Need help in adding a second thermostat

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Old 09-19-08, 01:13 PM
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Need help in adding a second thermostat

I built our 3 level home about 4 years ago. It has 3 zone manual dampers (one zone for each level) on an American Standard 2 stage furnace. I have a Honeywell 7 day programmable 5 wire thermostat on the middle level of the house.

The only problem with this setup is in the summer we need to set the thermostat very low to allow the AC to kick on and cool the 3rd floor enough to keep us comfortable (all the bedromms are on the 3rd floor). I have the dampers adjusted to have most of the flow run to the 3rd level during the summer, but at night the middle level cools off faster than the 3rd level so the thermostat doesn't kick on unless I have it set really low.

I have a thermostat wire run from the furnace to the 3rd floor and I was thinking it would be more efficient to install another thermostat on the 3rd floor to solve my summer cooling problem. I probably would only need to use this second thermostat during the summer.

Can I hook this second thermostat up in parallel with the other thermostat at the furnace or will I need some kind of zone controller?

Thank you for the help!!
 
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Old 09-19-08, 02:48 PM
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Not knowing the size of your duct work for each zone, you may be able to change the manual dampers to a damper that is controled by a zone panel.

Can you take a photo of your damper set up, and if it turns out you have what I think, you may be best to upgrade yoru system to a zoned system.

Do you have any returns upstairs? (where)
 
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Old 09-19-08, 03:02 PM
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The HVAC contractor said I could upgrade to automatic at a later date if I wanted with my current setup but since the current setup works well except for this summer cooling problem upstairs I was thinking a second thermostat would solve the problem and not be nearly as costly as converting to an automatic dampened/zoned system.

I looked at the Honeywell EMM-3 a little today and I think this would work with two thermostats. So maybe I'll have to get something like that if it does not would work to just hook up the thermostats in parallel at the furnace.
 
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Old 09-19-08, 03:17 PM
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I don't think you can just hook 2 in parallel, might be wrong, but the couple I've seen like that had multi pole rotary switch (like an A-B video or printer switch) to completely switch control from one to the other. Maybe just turning one to off would work, I don't know. Seems like it could cause problems tho.
 
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Old 09-19-08, 06:25 PM
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Zoned System

Tnixa,
I presume you have one furnace & air conditoner. If so, you have my condolences but I'm afraid you've been sold a bill of goods. I have NEVER seen a zoned warm air/cooling system which worked right from a comfort stand point, let alone operating efficiently.
 
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Old 09-19-08, 08:52 PM
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Originally Posted by Grady View Post
Tnixa,
I presume you have one furnace & air conditoner. If so, you have my condolences but I'm afraid you've been sold a bill of goods. I have NEVER seen a zoned warm air/cooling system which worked right from a comfort stand point, let alone operating efficiently.
I agree! Two systems would be cheaper to run!
 
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Old 09-20-08, 07:06 AM
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Right, I just have one furnace and one AC with the furnace plenum separated into the 3 zones. Maybe I'll just bite the bullet and get the zone controller and change my manual setup into an automatic one. Sounds like a fun winter project
 
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Old 09-20-08, 07:14 AM
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Being that you have a two stage furnace, you want to be sure you get a two stage zone contro and thermostatl with a duct sensor to prevent over heated furnace.

Do you have returns upstairs?
 
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Old 09-20-08, 11:53 AM
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Yes, I have returns on all floors. I don't think I'm currently using a 2 stage thermostat. I leave the fan on all the time and then when a call for heat or AC comes the fan speeds up. I also have an electric heat coil with a controller in my plenum so I don't use the gas furnace very often (cheaper to run electric).
 
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