Replace old Bard t-stat with new programable

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  #1  
Old 07-20-12, 12:42 PM
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Replace old Bard t-stat with new programable

http://sphotos-a.xx.fbcdn.net/hphoto...97892538_n.jpgI have an old Bard thermostat that I would like to replace with a digital one. I need to know which one will work with the wiring currently in place. The current wiring is as follows:
R
W2
B
W3
L
G
Y
E
X

Here is what I believe is the Bard model number: Q672L1185 8049
It is a heat pump and has emergency heat and cool selections
I tried to upload a picture of old t-stat, but having issues

Thanks for any and all help/suggestions!

Rebecca

I want to purchase a programmable thermostat, but I am having problems trying to do the wiring. This is a nine wire and I can not find a new thermostat that has the w2 and w3 wires....HELP PLEASE
 

Last edited by stickshift; 07-20-12 at 03:02 PM.
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Old 07-20-12, 02:22 PM
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You have what looks like single stage cool, 2 stage heat. I believe L and X will be unused on the new t stat and i believe w3 is a 3rd stage heating option that gives you heat pump and electric strips at the same time. So you need either a 1 cool, 2 heat or a 2 cool 3 heat thermostat.
 
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Old 07-20-12, 02:55 PM
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The terminal designations are on page 9 of: http://customer.honeywell.com/techli...0s/60-2485.pdf (i can post more info if needed)

The backup heat staging is controlled by the t-stat, meaning that a retail heatpump stat won't do the job. (they lack the W3 terminal)

You'll have to purchase one from a hvac supplier with the right terminals.

...it should be labelled at 4 heat/2 cool. (a 3 heat stat won't work, since the first two stages are compressor stages, the last one is aux heat on those models)
 
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Old 07-20-12, 03:09 PM
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electric strips at the same time.
Having W2 on at the same time as Y and G turns on 1/2-2/3rd of the heat strips at the same time as the heatpump.

W2 + W3 + Y + G energized allows the heatpump and elements (both stages) to run at the same time

E energized by itself disables the heatpump and turns on the heat strips (not sure how they're staged). The emergency heat setting should only be used when the heatpump can no longer provide usable heat. (generally in very cold weather)
 
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Old 07-20-12, 03:49 PM
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So I guess buying one from Honeywell or another site is out of the question? I was hoping to save some money and install myself. Are there any online resources anyone can recommend? Like many other people these days, I have limited funds available for this sort of "upgrad"....
 
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Old 07-20-12, 06:05 PM
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You could try finding a pro grade honeywell or white rogers online.

This is the cheapest stat I found which supports 2 stages of aux heat: White-Rodgers 1F95-1291 Universal Programmable Thermostat - Four Stage Heat Two Stage Cool (Touchscreen with Humidification Control)
 
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Old 07-20-12, 06:49 PM
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I am going to try and buy that one. Hopefully the company will walk me thru the wiring part....Thanks for your help! When I get the new thermostat I will let you guys/gals how it works out!
 
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Old 07-20-12, 07:32 PM
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Might want to cross reference the existing stat model on the white rogers website. White-Rodgers Model Number Search Cross Reference

Edit: The white rogers stat doesn't seem to have an E terminal. Prior to purchasing it, I recommend checking to see what the purple wire is connected to at the air handler. It may be connected to a separate relay which brings on both stages of aux heat in emergency heat mode.

Edit: What kind of heatpump is it? (air source split system, ground source/water source, wall unit)

At the bottom of the white rogers manual, there's a homeowner help line number - good to have.
 
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Old 07-20-12, 07:50 PM
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Does the old one look like what's in the pdf: http://customer.honeywell.com/techli...0s/60-2485.pdf

Q672L is the subbase model; the actual model might be on the back of the stat.
 
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Old 07-21-12, 03:16 PM
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Here are pics of the existing thermostat. Thanks so much for your help....I won't be purchasing the t-stat for a couple of weeks...money....lack of
 
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Old 07-22-12, 02:25 PM
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That's a relabeled honeywell stat for sure.

There are only 2 mercury bulbs in the picture, so the stat is most likely two stage (no separate call for W3 or 3rd stage heat).

Chances are that the base was designed for several t-stat models and W3 terminal is inactive. (it's also possible that W2 and W3 get energized at the same time when there's a call for aux heat) The only way to tell is to open up the air handler and see what's connected on the other end.
 
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Old 07-22-12, 06:19 PM
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I am definitely not comfortable with opening up the air handler. Maybe I can get my brother to check it out for me. Muggle I appreciate so much your help! Also do you think I could try a 2h/1c t-stat and just tape off the w3? I just don't want to ruin anything with the unit.....
 
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Old 07-22-12, 07:44 PM
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With W3 taped off, the entire set of heat strips may not come on.

Generally, both aux heat terminals can be jumpered off at the air handler if a 2 heat/1 cool stat is used. Yours is wired as if the stat is 3-stage even though the stat appears to be 2 heat/1 cool - the installer may have screwed up.

You can probably get away with putting both wires (W2 and W3) on the aux heat/w terminal; however, wiring up a heatpump stat incorrectly can cause damage, so it's probably a good idea to get a tech to check it out.
 
 

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