Residential Air Conditioning
Knowing your air conditioning system and how it is supposed to work can save
you big $$$$ on service and possibly prevent you from over paying for
service. Everything following on this newsletter is important for you to
know... unless you have money to burn.
You should record the name plate information off of your air conditioner and
your furnace. The out door part of your cooling system is called the
condenser and the nameplate will be on the outside of the unit and
accessible without the removal of any panels. The furnace inside your home
may require the removal of the front panel. The label will provide you with
the manufacturers name, model number and serial number. This is all the
information you require. The model number tells the capacity and the serial
number "dates" the unit. The same applies to your furnace. If you have
options such as a humidifier, high efficiency air filter or air cleaner, HRV
(heat recovery ventilator) or an air purifier (using ultra-violet light to
kill viruses, mold, bacteria and odors) you should record this information
This information when passed on to your contractor, that you call for
service will save time and money and get you back in operation sooner. You
should also record the phone number of your service contractor. Leave this
information with anyone that is house sitting while you are away on vacation
so they would know who to call incase something goes wrong in your absence.
Every year we get calls from "Widows" who say "my husband always looked
You should mark on your calendar to call for the seasonal maintenance
(spring and fall) before the system is needed. Don't wait until that first hot or cold
day to test your system!!!
Brief description of the components of your air conditioning system...
- The outdoor section is called a condenser rated in "BTU's" or "tons" of cooling, 12,000 BTU's per ton of cooling.
- A 2 ton unit would be 24,000 BTU's and a 3 ton 36,000 BTU's etc.
- The indoor cooling coil is called the evaporator and the size corresponds to the size of the condenser.
- The condenser and evaporator are connected with 2 copper lines called a lineset.
- One copper line has a rubber insulation on it (suction line). The insulation is required as this line is the cold line and will form condensation on it from the surrounding air if not insulated.
- The other, bare copper line is called the liquid line and will normally be neither hot or cold to the touch.
- The furnace that provides you with heat in the winter also provides the air circulation for the cooling system.
- The air filter cleans the air, but only when the fan in the furnace is running. Filters come in a wide range of efficiencies and sizes.
- The humidifier adds humidity during the heating season and should be off while in cooling mode.
- The thermostat controls the operation of both the furnace and air conditioner. There are many models to choose, from digital, wireless, high definition, programmable etc.
- The HRV (heat recovery ventilator) is common in new homes that are tightly sealed to exchange stale inside air with fresh outside air.
- The UV (ultra violet) air sterilizers, kill viruses, bacteria, mold and odors of all types.
The temperature set button or lever on your thermostat
is not an accelerator. "Cranking" the thermostat will not achieve set point
one milli-second faster than setting the temperature for the desired comfort
level. When your air conditioner is running it is operating at full capacity
The following are some helpful hints on the use of your air conditioner and energy costs.
If you are in the habit of turning your unit "off" or raising the
temperature when away, be advised that it will take about one hour per
degree to lower the temperature when you restart the system.
You can reduce the load on your system by doing any of the following...
- Turning off lighting, that is not required.
- Use the BBQ instead of the stove for cooking.
- Close draperies, to reduce solar gain from the sun.
- Turn the fan switch of your thermostat to the on position (particularly important for 2 story homes) to circulate the air and use ceiling fans.
- Wash the coil of the outdoor unit with your garden hose to rinse away dirt, grass clippings and debris.
- Keep shrubs and plants well back from the outdoor unit. Any blockages of the unit will make it run hot.
- If using the shower or bath, be sure to run the exhaust fan to clear the humidity from the bathroom.
- If you have a Heat Recovery Ventilator (HRV) turn it off during extreme heat periods.
- Keep the windows and doors closed as much as possible.
- Most important to make sure the air filter in your furnace is clean.
- Be sure your humidifier on the furnace is turned off, the by-pass damper closed, humidistat to off and the water turned off.
Willis Carrier developed air conditioning to dehumidify the
air in textile mills. The main purpose of your air conditioner is still to
dehumidify the air. The cooling effect is simply a by-product of that
process. The first building to be air conditioned for "people comfort" was
the Sears Tower in Chicago.
