Have O and B wires, but new thermostat... - http://www.hvacmechanic.com/ Forums
Original message
| mdupls
 |  "Have O and B wires, but new thermostat..."
, posted Wed 5 Nov 15:48  
Hi. My current system has the following 8 wires: B,0,L,X,W2,R,Y,G. I purchased a new Honeywell thermostat (RTH7600D1014 - touch screen model) which only has 1 O/B connector. I followed the instructions in the installation manual and connected the B wire to C, O wire to O/B, X wire to E, W2 wire to AUX. The rest of the wires i connected to the respected connectors. When I turn on the system, it only cools the house and the heat does not come on despite turning up the temperature. Honeywell says this has to do with the fact that my system has a seperate O and B wire. Is there any way to work around this? Or to modify my existing system to work with the thermostat?
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Replies:
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| mdupls
| "Re(1):Have O and B wires, but new thermostat." , posted Wed 5 Nov 21:41
Okay, I've found out that the common wire is actually X. This leaves an O and a B wire and only an 1 O/B terminal on the thermostat...
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| | mdupls
| "Re(2):Have O and B wires, but new thermostat." , posted Wed 5 Nov 20:18
Yes Function 170 was set to 7, and 190 was set to 0. My old thermostat is Coleman 3AAT83D13C1. The subbase (I think this is the furnace in the basement) is a Chromalox HAF-324D. There's also an add on heat pump system from Coleman 3024A7473 which is connected to the side of the furnace (I think this is the air handler panel you're talking about). I can't tell you if B is connected to common at the moment. I don't have a multimeter with me at the moment. How do I know if B is common just by looking in the air handler panel?
Thank you for your help!
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| | Houston204
| "Re(3):Have O and B wires, but new thermostat." , posted Wed 5 Nov 23:35
Couldn't find anything on that 3AAT83D13C1 stat. Any other numbers on it? A subbase is the bottom half of a 2 piece thermostat.
Your Chromalox HAF-324D furnace is electric heat and possibly 15 to 20 years old.
I could only get a French web page for 3024A7473 that may not have translated correctly.
"Description: coleman conditionning and heating system, a system of heat pumps Addition - 3024A7473 - electronic filters, a hot water tank burner included 40 gallons "
Common is almost alway labeled C at the furnace.
Just write down the field connection terminals used and the color of the wires connected to each.
I agree about that chart. I checked with my local Coleman dealer and their heat pumps use O not B. (Though your added controls seem to require both)
If we do require both the O and B terminals there is a way to make that stat work with the addition of a SPDT or DPDT 24vac relay.
"Tip of the Day" Remember to remove power first.
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| | mdupls
| "Re(3):Have O and B wires, but new thermostat." , posted Wed 5 Nov 20:23
I've also noticed that in the heat pump cross reference chart you attached, Coleman does not have an O terminal. My system does have an O terminal but it's a Coleman.
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| | Houston204
| "Re(4):Have O and B wires, but new thermostat." , posted Wed 5 Nov 23:43
I agree. (Refresh)
"Tip of the Day" Remember to remove power first.
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| | mdupls
| "Re(6):Have O and B wires, but new thermostat." , posted Thu 6 Nov 09:21
I've figured out that X is the common wire. I've taken a look at the white rodgers tstat you've mentioned. Is there any way of knowing that this thermostat will work for sure? It seems like the best bet as it has the correct terminals that my system needs.
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| | Houston204
| "Re(7):Have O and B wires, but new thermostat." , posted Thu 6 Nov 21:29
The 1F95 1271 would be a better choice for your application.
Hunter also has a stat that will support your system. This one is available at your local hardware store. I would only have a Honeywell, White Rodgers or Robertshaw stat on my house. (Unless I could afford an Infinity system)
It would feel dishonest not to at least inform you of this option.
"Tip of the Day" Remember to remove power first.
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| | mdupls
| "Re(8):Have O and B wires, but new thermostat." , posted Fri 7 Nov 10:38
I agree. I think I will go for a White Rodgers tstat. Would it matter if I was to purchase the 1F95-1277 or 1F95-1291 instead of the 1F95-1271?
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| | Houston204
| "Re(9):Have O and B wires, but new thermostat." , posted Fri 7 Nov 20:23:
http://www.white-rodgers.com/wrdhom/pdfs/instruction_sheets/0037-6914.pdf
The 1F95-1291 is the best choice but all 3 have your required terminals.
It is nice to see the humidity displayed with temperature.
"Tip of the Day" Remember to remove power first.
[this message was edited by Houston204 on Fri 7 Nov 20:29] |
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