Mechanical or electrical device used to control a heating, ventilation, and air conditioning (HVAC) system, or other temperature reliant system.

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228 views

Can I connect the R and C wires directly to the HVAC transformer?

I have a Rheem furnace and a Ecobee3 smart thermostat. I'm having a problem where the Ecobee3 randomly loses power and reboots. I've traced this back to the control board (IFC) inside the HVAC unit. I ...
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1answer
31 views

Can I add a slave to existing thermostat?

The bedrooms in my condominium looks something like this: A common HVAC unit provides heat and air conditioning between bedrooms, with the thermostat being in the Master BR. Problem: Bedroom 2 ...
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1answer
50 views

How to wire programmable thermostat that doesn't have an E termimal

I am trying to replace a manual with programmable thermostat that is missing emergency heat (E) terminal. There are bits and pieces of information I have gathered but am still not clear. Can I leave ...
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3answers
179 views

Thermostat is completely blank. How to troubleshoot

I have a thermostat that is completely blank (no display). I'd like to troubleshoot it myself even if I do ultimately hire a pro! We're in sunny southern california, so it's possible it's had no ...
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1answer
82 views

electrical range - oven temperature not set

I have a pretty old electrical range GeneralElectric RCBS536DN2WW. The problem is that I can't use the oven: whenever I set the temperature with a temperature knob, it raises up rapidly and everything ...
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1answer
78 views

When running AC, Heat turns on once thermostat reaches desired temperature

I just recently installed a new wifi thermostat for my system. I went from a Trane to a Honeywell. I followed the instructions and put the wires in the right terminals (i believe) Everything is ...
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1answer
85 views

switching out a heat/cool only thermostat to one with “auto” feature

I have a Honeywell deluxe programmable thermostat with a sub-base... Sub-base: 32207415-011/0008 Model: T8602D2000 The terminals that are used currently are: R W Y G (RC and O are not used) My ...
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1answer
288 views

How can I tell if I have a C wire?

Below is a photo of my current thermostat's wiring. I have a few questions: Why is the RC and RH are bridged with a black wire? I have an unused blue wire. Is there a way to find its function? Could ...
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1answer
1k views

what is this unused brown wire in my thermostat wiring?

I replaced an existing Honeywell programmable thermostat with a new Z-wave enabled CT101-L thermostat yesterday. All went well, and the C, W, Y, R and G wires found their proper target connectors. The ...
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1answer
280 views

How to troubleshoot heat that's always on?

My boiler (Weil Mclain CGA Gold ~2003 install) failed the other day. After some help from a plumber and reading the manual, I replaced a few parts (more below) to get it running again. Now one zone is ...
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1answer
118 views

Can I use Eneloop batteries in my thermostat?

I have this LuxPro thermostat http://www.luxproproducts.com/pdfs/spec_pdfs/PSD010Bc_NL_ENG_Manual.pdf There's a warning in the very first section that says to use only Duracell or Energizer Alkaline ...
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3answers
327 views

Is the Nest thermostat smart enough to turn itself on BEFORE you get home?

I'm wondering if in "Away" mode, is Nest smart enough to learn about when you come home, and kick on approximately 30-40 minutes BEFORE then? Or does it only kick on when it senses you've come home? ...
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1answer
185 views

Can I change my standard thermostat to a Wifi one?

I have a (quite standard) TR-010X T6360A thermostat that looks like this: And this is the wiring diagram: Can I install the Heatmiser PRT-TS WiFi Touchscreen Programmable Thermostat? This is the ...
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1answer
279 views

How to install thermostat with plug in heater?

My house has three electric wall heaters in different rooms used to augment the gas forced air that heats the whole house. These electric heaters are mounted on the wall, but plug into standard 120v ...
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3answers
168 views

can I install a new thermostat by just turning off the power instead of turining off the circuit breaker?

Can I install a new thermostat by just turning the power off at the servicemen's switch, instead of at the breaker?
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1answer
2k views

Why won't my shower fully heat up?

I have a thermostatic shower, but I can only get it to be luke warm. The aquastat is set at 60, boiler at 165. The tap water in wash hand basin beside shower is very warm. I have taken the cover off ...
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1answer
23 views

One thermostat with a switch to control 2 heating systems

I have a natural gas boiler and a pellet stove. I have a Honeywell programmable thermostat (2 AAA Batteries) that I have used independently with both of these systems. Switching from one system to the ...
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1answer
31 views

What could be causing my Thermostat “R” wire to only be 8 VAC?