Comfort is based upon a combination of temperature and humidity. If you have
been to Las Vegas you'll know that you can be very comfortable at 85 F
because the air is so dry. In the same respect you can "feel" uncomfortable
at 73 F (23 C) if it is a high humidity day. Your air conditioner can only
remove the humidity when the system is running and on the hottest day of the
summer your unit may run 22 hours of the day. System Design conditions for
southern Ontario for cooling is 15 to 20 degrees F. lower than the outside
temperature. If it reaches 100 on those few days of the summer the best you
should expect indoors is 80 to 85 F. In the same respect your furnace is
designed to maintain 70 F. on a day when the temperature outside is (-10
F.)or an 80 degree differential. For the mathematics geek's this is a 4 : 1
ratio in size (furnace to A/C)which is a reliable method of sizing your A/C
Knowing that your A/C is 1/4 of the capacity of your furnace, it is obvious
that recovery time from set-back or initial start-up will take longer to
reach set point temperature. One degree per hour is a close approximation of
what to expect.
A comfortable range of set-back is 3 - 5 degrees F., for cooling. You may
have experienced a phenomena where the temperature in your home increases
after the sun sets in the evening. This is referred to as the "Sling
Effect". The heat radiation from the sun has been doing its' best to beat a
path through the insulation in your walls and attic all day and it is around
sundown when this heat makes its' way into your home.
Questions and Answers on Air conditioning
Question: My unit does not reach set point on really hot days. Is there a
Answer: Your system (for southern Ontario) is designed to provide 15 to 20
degrees F. (10 to 12 degrees C.) lower temperature than outdoors.
Question: My furnace fan is running, but there is little or no air flow at
the registers and house is getting hot.
Answer: If your filter has not been changed in months, it is possible that
the filter is so dirty that it is restricting the air flow. This can result
in the cooling coil (built into the sheet metal "plenum" on top of your
furnace) turning into a large block of ice that will totally block the air
flow. There are only 3 conditions that will cause the system to ice up... A)
any restriction of the air flow through the furnace (dirty filters, too many
vents or return air intakes blocked off or shut, failed fan motor or fan
belt) B) a leak in the system that has allowed some of the freon to escape
from the sealed system or C) operating the system at too low a set point
when the outdoor temperature drops down into the low "teens digits" on the
Celsius scale or below 60 on the Fahrenheit scale.
Question: How many degrees should I set back my A/C system when at work or
in the evening.
Answer: 3 to 5 degrees Fahrenheit or 2 to 3 degrees Celsius when away for
more than 4 hours, but bear in mind on a hot day the system may take one
hour per degree to recover when you come home. Your A/C system is about 1/4
of the capacity of your furnace and therefore will take longer to cool than
it would to heat up.
Question: The temperature is okay, but it is still very humid in the house.
Answer: Your A/C will only remove humidity when it is operating. If the
system was oversized for your home it will lower the temperature more
quickly and shut down before the humidity is under control. Big is not
better when it comes to air conditioning. There could be other problems with
the home in that too many basement outlets have been closed off or
insufficient return air from the basement. It is still a wise idea to
operate a dehumidifier in the basement during the spring and summer months.
If you do, it is wise to position the dehumidifier over a floor drain so
that the reservoir can be eliminated. This will save you having to remember
to empty the reservoir every other day.
Question: Water is leaking out around my furnace. What could be the cause.
Answer: This could be a simple matter of the drain line becoming clogged to
the cooling coil freezing as described earlier. The cooling coil in the top
of your furnace acts like a secondary filter during the cooling season as it
is wet with condensation when the system is on. The wet coil will trap dust
and dirt that your air filter may not have removed. The dirt will wash down
into the drain pan around the base of the coil and can plug or clog the
opening to the drain pipe that takes the water to the floor drain. Some
installers like to cut a corner or two to save money on the install by
reducing the size of the drain line or by using flexible hosing that can
create a "double trap" in the line. Size matters when it comes to drain
lines. The pipe should be of rigid plastic or copper and slope continuously
to the floor drain. If the end of the pipe is open at the floor drain you
could try "blowing through the pipe". If there is resistance then a release
you may have solved the problem for a period of time, but really what you
have done is pushed the dirt around... not removed it. You may have to call
a technician to open the sheet metal and flush the drain pan of the cooling
coil or cut open the drain line. A plugged drain can make quite a mess if
your basement is finished so it is wise to check the furnace room every so
Question: My system is blowing hot air and the unit outside is not working.
