should be coming on, go outside and listen for a humming noise. If you hear no noise, then you probably have no power to the unit.

Check the power disconnect outside at the unit (if breaker type, flip off then on again; if fuse type, pull out then push back in), then check the breaker inside at the breaker panel. Once you have checked these and still have no power, make sure the thermostat wire (small brown wire entering with copper tubing) has not been cut while trimming grass.

If you find none of the above, then you should call for service.

3.  At what temperature should my thermostat be set?

 

During the cooling season, most homeowners keep their thermostat set between 76-78 degrees.

During the heating season, most homeowners keep their thermostat set between 68-72 degrees.

Any setting will work, but please keep in mind that varying from these settings will effect your utility bills.

4. What is happening with refrigerants in air conditioning systems?

 

Due to environmental concerns, our federal government has issued regulations that restrict the future production of HCFC refrigerants such as R22. Because of this, many companies are trying to respond to the challenge of developing new systems and new coolants.

The HCFCs have been used for decades in a safe and efficient manner in all air conditioner and heat pump products. But, many reports have indicated that these coolants are having an impact on the earth's ozone layer.

The United States Congress, in response to an international treaty, have provided the Environmental Protection Agency (EPA) with tools through the Clean Air Act to regulate the use of refrigerants in air conditioning systems. The current refrigerant, R22, must stop being produced by the year 2020. All products that use this refrigerant must stop being produced by the year 2010.

Many companies are developing new refrigerants and new systems.

5. What do all those heat pump and air conditioner ratings mean?

 

EER - Seasonal Energy Efficiency Ratio. This is a system for rating the efficiency of cooling equipment. It is calculated by dividing the cooling capacity of a continuously operatingair conditioner by the electric power input.

The higher the SEER rating, the less the unit will cost to operate.

Other ratings include:

HSPF - Heating Seasonal Performance Factor. This is similar to the SEER rating, except it measures the efficiency of the heating portion of the heat pump.

db - Decibel. A term to describe the relative loudness of a sound. Typically, heat pumps and air conditioners are between the sound of a human voice (70 db) and a blender (88db).

6. What are my choices when it comes to filters?

 

Disposable filters are generally made of coarse fiberglass mats in a frame mounted on a filter rack. They are often referred to as "throwaway" filters. Very large particles are collected by straining, as they are too large to go through the openings in the filter. Particles are also deposited on strands of the filter when they come in direct contact with one another. The filter efficiency increases as it fills with particles, until it reaches the point of saturation and begins to lose as many particles as it gains. The disposable filter's capacity is limited to larger particles.

Reusable foam or metal filters have slightly higher performance capabilities than disposable filters due to the use of oils and adhesives applied to the filter to cause the particles to adhere to them. They are washable and must be recoated after washing to obtain their efficiency for reuse. They are most effective on large particles.

Electrostatic filters have a means for electrically charging the filter or the entering particles, much like a magnet, to attract particles to the strands of the filter as well as collecting particles by straining.

Pleated filters are constructed of fiberglass or synthetic fibers woven into a more dense material. The filter is arranged in V-shaped forms to increase the area of the filter material without increasing the face area. This increases the particle holding capability.

High-Efficiency Particulate Air (HEPA) filters generally have an efficiency rating of 90% and above and are considered to be very effective at small particle removal. There are many models of portable HEPA filters intended for use in a room that are self-contained with their own air mover and electrical system.

Electronic Air Cleaners are highly efficient filters that use an electrical charge to remove and collect particulate matter such as dust, smoke, pollen, etc. The charged particles are then attracted to each other and forced to a series of alternately-charged metal plates where they are collected. These cells must be periodically cleaned with detergent and hot water to maintain the efficiency of the collection. Generally they are used with a pre-filter to remove the large particles before entering the cells.

7. When should I replace my filters?

 

The need to replace or clean filters is a function of many variables such as run time, efficiency, size and type. Typically, low-efficiency disposable and permanent filters need to be replaced or cleaned every one or two months in peak heating and cooling seasons. Electronic air cleaner cells should be serviced at this frequency also.