I am trying to install a Nest thermostat. It says Rh not powered. I checked with a meter and I get approx 8 VAC reading. What could be causing this? The furnace itself ain't pretty. Update: ...
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1answer
202 views

Controlling 110v swamp cooler using Nest thermostat

I currently have an HVAC system that is connected to a Nest thermostat (2nd generation) and I'm planning to use the same Nest thermostat to control a 110 swamp cooler that is currently not connected. ...
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2answers
68 views

What's the name of this kind of valve?

I would like to install the smart radiator thermostat from my previous apartment: However, in the new apartment there are different kind of valves, with clamps, as seen here: Does anyone know ...
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1answer
34 views

Why would a 240v line voltage thermostat have a blank display?

In a bathroom I have a single 500w 240v electric baseboard heater, and AUBE/Honeywell TH305 digital line voltage single pole thermostat. I noticed yesterday, that the display had gone blank. A quick ...
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2answers
80 views

Connecting a light-switch to turn thermostat on/off? (re: basement heat)

Is it possible to connect a simple light-switch to a thermostat? I'd like to have a thermostat in my basement set to 72 degrees. However, I want it completely turned off most of the time. I was ...
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1answer
33 views

Water heater pilot not staying lit

A customers 70 gallon gas fueled Bradford White water heaters' pilot light goes out immediately after releasing the red pilot button when relighting it. I concluded (in order of most likely suspects) ...
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1answer
102 views

How to hook up C wire to Crown air handler

Sorry for the newbie question, but I would like to hook up a C wire so that I can get a Nest, Ecobee, etc. My current thermostat is just a regular battery operated Honeywell and looking at the ...
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1answer
38 views

Thermostat broken or central air system?

Thermostat works sometimes, other times I have to shake the switch to get the air conditioner working. Is this a problem with the thermostat or the central air system? Thermostat is about 15 years ...
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2answers
1k views

Can I use a WiFi thermostat without a C wire?

I have a very old Honeywell programmable thermostat. I am going to replace it with a White-Rodgers UP500W Emerson Sensi WiFi Thermostat. I just want to know if the WiFi unit will work without a C ...
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1answer
2k views

Can I connect two wires to a single screw terminal in my HVAC system?

I am installing a new honeywell WiFi thermostat but the old battery operated thermostat had batteries and no "C" wire. I look at both the thermostat and the air handler and found an extra un-used blue ...
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2answers
403 views

Smart Thermostat - No C-Wire - No Controller Board

This one seems to be a little different from previous questions on the subject. Here is the dilemma, I don't see a transformer. I have included a few pics. There are Three wire bundles. For ease ...
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1answer
48 views

How can I disable cooling with a White Rodgers thermostat?

1F56W-444 White Rodgers Thermostat I am fairly sure this is the thermostat that I have. How do I disconnect the cooler/air-conditioner as to avoid my penguin visiting relative waking me to 55°F ...
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1answer
5k views

Thermostat Where Do The Two Wires From Condenser Go?

First let me say that I'm a newbie and have zero electrical experience. I'm an IT Guy and thought "Hey, its electronic, so I can probably figure it out." WRONG I appreciate any feedback/suggestions ...
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1answer
475 views

Why does adding a C wire for a thermostat blow the fuse?

I am adding a WiFi thermostat. I have R,W,G,Y wires. Plus 2 extra coming from upstairs that go between humidifier and humidistat. So I ran an extra wire for the C wire. When I attach it to the C ...
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2answers
10k views

On a thermostat, are “R” and “Rh” terminals the same thing?

I have an older thermostat controlling an old ass Trane furnace with A/C. It has an "R" terminal and an "Rc" terminal (they are jumpered - see photo). I see references to an "Rh" terminal online. Are ...
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1answer
329 views

Can't find the circuit board of my HVAC system

I'm trying to install a wireless thermostat for my church building's HVAC system. Currently there is no C wire, so I tried to see where the circuit board was so I could install one. I couldn't find ...
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1answer
437 views

New Furnace won't turn on after trying to install thermostat

I had a furnace installed about a year ago in my basement. The installer left the wires sticking out of the wall for me to install a thermostat. He said if you want to turn the furnace on, just ...
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1answer
664 views

Why did I have to change the wiring to use a smart WiFi thermostat?