Answer: There are separate circuit breakers in your hydro panel for the
furnace and the A/C. A single width breaker controls your furnace and a
"double" width breaker powers your outdoor section of the system. Check the
breaker and reset if necessary. Should the breaker "trip" when reset... do
not try to reset again as there is a problem and you need to call your
contractor. Even if the breaker is "off" you may still hear a buzzing or
"hum" at the outdoor unit. This sound is from the electrical switch (called
a contractor) that is energized by a low voltage signal from your thermostat,
through the wiring in your furnace. Should all the breakers be in the on
position, check the outside unit and listen for any noises or the unit
trying to start. It is possible the outdoor fan has failed and the
compressor that circulates the freon gas through the system will get soooo
hot that it will shut off to prevent damage to the compressor. Sticking a
popsicle stick or piece of wire through the fan grill on top to see if the
fan spins freely or is seized will also direct your contractor to knowing
the problem before incurring an unneeded service call. We have seen all
kinds of little creatures from cockroaches to mice burnt to a crisp on the
contacts of the contractor. Unless you are very sure of your understanding of
electricity, I would advise you call a contractor for further investigation.
Even with the breaker turned off there is a part in the unit that holds an
electric charge called a capacitor. The jolt you can receive from a
capacitor can "stop your heart". If the fan motor is thought to be the
cause, turn the A/C off at the thermostat to prevent the compressor from
cycling on and off, as this could cause further damage.
Question: My contractor has reported the compressor has failed and requires
replacement. What should I ask?
Answer: Most manufacturers have a five (5) year warranty on the compressor.
The labor warranty is normally only one year. After the first year and
before the end of year five, only the compressor is provided under warranty.
Additional costs such as, freon recovery, welding charges, a freon drier,
system evacuation and labor would be charged extra. A normal residential
compressor can normally be replaced in 4 - 6 hours. If your system is over
15 years old it would be wise to consider replacement of the unit for a
higher efficiency unit. The newer systems use a different refrigerant gas
called R-410A or "Puron" and circulates a synthetic oil throughout the
system with the freon. This oil is not compatible with the oil or freon of
the old R-22 systems and therefore requires replacement of the outdoor unit
(condenser), the indoor coil (evaporator) and the copper connecting lines
(lineset). The same electrical supply can be used with the new system.
Compare the cost of replacing the compressor and the general condition of
the unit with the cost of a new system. A new system may qualify for a hydro
rebate, but in either case the new unit will use less electricity and most
likely be considerably quieter. Knowing what caused the original compressor
to fail could prevent it from happening again. Dirty coils on the outdoor
condenser cause the compressor to run hot and also result is a loss of
efficiency. This could be compared to running your car engine without
antifreeze coolant in the radiator... your engine will overheat and burn
out. Not all compressor failures are "burnouts". Mechanical failure can also
occur and there is usually a reason for this also. Ask you technician why?
The new compressor will only carry a one year warranty and the labor for the
replacement may only be 30 to 90 days... ask for the warranty in writing.
Question: Can I turn my furnace off for the summer, now that we are into
Answer: You can, but only if you don't want cooling either. The fan in your
furnace used to circulate the heat throughout the home in winter is the same
fan used to circulate the cool, dehumidified air in summer. The furnace
electrical power also provides the electrical power to your thermostat and
the electrical signal to the outdoor condenser to turn it on.
Question: Does it help to turn on, or leave on an exhaust fan in the
washroom or at the kitchen range to "suck" out the heat.
