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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1answer
414 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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Why Does My Heil Furnace Start When It Should Be Off?

My Heil furnace starts with the thermostat set to off. I disconnected the thermostat wires at the thermostat and it still starts randomly. I disconnected the heating wire at the board and it still ...
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2answers
9k 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
152 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, ...
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151 views

C Wire in HVAC Unit

I am looking to install a new style thermostat in my apartment and it requires a C wire. I do have an extra wire run from my HVAC unit to where my thermostat is. But when tracing it back to my HVAC ...
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5answers
4k 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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1answer
74 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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1answer
1k views

Replacement thermostat wiring for new Honeywell Wifi model

I moved into a home recently and found the old thermostat temperature controls to be inaccurate at turning on and turning off A/C as set so I purchased a Honeywell RTH6580WF thermostat as a ...
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1answer
2k views

How to find the right thermostat for my gas fireplace?

I have a Superior SSDVR3530CNM gas fireplace, which I'm trying to find a proper thermostat for. The manual recommends this one: However, it doesn't seem like they are sold anymore. (Or I'm not ...
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1answer
74 views

Please help me! [closed]

When setting my programmable thermostat should the 'heat to' or the 'cool to' setting be higher? Please ask me if you need any more info to answer this question
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1answer
376 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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0answers
347 views

Installing new thermostat without a C wire. Can I use my heater/R wire instead? Random 13V as well

I'm installing a thermostat, but I don't appear to have a C wire. My old thermostat had R/RH,Y,G,and W. It's an AC system that was setup before I got here. The actual AC unit is a long way away and ...
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1answer
848 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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2answers
5k 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 ...
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2answers
905 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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1answer
17k views

Wireless Thermostat C-Wire Substitute

I've read How can I add a "C" wire to my thermostat? and checked out the Venstar Add-A-Wire Accessory. I've watched Honeywell's YouTube video on "DIY Wi-Fi Thermostat Substitute G-Wire for C-Wire," ...
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1answer
359 views

HVAC Fan Set to Continuous By Landlord- Please help me rewire

I live in an apartment in which the landlord has set the HVAC fan to be continuously blowing even with Auto Fan setting on. Fan will also blow when Thermostat is turned off. Please help me rewire ...
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2answers
94 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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0answers
53 views

Added load to thermostat circuit?

I have a couple Nest thermostats that I want to power when my boiler is powered off. My plan is to hook them up to a 24v transformer using the existing R/W wires (no C wire and I don't want to run ...
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2answers
2k views

Can the cooling wire (Y) be used to activate the furnace fan with a programmable thermostat?

Simple question I think, but you guys make the call. Can the cooling wire (Y) be used to activate the furnace fan? My neighbor has a Honeywell RTH7400 programmable thermostat used for natural gas ...
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2answers
104 views

C wire - Where does it go?

Got a wifi thermostat. Behind the old thermostat was a blue wire. The other side of the blue wire in the equipment isn't plugged into anything. I need to get the 24v common hooked up to this blue ...
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1answer
2k 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 ...
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2answers
620 views

My furnace has a vibration for about a second at the end of the heat cycle.

It runs fine for the approximately 15 minute heat cycle. It appears as though it happens as the thermostat is satisfied and the gas valve shuts off. The vibration is heard upstairs and throughout the ...
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2answers
478 views

Zoned thermostat in every bedroom

I am getting a new AC and coils new use old one died This is for second floor where we have 4 bedrooms Question Is it possible to have thermostat in every bedroom Is it allowed under code ? What ...
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1answer
2k views

Multiple C wires? [duplicate]

I recently received a wifi enabled thermostat which I thought I could install easily since I saw an unused wire (Blue) which I assumed would be the C wire behind the current thermostat. When I went ...
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0answers
2k views

Trane Weathertron Stat to Honeywell RTH2510

I have a Trane Weathertron thermostat thst I am replacing with a New Honeywell RTH2510. This is a heat pump with auxiliary electric heat. The wires on the Tran thermostat are. R, T, O, G, Y, B, X2 ...
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0answers
645 views

Adding a C wire

I know this question has been asked multiple times and I'm going to try some of the methods I have read in other threads but wanted to ask this question since I didn't see anyone else's wired the way ...
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9answers
299k 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 ...
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1answer
898 views

Can I easily add a thermostat to a whole-house fan?

