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vairxpert
 
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Default Heat Functional, But Heating Zones Not?

On 18 Feb 2004 16:56:35 -0800, (Jim) wrote:

Well I foolishly tried posting this question at the obvious alt.hvac.
Now I'll try where REAL people try to give REAL answers.

I have a two-zone furnace. Zone 1 controls upstairs heat, zone 2
controls downstairs. However, while the upstairs maintains its heat,
and in some cases, even registers above temp setting (2-3 degrees F
greater on occasion), I never seem to see that zone calling for heat
(I'm watching damper control LED's in the basement to see which is
active. Green = active; red = inactive).


Hot air rises. The furnace is going to run a long time in order to
keep the basement heated. You're not going to stop all that hot air
from rising.
Cold air drops...what do you think is going to happen when summer
rolls around and your AC is on?

Both floors are set at same temp setting. I have observed that with
zone 2 calling (green LED at damper) and with heat flow through the
zone 2 ducts, I am sometimes also feeling heat flow through my zone 1
ducts at the same time, although the zone 1 dampers are still inactive
(red LED). The only time that I actually see zone 1 call, is if I set
the upstairs temp higher than the downstairs temp at which point zone
1 dampers then go active (green LED). Why does zone 1 never seem to
call on
its own, and while I recognize the air flow I feel at zone 1 while
zone 2 is active might be 'residual' flow from zone 2, how can the
upstairs temp be exceeding its set point?



The dampers are not sealing 100%, many are actually designed to allow
XX amount of CFM to pass through even when closed.
Common sense says to feel the air flow with the thermostat satisfied
and then crank up the thermostat so that it's calling and feel the air
flow again. Big difference? Then odds are the damper system is
working normally. With a whopping 2º overshoot (once in a while), I'd
say it's most likely working. If you set the basement stat to 70º and
the upstair was hitting 80º, then I'd say you have a damper failed
open.

You already mentioned that the upstairs is at or slightly above the
preset temp. so why do you expect to see Zone 1 calling for heat?

It sounds to me as if the system is keeping you comfortable and the
only problem is your obsession with the LEDS.

Now if a 2º overshoot upstairs is so critical to you, then rip out the
downstairs ceilings and insulate the hell out of the floor joist
areas.

If it's still bugging you, open the yellow pages and call out a tech.
Just be prepared to pay for his time even if he finds nothing wrong.


George