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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I installed a new thermostat "Chronotherm III" (the older

Customer Question

I installed a new thermostat "Chronotherm III" (the older model was also "Chronotherm III), but this one has no connection for a black wire, it is cooling OK in summer but is NOT HEATING at all. What is wrong?
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: All OK, I checked it.
JA: Do you plan on doing the work yourself?
Customer: Yes.
JA: Anything else we should know to help you best?
Customer: WHERE to connect the black wire?
Submitted: 7 months ago.
Category: HVAC
Expert:  airheatman replied 7 months ago.

What did black go to on old?

Customer: replied 7 months ago.
In the old thermostat "Black wire" was connected to "E".Old thermostat connections: "R" - red, "C" - blue "O" - orange, "B" - not connected,
"Y1 and W1" - bridge installed by factory, yellow, "E" - black, "W2" - white, "G" - green (total: 7 wires)NEW thermostat (the same model!): connections "O", "W", "G" "C" (no connection) , "R and Rc" - bridge installed by factory, "B", "Y" (6 wires to connect?)Question: how to connect those 7 wires to a newer thermostat? I already connected this way:"O" - orange, "W' white, "G" - green, "C" - no connection, "R and Rc" bridge by factory, red wire, "B" - blue,
"Y" - yellow, "black wire" - not connected and isolated.
In this configuration the heat pump was cooling in the summer but now there is NO HEAT.
Question: HOW to wire it with a new thermostat, so cooling and heating would work?Thank you,
Expert:  airheatman replied 7 months ago.

Sorry I got called away. If you connected blue to B you probably blew a fuse or transformer.Does anything work Now?

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