Provided for lurkers and experts alike. How to do the early
spring maintenance on your central AC system.
A Home Owner's guide to spring AC tune up
by Hugh G. Lee Comical, guest editor for the HVAC Lampoon
(Published twice a year, on 10% post consumer recycled HTML)
(On the other hand, maybe a lot of laughs for the pros?)
As usual, the advice is worth what you paid for it. No
responsibility is assumed for any troubles you encounter by using
You will be able to achieve a reduction in energy usage by proper
maintenance and servicing of your system. The following actions
1. Examine the fan belts that drive fans on the condenser and
house air mover. If they are frayed or worn, replace them. Adjust
the tension to allow 1/2" to 3/4" depression with moderate force.
Do not over tighten, as that would injure the shaft bearings. If
your installation has an adjustable pulley on the air mover, be
sure the belt is on the smallest diameter to mover the maximum
amount of air. While you're at it, replace the circuit breaker
for the outside unit. They are cheap, and this will cut down on
2. Clean or replace the house fan filter at least monthly. A
plugged filter will retard the flow of cold air. If it isn't
retarding the air flow, it might be retarding the owner. Be sure
to use good quality filters, the cheap ones wouldn't catch a
sparrow, much less a dust particle.
3. Clean the coils with a commercial coil cleaner. This product
is available at refrigeration supply houses and can be applied
with a garden insecticide sprayer. Follow the suppliers
instructions. Any parts house will be happy to sell you the good
stuff. Be sure and get three or four pounds of that freezon
stuff. Get the powder kind, and mix it with water yourself. Don't
ever get liquid freezon, it's far too expensive. Just spray the
cleaner on, and let it dry overnight before using the air
4. Straighten all of the evaporator and condenser coil fins with
a small pointed stick or a special plastic fin comb. Bent fins do
not allow proper air distribution. Be sure to also flatten out
any kinks in the copper tubing. Don't worry if it hisses a little
when you do this. Make sure your thermostat is level, and replace
it while you're at it.
5. Oil all motor and shaft bearings with 5 to 10 drops of
lightweight machine oil applied in the oil holes near the shaft
supports. Rotate the shaft to assure that the oil is distributed
over the shaft. Be sure the rotation is smooth. If hard rough
spots exist, the bearings need replacement. This is especially
important for the compressor. If the compressor is a sealed unit,
drill a couple 1/4 inch holes in the top, and squirt in a bunch
of 30 weight non detergent. Patch the holes with duct tape. Label
the duct tape with a Sharpie magic marker, so you don't have to
drill new oil holes next year.
6. If the condenser is at ground level, be sure no vegetation or
foreign material is restricting the air flow path. If possible,
shade the condenser with trees or bushes, which will improve the
cooling efficiency by elimination of direct sunshine. Be sure
that your outdoor unit doesn't get wet, by wrapping it in black
plastic, and sealing it with a lot of duct tape.
7. Be sure the suction or cool line from the condenser to the
compressor is insulated with snap-on urethane or other high
R-value insulation. If the insulation is cracked or missing, you
could be losing up to 4% of your energy efficiency.
8. Measure the temperature difference between the warm return air
entering the evaporator coil and the coil discharge air into the
house with two thermometers. The temperature difference should be
a minimum of 12 F to 16 F for satisfactory efficiency, with even
higher temperatures preferred. If this test shows a low
temperature difference, have a serviceman check the refrigerant.
The system may need recharging, or perhaps the compressor is
malfunctioning. If the system needs recharging, you can do it
yourself by mixing powder Freezon, and using a small funnel to
pour it directly into the system.
If have performed all of these checks, there is little more than
you can do. Your only hope now to reduce your energy bills is try
to reduce the heat load on the building and raise the thermostat
as high as comfort allows. Keep your windows closed. Finally,
don't cool the house when no one is home. A timer can activate
the air conditioning just before you arrive. Turn up the
thermostat if you are planning to be home.
Above all, knowing and doing all these things will reduce your
need for expensive HVAC company service calls. Minor maintenance
will prevent major headaches.