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1

I've highlighted the C wire for you in the schematic. And in the actual wiring


2

The jumper is installed between Rh and Rc, because your setup does not use two transformers. Rh is powered from the heating system transformer, while Rc is powered from the cooling system transformer. However, it's common to only have a single transformer for both systems. In which case, the jumper between the terminals may be required. The only way to ...


0

The schematic image you've attached is difficult to see, so I can't say for sure. Based on the wiring, I would say that the B terminal would work as C. Since I'm not there and can't test things, I have to make some assumptions. Based on the wiring, it looks like the one cable goes to the thermostat and another goes to the outdoor air conditioning unit. ...


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Here is how a furnace controls it's 2 speeds high and low, high is for cooling and fan on. Low is for the heat mode. Note the fan relay has 1 normally open and 1 normally closed switch, the fan relay is controlled by the thermostats Green circuit shown on the thermostat diagram at the left side of the diagram. Cool mode and the fan on speed is high speed ...


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Jump red to green and see if the indoor blower runs, if so you have 24 volt power and the transformer and 3 amp fuse on your circuit board are fine,if not check the 3 amp automotive type fuse found on your circuit board. If you have no fuse the transfomer may be bad from touching red to Common a direct short which fries the transformer. Is there a diagnostic ...


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Nest states their thermostats do not require a Common 24 volt leg of control power to be provided to the Nest, However there are some situations where the Nest will not stay charged after a bit thus requiring a Common leg of the 24 volt power sent to it, they allege the Common leg back feeds to the thermostat by unused circuits and it does in many if not ...


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Your pictures have no 24 volt wires going to an AC unit, you show 4 wires at the stat and the 4 wires at the air handler with the G jumped to Y and the Green wires used for Common that looks ok, but nothing from the air handler to any AC unit outdoors as in Yellow and Common. You have a direct short in heat or cool modes yet for cool mode nothing is ...


1

TR is Common on your unit, Every 24 volt device will have a Common leg as well as the 24 volt hot leg, just as a car battery has pos and neg, common is akin to neg in this case. Common is called this cause every 24 volt circuit terminates upon Common to complete the circuit. The last pic shown is the "time on" "temperature off" fan delay, the 2 lighter ...


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n here]1 This is a Heat Pump wiring diagram, if you only have an AC unit then the AC unit outdoors will only require the Yellow and the Common wire as far as the 24 volt control circuits go. Common is the side of the 24 volt control circuit that every 24 volt circuit returns to, to complete the circuit, this is why it is called Common, cause every circuit ...


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this turned out to be a bad thermostat. The manufacturer sent me a new one and it works great with the C wire attached. One test they had me do was attach just the C and R wires. When I attached the old thermostat, the fuse blew.



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