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
31 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 ...
0
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0answers
362 views

My furnace has a C - common wire but air conditioner uses it - how to hook up smart thermostat?

I bought an ecobee3 smart thermostat which requires the C wire. At my furnace there is no circuit board but there was a diagram and I was able to locate the C - common wire, but it seems to be used ...
0
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1answer
29 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, ...
1
vote
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 ...
0
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2answers
26 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 ...
3
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1answer
379 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 ...
0
votes
1answer
45 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 ...
0
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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
36 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 ...
3
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1answer
151 views

Why does my gas furnace run once then wont come back on until reset when temps are below 30 outside?

THE PROBLEM: My gas furnace will run one cycle and then not come back on until the switch is reset. Once the switch is reset it will kick on immediately run once and again I will have to reset before ...
1
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1answer
181 views

Wiring new 'c' wire to heat pump system. Do I need to connect at both air handler and condenser?

I am planning on installing a new WIFI thermostat (Honeywell RTH6580WF). I have a heat pump system (outdoor condenser unit and air handler in attic). Old thermostat did not have a 'c' wire, but it ...
2
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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 ...
1
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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 ...
1
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0answers
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 ...
0
votes
1answer
32 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 ...
0
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1answer
293 views

Can I shorten my in floor heating cable?

Just wiring up an in floor heating thermostat. I have two separate two wires going into my flooring as well as another coming from the panel. I am wondering about the two wires going down to the ...
1
vote
1answer
2k views

Where do I connect the C wire in my furnace?

I am upgrading my thermostat to a Nest, and would like to add a common wire. My current furnace controller doesn't have a C terminal, but the current thermostat wire has 2 unused wires (black and blue)...
0
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1answer
4k views

why does my heat pump wiring diagram show 7 wires going to the thermostat but the thermostat only says it needs 5?

Here is a link to the wiring diagram for my heat pump. The thermostat that I am planning on buying has the following terminals C, G, Y, O/B, RC, R, Aux, E, and L. The instructions say to jump the RC ...
0
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1answer
763 views

How can I add a C-wire to a Venstar T5800 thermostat?

I am trying to replace my existing thermostat. My old thermostat has: Rh, W (coming from the heating unit). Rc, Y, G (coming from the AC unit). On the Venstar T5800, I can map as follows: Rh+Rc -...
2
votes
9answers
97k 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 ...
0
votes
1answer
78 views

Wiring for New Thermostat

I just bought new programmable z-wave thermostats (Honeywell TH8320ZW). I thought I had the wired correctly, but I woke up to a pretty chilly house this morning. The fan is working, but it seems to ...
0
votes
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 ...
1
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1answer
571 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 ...
0
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1answer
773 views

Correct Wiring for Furnace Blower Motor

After getting my furnace blower motor replaced, it now runs only in the following scenarios: 1. Mode "Cool" Fan "Auto" 2. Mode "Cool" Fan "On" 3. Mode "Heat" Fan "On" In other words it will not run ...
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0answers
47 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 ...
0
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1answer
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 ...
0
votes
2answers
148 views

Diode in a link wire for Thermostat?

What I have is a back boiler that runs my central heating via a pump. The domestic hot water is gravity fed. At present I have to turn the domestic hot water on via a timer switch this then gives me ...
1
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1answer
110 views

New Thermostat installed but compressor comes on immediately

I have a new Insteon Thermostat that I'm using to replace my prior Honeywell t-stat. This is installed to a relatively new HVAC system (both AC and Heat) that DOES have a "c" wire. I've attached the ...
0
votes
1answer
40 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 ...
0
votes
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 ...
2
votes
1answer
61 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 ...
1
vote
1answer
107 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, ...
1
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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 ...
0
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2answers
59 views

Boiler heating extra zones

Background: This is a new house, with a boiler system I'm not familiar with. Instead of zone valves, each zone has its own pump (4 zones). There is a fifth pump on the other side of the boiler. Not ...
1
vote
1answer
1k 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 ...
0
votes
1answer
37 views

RUUD Furnace blowing air but not heat

I have a RUUD furnace that stopped blowing hot air last night. I was thinking that it was the high limit switch gone bad BUT the coil ignites and lights but then goes out again after a minute, so ...
1
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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 ...
1
vote
1answer
139 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 ...
0
votes
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 ...
0
votes
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 ...
0
votes
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 (...
0
votes
1answer
58 views

Why might a central heating programmer no longer override a room thermostat?

My central heating and hot water is governed by a Danfoss FP715 Si. Using this I can set the time each day when the central heating and the hot water come on and off. When the central heating is on it ...
0
votes
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 ...
0
votes
0answers
245 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 ...
0
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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.
0
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2answers
42 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 ...
0
votes
2answers
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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vote
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. ...
2
votes
0answers
2k views

Can I use the T terminal in my furnace as the C for a Wifi Thermostat?

I've read many posts on this, and believe I know what to do, but want to make sure. My furnace (a Lennox G14 Series) does not have a C terminal which needs to be connected to the C terminal in my new ...
0
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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 ...