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

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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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2answers
25 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
39 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
13 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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1answer
36 views

wiring two thermostats in parallel

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
29 views

Finding “C” wire on old heat pump HVAC unit

I am wanting to replace my old round mercury filled Honeywell thermostat with a new wifi smart Honeywell thermostat, the only problems is I don't have a "C" wire on my current thermostat and need help ...
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35 views

Installing c wire for Ecobee3 Thermostat in a 2 zone configuration

I have hydronic baseboard heating that uses an oil boiler by Weil McClain. It has two zones, one for the first floor and one for the second. I'm unfamiliar with A/C terminology, so I'll describe it ...
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1answer
26 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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15 views

How do I disable a main floor thermostat and add one in a basement suite?

We are thinking of renting out the main floor of our home but don't want the tenant to have control of the only thermostat. Perhaps we could disable the one on the Main floor and add one to the ...
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46 views

temperature on thermostat not going down with fan running

I just had a new ac unit installed but it does not blow cold air. the techs have checked it 5 + times and have said that all the numbers and stuff check out. so while i have it on auto fan cold, i ...
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1answer
39 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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108 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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0answers
41 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
36 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
25 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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89 views

How to move from RH/RC thermostat to C thermostat in AC only system?

I see this is a pretty common question, but the answer seems like it might be dependent on your thermostat and air handler, so I'm posting with my specific questions. I'm upgrading from a White ...
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2answers
41 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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0answers
10 views

C wire hook up when c wire is occupied on furnace only, what do I do? [duplicate]

Originally my old thermostat had red white green yellow and a spare blue the new thermo connected the same way but I added blue to the c terminal... On the furnace there are red white green yellow in ...
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51 views

Smart Thermostat C-Wire wrong voltage

I'm looking to upgrade the thermostats in my apartment to ones which I can control programmatically over WiFi. I opened up one of the old thermostats and discovered I have the classic "C-wire" ...
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27 views

Nest technical question

I am trying to connect a Nest to wirelessly control a heating system. I plugged a 110V-24V transformer to the C and Rh connectors, and a wire to W (still unconnected). Everything looks good, but I ...
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1answer
103 views

Less than 24 volts on the thermostat C wire

We have a brand new air handler at work, but the thermostat is mounted on a wall next to a server/computer room which is always warmer than the rest of the office. I want to install a thermostat that ...
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0answers
29 views

thermostat wiring: pick terminals that have wires connected

in case of my home ac thermostat, wires are directly connected to O, W, G, RH. There are jumper cables between RC and Rh, Y and W. I want to install the new thermostat. How should i select wires in ...
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46 views

2 Common wires to 1 Thermostat

I am consolidating 2 separate thermostats, one just for heat and one just for AC, into one to do double duty. If each has its own common wire, is it safe to hook both up to the same terminal on the ...
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1answer
30 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
181 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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2answers
237 views

My AC is set to 77F and the thermostat reaches that temperature but the AC keeps running. Why?

My AC is set to 77F and the thermostat reaches that temperature but the AC keeps running. What could be the causes for this? This is in connection with this post How long should it take to a 1.5 tons ...
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133 views

AC Unit does not receive 24 volts on outside unit

My outside unit does not turn on itself, but it does work. I just did a quick repair just thinking it was the capacitor and it was only 15 dollars for a new one so I changed that out and still had the ...
0
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1answer
28 views

HVAC compressor turns on when calling for fan only

I just moved into a new apartment with HVAC, and I'm looking to control the thermostat with a few Phidgets (I had already invested in that ecosystem, so I just needed a couple of relays). Anyway, ...
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243 views

How do I connect a honeywell wifi thermostat with no C wire at the furnace?

I purchased a Trane XV90 furnace in 2001 & I'm upgrading the thermostat to a Wi-Fi model. This thermostat needs a wire labeled C from the furnace & of the 4 wires coming from the furnace none ...
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1answer
143 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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1answer
26 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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66 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
36 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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13 views

AC electronic thermostat went black

I have a new (2013) Lennox AC unit. There is an electronic thermostat that just went black a few days ago. This has never happened before as, even when the AC is off for the winter, the thermostat ...
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1answer
18 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
47 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
43 views

Why might a thermostat refuse to switch from Heat mode to Cool mode?

I have this Honeywell RTHL2410C programmable thermostat and typical Florida electric AC system. Starting this Spring, it has started behaving strangely when switching from Heat to Cool mode. The ...
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1answer
45 views

Temperature of water in the shower fluctuates - will a cheap thermostatic tap help?

I recently moved to an apartment where temperature of water in the shower fluctuates and we called for a plumber. He either cleaned up or replaced one part (I think it was the mixer - nothing visually ...
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1answer
41 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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28 views

Thermostat replacement in a double wide

We have a new double wide and I want to replace the thermostat with a new programmable one. We took off the old one and it has 3 red wires, 2 yellow, 1 white and 1 green. I get the 2 red indicate a ...
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1answer
25 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 ...
0
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1answer
137 views

How can I connect a WIFI thermostat to a Honeywell R845A switching relay?

I'm trying to install a wifi thermostat and it won't power up. The old thermo was battery operated 2 wire but there were spare wires. At the R845A relay, red and white whites connect to terminals 5 ...
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48 views

Installing Honeywell wifi thermostat - weird wiring

I bought a Honeywell 7 day programmable wifi thermostat (non touch screen model). My old thermostat was wired as: Red - rh & rc Blue - b Green - g White - w I also have an unused blue wire (not ...
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1answer
183 views

How do I wire a thermostat with an external 24V transformer?

My current wiring has 5 wires, R, Rc, Y, G, and W wires. No C wire. I've added an external 24V transformer and connected one wire to the C connector but don't know what to do with the other. If I ...
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0answers
56 views

Nest thermostat - combi boiler and UFH set up question

We recently had some work done, a new open plan room, a new boiler and underfloor heating (UFH) put in. We had some confusion, a lot of which comes from not having a basic understanding of how the ...
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2answers
25 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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1answer
30 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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1answer
58 views

Vent now blows on thermostat

A long story how this got this way but there's a house with two furnaces and two thermostats. One of the furnaces feeds a long hallway with the return vent at one end and four feeder vents evenly ...
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2answers
1k views

Controlling 110v swamp cooler using Nest thermostat

I currently have an HVAC system that is connected to a Nest thermostat (2nd generation) and I'm planning to use the same Nest thermostat to control a 110 swamp cooler that is currently not connected. ...
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14 views

WiFi thermostat won't run. Not sure where to connect C wire [duplicate]

I just replaced a 2 wire thermostat with a wifi one that required a c wire. There was an unused blue wire which I attached to the C connector on the transformer at the furnace. At the thermostat, the ...