Questions tagged [thermostat]

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

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2k views

“C” wire in wall! Where does it go in air handler/furnace?

Got a wifi thermostat. Behind the old thermostat was a blue "C" wire. The other side of the blue wire in the equipment room isn't plugged into anything. I need to get the 24v common hooked up to this ...
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1answer
1k views

How to add C wire to a very old 2-wire Lennox G16 Gas Furnace?

I recently bought a Sensi Thermostat with Wifi to replace my vintage one. I thought it would work with my 2-wire heat only system because it has batteries , but found out that using the Wifi feature ...
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2answers
3k views

Nest Thermostat Wiring for Baseboard Heaters

I'm using a Nest Thermostat to power baseboard heaters (240VAC). I have 4 wires that I have access to: 2 wires: Red/Black from a transformer which outputs 24VAC 2 wires: 24VAC from a thermostat ...
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1answer
347 views

Added a new 5th wire for my wi-fi thermostat, now where to connect it?

4 wires at thermostat: R G B W (red green blue white) 5 screws at furnace: G C W Y R Single-stage gas furnace with A/C unit The home's previous owners kind of did everything in a very make-shift way. ...
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2answers
129 views

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 ...
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1answer
154 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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1answer
948 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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2answers
2k 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
9k 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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2answers
7k 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
161 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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7k 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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1answer
50 views

Where does my C wire go in this splice connection?

I'm looking to install the Ecobee3 Lite thermostat. My current thermostat has a blue C wire running to it, so my understanding is the PEK doesn't help because that is used if you have no C wire. On ...
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2answers
68 views

No C terminal on furnace to connect a wifi thermostat

I have an new Emerson thermostat and would like to connect a c wire so it always has power. I have an extra wire that's not being used, but I don't have a C wire terminal on my furnace. I'm wondering ...
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2answers
111 views

Electric Baseboard Heater Thermostat Replacement

My house is mostly steam heat, but prior owners put on a small addition and also turned an upstairs closet into a bathroom. These new rooms have electric baseboard heat. Heaters work fine, but ...
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1answer
54 views

Upgrading from a two wire analog tstat to a Nest, need help

I am looking to upgrade from an old analog tstat to a Nest. My old stat had only two wires connected (R and W) but the wire bundle had three. So I tried connecting the green wire to C and then turned ...
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2answers
295 views

Nest E Thermostat Power

My thermostat is in the basement, connected to a Honeywell R845A to run a circulating pump for heat. I bought an Nest E for the main house and it works great. I want to replace the thermostat in the ...
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2answers
107 views

Upgrading baseboard thermostat -wiring help

Going from old analog thermostats to programmable digital. They're all 240v but appear to currently be wired as single pole and new stats are double. Photos attached of line in, and two out for load- ...
2
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1answer
7k views

Ecobee3 not turning on heat, but fan is on

I have an Ecobee3 that has been successfully working (both heat, fan, and AC) for the past 6 months. Recently I was trying to get my humidifier working so I was playing around with some wires, which ...
2
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1answer
2k views

Wiring Fresh Air Damper to New Ecobee Thermostat

Ok, here's the deal. I currently have a zoned system with a fresh air "ventilator" (actually just a fresh air damper) and I want to install an ecobee thermostat. The can either be 1 wire (requires ...
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1answer
877 views

Installation Ecobee3 Smart Thermostat Confusion

So Ecobee' website says my configuration is compatible but after looking at my wires (Im not an AC guy) I have lots of questions as the wiring doesnt just align perfectly. Im assuming because my unit ...
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1answer
2k views

Can I use a separate 24V transformer with an Ecobee 3 and an Aube relay?

I've purchased an Ecobee 3 Lite smart thermostat which requires 3.5 VA to operate but I'm using an Aube RC840T-240 electric heating relay with 24 V transformer which only provides 1.2 VA. Can I ...
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3answers
5k views

thermostat causing heating element to click on and off repeatedly

I have an electric heater central air/heat system with a standard thermostat. I have replaced the thermostat with no change (that was some time ago), so I believe it's not the thermostat causing the ...
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2answers
6k views

Need help wiring a new double pole line voltage thermostat

[ Just bought my first home and this is my first time posting, so please forgive me if my terminology is incorrect. I currently have bedrooms upstairs each with 1 baseboard heater and thermostat for ...
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2answers
2k views

Can I install two thermostats on one furnace/act unit? I will be using one in living room, the other in a hallway

The reason is that there is a gas fireplace(stove) in the living room that has the pilot on all year. Currently the thermostat is in the hall keeping the back of the house cool. The heat from the ...
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1answer
13k views

How do I turn off the power to my thermostat?

