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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2answers
1k views

Any suggestions for incorrectly-wired thermostat?

I foolishly got myself into this mess. Any suggestions? 1923 house with original steam heat (gas). The addition (~1998), has hot water (baseboards). I tried to replace the addition's thermostat, and ...
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4k views

HVAC wiring for wifi thermostat installation (Ecobee) gas furnace + AC

I'm trying to determine whether I can install a wifi thermostat (Ecobee or possibly Nest) with my existing gas furnace (dual stage) and electric air conditioner, ideally using existing wiring but able ...
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1answer
119 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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6answers
17k 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
4k 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
1k views

How to Wire 3 baseboard Heaters with 2 Thermostats

I have one 20 amp double pole circuit that I am planning to run 3 baseboard heaters on with 2 line voltage thermostats. I have already made sure the watt consumption for the 3 heaters will not exceed ...
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3answers
2k views

Circuit to make Nest thermostat think there are separate heating and cooling systems

I have a Nest thermostat that I am trying to wire in a simple but unique configuration. My apartment uses fan coil units for heating and cooling. The building changes over from hot to cold water for ...
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1answer
157 views

VT1001 talking thermostat has started saying “two sixty four”

I have a energy star rated VT1001 talking thermostat installed sometime in the early to mid 2000s. This morning it began to periodicall speak the words “two sixty four” (264). I cannot find anything ...
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829 views

Question on Honeywell Thermostat

Have an older round Honeywell Stat with 5 wires, G,Y,W,R, RH. I have hot water heat (no fan) and a Central AC with air handler. New stat has terminals for G,Y,W,R,RC. Question is does the RH from ...
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3answers
89 views

Use 110 thermostat for 220?

I wish to change my greenhouse fan from a 110 unit to 220. I have the fan. The price was right. It was free. The 220 is available. Is there a way to use the 110v thermostat to power a switch (or ...
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1answer
1k 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
736 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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1answer
3k 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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238 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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1answer
35 views

Install a Wi Fi thermostat

Trying to install a WiFi thermostat. I have the unused blue wire which I believe is the common wire. It is unused both and the furnace level as well as on my current thermostat. However there is ...
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1answer
42 views

Aquatherm - thermostat is dead. What to check?

(Thermostat: White-Rodgers 1F80-51 Heating Unit is aquatherm, XUAQ22-2, this is a heat exchanger hanging off a hot water heater, and giving us forced air heat for a 500 sqft space. Unit and ...
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4answers
221 views

Connect two thermostats in parallel

I saw a thread about connecting two thermostats in parallel. I could not add comment to that thread , so I put question here again. My tenants always shut off thermostat or reduce temp when they are ...
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1answer
39 views

C-Wire identification

I am interested in replacing an older thermostat with a modern networked 'smart' thermostat \ humidity monitor. That being said, does the photographed thermostat have a C-wire? The thermostat ...
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1answer
159 views

My AC and Heat systems are separate, Can I wire one or both fan(only) controls to my thermostat?

My house used to have just Forced Air heat, but a year and a half ago, I had central air installed. When it was installed I had questions about the wiring they weren't addressed to my satisfaction. ...
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2answers
97 views

Need to identify a common wire on my old HVAC

For Nest Thermostat 3, I am trying to identify a common wire on my old HVAC. The diagram can be found on the link below:
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2answers
62 views

Gas Furnace only, is Y wire needed?

I have force air (propane furnace). I would like to upgrade to a new "smart" thermostat, but they didn't run a C (common) wire which is required for most of these units to run properly. I do however,...
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1answer
906 views

Wiring a new thermostat without a C wire, extra wires from furnace

I have checked other posts regarding this and don't see a solution yet. I have purchased a new thermostat that requires a c wire. My old thermostat's c wire didn't work so I went ahead and added a ...
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2answers
1k views

Thermostat set at 65 - Furnace went to 90 - possible causes?

Oil furnace. Honeywell programmable thermostat (not WiFi-battery operated). Heat set as always at 65 degrees F with auto fan. No changes to settings whatsoever. Had been working fine all winter. ...
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1answer
31 views

Can a Thermostat Common Wire (C-Wire) Be Added to a DNV40NB Heater?

