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

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Cost of adjusting the thermostat

Is it more cost effective to (1) play with the thermostat by lowering it at times that you're not home or needing the heat and raising it back later or (2) leaving the temperature on a set amount and ...
2
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2answers
17k views

Why is my A/C unit running when the heater runs?

So it finally got cold here in AZ. We switched our thermostat from A/C to Heat. Now for some reason when the electric heater runs, the A/C condenser unit outside kicks on too. This is our first winter ...
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1answer
38 views

0v at DC thermostat terminal in furnace

I have an old (mid 80s) Rheem gas furnace I hope will last me through at least one more California winter. It's been known to go down into the upper fifties, so it has its work cut out for it. In any ...
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2answers
4k views

Can you terminate more than one common on the furnace C terminal?

TL;DR: Can you terminate more than one common on the furnace C terminal? Background: I've linked a diagram of how my non-programmable thermostat is currently hooked up. I want to replace it with a ...
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1answer
151 views

When I set the thermostat to X degrees, is that the temperature at which air is pushed out through the vents?

My hunch is that most ac units aren't that sophisticated, and they just pump air that is "cold enough" or "hot enough" and pump it until temperature rises to the specified value. Is that right?
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1answer
281 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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1answer
402 views

How do I determine/control which heat source is used (heat pump, oil)

I have a heat pump and an oil furnace for backup. How does the HVAC system know when to use the heat pump and when to use the oil furnace? Specifics: I have a Honeywell TH8320U1008 thermostat ...
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1answer
333 views

Is it a problem that I have two of each color wires on my Honeywell thermostat?

I am thinking about upgrading my Honeywell thermostat. Every thing I have seen describes / shows a single wire for each color. My current thermostat has two wires connected to each terminal (two green ...
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2answers
530 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 ...
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1answer
9k views

How do I properly install a replacement thermostat in my refrigerator?

My fridge stopped cooling - compressor was always off - so I tested if the thermostat could be the culprit by bypassing it - bang, compressor powered on. So I bought a new thermostat. It is not ...
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2answers
3k views

What could be damaged if I shorted the R wire to the C wire at my thermostat?

OK... so in trying to install a thermostat (and testing to see if the old thermostat was bad) I inadvertently jumped the R and C... (I actually jumped the R and G terminals but the G terminal was ...
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1answer
182 views

Is there a way to make a thermostat based heating system more accurate through either adding probes or hacking?

In my Brooklyn apartment, heated via steam radiator, my thermostat is in the unheated hallway between all the rooms. The temperature it reads is often different, than both the rooms with heaters and ...
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3answers
15k 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. ...
2
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1answer
611 views

Will I see any performance gains if I reconfigure my thermostat to control the second stage of my 2 stage furnace?

Our furnace is a two stage one that was installed last year (a Bryant 80t). When it was installed, it was installed with a thermostat for a one stage furnace. This appears to be because this model ...
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2answers
4k views

How can I tell what kind of heating system I have?

Seems like a simple question, but I've had a very hard time finding a definitive answer to this. I went to the hardware store to buy a replacement for a faulty thermostat and when I arrived and ...
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1answer
1k views

What is causing the high limit switch to pop on my electric water heater?

The high limit switch has popped twice on my electric water heater, both times at night. I reset the switch and the water heats and it's ok throughout the day. Wake up in the morning and it's ...
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2answers
1k views

How can I wire my WIFI thermostat to control my millivolt fireplace?

I have a gas fireplace that has an millivolt on/off switch on my wall (and a remote that includes flame on/off, a countdown timer and a thermostatic flame control). I want to be able to program ...
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1answer
179 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
470 views

How do I connect a C wire to an Utica PEG112CDE steam boiler?

I want to upgrade my old mercury thermostat that I currently have to a newer programmable thermostat. This little DIY project is for my first late 1920's home that I recently purchased. I currently ...
2
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1answer
367 views

Can I insulate between a brick chimney and drywall?

Can I insulate the space between a brick chimney and the drywall inside my home? I am getting heat transfer from the brick to the drywall in the summer from the sun heating the brick. My thermostat ...
2
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1answer
2k views

Is it possible to control the speed of the fan on my central A/C unit?

I have one of those medium sized AC-units (don't know the model name at the moment) and a very basic Honeywell thermostat that the installers put in when the house was built. However, there doesn't ...
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1answer
271 views

HVAC electric thermostat panel “goes dead” and then live again all the time

I have this digital thermostat controlling my heater (gas). When I turn it on to lets say 66 deg, and the house is at 60, the HVAC will start working of course. Problem: After few minutes, the ...
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1answer
44 views

Can't get fan working on thermostat

I recently purchased a new thermostat. My old thermostat worked for heat (no AC either) but the fan wouldn't go on when I turned to "On" (in hopes to move some cool air from the basement up during the ...
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1answer
305 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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0answers
60 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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490 views

Are w1 and w2 both energized during a second stage heat call from the thermostat?

