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

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19 views

Where is my Common Wire? [duplicate]

I purchased a wifi thermostat and cannot located the common wire. My unit is old and is a Coleman 70 with no terminals inside labeling the wires. As you can see in the second image, there is a ...
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1answer
19 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
80 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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0answers
19 views

How to Change Chinese HVAC Thermostat

I am looking to put Nest thermostats in the house, I have now found out my entire house (one in each room, 6 of them) has been wired with HVAC Chinese U12A UNIVERSAL A/C CONTROL SYSTEM urrgh – they ...
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1answer
33 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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40 views

Why would my AC turn on and off randomly?

My AC unit turns on and off randomly regardless of whether the thermostat is set on or off. I've even tried removing the batteries. Does anyone know why this might happen?
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1answer
19 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
67 views

How do I wire this 240v fan motor and thermostat

I'm trying to wire a two stage exhaust fan for my greenhouse. The motor comes set up for 240v wiring and is to be controlled by a thermostat. I undertsand how to get the 240v from the panel, but can't ...
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1answer
47 views

What could cause my boiler to provide hot water, but not heating?

My boiler kicks in when the thermostat asks it to, but when my room thermostat asks the boiler to fire up, nothing happens. My room thermostat clicks on, and lights up so I think it can tell the ...
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1answer
172 views

Trying to figure out 'C' wire

I'm looking to upgrade my programmable thermostat to a wifi thermostat. I purchased a basic Honeywell wifi thermostat but upon installation could not find a 'C' wire. I started to investigate more ...
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1answer
136 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
63 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
96 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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18 views

Why does my gas furnace run once then wont come back on until reset when temps are below 30 outside?

THE PROBLEM: My gas furnace will run one cycle and then not come back on until the switch is reset. Once the switch is reset it will kick on immediately run once and again I will have to reset before ...
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1answer
213 views

Adding a C/Common wire to HVAC system

So I'm looking for some help in identifying where I can attach a C/Common Wire to my HVAC system, but unfortunately my system doesn't have a control board that I can easily attach a powerkit to. For ...
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1answer
77 views

Wiring new 'c' wire to heat pump system. Do I need to connect at both air handler and condenser?

I am planning on installing a new WIFI thermostat (Honeywell RTH6580WF). I have a heat pump system (outdoor condenser unit and air handler in attic). Old thermostat did not have a 'c' wire, but it ...
2
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1answer
48 views

Is there any liquid to stop leakage inside pipe or fitting

i want to ask i have doubt there is a leakage in UPVC pipes or fittings but i am not able to find out this leakage is there any liquid to stop the leakage ( like i just put some kind of liquid inside ...
2
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1answer
136 views

Is it possible to add a “C” wire to my electric heater?

I bought a Wifi Thermostat but my old thermostat did not have a Common Wire. I can't use any of the swapping the G for the C solutions because I have an electric heater. I was told by Honeywell that I ...
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21 views

How to replace a line voltage thermostat with a low voltage one? [duplicate]

I have one of those round mechanical knob thermostats (line voltage). I would like to replace it with a wireless thermostat which is controllable from an Android phone. It seems those thermostats are ...
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1answer
47 views

What should I do with an unused C wire when installing a thermostat?

Replacing a Carrier programmable with a Honeywell RTH6350D1000. Carrier had blue/gray wire in the C connector. Honeywell does not have a C connector. In install book "Advanced" wiring it says to ...
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1answer
61 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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28 views

Replaced Thermostat, Furnace worked for 1 cycle now blows cold

Hello I just replaced my old White-Rodgers thermostat because it just wasn't working consistently (sometimes it would turn on the furnace, but mostly it wouldn't). I swapped it with a White-Rodgers ...
3
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1answer
69 views

Is it OK to leave the thermostat unwired?

So I went to replace the batteries in my thermostat and when I pulled it off I noticed a black wire was unplugged. I'm not sure if it's suppose to be like that or if I accidentally pulled the black ...
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22 views

Why would one of the zones of my Slant Fin gas fired hot water baseboard heating system not be heating?

Thus far I have: replaced with new batteries. turned down temp and switched the breakers turned heat back up, no response Can a pilot be out for one zone? The other two are warm and cozy. Did ...
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1answer
83 views

Do I need a 24V or 120-240V thermostat?

My Honeywell thermostat just broke. I want to get a new one and install it myself but I don't know whether to get a 24V model or a 120-240v model. There is no indication of this on the one I have. How ...
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140 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
44 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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2answers
117 views

Which furnace thermostats support variable swing/deadband?

My home furnace is currently controlled by a programmable Honeywell thermostat, but it regularly thrashes the furnace by turning the furnace on for just ten or twenty seconds. It seems that the ...
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18 views

How do I wire a Honeywell ultrastat TB7220U for second stage cooling?