During recent renovations, we had to move our existing thermostat. Instead of replacing it with the same dumb 2-wire knob (white/red), I'd like to get a smart thermostat like the ecobee3. All of these ...
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1answer
2k views

Thermostat won't always start heater on its own

I have a gas furnace that seems to work fine; it keeps the house warm when things are running as expected. Sometimes, however, we'll notice the house is getting cold. The temperature on the ...
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1answer
363 views

Removing a room stat from central heating (in order to fit Hive)

I'm about to fit a Hive wireless thermostat to my central heating system and have a couple of questions. I need to disconnect the existing room stat - a Horstmann Centaurstat 7 - as this will be ...
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1answer
1k views

Honeywell thermostat oozing yellow and programing not working

I installed a Honeywell thermostat last year for our boiler and it worked perfectly. This year we were having issues with it not following the program schedule. The thermostat should be sleeping and ...
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2answers
2k views

Installing double-pole line-voltage thermostat

I'm trying to replace a mechanical double pole thermostat with a programmable electronic one. Existing setup: The old thermostat model is 859M and it's wiring is pictured below. There's 2 pairs of ...
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1answer
2k views

Locating HVAC Breaker To Replace Thermostat

I'm looking to install a smart thermostat in a single family home built in 1997 (southern California). My issue is that I cant seem to locate the breaker for the HVAC equipment. I was only able to ...
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2answers
486 views

Max Current Supplied by Thermostat Wire

So I want to run a Raspberry Pi 3 off of thermostat wire. My question is, will the thermostat wire supply enough current for the raspberry pi (2.5 amps)?
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3answers
7k views

Do thermostats coordinate with each other in a multi-zone system?

Say I set my thermostat to 72 F. (Yes, I'm in the crazy U.S. and use their strange measurement system). I am under the impression that an HVAC system will wait for the temperature to be off by a ...
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1answer
688 views

Smart thermostat for single-zone HVAC

I bought my first home (townhouse) I want to install a smart thermostat I have only one HVAC and the thermostat is located in the main floor. I have noticed that upstairs is hotter than the main ...
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745 views

Whats more efficient for AC and Blower Fan, lower temperature/fan auto or higher temperature fan on?

This summer i want to be more efficient and save money on my AC usage because I can remember last year it was an disaster. For example, on a typical 100 degree day, the highest the temperature would ...
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1answer
461 views

Install Common Wire (unable to find terminal or 24 VAC)

I bought a Nest 3rd Generation Thermostat. Live in a 2 family home, where my floor/basement has the boiler room/furnace. I have a Laars Mini Therm Furnace Model JVT. There's a thermostat upstairs as ...
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2answers
450 views

Can I put the unused blue wire in the C port, while still having the existing wire there?

I am installing a Honeywell Wi-Fi thermostat. I do not have a C wire, but there is an unused blue wire in the thermostat wiring, and also in the furnace wiring. The videos I've watched say that I ...
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1answer
1k views

Install New Lyric T5 on second AC, first one went great, this ones confusing, help!

Ive got 2 thermostats hooked up to 2 heat pump style AC units at my house. Over the weekend I impressed myself and installed a Lyric thermostat to replace a broken thermostat (on the inside of my ...
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4answers
300 views

Why does my house feel toasty when it's very cold outside, but cold when it's only a little chilly out?

My house has gas-powered hot-water radiators for heat. Ever since we moved in, I've noticed that if the temperature is just a bit chilly outside (40°F to 50°F), the house feels very cold and everyone ...
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3answers
15k views

Figure out if I have gas or electric heating

I have a year 2000 house in Bay Area California. The Honeywell RTH2520 thermostat that came with the house doesn't work anymore because the metal things on the side of the AA batteries became aqua ...
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1answer
345 views

How to reduce temperature difference between the second floor and basement?

I have one thermostat on the second floor and while it is achievable to get a desired temperature on the second floor, the basement is always cold.
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2answers
6k views

Can I run my furnace in fan-only mode without a G wire?

The house I bought has a programmable Honeywell furnace. It only has a 2 wires connected to it - a black wire and a white wire. The heating system is working fine, except that when the heater is not ...
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1answer
65 views

How can I add “smart” functionality to an old thermostat?

I recently moved to an apartment, and my roommate and I were talking about how much better it would be if we had a smart thermostat. We're going to ask the landlord about an upgrade, but I thought I ...
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2answers
92 views

Is it safe to replace the thermostat when furnace is shut off?

I need to replace the thermostat in my basement. It is an old style round shape Honeywell mechanical non-programmable thermostat. The gas furnace is turned off (The switch is at OFF now). Is it ...
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1answer
600 views

wiring two thermostats in parallel [duplicate]

I wqant to add a wifi thermostat to a millivolt system. I would like to keep the current thermostat in case of power lost so that it would kick in at a minimum temp say 45 degrees. How do you wire a ...
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1answer
1k views

Outside A/C Unit Keeps Running 30+ Minutes After Inside Unit Stops

I installed a new programmable thermostat back in December and it has been wonderful. It replaced a (probably) 50+ year old dial thermostat. To my question - now that it is really hot outside (85+ ...
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1answer
2k views

New thermostat for electric radiant ceiling heat

I live in the Pacific NW where radiant ceiling heat is common in older homes. I a have home built in 1969 and want to upgrade the thermostat to something newer that we can program and save money. This ...
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1answer
149 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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12k 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
118 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
401 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
438 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 ...