Thermostatic Controls - Chronotherm III: how it works?
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Frazzled
10-15-09, 10:23 AM
Old-style thermostats were basically switches of some sort, and you could get your furnace to come on by simply jumping two terminals.
However, the III apparently supplies 24 V power to the furnace controller, altho for cooling, there appears to be an external 24 V transformer.
But here's the kicker:
With the two wires (going to the furnace) disconnected from the III, and with a *separate* 24 V source connected to those wires, the furnace will not go on!
Why does the furnace go on with the III's 24 V power, but not with MY 24 V power?
However, the III apparently supplies 24 V power to the furnace controller, altho for cooling, there appears to be an external 24 V transformer.
But here's the kicker:
With the two wires (going to the furnace) disconnected from the III, and with a *separate* 24 V source connected to those wires, the furnace will not go on!
Why does the furnace go on with the III's 24 V power, but not with MY 24 V power?
Jay11J
10-15-09, 09:20 PM
However, the III apparently supplies 24 V power to the furnace controller, altho for cooling, there appears to be an external 24 V transformer.
Huh? What is the make and model of the furnace? All furnace/boilers has their own power...
What other wires are hoooked up on the current t-stat? Do you have A/C?
Huh? What is the make and model of the furnace? All furnace/boilers has their own power...
What other wires are hoooked up on the current t-stat? Do you have A/C?
Frazzled
10-16-09, 11:06 PM
"Huh?" indeed!
I eventually figured out my problem, and yeah, the stat does not provide the 24 V.
I can jump out the thermostat by jumping Rc and W1. There is A/C, but only 1 external 24 transformer.
The make of the furnace is a Bryant High efficiency "Plus 80" 2 speed gas furnace. I am in fact looking for the model/serial number, but don't have the original paperwork or manual, and don't know where to look on the furnace. I guess I could call the original installer, but it would be easier to just find a tag somewhere.
Any ideas?
Thanks.
I eventually figured out my problem, and yeah, the stat does not provide the 24 V.
I can jump out the thermostat by jumping Rc and W1. There is A/C, but only 1 external 24 transformer.
The make of the furnace is a Bryant High efficiency "Plus 80" 2 speed gas furnace. I am in fact looking for the model/serial number, but don't have the original paperwork or manual, and don't know where to look on the furnace. I guess I could call the original installer, but it would be easier to just find a tag somewhere.
Any ideas?
Thanks.
furd
10-17-09, 12:20 AM
Chronotherms often have an external 24 volt transformer to power the clock circuits in the unit. You may also have a separate 24 volt transformer for your cooling system but it is extremely rare to have an external 24 volt transformer on the heating circuit.
The heating circuit consists of Rh closing to W (or W1 in the case of a multi-stage heating system) on a drop in temperature from the set point when in heating mode. The Rc connection closes to Y (or Y1 in the case of a multi-stage cooling system) on a rise temperature from the set point when in cooling mode. Rh and Rc are jumpered together when the same 24 volt source is used for both heating and cooling.
If you have a separate 24 volt transformer for cooling then jumping Rc to W1 would NOT energize the heating system.
The heating circuit consists of Rh closing to W (or W1 in the case of a multi-stage heating system) on a drop in temperature from the set point when in heating mode. The Rc connection closes to Y (or Y1 in the case of a multi-stage cooling system) on a rise temperature from the set point when in cooling mode. Rh and Rc are jumpered together when the same 24 volt source is used for both heating and cooling.
If you have a separate 24 volt transformer for cooling then jumping Rc to W1 would NOT energize the heating system.