I just installed a Emerson Sensi wifi thermostat.It works, and I ran a separate C wire. I had a 24 volt 5 wire Robertshaw programable thermostat that ran my boiler, air handler and AC. It is all ...
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1answer
509 views

How can I replace an old dial thermostat on an oil furnace with Hydrostat 3250 Plus?

I recently bought a home with an oil fired Biasi furnace that has a Hydrostat 3250-Plus attached. It uses an old analog round dial thermostat, and I'd like to replace it with a new digital (wifi) ...
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2answers
2k views

thermostat batteries replaced, AC unit won't start

Came home from work to find no AC. I checked the thermostat and the display was blank. After replacing the batteries and resetting the program, my AC unit never started up. I checked: - The AC unit ...
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1answer
366 views

Replacement thermostat wiring

I have an American Standard heat pump AC. I'm replacing a White-Rodgers manual thermostat (where I move a switch from cold to heat) with a Honeywell RTH7600 (which will automatically switch from cold ...
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3answers
28k views

Adding a C wire to a new Honeywell WIfi Thermostat

I am trying to install a new Honeywell touchscreen WIFI thermostat and need to add a C wire to my terminal inside the furnace (using the help found at How can I add a "C" wire to my ...
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2answers
1k views

Wifi Thermostat wiring

Replacing 2 Hunter thermostats with a Honeywell RTH9580 Wifi. Neither unit has a C wire - I'm comfortable with the upstairs high efficiency unit, but the downstairs older unit has thrown me for a ...
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1answer
927 views

Need to add common “C” for thermostat; can anyone indicate where to connect it?

We just got a new WiFi capable thermostat that, unfortunately, seems to use a form of power stealing in order to charge itself. The problem here is that our house is actually quite well insulated; the ...
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2answers
730 views

Thermostat / Oil Furnace Question

I have an old oil furnace and I am looking for some clarification as to how it is supposed to work. It heats water filled radiators through out the house. Currently it is connected to a thermostat ...
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2answers
5k views

Which terminal should I connect it to for a “C” wire when none are labeled “C”? [duplicate]

I am looking to replace my old battery operated thermostat with a new wifi model. There is no "C" common wire connected to my old thermostat. There is a blue wire that is at the thermostat but cut ...
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1answer
1k views

How to wire a new Honeywell RTF6580WF thermostat to replace a Chronotherm IV?

I have an old Honeywell Chronotherm IV thermostat that I am trying to replace with a Honeywell RTF6580WF wifi thermostat. I have a gas furnace and an air conditioner. Wiring for Chronotherm IV ...
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1answer
1k views

How do I wire this thermostat?

Hello I have a Honeywell FocusPRO 5000 Non-Programmable 1 Heat/1 Cool Thermostat, Large Screen. The wires it needs are: Conventional Terminals: Rc 24VAC power from cooling transformer R ...
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1answer
516 views

thermostat c wire question [duplicate]

I am looking to install a new thermostat that will require a C wire. I have a single stage A/C unit and my current thermostat has Rc, G, and Y wires. There is also an unused blue wire which I traced ...
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1answer
1k views

Why isn't my thermostat clicking on/off automatically?

My thermostat is not clicking on/off automatically, I have called my landlord and they replaced a very old one with a brand new one and it is still not clicking on off automatically, but will ...
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1answer
992 views

Which wall should I install a replacement thermostat on?

I'm replacing an old thermostat that is behind a door to our dining room, that is usually kept open, hiding the thermostat. Given that the wires come from above and I have some flexibility as to ...
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1answer
939 views

How to balance thermostat settings between zones to maximize efficiency?

I recently purchased a house so this is my first winter in it. The house was built in 1939 so most of the house is on a single heating zone using hot water radiated heat. The radiators are cast iron ...
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2answers
2k views

How do I diagnose a thermostat and HVAC that intermittently doesn't respond?

My gas heater for the whole house does not follow the thermostat settings on some mornings. I have set it to 70 degrees at 6 am but now it is still 60 at 8 am. This happens weekly once or so and seems ...