Is there a straightforward way to add a thermostat to an existing (basic no-frills) whole-house fan? I'd like to be able to set it to shut off when the outside temp rises to a certain point--so that ...
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1answer
939 views

How to wire A/C Thermostat given different wiring conventions

I've just moved to a new apartment in which I'd like to replace the current central A/C thermostat with a new one with WIFI control. I hope it's possible! I have basic diy electric skills but no ...
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0answers
2k views

Is Nest 3rd Gen Thermostat compatible as a replacement for Honeywell TH3110D1008

I have an Ultra-Zone EWC-ST-2E controller unit for my gas AC unit at home (heating and cooling). It is set for two zones. Where the first zone has to be on (heating or cooling) in order to enable to ...
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1answer
455 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
431 views

Wire in parallel thermostat and timer to an air extractor [duplicate]

as the title: i have a room with with a heat generation that i need to keep under a certain temperature. Anyhow, i want to grant a minimum of air circulation even if the temperature is not reached (...
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1answer
142 views

HVAC thermostat current

What is the typical current (in mA) carried by the 24v thermostat HVAC wire bundle in a typical low voltage application? I'm using 18/7 wire.
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2answers
4k views

Upstairs bedrooms are too hot. Would like to put in another thermostat.

I've been searching for an answer to this question but have yet to find one that applies. I'm looking to put in a new thermostat on the 2nd floor where the bedrooms are that would take over in the ...
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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
1k views

Bypass Thermostat Heating UK

I have a Smart Thermostat installed called Tado, with a pretty standard UK heating and hot water set up. In my airing cupboard there was a timer that controlled when the hot water and heating was to ...
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1answer
150 views

Stove Temperature Control broken

I have a (Simpson Mercury) electric stove - and 2 of the 4 elements do not work properly. They heat up, but it is not possible to set the appropriate temperature for them - they are either on or off. ...
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2answers
4k views

Can I piggyback a thermostat with a C Wire hookup on a furnace?

I'm trying to install a new thermostat that needs a C wire hookup. There are currently 4 wires running from the thermostat to the furnace, none of them are a c wire. When I look at my furnace itself ...
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1answer
14k views

Central Air Unit not Sending Enough Power to Thermostat

Right now I don't have specifics on my central air unit (make, model, etc) but hopefully the info I provide will help. I have a Second Generation (and Third Generation) Nest Thermostat hooked up to ...
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2answers
13k views

thermostat batteries replaced, AC unit won't start

Came home from work to find no AC. I checked the thermostat and the display was blank. After replacing the batteries and resetting the program, my AC unit never started up. I checked: - The AC unit (...
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1answer
1k views

How to power Honeywell wifi thermostat with external transformer

I want to install A Honeywell RTH 6580 WF thermostat in my garage for heat only . My heater is a simple LP gas, hanging unit heater; heat only and my thermostat has two wires labeled W and R . I ...
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1answer
4k 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
140 views

One thermostat with a switch to control 2 heating systems

I have a natural gas boiler and a pellet stove. I have a Honeywell programmable thermostat (2 AAA Batteries) that I have used independently with both of these systems. Switching from one system to the ...
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1answer
157 views

What could be causing my Thermostat “R” wire to only be 8 VAC?

I am trying to install a Nest thermostat. It says Rh not powered. I checked with a meter and I get approx 8 VAC reading. What could be causing this? The furnace itself ain't pretty. Update:
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2answers
3k views

How do RH/RC/R and Y/W relate for HVAC?

I have the following notes for HVAC (that I've compiled from reading through here): Thermostat wiring: C low voltage power wire that brings power from heating/cooling equipment to thermostat ...
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1answer
1k 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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1answer
172 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
64 views

Why does my heating work poorly in moderately cold temperatures?

My house has a gas-fired boiler and hot-water radiators. I've noticed a strange problem since moving in a few months ago. If the weather is moderately cold (in the 30F - 40F range), my house feels ...
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1answer
1k views

Does thermostat need to be grounded?

If a thermostat is connected to an air handler, which is connected to the main panel and has a ground wire, should one of the thermostat wires be connected to the ground?

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