New answers tagged thermostat
1
The most common way that two thermostats work with one HVAC system is through the use of a zone controller like one of these. They can be installed near the air handler, but it could also be in a nearby closet so it can be monitored or adjusted without going in the attic.
The zone controller makes all the decisions about controlling dampers and calling for ...
0
I just installed a nest on an oldish furnace.
If you read the documentation from Nest its says "it draws power from the leads leading to the furnace by briefly turning the furnace ON and OFF faster than the furnace is capable of registering. .... In most cases.
However, in my case I had to run additional wires so I could hook it to a 24v transformer ...
5
This is probably a matter of not knowing where your service panels are. Plural!
Find the meter and follow
You need to "follow it from the meter" as it were. Find the meter; easy. Then you'll have one of three things:
Additional compartments in the meter cabinet that open up (do not break any seals).
Very obvious conduit to another equipment box ...
answered Jan 9 at 22:09
Harper - Reinstate Monica
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1
The transformer(s) that power hvac systems have a primary winding that is 120v in most U.S. cases (some are 240). These are controlled from the service panel or a sub panel. The secondary side of the transformer is normally 24vac I have seen 6v to 32v systems all considered low voltage on the secondary the transformer primary is powered in most systems If ...
14
There are two very different issues here:
Power to the Thermostat
I flipped off all the circuits in the fuse box, and the thermostat on the first floor powered off. However, the thermostat on the second floor still had power.
A thermostat is typically powered primarily by a transformer. However, many thermostats include battery backup. There are a ...
answered Jan 9 at 21:47
manassehkatz-Reinstate Monica
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6
Thermostats get power from a low-voltage transformer that is either inside your air handler or very close to it. That same transformer also powers the circuit boards and controls of the air handler. That transformer, along with every other electrical device in the house will be connected to a breaker.
If you turned off all the breakers and one thermostat ...
1
As I mentioned in the comments, I was able to get the correct wiring by referencing an identical heating set up.
It is:
Red = R/H, jumpered to R/C
Blue = G
Yellow = W/E
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You say, "the fan would come on with a manual switch". Do you mean the "fan" switch on the old thermostat? Or a line voltage switch elsewhere, like on the fan itself?
Normal T-stat wiring is 24v with one wire as the "hot", another as the common and the third as "switched", IE controlled by the t-stat set point, turning on or off the heating equipment. ...
3
With the limited info provided I will guess that it is a 240v heater as the other one was but this time they only used a single pole thermostat to control the power, it works the negative here is that there will always be a hot conductor in the baseboard unless the breaker is turned off, this used to be quite common, or was used with multiple heaters in 1 ...
2
My advice is to gently pull straight out. I did it but I was not sure due to the difficulty of the release. Secondly, I would not ever buy an AC system that would only work with a special Thermostat! A replacement for my Infinity by Carrier is $960.00 (not customer friendly). The only reason my Thermostat is a problem is that the AC button broke. Otherwise ...
4
Most HVAC systems connect the 24 Vac Common to Earth ground. You can try measuring the AC voltage with one lead of your AC voltmeter connected to the Earth terminal of the closest AC electrical outlet. Then touch the other lead of the voltmeter to each of the thermostat connections.
The is not guaranteed to work but it is a test that is simple to perform ...
0
This wiring could do with a bit of cleaning up
As you pointed out that Cable 3 (the rightmost cable in the photo) at the air handler goes nowhere, we can take it out of the circuit entirely by nutting the red wire from the air handler to the red wire from Cable 1 instead of the red wire from Cable 3. (This means that the blue wire from Cable 3 is no longer ...
1
Go for it
Any modern furnace will have enough capacity on the C wire to support a "smart" thermostat as well as powering the control board and the compressor contactor, so I would simply take the coiled-up blue wire ends at the splice, nut them together, install your new thermostat, and enjoy!
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