I have a 40 year old, 1700 square foot house, California. Gets to a low of
30 degrees in the winter and 110 in the summer. Five years ago had new
ductwork installed, along with Trane furnace and 3 ton air conditioner.
Honeywell motorized MARD dampers and zone controller used to regulate air
flow for upstairs family room/home office and the rest of the house
downstairs. We went with the zone control as the upstairs room was at the
time used as a home office, and the rest of the house was unoccupied. And
now most of the time the lower section of the house is used and the
upstairs room is unoccupied most of the time. In the summer though the
upstairs room is like an oven, it can easily be 25 degrees warmer than the
downstairs and can get up to 100 in the room.
There are two problems with the system now. The most serious is that the
damper that opens to allow air to go upstairs seems stuck in a halfway open
position. The second problem is that on the very hot summer days and both
upstairs and downstairs t-stats are calling for air conditioning, the
system really can't keep up. The temperature of the upstairs continues to
rise even though the compressor runs constantly. I specifically mentioned
to the people who installed the system that I wanted ice cold air blowing
out of the vent upstairs, and I was assured that 3 tons would be enough.
Then a year later one of the a/c techs came by to service the damper, I
mentioned that the system couldn't keep up, he mumbled something about how
we should have gone with 4 tons.
Now I just don't know what to do. I don't want to call the people who
installed the system, as they just can't seem to get things right. The
tech who came by to fix the damper the first time (the motor slipped off
the damper shaft) burned out a zone on the zone control board. Moved the
wires to an unused zone on the board and things sort of work. And then he
said that it's very difficult for a motorized damper to close completely
when the blower is operating full blast, almost like he was hinting it's
not going to be the last time we have trouble with the dampers. I've also
never been completely convinced the system is fully charged, although their
expert tech said the pressure is at the high end, he can't put in any more
R-410A or the overpressure switch will kick in, it was doing that when they
first charged the system. They keep saying the system will only drop the
air 20 degrees from the outside temp, so if it's 100 outside, I should be
happy to get 80 degrees coming out of the vent.
If I can get somebody to crawl under the house and fix/replace the bad
damper, the system itself is still not going to work as I wanted as the
compressor just doesn't seem to be able to cool down the entire house on
the hottest summer days. If a larger compressor were installed outside,
does that mean a larger coil has to be installed inside the house and
replace the existing coil? Or maybe the whole zone control thing with
dampers is going to be a money pit and never work, and should be scrubbed?
And how do I know if 3 tons is enough to cool the house. 4 tons? 5 tons?