I'd like to replace my thermostat with a new one. My current thermostat is one that doesn't have a C-wire and is powered by batteries. Now, my question is... is there a switch for the power that I ...
2
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1answer
385 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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2answers
60k 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
605 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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2answers
2k 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
27k 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
26k 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
190 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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1answer
850 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
5k 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
2k 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 popped....
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1answer
33 views

Furnace blower comes on full time when the thermostat is set to Auto

I have a Maytag furnace and the blower motor comes on right away when the thermostat is placed in auto and stays on when reaching the temperature set point and the heat goes off. I have replaced the ...
2
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1answer
180 views

How should the thermostat wires be connected to my furnace?

I have an Amana AMV90704CXBB furnace, and regular programmable thermostat. I took the furnace apart because I have to wash the blower motor wheel. It was covered in construction dust. In order to ...
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2answers
10k views

Nest Thermostat - Not cooling

First warm weather using my nest thermostat and now trying to use the central air. However, only the fan turns on and it doesn't actually cool no matter how long I run it. (It worked perfectly in the ...
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2answers
4k views

Converting from a Trane XT500C AC Thermostat to Honeywell TB8220U1003 VisionPro 8000

All, I am trying to upgrade my Thermostat and am very confused how to connect the wires correctly (Florida house built 1991, AC and heat strips, no furnace): As is, Trane XT500 Blue to B Red to R ...
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1answer
4k views

Heater will not shut off when it reaches desired temperature

I am just noticing this running the heat. If I set the thermostat to 70 it will run and run and the temperature reads 70 but the unit does not shut off. If I turn it up to 72 and then when it reaches ...
2
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1answer
203 views

Where to connect c wire

I’m installing a new WiFi thermostat that needs the c wire. I ended up running new thermostat wires that contained the common wire but now I’m stuck on where to connect it to the furnace. Can ...
2
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1answer
3k views

Where to connect c wire in furnace

I have 5 wires running to the thermostat from the furnace. The blue wire is not connected on either side. I'd like to connect it as my c wire for a smart thermostat. On the furnace I see W R Y G and ...
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2answers
92 views

Forgot to unplug fridge while replacing thermostat, smelled electrical burning

I went to replace the fridge thermostat today. I unscrewed the housing found the cables popped out the metal thermostat from the plastic casing. I should have stopped to unplug the fridge here since ...
2
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1answer
166 views

How should I hook up my WiFi thermostat given my current wiring situation?

I've upgraded a few thermostats before, and they have been quite straightforward; i.e. take pictures and connect the wires as the the original. However, this is my first attempt at a "smart" WiFi-...
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1answer
28 views

Will the Honeywell wifi thermostat work

Can I get the thermostat with this configuration?
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2answers
2k views

Trying to set my thermostat to use FAN only for cooling

I have a Bryant 60k BTU gas furnace(about 6 years old) and no AC. I can manually turn on just the FAN or leave it on AUTO for heating. I have the RITETEMP 6025 thermostat. At the moment I am cooling ...
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1answer
677 views

Can't get 3rd Gen Nest to power fan on Trane XR95 furnace

I have a Trane XR95 furnace and I replaced my original Honeywell Pro 4000 thermostat with a 3rd gen. Nest. I noticed, however, after installing the Nest that I can't get the fan to run on its own ...
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2answers
1k views

Help wiring a Nest thermostat in an unusual situation

The attached picture shows my current wiring. Notice there are two thermostats. The top one (Carrier, with four conductors) controls hot air heating. The bottom one (with two conductors, old mercurty ...
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1answer
86 views

I'm not sure what kind of thermostat I can use — two wires, red/beige? and a millivolt thermostat

I've been wanting to upgrade my thermostat to a smart one -- I only have an in-floor furnace, so the utility isn't super necessary, but I'd like to have a smart thermostat anyway (so I can turn my ...