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 01-24-00, 08:03 PM
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hi bscholz, i have moved your topic to heating and cooling as i dont have the answer to this and wount even gess at it, they shuld be abel to help u out on this as they r more famuler with this than i am.

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