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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Installing a Honeywell HZ432 for four zone wireless heating

need help with wiring setup. Current setup Gas furnace (heating, no cooling): standard four zone gas furnace setup with hot water circulator 4 zones (3 wired, 1 wireless) Setup: Honeywell THM5320R (...
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16k views

Can I pair two thermostats to work with a single zone system?

I have a southern California two-story home built in the late '70s. It's a single-zone system with both heating and cooling. The thermostat is located downstairs. In the summer the upstairs gets too ...
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6answers
1k 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. My tenants always shut off thermostat or reduce temp when they are not in ...
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Tracing a dead thermostat wire conductor in wall

My home was rewired and remodeled in 2014 but I am finding out that the electrician did not run a new thermostat wire from my upstairs thermostat. I have a newer-looking 4-conductor wire coming out of ...
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1answer
449 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 ...
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1answer
523 views

Figuring out electrical connections for THREE electric baseboard heaters with single pole thermostats

I recently purchased a home (triplex) and in the basement unit, which is a one bedroom apartment, there are three baseboard heaters (bedroom, washroom, and living room). The issue is that the living ...
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2answers
279 views

Lennox G23Q3/4-100-2 And Ecobee4

**Pictures attached to go along with my rambling explanation I have my Lennox G23Q3/4-100-2 natural gas furnace and my central air system that has been working since 1995 on a basic programmable ...
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1answer
132 views

Honeywell T6 PRO Z-Wave Thermostat (model th6320zw2003) exhibits very erratic behavior after battery replacement

Background: My apartment complex installed Honeywell model th6320zw2003 thermostats in all units about six months or so ago, and it had been working well for all that time. The only issue was that ...
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Connect separate Heat / AC systems to a Nest E

I have oil/hydro zoned heat, and a separate AC system. I have Honeywell ProSeries thermostats that have some 16 wire connectors (apparently designed to handle a nuclear power plant or something). I ...
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1answer
393 views

Furnace Connect G Wire

I have a dual energy electric/oil furnace that is wired to a thermostat with 2 wires R and W. I don't have any AC. Inside the furnace there is a switch relay to control the fan but it is not connected ...
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1answer
198 views

Nest Thermostat says “delayed” and never turns AC on

New Nest, replacing an old thermostat. Image of old setup: Nest setup: The Nest says "cooling" with the blue screen for about 1 second, then switches to "delayed", then just ...
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Honeywell T6360 stopped working

When decorating I opened the thermostat cover to unscrew it from the wall. I never touched any wiring, decorated, screwed it back, closed cover, done! Now the thermostat won't work. Any ideas why this ...
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1answer
14 views

Trane VX99 furnace fan to run

I would like to have the fan turn on and blow non-a/c. I only see 2 wires coming from the thermostat. In
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2answers
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how to add c wire to heat pump ac unit (only have wires with nuts)

I can’t figure out which is the C wire or how to make a C wire and how to connect it to my ecobee 3lite Power extender kit. My old thermostat has wires G,Y,RH, W/E, and O/B plugged in. No "C"...
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HVAC is heating when thermostat is off

I seem to have a problem with my thermostat. I have tested the wiring of my HVAC system by wire nutting the the power (R, red wire) to the AC (Y, black wire), heat (W, white wire), and fan (G, green ...
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1answer
56 views

Is this wiring dangerous? Smart Thermostat C-wire AC adapter twisted together

Is this wiring scenario dangerous? Is it likely produce sparks or damage my HVAC system? Please read the description and see the image below. Description I didn't have a C-wire for my Emerson Sensi ...
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1answer
27 views

Air Conditioning Thermostat Wiring

A set of three air-conditioners cool a storage building in an American sub-tropical environment. There is no heat: AC only. Cooling is signaled by switching the RED (24V) to: Yellow wire (cooling ...
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Where to connect C wire if no C terminal

Hi wanting to connect Nest and want to install a C wire. HVAC only appears to have G,W,R so not sure where to connect C.
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1answer
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Honeywell C wire on a dual transformer system

Currently I have dual transformer system From heat >> RH & W1 From cool >> Y1, Rc, G Honeywell provides a C wire adapter and also mentioned turning an unused wire into a C-wire. I do ...
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4answers
4k views

Connection for C wire on Mastertrol Mark V zone control panel

I have spent hours searching the web for information on this 20+ year old zone control panel, which supports 3 zones of Heat and A/C. The thermostat I'm replacing (on Zone 3) connects to T4/T5/T6 as ...
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1answer
2k views

Honeywell Mercury Themostat 3 Wire, replace with Digital/Programmable?

Have an old Honeywell thermostat (house is 17 years old). Wondering if I can replace it with a newer Digital or Programmable one? Here are some pictures of it.
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1answer
1k views

C wire - thermostat - not providing power

I'm replacing my old Honeywell thermostat with a new Wifi thermostat. My old/current one is battery powered and doesn't use the C wire. I found the C wire behind the plate. I connected the c wire to ...
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1answer
44 views

Can an SPST switch be used instead of a thermostat for a gas stove?

We have a gas stove that can be either on or off. It has two wires going to a thermostat that has more capability than the stove, such as control of non-existent air conditioning and fan. The wires ...
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1answer
237 views

Can't get wifi thermostat to work with gas boiler

I bought a Sensi WiFi thermostat and I have been trying to install it. I can't quite figure out how this wiring should work. Here is a link to pictures of the boiler and the current thermostat. The ...
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1answer
64 views

Is my control board bad?

