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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 ...


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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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Disconnect the wire connected to the Y terminal. This is the terminal that's energized when the thermostat calls for cool, so disconnecting the wire will prevent the thermostat from calling for cool.


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The room thermostat does not control the boiler directly. Instead, it controls a circulating pump that draws heat from the boiler and delivers it to the radiator(s) in the room. It is the removal of heat that subsequently causes the boiler to fire, when its thermostat indicates that its internal temperature has dropped because of the heat removal. It sounds ...


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Everything at the furnace looks good. There seems to be an extra cable at the thermostat, which might be an old abandoned two wire thermostat cable. You'll also notice the C wire just hanging out, which should be either used or capped off. besides that, everything looks good at the thermostat too. I'd investigate where that abandoned cable goes. ...


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I'm not sure exactly what's going on with the wiring, since in the one photo there's a giant ball of wires and cables, and in another there's extra wires hooked up. Here's what I see in the photos you've posted. In this photo, you'll notice the cable with a red and white wire. That cable should go between the furnace and the A/C unit. The white wire from ...



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