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26 votes

Doorbell transformer is this it?

As indicated by Ecnerwal the picture you show is an old style telephone line hookup. When you go looking around for your doorbell transformer it may look like one of these: Mounted on cover of an ...
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  • 61.7k
18 votes

Doorbell transformer is this it?

Nope. That's a phone line terminal block. Old school. May have rudimentary surge supression built in. The heavy black wire is drop cable (from the pole to your house) It's not your doorbell ...
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  • 137k
6 votes

Why do I have to tell my Nest thermostat to either cool or heat my house?

You don't. There is a feature called Heat*Cool: https://nest.com/support/article/What-is-Heat-Cool-mode
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  • 263
5 votes

Nest thermostat heating way beyond set temperature

Did you put fresh batteries in the Nest? No. Because the Nest doesn't take batteries :) So that raises a question. How does Nest power itself? It has a lithium battery (like a phone) but that has to ...
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4 votes
Accepted

Improve HVAC in single upstairs room with vaulted ceiling

I would adjust the dampers so the ones in the smaller rooms are not fully open this will put more flow to the larger room. Things to think about that can reduce flow to a room is the bottom of the ...
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  • 98.4k
4 votes

Can I use this unused blue wire as my C wire for my new Nest thermostat?

Yes. What's happening there is that R and C are coming from a 24-volt transformer. (you can think of C as "common" in electronics or "chassis" in car wiring, if you want.) R is 24 ...
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3 votes
Accepted

Old house--no neutral wire for Nest Protect?

Which Nest Protect should I get? Just check the smoke alarm you have now. If it connects to [line voltage] wires, you’ll want Nest Protect (Wired 120V). If it doesn’t, you should get Nest Protect (...
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  • 12.8k
3 votes
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Nest Thermostat Wiring for Baseboard Heaters

Since you have a R841C (with an integral transformer) You have your terminals on the relay confused. Connect RH to the HOT terminal from the relay and W1 to to the NEUTRAL terminal from the relay. C ...
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3 votes

How to add C-wire from Laars mini-term

With only two wires between the thermostat and the boiler, you're not going to be able to power the thermostat, and call for heat. You'll need at least three wires for that. The C terminal on the ...
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  • 128k
3 votes
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Nest thermostat E74 error - no power to Rh Wire

Bit of Nest history Nest often has a sub base issue. Usually the issue is contained to the cooling side. Rh is power input for the heating side. So that wouldn't be my first guess. Test Remove Rh ...
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  • 6,106
3 votes
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Would it be dangerous to tap an existing flame sensor circuit to create a common connection for my thermostat?

Yes, it would be dangerous. The power supply embedded inside your Honeywell controller is not designed or documented to provide power to arbitrary external devices, and the exposed terminals are meant ...
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  • 18k
3 votes
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How do I replace my old Honeywell thermostat with a Nest?

I have never done this before but with my life knowledge I'm assuming the following: The colors of the cables follow a standard for which signal they carry. The torn diagram just shows what color ...
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3 votes
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Installing Nest Smoke Alarm against capped wires

You can't use those wires. They're likely left over from a 12V DC alarm system. The Nest smoke detectors require 120V AC which those wires are not capable of supplying. You'll need to figure out a ...
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  • 3,488
3 votes

Can I use this unused blue wire as my C wire for my new Nest thermostat?

Connect the blue wire to C Simply connect the blue wire to the C terminal at the furnace end, in addition to the wire which is already there (which goes off to your air conditioner's outdoor unit/...
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2 votes
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HVAC wiring for wifi thermostat installation (Ecobee) gas furnace + AC

I ended up finding the problem - the black (Rc) and red (R) wires going to my thermostat were joined together in a junction box between the furnace and the thermostat (why I don't know). I've now ...
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  • 131
2 votes
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Is it possible to wire an electric radiant floor as a heat pump in my Nest thermostat?

Just remembered that I never circled back here. I was able to get this behavior by wiring the floor as "Stage 1" heating and the main furnace as "Stage 2". To do this, the white wire from the floor ...
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  • 131
2 votes
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Why won't my Central Heating Boiler turn off with Nest thermostat installed?

I fixed it myself. In the manual (page 18) there is the following image. As shown on the photo in the question: From left to right: The red "bridge cable" is meant to close the circuit in order for ...
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  • 171
2 votes

Smart thermostat for single-zone HVAC

Zone system A true zone system allows different areas of the house to be isolated, by closing off certain areas using dampers, or just having completely isolated air handlers. This allows fairly ...
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  • 28.3k
2 votes

Electricity tripping off after installing Nest

The guidance we are/have been providing in the comments. The direct answer, is that you have a current carrying wire directly tied the return. (E.g., Neutral & Live In wired together). While this ...
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  • 1,976
2 votes

Electricity tripping off after installing Nest

The object in the photos is a 230V "immersion-heater timer". Most traditional UK heating systems have a "programmer" instead but I guess you could have an installation that just uses the timer. I'm ...
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2 votes
Accepted

Where is "C" wire on Honeywell 8043F1036

According to the wiring diagram I found, typical wiring is as follows. 1 END SWITCH (To circulator or another valve) 2 END SWITCH (To circulator or another valve) 3 TH/TR (Thermostat and Transformer) ...
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  • 128k
2 votes

Do I have one or two 24V transformers in HVAC control circuit

If you have forced air A/C and radiant heat, you almost certainly have two separate transformers. So you'll have to use a thermostat that can work with separate transformers. If the thermostat you ...
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  • 128k
2 votes
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Gen 3 Nest not charging suddenly

Nest customer service is probably your best bet, but I'm going to give you a guess. In a two wire install the Nest charges itself when the boiler is off, using the difference in voltage between the ...
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  • 1,247
2 votes
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Is it normal for my boiler transformer to show intermittent drops in voltage?

The voltage drop I saw was due to the triggering of the low water cut off system. When the LWCO kicked on it dropped power to the thermostat. Thank you for the tip @ThreePhaseEel ! Gotta get some of ...
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  • 121
2 votes

Nest E Thermostat Power

The Honeywell device does not provide a C wire out. There is fairly open access to it; perhaps you can pull a rabbit out of a hat. Otherwise add a second transformer (2 wires from this new ...
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2 votes

Nest, Blue Wire, W1 and W2

The wire currently hooked to Y and C will be going off to your air conditioner condenser unit. Y is cooling. C is common, and yes, you can connect another wire to that terminal. You appear to have a ...
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  • 28.3k
2 votes

Does the Nest thermostat automatically change modes?

In my experience with the Gen 2 it will not. That would be a bit heavy-handed and folks would not be happy to have their AC compressor come on with the winter cover still in place, for example. It ...
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