Programmable thermostat wiring


Old 01-22-00, 07:41 PM
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I was replacing a standard mechanical thermostat in my house with a programmable electronic one, but there were more wires attached to the old t'stat than the new one accepts. Specifically, I have a B and an O wire that don't attach to the the standard R, G, W, Y terminals on the new t'stat. I tried just capping them off and installaing as if they weren't there, but the furnace wouldn't start after this.

I know the standard thinking is that B and O wires have something to do with a heat pump system, but I think my house just has a standard oil furnace and central air conditioning system in a two-zone configuration. Another source tells me that the B and O wires control the electric heating and cooling dampers, which makes more sense.

The t'stat is a cheapo Lux TX500, but even the more expensive ones I looked at didn't have B and O terminals.

Is this a common problem, and is there a way to wire this so that my system will work correctly?

Any help would be appreciated.

Old 01-27-00, 05:37 AM
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Based on what you discribed, my best guess is you have the wrong T-Stat for your heating system. Your new T-Stat is the standard one and the old one is special one designed for your type of system.

Take that 'old one' with you and go to your local heating and cooling agencies retail parts supply store to get the correct programable T-Stat for your system.

It may be helpful to the parts person if you also take some notes with the units brand name, model, serial number and BTU rating.

Good Luck,

TomBartco Enterprises.
Trade:Natural Gas Energy Consultant & Technician.
Appliance Service & Repairs Rep.
Vocations:Saw & Tool Sharpening. Small Engine Repairs.
Accurate Power Equipment Company.

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"Drive Safely. The Life You Save, May Be Your Own."


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