Question:
The house I moved in last winter has a Lennox central air conditioner. I do
not dare to re-start it before any preparation. The outdoor unit is pretty
dirty with lots of tree leafs in it. Should I do a clean-up? How? Any
procedure to re-start it, or just simply turn it on from thermostat?
Anything to take care of in the process to see if things goes fine?
Answer:
Turn the thermostat to OFF. Turn the 240V breaker for the AC ON. Open
up the filter access panel in the furnace or inside air-handler and
check the filter. Heck, don't just check the thing, change it! Open up
the outdoor unit (the "hot" wiring should be in a separate compartment
that you needn't open) and sweep/vacuum/whatever out the worst of the
collected crap, then hose down the coils. You don't need to get it
spotless, just eliminate anything that might block the fins, etc.
Finally, after the breaker has been on for at least an hour and
preferably four or so, turn the thermostat on and turn it down to 65 or
so -- cold enough that you're sure it will come on. Either immediately
or within two minutes or so the fan should come on in the outside unit
and you should also be able to hear the drone of the compressor there.
The fan should also come on inside.
Wait about two minutes and then feel the two pipes feeding between the
outside and inside units. The larger pipe should initially get fairly
warm, then cool down to lukewarm. The smaller pipe should get fairly
cold -- cold enough to be uncomfortable to hold continuously -- after
five minutes or so. If you don't feel any cold in the smaller pipe then
something is wrong.
Finally, you can get a thermostat and measure the air coming out of a
cooling duct after the system has been going 20 minutes or so. It
should be 15-25 degrees F cooler than room temperature.
Follow the condensate line from the air-handler/furnace and see where it
drains. Make sure there is water dripping out of it at a fairly fast
rate. (If not then you likely have a clogged condensate line.)
Adjust the thermostat to a reasonable setting -- somewhere in the range
from 72 to 78 for starters.
The other thing that I didn't cover is changing the fan speed. On some
units you don't do this, on some it happens automatically, and on some
you have to do it manually. But the unit should function reasonably
well even with the wrong speed, while you study up to see what you need
to do for the fan.