Has anyone wired this commercial thermostat in before? Honeywell TB7220U ultrastat I had needed to know about the 2nd stage cool wiring set up -y2? And changing the wiring correctly for install ...
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1answer
68 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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229 views

How can I tell if C wire is active and connected to Thermostats?

We are trying to install a smart thermostat (Ecobee 3) so we are in need of a C wire from our boiler. We see a green wire in the wall, but it's not connected to our thermostat currently since it ...
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16 views

Can I use the following parts to create a remote duct temperature sensor for my thermostat?

Parts: DS18B20 Temperature Sensor (PDF) or TMP36 Temperature Sensor (PDF) Cat5 cable Would those parts make a viable replacement for a remote duct sensor replacing a Venstar Remote Duct Digital ...
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36 views

Can you hardwire a residential through wall A/C to a 3H/2C thermostat?

I have a boiler with radiant baseboard throughout my home with four zones of heating and two through wall air conditioners and Aprilaire 350 Humidifier. I am upgrading my thermostats to the Honeywell ...
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2answers
86 views

Is there any risk of running both the fan and furnace at the same time?

I am attempting to build my own thermostat using an arduino and a few relays and have been trying to map the appropriate wires so I don't damage my furnace/AC unit. This is a picture of my ...
2
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1answer
81 views

Why won't my thermostat control the HVAC anymore after trying to switch thermostats?

I bought a new Nest thermostat which is supposed to be compatible but needs a professional installation (advice that should have been heeded by non-professional electrician me). This is to replace an ...
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19 views

What type of control systems are available for a home with multiple HVAC systems?

Our new (used) home has two HVAC systems, one for upstairs and one for down. There is a thermostat in the dining room, which is directly affected by sun. And one in our bedroom, that clicks all ...
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1answer
376 views

How to add “C” wire using a/c fan wire?

Honeywell has a video that shows how to use the fan wire ("G") of the cooling system as the "C" wire for the thermostat. It is in the video - "Honeywell DIY wifi...substitute g-wire for c-wire" on ...
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30 views

Why are certain radiators hot during the night when the thermostat is very low?

We have a gas central heating system and we have set the thermostat to come on at different temperatures during the day. Generally between 7.00 and 22.00 it is set between 19 to 22 centigrade. From ...
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1answer
57 views

Possible to check NEST system compatibility by looking at current thermostat model?

I'd like to replace my Honeywell CT87A thermostat with a Nest thermostat. I see that Nest has a page to check system compatibility. Is it possible to identify if my system is compatible without taking ...
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193 views

Can I use the T terminal in my furnace as the C for a Wifi Thermostat?

I've read many posts on this, and believe I know what to do, but want to make sure. My furnace (a Lennox G14 Series) does not have a C terminal which needs to be connected to the C terminal in my new ...
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2answers
155 views

Can a wifi thermostat to control milivolt operated fireplace?

Have a propane gas fireplace, controlled by a hand held remote control thermostat. Wish to install a wall mounted wifi controlled thermostat, heat only. Seems that all available thermostats operate ...
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1answer
25 views

Wall mounted dial thermostat

I recently bought a wall thermostat I broke the plastic front on the box to remove The thermostat as I tried to pull it out of the box the dial came off in my hand and I do not know where it ...
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36 views

Thermostat needs to be set very high to work

Our home thermostat is behaving strangely. Let say it shows that the current room temperature is 60F. If we set it to 63F it will start the Fan (ventilation) but will not actually start the heating so ...
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1answer
63 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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14 views

Zones and setback thermostats

I've got a two-floor house, forced-hot-water and traditional radiators, with a thermostat and zone for each floor. I'm working from home at the moment, so the ground floor is set up to be "office ...
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2answers
135 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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327 views

Honeywell WiFi Smart Thermostat Wiring

The Honeywell WiFi Smart thermostat was operating fine when on AC until the heat went on this fall. Now, each time the fan goes on, the thermostat loses the connection, turns blank, then reboots ...
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1answer
512 views

Where do I connect the C wire in my furnace?

I am upgrading my thermostat to a Nest, and would like to add a common wire. My current furnace controller doesn't have a C terminal, but the current thermostat wire has 2 unused wires (black and ...
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1answer
361 views

My attic unit already has a wire connected to C, can I still connect a wifi thermostat? [duplicate]

I have an extra wire I can use for the C wire on both ends but in my attic the main unit has a wire already attached to the C spot and going away from the unit to something else. Can I attach two ...
0
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1answer
479 views

Where to add C wire on this air handler?

Thanks for helping me here. I am adding a new wifi thermostat to my system but need to add a C wire directly to the air handler (system is a First Co air handler with hot water boiler for heat and ...