Answer: A simple little bathroom fan will exhaust about 100 CFM (cubic feet
of air per minute) Should the fan be left on for an hour it will exhaust 100
cubic feet of air X 60 minutes =6,000 cubic feet of air. The average house
is around 1,600 square feet with 8 foot ceilings for a total volume of
12,800 cubic feet of air space. Divide the cubic footage of the home by the
air exhausted in only one hour of the average bathroom fan (12,800 by 6,000)
and you can see that every inch of air in your home will be removed in just
over 2 hours. That is a ton of air for a simple little fan. Now because your
home cannot go into a "vacuum" it is obvious that the replacement air has to
come from somewhere. It comes from outside, through every crack in the home
and every time the door is opened. This air is unfiltered, hot and humid and
your A/C system cannot keep up with the additional load. Other appliances in
the home that exhaust air are, clothes dryers, central vacuum systems,
kitchen range hoods. Each of these items exhaust more air than the average
bathroom fan. Houses of newer construction, built from 1995 and on are
effectively sealed against outdoor air leakage. This is as a result of
better windows, vapor barriers, door seals and insulation.
Question: My old house was a 1,200 square foot bungalow with a 2 1/2 ton
(30,000 BTU) air conditioner. My new home is almost 3,500 square feet and
the builder has only installed a 2 1/2 ton unit. Have they made a mistake?
Answer: Not likely. New home construction is more energy efficient than the
old house, meaning you can easily get by with a furnace and A/C of smaller
Question: I'm shopping for a new A/C for my home.... what should I look for.
Answer: More important than what to look for is what to LOOK OUT for. You
could buy the best unit on the market, but if the unit is not properly
installed it will not work as well as a BRAND "X" unit that is installed
correctly. Air conditioning units are like cars in the sense that they come
in different colours, sizes, prices and options. Any of the big
manufacturers of A/C units will also have more than one line of unit ranging
from the Chevrolet to the Cadillac and the price can vary greatly between
the quality or features you wish to budget or pay for. Surprisingly enough
most of the manufacturers do not make the components for their systems. They
will purchase compressors, fan motors, thermostats, electrical switches,
copper and electronics from the same company that all the other
manufacturers are buying from. Even the cabinets could be identical on some
units from different makers. The Sears Company is a good example of this as
they simply have their nameplate on ICG (Keep-Rite) units. Then there is
Carrier, Lennox and York that sell their "brand name" to only authorized
dealers that meet a long list of qualifications in order to sell their
product line. These same manufacturers sell "Knock-offs" under a different
name to wholesale outlets and the only difference in the equipment may be
the paint finish. The important selling features of one unit over another
are as follows...
SEER (seasonal energy efficiency ratio). This is a number that will
presently range from 13 to as high as 17.5. The higher the number the
more efficient it is. Your old system may be as low as a SEER 10. The
Canadian Gov't has a minimum standard presently of SEER 13.
SONE or DBR (decibel rating) The numbering on this is opposite to
the SEER. The lower the Sones or DBR the quieter the unit is. Things that
make one unit more quiet than another are the type of compressor (scroll
compressors are quieter than reciprocating compressors)
A 2 speed outdoor or condenser fan motor will make less noise on low
speed on moderate days than a single speed unit.
The "Pitch" or angle of the fan blades on the outdoor unit can cause
air turbulence and noise, but all have to circulate enough air to cool
the freon inside the coils.
The compressor on some units can be equipped with a sound blanket to
reduce the noise or on some deluxe units the compressor will be inside a
separate compartment of the outdoor unit that is insulated to dampen noise
The paint finish, design and actual style can vary between
manufacturers that has no bearing on how the unit functions and is therefore
a personal choice of aesthetics. It could be a square box or have sweeping,
sculptured corners with a automotive finish.
Copper coils are a must. The new environmental refrigerants operate
at much higher pressures than the old R-22 systems. Some makers used aluminum
tubing and it could not last and was near impossible to repair if a leak
Price: Picture a company that has met the qualifications for a
"dealership" and hires factory trained, experienced staff. They will be
paying their staff more money per hour than the guy selling BRAND X units
and working out of his garage. It is understandable then why the low ball
price should be avoided. The dealership will also have the staff and parts
available to service and maintain your equipment.
Question: Can I install a fence or shrubs around my condensing unit to hide
it from view?
Answer: The condenser must have free air flow around it to permit the
refrigerant gas in the system to be cooled to the condensation point. Any
obstruction such as fences, bushes or even dirt on the coil section will
cause the unit to run hot. Excessive heat can "burn out" the compressor
which is the most costly component of the system. Any blockage of air can
also result in a loss of capacity to cool your place on a hot day.