I have a Goodman evaporator/gas heating unit that runs the central fan motor constantly after it is powered up a couple of seconds. This happens regardless of what wires are hooked to the control ...
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1answer
65 views

Swapping to Hive thermostat. 4 wire communicator has 2 wires per post

I'd previously asked if I could swap my wires from the 4 wire communicator to the larger board and was told I could. I finally found time to do it. However, as I was preparing to move the wires, I ...
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21 views

My thermostat will not start my air conditioner

I remember the same thing last summer where occasionally it would take a number of hours for the ac to kick on after I switched to cool and the temperature was above the threshold. The funny thing is ...
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1answer
58 views

Wiring for 2-stage thermostat and 2-stage furnace with single stage cooling

I got my furnace and A/C unit replaced last summer. The new furnace has 2-stage heating, the A/C unit is single stage. The installers put in a single stage thermostat, so as far as I could tell it was ...
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1answer
3k views

Where to connect my “c” wire on the boiler side. Weil mclain gas boiler

Im just curious if the “c” terminal on the plug in relay is where im suppose to connect my “c” wire on the boiler side. I have 18/5 wire ran already. Just need to find out where to terminate. To the ...
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Heater does not start without a power reset

I have a Bonaire MB3-20I and it won't turn on unless I go in the roof and turn the socket off and then on again. When this is done, it stays on for as long as needed, but when we turn the heating off ...
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2answers
17k 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 ...
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Programmable Thermostat wiring Question

Existing thermostat is a Honeywell and has a separate connections for Aux (white wire) and E (Emergency black wire) The proposed Honeywell T'stat only has a single terminal labeled "Aux E". ...
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1answer
59 views

Main burner in NG fireplace goes out

What could be the reason of main burner going out intermittently. The pilot stays on. The voltage of the thermopile is 638mv when burner is off. The thermostat is a manual heat only. When I short out ...
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1answer
133 views

how to connect C wire for ecobee lite to Weil-McLain EG Series-5 gas steam boiler

I want to upgrade from a battery powered Honeywell thermostat to an ecobee3 lite. This is for heat only. My current Honeywell has two wires: Red and White. Missing is the C cable. There are enough ...
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1answer
127 views

Old thermostat to Hive thermostat

My wife decided we needed a smart thermostat... which means I need to install said thermostat... Currently a Bryant Evolution series is mounted. She purchased the Hive with Hub when it was on sale. ...
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1answer
38 views

multiple thermostat boiler connection

I have a boiler system with thermostats and valves for three floors. before i changed the boiler what ever thermostat called for heat worked for that floor. Now all thermostats have to be on or ...
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1answer
35 views

Thermostat not getting power and won't turn on fan or AC. Does have power with batteries, still no cooling

So first things first, I live in a condo. I don't have a lot of easy access to my AC (and I would imagine my furnace? I'm only guessing where that is though it might be near the water heater instead). ...
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49 views

Can someone assess my original thermostat's wiring setup?

This is a new world for me, I haven't messed with circuits since physics 101. When I watched a quick youtube tutorial on setting up my Nest E, I thought it'd be a simple "move wire in old C, to new C ...
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2answers
2k views

How do I make a 110V fan turn on when the thermostat turns the AC on?

I have installed a new a/c with thermostat...easy enough, but thought to add a fan to the mix. Basically, I'd like to add a fan to increase ventilation into a second room that would turn on whenever ...
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1answer
45 views

Replacing old 3-wire line voltage single-pole thermostat with a 2-wire one

I'm trying to replace an old Mears M21 SP thermostat controlling the baseboard heater with a new one (Honeywell RLV3120A to be specific). Problem is, the old thermostat has 3 wires (Black, Red, and ...
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2answers
527 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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2answers
368 views

Connect Wifi Thermostat to Goodman GMP050-3?

I'm trying to connect up a wifi thermostat to Goodman furnace, specifically the GMP050-3. I've done some reading on this but I'm still not quite sure how to go about it. Specifically, I'm not sure ...
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19 views

Rewiring for Nest Thermostat - Current ABCD Configuration Carrier

So I would like to use a Nest thermostat on my carrier system. I have the ABCD wiring configuration from current thermostat to the board on the furnace. On the attached image, you'll see three brown ...
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1answer
70 views

Furnace with no “C” connection

I have a mobile home furnace. This furnace only has a 4 wire connection terminal, G,W,R,Y. I also have a condensing unit outside with the 24 volt 2 wires coming to the furnace. I know I connect one to ...
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1answer
7k views

Honeywell RTH6500 WiFi Thermostat wiring questions for a heat pump

I'm trying to install a new Honeywell RTH6500 thermostat on an old heat pump system that has regular plus emergency heat and the closest matching diagram says to put both the white "W2" wire and black ...
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1answer
118 views

How to connect a new C wire

I have a 2 zone, single stage, heat only system with 2 wires running to each thermostat. I'm looking to install 2 Ecobee's; I have a second Honeywell AT72D1683 that I can install if needed and have ...
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2answers
2k views

Old furnace with no “C” terminal for wifi thermostat

I'm new to this forum and was wondering if I could get some help regarding installing a Honeywell WiFi thermostat that requires a "C" terminal. I currently have an older thermostat that has only 4 ...
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0answers
67 views

Nest Thermostat E wiring with a C-wire adapter

I wanted to get a Nest Thermostat E, but my current thermostat doesn't have a C wire. From what I read online, it's better to use a C wire, so I was considering adding a Venstar Acc0410 adapter. ...
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1answer
736 views

Converting I+ I- thermostat to 'standard' wiring

I've been replacing my thermostats with the RadioThermostat CT50, which reports to my home-brew home control/alarm system. I have a 3-year old AireEase 4-ton unit in the shop that has a Comfort Sync ...
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0answers
68 views

Thermostat not getting power (Nest E74)

I replaced an old Honeywell thermostat about a month ago with a Nest thermostat. Friday Nest started displaying an E74 error. I have two furnaces and two outdoor units, one for upstairs and for ...

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