Short version: does two-stage thermostat always close W1 circuit when it closes W2 circuit, or they might be closed independently? Long version: I have two-stage furnace, currently connected to older ...
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1answer
5k views

How can I add a “C” common wire to this system? [duplicate]

I would like to add a "C" / Common wire hookup to my hvac system and get a fancy new thermostat. I've read Options for adding "C" wire to thermostat and still have some questions. First of ...
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3answers
2k views

Is there a filter-reminder thermostat that uses run-time instead of total time?

My HVAC filter is in my crawlspace and is a hassle to change. I don't want to change it more than needed. "Change it every month" is bogus advice because in some months (like May) we don't have to run ...
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3answers
391 views

At what temperature does a WiFi thermostat stop sending a signal to the router?

I recently purchased and installed a Honeywell WP6500 WiFi thermostat and thanks to Stack Exchange, got it up and running. I have a house in New Hampshire, which I use occasionally during the winter. ...
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3answers
722 views

A/c makes the lights turn on and off! No Joke!

The lights on the first floor, upstairs bathroom and upstairs Laundry room won't work. The breakers did NOT pop The air conditioning was running this morning but is not working now. When the ...
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5answers
2k views

Can I provide a secondary power source for my thermostat?

The thermostat at my home is set up with only the 24 power and return through the relay. I would like to add a 'smart' thermostat, however the line is fairly well buried in the wall/basement ceiling ...
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4answers
11k views

Is it alright that I did not turn off the power while installing my thermostat?

I just installed the Nest thermostat, I forgot to turn the breaker off everything seems to be working fine. Is it safe to assume it is ok?
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5answers
13k views

How do I control a heat lamp with a thermostat?

My girlfriend is crazy about making bread. However, as the temperature is often very cold around here, I would like to make her a box in which the temperature can be controlled. I have purchased a ...
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2answers
72 views

Electric baseboard wiring

I have a 240v 1500w 6.5a electric baseboard heater with a wall mounted thermostat. What I found out is that the the thermostat and all the outlets in the room are on the same 20a breaker with this ...
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2answers
911 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 ...
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2answers
2k views

Honeywell T6360 wiring - follow installation wiring guide positions or numbers?

The following picture shows a Honeywell T6360 Room Thermostat wiring connections. You will note they are numbered in the order 2 3 4 1 5 6. The Installation Instructions that accompany this unit, ...
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2answers
3k views

What could cause a clicking sound in an underfloor heating controller?

I have a underfloor heating system installed in my apartment. Each room has a Uponor T-37 thermostat, hooked up to C-35 controller. The system is about four years old and recently I have noticed a ...
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4answers
1k views

Is there a special low temperature thermostat?

I have a gas ceiling mounted furnace for my garage. I want to set my garage at 35-40° F (1-4° C). Is there a special thermostat to control furnace at that low temp? (I've seen one works as low as ...
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1answer
16 views

12 gauge on 30 amp circuit - after thermostat

I have 2 2500 watt baseboard heaters that I'm planning on running off of a 30a 240v breaker. My question is, because the thermostat is close to the panel, can I run the 10/2 JUST to the thermostat, ...
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2answers
5k views

How should I install a thermostat for a baseboard heater?

How would I go about installing a thermostat for my bedroom's baseboard heater? I've seen lots of articles on how to replace an old thermostat but I'm installing a thermostat for the first time here. ...
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3answers
3k views

Should I replace my mercury switch thermostat?

We have an old mercury switch thermostat in our house, You know the type, gold ring, very common. We are in new England on a gas/steam system. There is no central AC. We have been told by more than ...
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2answers
1k views

Switching from multiple thermostats to a single one

I have a heating system that has a separate "smart" heater in each room, each controlled with a separate thermostat (a simple one, like Honeywell T410A1013). What I would like to do is to convert to a ...
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1answer
156 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
253 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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3answers
2k 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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2answers
18k views

Controlling separate heat and AC devices from a single thermostat

I have hydronic radiator heat powered by a gas furnace situated in one mechanical room of my house and a currently being installed central AC whose air handler is situated in another mechanical room ...
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2answers
2k views

How far apart is it okay to set thermostat during night and day

This isn't home improvement, per se, so please feel free to let me know if there is a better forum for this. I have been told by two people, one of whom is a boiler repair technician, that it's not a ...
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2answers
221 views

Can anyone identify this heating timer?

So, It's getting quite cold now and my central heating is just going on and off randomly. There is what seems to be an unbranded heating timer below the combi-boiler (Baxi). However I have no idea how ...
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2answers
3k views

How do I disable a thermostat to prevent it from turning on the AC?

I need to disable my thermostat from turning on the AC. Yes, covertly. I think one of my housemates is missing his native Antarctica. So, the thermostat still must be active & setable, but I want ...
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2answers
221 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 ...