Skip to main content
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 ...
Michael Karas's user avatar
  • 65k
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 ...
Ecnerwal's user avatar
  • 218k
9 votes

Mechanical doorbells (connected to NEST doorbell) won't stop moving

That's how the Nest doorbell powers itself when you don't bring 3 wires to the doorbell location. It leaks small amounts of current through the chime. Nest thermostats do the same when you don't ...
Harper - Reinstate Monica's user avatar
7 votes

Heating and Cooling controlled via one thermostat

Rh and W1 to the red and white from the heat would be worth a shot. Not clear what the black wire is up to, (you could investigate with a voltmeter, or show how it's connected in the old thermostat) ...
Ecnerwal's user avatar
  • 218k
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
Stavr00's user avatar
  • 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 ...
Harper - Reinstate Monica's user avatar
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 ...
Ed Beal's user avatar
  • 103k
4 votes
Accepted

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 ...
gnicko's user avatar
  • 5,605
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 ...
Harper - Reinstate Monica's user avatar
4 votes
Accepted

Could my Nest thermostat be reducing my AC cooling?

With most standard residential HVAC, the fan speeds are set by connecting fan leads to terminals on the control board. You connect one lead from the fan to the COOL terminal (usually highest speed) ...
Chris O's user avatar
  • 6,795
3 votes
Accepted

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 ...
ThreePhaseEel's user avatar
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 ...
Tester101's user avatar
  • 132k
3 votes

Nest E thermostat on ancient 2-wire Bryant boiler system with 2 zonesq

I just realized I never followed up on this. I was chasing a red herring, as the Next E turned out to be defective, and wouldn't charge under any circumstances. Nest replaced it for me and the new one ...
Polly Cat's user avatar
3 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 ...
gregmac's user avatar
  • 29.1k
3 votes
Accepted

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 ...
Joe Fala's user avatar
  • 6,374
3 votes

Nest Protect Expiration Date

As you can see mine shows replace by April 2026 although I didn’t buy them until end of Aug 2018 and fitted them a couple of months later. I’d better start saving up for the next ones now! So i didn’...
Zip13's user avatar
  • 31
3 votes

One of two Nest Thermostats won't run Fan Only, fan runs with heat though

I have had the same problem for over a month. A/C and heat works fine but when I want to schedule for fan only then thermostat shows fan running but nothing happen. I googled the solutions and tried ...
Khalid's user avatar
  • 31
3 votes
Accepted

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 ...
jay613's user avatar
  • 39.3k
3 votes
Accepted

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 ...
heyitsmyusername's user avatar
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/...
ThreePhaseEel's user avatar
3 votes

Connecting “C” (common) wire for Nest thermostats

Your thermostat C terminal is right there in front of you, between G and the motor terminals Your zone board indeed provides C terminals on the zone terminal blocks. They're between the G terminal ...
ThreePhaseEel's user avatar
3 votes
Accepted

Google Nest Causes Furnace to Need Reset

The solution that seems to be working so far is adding a 1kOhm 5W resistor between W and T, that being the call for heat voltage. After contacting Johnson Controls, I was redirected to an engineer at ...
Correllion115's user avatar
3 votes

Heating and Cooling controlled via one thermostat

You can find the installation instructions here, along with what each terminal on the back of the thermostat is supposed to be connected to. https://nest.com/support/images/misc-nest-thermostat/nest-...
GrassMan's user avatar
2 votes
Accepted

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 ...
JJ.'s user avatar
  • 131
2 votes
Accepted

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 ...
Bob Ortiz's user avatar
  • 169
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 ...
gregmac's user avatar
  • 29.1k
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 ...
RedGrittyBrick's user avatar
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 ...
noybman's user avatar
  • 2,025

Only top scored, non community-wiki answers of a minimum length are eligible