On Sun, 25 Aug 2013 10:49:32 -0600, bud--
wrote:

On 8/24/2013 1:56 PM, wrote:
On Sat, 24 Aug 2013 12:30:32 -0700 (PDT), "
wrote:

Three zones on a single system, like the poster
is talking about? Or a two story house that has two entirely
separate systems. The latter is common here too, but not zoning
within a system.

Zoning is not common.

If you zone a conventional system you have less air over the evaporator.
Less heat will be transferred to the evaporator. The evaporator can get
too cold and freeze up. I assume this can be prevented by a 'freeze
stat' on the evaporator to shut down the compressor, but it is added
complexity and short-cycling also has to be avoided. I suspect
dehumidification may not be as effective.

Good point about the freezing. I would think dehumidification would
be better with a colder coil, though (until it froze).

The biggest problem with our current system is dehumidification. If
it did a better job I'm sure I could bump up the temperature a few
degrees. I'll probably have to replace the system(s) in a couple of
years, though. I replaced one of the coils last year and the guy said
the system wasn't long for the world (it's only six years old now).


I haven't seen a zoned conventional system. One major company that adds
air conditioning to existing forced air houses wanted existing zoning
defeated for air conditioning so all zones were open and only one
thermostat controlled the system. Do they make 2-stage compressors?


My understanding is that room outlets may have to be rebalanced between
heating and cooling, particularly 2 floor. Outlets could be closed in
rooms that are not used, but freeze-up may be a problem.

I assume it's a matter of how many are closed. One or two bedrooms
and closets(!) shouldn't cause much of a problem.