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

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2answers
1k views

Why doesn't the “fan on” mode work after I installed a new thermostat?

We moved into a new house. I installed a new Hunter Thermostat. I have a furnace only and the old thermostat only had 3 wires connected. SO I connected those three wires (G, RH and W/B). The ...
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1answer
512 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 ...
0
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1answer
669 views

Where is my common wire on the unit?

I have 2 systems in my house, my heat is gas hot water radiator heating and A/C is a separate newer system. I'm trying to figure out if I can run a C wire off air handler from the A/C system to run ...
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1answer
503 views

Can I replace this Airwell thermostat?

I am in market to replace my simple A/C control unit with one that integrates with home my z-wave based home automation system. However, before I make the splash and buy a compatible thermostat, I ...
1
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1answer
27 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
75 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
20 views

Why “W” (heat contactor) and “E” Aux Heat connected in Thermostat

I'm trying to update my thermostat to one that has a scheduling feature. My plan is to just copy how it was hooked up in an old 129N Thermostat from Armstrong however, I can't figure out why the "W" ...
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1answer
327 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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0answers
18 views

Should I install a doorway fan or dehumidifier?

I have central air in a rancher (one floor), and the living room is on one end of the house. That room is on a slab, and has always been noticeably hotter in the summer and colder in the winter than ...
2
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1answer
119 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 ...
3
votes
1answer
111 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
77 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
64 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 ...
1
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1answer
85 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 ...
3
votes
1answer
77 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 ...
1
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1answer
124 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 ...
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1answer
660 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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2answers
563 views

No electricity going to thermostat

Our old thermostat is working but I want to change to a new one (nest thermostat). I have two exact HVAC unit at home. I change one it works but when I change the second one it doesn't work because ...
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1answer
33 views

Honeywell RTH7600 does not responsd

Just installed new Honeywell RTH7600. All wires are correct and the unit displays fine. The issue is that heater and AC do not turn on at all. I even put the fan to ON instead of AUTO and that does ...
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2answers
17k views

Why won't my heater turn off when it reaches my desired temperature?

My wife and I purchased our first home this past year and we did a bunch of repairs up-front via a rehab loan, and one of the things we replaced was a very old thermostat with a new digital one. I ...
0
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1answer
33 views

AC continues to run for several minutes after shutting off

When I turn off the AC it continues to blow cold air for several minutes. I realize this may be an energy savings feature, but I'd like to know if it is possible to disable it. In other words, what ...
8
votes
1answer
6k views

How do you trigger the HVAC with wiring only?

I have a HVAC that has the usually wiring C R G W Y Pinouts What wires do I need to connect to turn on Heating? What wires do I need to connect to turn on the A/C? Is there a risk of damaging any ...
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1answer
573 views

How can I add a C-wire to a Venstar T5800 thermostat?

I am trying to replace my existing thermostat. My old thermostat has: Rh, W (coming from the heating unit). Rc, Y, G (coming from the AC unit). On the Venstar T5800, I can map as follows: Rh+Rc ...
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1answer
1k views

why does my heat pump wiring diagram show 7 wires going to the thermostat but the thermostat only says it needs 5?

Here is a link to the wiring diagram for my heat pump. The thermostat that I am planning on buying has the following terminals C, G, Y, O/B, RC, R, Aux, E, and L. The instructions say to jump the RC ...
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1answer
242 views

Using a second thermostat to balance temperatures thru fan-only control

Like many others, temperatures between the two levels of my house are uneven. This is particularly noticeable as spring arrives and the upper floor (above ground) enjoys solar heating (so the heater ...
2
votes
3answers
10k views

Are there any ductless mini split systems that offer standard HVAC wiring controls?

Have been looking for in the US a ductless mini split heat pump system something like the Mitsubishi Electric Mr. Slim that uses a non proprietary wiring scheme for its wall mounted thermostats. ...
5
votes
3answers
22k views

Should I use 12/2 or 12/3 to wire a 220V electric baseboard heater and thermostat?