8. Why do I need regular maintenance on my heating and cooling systems?

  PREVENT PROBLEMS BEFORE THEY START

One of the best ways to avoid problems with your home comfort equipment is to prevent them from occurring. The best way to do that is scheduling regular maintenance. We are qualified to maintain all of your heating and cooling equipment year-round.

Even the best equipment, if not properly maintained, can cause problems.

BENEFITS OF PLANNED SERVICE

Having your equipment serviced on a regular basis has many benefits for you:
    • Regular service lengthens the life of the equipment by keeping it in good working condition,
    • It maintains efficient operation which saves you energy dollars.
    • It will save you money by eliminating costs of repairs and reducing any major repair expenses.
    • It will establish you as a priority customer which you'll appreciate if you ever needed cooling during the hot days of summer or heating during the coldest blizzard of the year.
    • It assures you of service by experienced and qualified technicians from an established company who will be there when you need them.
    • Regular service protects your warranty.
PLANNED SERVICE WILL HELP KEEP YOUR HOME SAFE

Carbon monoxide in your home is an invisible threat to your safety, but it is a threat that is preventable. Cars and trucks, lawn equipment, water heaters, stoves, clothes dryers, furnaces, space heaters and other combustion appliances are some of the potential sources of carbon monoxide. Though designed to be safe and not produce carbon monoxide, home heating systems are only one of the many sources. In addition, negative pressure in your home coupled with improper combustion can lead to carbon monoxide entering your living space. Negative pressure can be caused by central vacuum systems, high volume kitchen range hoods, countertop range exhaust systems, bathroom exhaust fans and particularly fireplaces which can remove an enormous amount of air from your home when burning.

Prevention is the most important step to take to reduce carbon monoxide problems.

Scheduled maintenance by a qualified technicain to check combustion appliances to make sure they are properly operating, and to be sure that all chimneys and vents are connected properly and not blocked, will ensure safety and efficiency.

9.  How big of a system should I plan for when building a house?

  Sizing Residential Heating and Air Conditioning Systems

Older space conditioning systems (more than 10 years old) are often unreliable and much less efficient than a modern system. When it's time for a new replacement, choosing one of the correct size (heating and/or cooling output) is critical to getting the best efficiency, comfort, and lowest maintenance and operating costs over the life of the new system. Some national surveys have determined that well over half of all HVAC contractors do not size heating and cooling systems correctly.

The most common sizing mistake is in over-sizing. This not only makes the new system cost more to install, but also forces it to operate inefficiently, break down more often, and cost more to operate. Over-sized air conditioners (and heat pumps) do not run long enough to dehumidify the air. This results in the "clammy" feeling and unhealthy mold growth in many air conditioned houses. Over-sized heating equipment often creates uncomfortable and large temperature swings in the house.

It is the installer/contractor's job to perform the correct sizing calculation for the building. However, many poorly trained installers only check the "nameplate" (a metal tag that tells you the Btu per hour, output among other things) of the existing system and sell you one just like it, or even worse, one that's larger. This is not a correct sizing method and not in your best interests! Before the era of tightly constructed homes, it was not uncommon to install furnaces and air conditioners that had two to four times the needed capacity. Also, since many people like to try to conserve fuel and make their homes more comfortable by installing new windows, caulking, and weatherstipping, and adding more insulation, going by the nameplate will most certainly result in the wrong size being installed. Making improvements to the way the house holds energy in allows you to install a smaller system while still being comfortable, as well as saving large amounts of energy.

Correct sizing requires a great many more items (i.e., level of insulation; size, type and location of windows; air infiltration, how many people live there, the local climate, etc.) than simply reading the nameplate of the existing unit.

Correctly Sizing Heating and Air Conditioning Systems

Building owners should insist upon a correct system sizing calculation before signing a contract. This service is often offered at little or no cost to homeowners by gas and electric utilities, major heating equipment manufacturers, and conscientious heating and air conditioning contractors. Manual J, published by the Air Conditioning Contractors of America (ACCA), is the most common method in use. Many user-friendly computer software packages or worksheets can simplify the calculation procedure. You should make sure that the procedure used by the contractor follows Manual J or one of the approved standards in the Bibliography below.

