[original post is likely clipped to save bandwidth]
On Sun, 12 Sep 2004 13:12:45 -0400, TN wrote:



Edwin,
Can you explain the difference between two and three zone heat? Does
that mean a bigger furnace and an extra thermostat, or something more
costly and complex?
Thanks.

Not Edwin here

A zone is just a area of the house with independent controls (and
sometimes equipment) and can restrict supply of heating/cooling to that
area. An extreme case might be each room has its own zone, own thermostat,
own duct dampers if forced air or circulator/valves if hydronic heat. A
zone can even have a completely in dependant system.

Forced air systems are much more complex to zone than hydronic systems.
Hydronic furnaces tolerate variable loads very well, often even include
domestic hot water. This is because the furnace often has a thermostat to
control it's water temperature, zone controls merely turns on circulation.
Of course, this is a heat only setup/

Forced air systems have significant problems with heavy zoning. Both AC
units and forced air heat systems don't take kindly to variable loads
(different number of zones calling at a time) without more complex
variable output designs. Traditional forced air equipment just doesn't
handle variable air flow or loads well.

So zoning is just partitioning off areas with separate controls, maybe
separate equipment.

Back to heat pumps: Common air exchange heat pumps are a total disaster in
the northeast. Air exchange heat pumps don't work well (or at all) as one
nears freezing. The cheap way out (installation) is electric backup. $$$ I
know of some geothermal installations west of Albany NY, not clear if
their lifetime costs will prove effective.

gerry

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