When I bought my baseboard heaters, thermostats and 220V breakers I was advised to get 12/3 wire. When I attempted to install the heaters I found that the thermostats, heaters, and even breakers have ...
0
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1answer
241 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) ...
0
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1answer
286 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 ...
1
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1answer
639 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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0answers
23 views

Residential HVAC: one main thermostat, what do the other thermostats in the rooms do?

Are the other thermostats only meant for non-force air heat only? Does it mean only one thermostat in the house needs to have both heating and cooling, and auto or fan-only switches? It sure make ...
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0answers
44 views

AC Compressor outside is not running with new thermostat

my old thermostat stopped working, so I purchased a new one to replace that. The old one was powered by two AA batteries. A green wire connected to G, a white wire connected to W, a blue wire ...
0
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1answer
26 views

Issue with Thermostat

I bought and installed a Trueway thermostat before 2 years. It was working well for the past years. But then a twist! the thermostat started to go nuts, the tempeature would race over 60 degree, even ...
1
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1answer
51 views

Updating thermostats to single system

I have a three floors in my house, each controlled by it's own thermostat (separate air handlers and mechanical valves on furnace). Baseboard heat. The three thermostats are controlled separately, ...
1
vote
1answer
33 views

How to override an attic thermostat with a wall switch?

I want to install a fan in my attic. I want the fan to be controlled by a thermostat in the attic, but I want the ability to bypass or override the fan from within my house. Ideally I would like to ...
1
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3answers
44k views

Why won't my A/C turn on after I replaced the thermostat batteries?

Our thermostat died yesterday, but after replacing the dead batteries with fresh batteries, and confirming the LCD screen was operable, our AC no longer turns on. I have attempted a factory reset on ...
0
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0answers
32 views

Changing Trane Baystat240a to another thermostat

I want to change my current thermostat to a programmable electric one (no batteries). Could someone verify if it does have a common wire and if all wiring could fit modern thermostats? Looking at the ...
3
votes
4answers
7k views

Why won't my AC system turn off after I flipped the breaker?

We've got a central cooling air conditioner that was installed in 1984 with a thermostat from that same year. We are replacing the thermostat with a new programmable one (which has a 100% ...
0
votes
1answer
529 views

Please help establishing a C wire for new tstat

I bought a new WiFi tstat as a replacement. The tstat controls my second floor hot water baseboard heat and my central air conditioning. I've located all the wires....the ones coming up from the ...
42
votes
4answers
192k views

How can I add a “C” wire to my thermostat?

So, the spiffy new wi-fi thermostats want power on the C wire from thermostat, but the old thermostat doesn't have a C wire at it. What's the easiest way to add the C wire/24 volt to the thermostat ...
0
votes
1answer
127 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 ...
1
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1answer
134 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 ...
0
votes
1answer
267 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 ...
0
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0answers
88 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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0answers
29 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 ...
0
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4answers
3k views

How can I modify a 4 wire thermostat to a new thermostat requiring c wire?

I attempted to replace my thermostat with a fancy new Trane z-wave enabled model. To my dismay my home was only wired with a 4 wire setup with no 5 hidden in the bundle. I followed Insx on the web ...
0
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1answer
1k views

Where to connect a c-wire on a furnace with existing two wire mercury thermostat

My existing thermostat is an old mercury two wire device, heat only. Looking to upgrade to a better model, but I need to run a c-wire. I don't know where to connect the wire at at the furnace, any ...
2
votes
2answers
273 views

Honeywell home ventilation system with no c wire for thermostat. How can I substitute the g for the c without blowing a fuse?

I'm hoping to get some help with my thermostat problem. We bought our home brand new and it came with a very basic thermostat (non programmable and runs on batteries). I want to upgrade it to a wifi ...
2
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0answers
20 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 ...
2
votes
1answer
56 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 ...