Many factors effect a home's heating or cooling load. A good estimator will measure walls, ceilings, floor space, and windows for the accurate determination of room volumes. Also, a good estimate takes into account the R-value of the home's insulation, windows, and building materials. A close estimate of the building's air leakage is necessary. A blower door test is the best way to measure air leakage.

A good estimate will also include an inspection of the size, condition (how well joints are sealed and the ducts are insulated), and location of the distribution ducts. The placement of supply and return registers, should be appropriate for the system type and size. The orientation of the house also effects heat gain and heat loss through windows. Overhangs can reduce solar gain through windows. Make sure the contractor uses the correct design outdoor temperature and humidity for your area. Using a higher summer design temperature results in over-sizing air conditioners. Underestimating the latent (humidity) load (energy used by the air conditioner to remove moisture from the air) results in undersized air conditioners.

Any bid should include an agreement to provide written calculations (listing the procedures and standards that will be followed), equipment and installation warranties, a payment schedule, and a firm completion date. When the contractor is finished, get a copy of their calculations, assumptions, and the computer output or finished worksheet. This is your only proof that they did the job right.

Sizing Heaters and Air Conditioners: Quick but Inaccurate Methods

Here is a list of "quickie" methods some contractors may use. They are also somewhat useful for a very rough idea as to what you need to buy. NEVER use any of these to determine the final size.
    • The contractor walks in the house, looks at the existing unit, and recommends that the replacement unit be the same size, or larger. This obviously does not take into account any improvements made to the house or mistakes made in sizing the original unit.
    • The contractor asks you how many square feet of living space there are in your house, then tells you what size unit you need. This is called "sizing by square footage" and is the most commonly used inaccurate method of sizing. A typical value used for air conditioners is one ton (12,000 Btu/hour) per 500 square feet (46 m2). This does not take into account differences among house orientation, design, construction, and energy efficiency or intended use of the system.
    • You may get different answers from different contractors who use the previous technique. In that case, they may have a different "rule of thumb," or one of them may be using the "lowest cost" method. This involves adjusting the square footage rule so that whatever the contractor has in their warehouse becomes the right size for you. Since the "in-stock " unit costs the contractor (but not necessarily you) less to install, this becomes the "lowest cost" method.
    • Another poor method involves a prepared chart such as the one below, which is for heating systems. You use the chart in the following way. First, determine the floor area of all the heated rooms, and the levels of insulation in the floors, walls, and ceilings. Next, find the category (under description) that best describes the home. Then, multiply both the upper and lower values for heat loss in Btu per hour per square foot (from the table) by the floor area of the home to roughly estimate the required heating range.
Home Type or Characteristics ..... Heat loss (Btu/hr/ft2)
    • No insulation in walls, ceilings, or floors; no storm windows; windows and doors fit loosely .... 90 to 110
    • R-11 insulation in walls and ceilings; no insulation in floors over crawl spaces; no storm windows; doors and windows fit fairly tight. ..... 50 to 70
    • R-19 insulation in walls, R-30 in ceilings, and R-11 in floors; tight-fitting storm windows or double pane windows. ..... 29 to 35
    • Superinsulated house with R-24 wall insulation, R-40 in ceilings, and R-19 in floor; tight-fitting storm windows or double pane windows; vapor barrier sealed carefully during construction. ..... 21 to 25
    • Earth-sheltered house with little exposure; well insulated. ..... 10 to 13

For example, if a home's energy-saving features are best described by category 2, and the home has a heated space of 1,500 square feet (139.35 m2), then the design heating load is roughly 75,000 to 105,000 Btu/hour (18,900 to 26,460 kilocalories/hour) (1,500 X 50 and 1,500 X 70). Although a chart like this looks official, not all houses fit the profile given. There is also no accounting for the thermostat temperature setting, the location of the house, the shape of the house, or many other factors.

