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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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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3k 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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515 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
873 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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113 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
3k 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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2answers
4k 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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1answer
546 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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2answers
4k 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
574 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
146 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
690 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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3answers
22k 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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0answers
650 views

Honeywell WiFi thermostat newly installed--not working

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 ...
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2answers
559 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 ...
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2answers
113 views

What's the name of this kind of valve?

I would like to install the smart radiator thermostat from my previous apartment: However, in the new apartment there are different kind of valves, with clamps, as seen here: Does anyone know what's ...
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1answer
16k views

How do I turn off the power to my thermostat?

I'd like to replace my thermostat with a new one. My current thermostat is one that doesn't have a C-wire and is powered by batteries. Now, my question is... is there a switch for the power that I ...
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1answer
149 views

I changed my thermostat, not my heat does not work… help!

I know I made a mistake, but here's the storey. When I was hooking up the new thermostat I did it with live wires, and I used metal pliers (metal touching metal). The wires may have also touched ...
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1answer
288 views

Why would a 240v line voltage thermostat have a blank display?

In a bathroom I have a single 500w 240v electric baseboard heater, and AUBE/Honeywell TH305 digital line voltage single pole thermostat. I noticed yesterday, that the display had gone blank. A quick ...
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1answer
690 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 ...
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2answers
3k views

Can I connect the R and C wires directly to the HVAC transformer?

I have a Rheem furnace and a Ecobee3 smart thermostat. I'm having a problem where the Ecobee3 randomly loses power and reboots. I've traced this back to the control board (IFC) inside the HVAC unit. I ...
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2answers
2k views

Connecting a light-switch to turn thermostat on/off? (re: basement heat)

Is it possible to connect a simple light-switch to a thermostat? I'd like to have a thermostat in my basement set to 72 degrees. However, I want it completely turned off most of the time. I was ...
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2answers
706 views

Which Transformer for 220v to 24VAC for Heating Smart Thermostat

I have a 220V electric baseboard heating system which is controlled by a 24 VAC 2 wire thermostat (RH, W). There is a 220V to 24VAC relay in the circuit from the thermostat to the heating system. I ...
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1answer
589 views

Water heater pilot not staying lit

A customers 70 gallon gas fueled Bradford White water heaters' pilot light goes out immediately after releasing the red pilot button when relighting it. I concluded (in order of most likely suspects) ...
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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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4answers
1k 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 ...
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2answers
359 views

Confused by ~115VAC 5-wire cabling to UK thermostat

I have a 5-wire cable as used for 3-phase (i.e. stripes/blue/brown/black/grey) coming to a hole where a thermostat was - only the earth, live (brown), and switched live (black) were used by this ...
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0answers
73 views

Possible of override 2 zones with one thermostat

I have a vacation home with 2 zone heating. In the winter, it would be nice to be able to have remote access to the thermostat and 'turn on the heat'. Normally when vacant the 2 zones will be set to ...
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2answers
923 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 ...
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2answers
130 views

Cost of adjusting the thermostat

Is it more cost effective to (1) play with the thermostat by lowering it at times that you're not home or needing the heat and raising it back later or (2) leaving the temperature on a set amount and ...
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1answer
309 views

How to hook up C wire to Crown air handler

Sorry for the newbie question, but I would like to hook up a C wire so that I can get a Nest, Ecobee, etc. My current thermostat is just a regular battery operated Honeywell and looking at the ...
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1answer
200 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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1answer
440 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
2k views

Add a c-wire to 25+ year old Rheem furnace

I've looked at just about every post on adding a C-wire to power a WiFi thermostat but remain uncertain on how to proceed. The current installation on a Rheem RGAC-080A is two wire as here: XFMR - ...
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1answer
356 views

1 nest to control all vales on UFH manifold?

We are having an extension done and intend on having all underfloor heating in the new area. Currently we have a valiant combi boiler supplying the main house which has been T'd off with a valve for ...
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1answer
758 views

Need help adding a C wire for a wifi thermostat

With the increasing popularity of wifi thermostats I know this question has been asked many times, however I'll ask it again fr my specific situation. How do I add a "C" wire to my existing air ...
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1answer
261 views

How to wire programmable thermostat that doesn't have an E termimal

I am trying to replace a manual with programmable thermostat that is missing emergency heat (E) terminal. There are bits and pieces of information I have gathered but am still not clear. Can I leave ...
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1answer
446 views

How to simply turn heating on/off with VRT 340f thermostat?

I've just moved into a new house and it has a Valiant boiler with a VRT 340f thermostat and I have to say it is completely perplexing even after having read the manual several times! It seems ...
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1answer
643 views

New Thermostat Ecobee3 to Old Galaxy GG-75 boiler - Needs common wire

I would like to replace my old thermostat with a new Ecobee3 thermostat. HVAC system is a Slantfin Galaxy GG75 boiler - single zone. (No air conditioner.) Current set-up has only a red and white ...
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0answers
8k 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 ...
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2answers
1k views

How can I know if my boiler is supported by Nest 3rd Gen thermostat?

Here are the pics How do I know if my hot water boiler is compatible with Nests domestic hot water control
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3answers
14k 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
74 views

Thermostat/electrical

I have a Honeywell RTH2510 series thermostat that I want to install in a condo with baseboard heating. I took off the very old thermostat that was previously installed and there are only two very ...
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2answers
350 views

Rented Property: Install Nest

I have a Worcester boiler (Greenstar HE?), with a TR2 thermostat. I was looking at replacing the thermostat with a Nest (or equivalent). To complicate matters, I'm in a rented property, so I cannot ...
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2answers
222 views

Electric baseboard wiring

I have a 240v 1500w 6.5a electric baseboard heater with a wall mounted thermostat. What I found out is that the the thermostat and all the outlets in the room are on the same 20a breaker with this ...
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2answers
2k 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 ...
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1answer
169 views

0v at DC thermostat terminal in furnace

I have an old (mid 80s) Rheem gas furnace I hope will last me through at least one more California winter. It's been known to go down into the upper fifties, so it has its work cut out for it. In any ...
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1answer
642 views

Can I share “C” wire on two thermostats?

I am wiring a second thermostat right next to the original one. The new needs a C wire. Can I share it from the old one? Old: 8 wires, used to run heat pump (w/ heating and AC) and backup oil. Now ...
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3answers
40k 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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3answers
61k views

Hvac Fan only blows in 'fan on' mode while heating

Our HVAC Fan only blows in 'fan on' mode while heating. In other words the fan will not blow in heat mode if switched to "fan auto". Both fan on and fan auto modes work when cooling. See image below, ...

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