To save some time the above methods are often used for a first "guess" or rough estimate. If so, then it should be plainly stated to you that this is the case. However, DO NOT USE THESE ESTIMATES for the final sizing.



Bibliography

The following publications provide additional information about load calculations and sizing heating or air conditioning systems. The publications are based upon standards approved by professional organizations. This bibliography was reviewed in December 1999.

ANSI/AHAM RAC-1-1992, Room Air Conditioners, Association of Home Appliance Manufacturers (AHAM), 1992. Available from AHAM, 20 North Wacker Drive, Chicago, IL 60606, (312) 984-5800 x315. 25 pp., $7.50.

ASHRAE Standard 90.2-1993: Energy Efficient Design of New Low-Rise Residential Buildings, American Society of Heating, Refrigerating, and Air-Conditioning Engineers, 1993. Available from ASHRAE (see Source List below). 107 pp., $84.00.

Cooling and Heating Load Calculation Manual, GRP 138, American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc., 1992. Available from ASHRAE (see Source List below). 209 pp., $80.00.

Heat Loss Calculation Guide No. H-22, (1st ed.), Hydronics Institute, 1989. Available from Hydronics Institute, 35 Russo Place, P.O. Box 218, Berkeley Heights, NJ 07922, (908) 464-8200. 63 pp., $14.00 plus shipping.

Residential Duct Systems, Manual D, (2nd ed.), Air Conditioning Contractors of America, 1995. Available from ACCA (see Source List below). 200 pp., $30.00.

Residential Equipment Selection Manual, Manual S, Air Conditioning Contractors of America, (2nd ed). Available from ACCA (see Source List below). 115 pp., $40.00.

Residential Load Calculation, Manual J, (7th ed.), Air Conditioning Contractors of America, 1988. Available from ACCA (see Source List below). 126 pp., $30.00.

Source List

Air Conditioning Contractors of America (ACCA)
1712 New Hampshire Avenue NW
Washington, DC 20009
Phone: (202) 483-9370 Email: webmastr@acca.org
World Wide Web: acca.org

The following publications provide additional information about load calculations and sizing heating or air conditioning systems. The publications are based upon standards approved by professional organizations. This bibliography was reviewed in December 1999. ANSI/AHAM RAC-1-1992, Room Air Conditioners, Association of Home Appliance Manufacturers (AHAM), 1992. Available from AHAM, 20 North Wacker Drive, Chicago, IL 60606, (312) 984-5800 x315. 25 pp., $7.50. ASHRAE Standard 90.2-1993: Energy Efficient Design of New Low-Rise Residential Buildings, American Society of Heating, Refrigerating, and Air-Conditioning Engineers, 1993. Available from ASHRAE (see Source List below). 107 pp., $84.00. Cooling and Heating Load Calculation Manual, GRP 138, American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc., 1992. Available from ASHRAE (see Source List below). 209 pp., $80.00. Heat Loss Calculation Guide No. H-22, (1st ed.), Hydronics Institute, 1989. Available from Hydronics Institute, 35 Russo Place, P.O. Box 218, Berkeley Heights, NJ 07922, (908) 464-8200. 63 pp., $14.00 plus shipping. Residential Duct Systems, Manual D, (2nd ed.), Air Conditioning Contractors of America, 1995. Available from ACCA (see Source List below). 200 pp., $30.00. Residential Equipment Selection Manual, Manual S, Air Conditioning Contractors of America, (2nd ed). Available from ACCA (see Source List below). 115 pp., $40.00. Residential Load Calculation, Manual J, (7th ed.), Air Conditioning Contractors of America, 1988. Available from ACCA (see Source List below). 126 pp., $30.00. Air Conditioning Contractors of America (ACCA)1712 New Hampshire Avenue NWWashington, DC 20009Phone: (202) 483-9370 Email: webmastr@acca.orgWorld Wide Web: American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE)1791 Tullie Circle NEAtlanta, GA 30329-2305Phone: (800) 527-4723; Fax: (404) 321-5478Email: ashrae@ashrae.org World Wide Web: