Questions tagged [thermostat]

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

230 questions with no upvoted or accepted answers
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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
75 views

Thermostat settings two hvac units older house

So I purchased a historic house built in 1920. The house has two HVAC units, one for the upper floor, one for the lower. Total sq ft 3300. I had been setting the upstairs thermostat at about 83 ...
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1answer
392 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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95 views

Can I use this White Wire for a thermostat C wire?

An AC-only machine cools a storage facility: no heat. The 30 year old thermostat is to be replaced with a wifi thermostat, which requires a C-wire to power the electronics. There are 4 wires: Red (...
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2answers
109 views

Thermostat White-Rodgers 1F82-261 switches to stage 2 heat for no apparent reason

I am running a central heat system that uses a heat pump as stage 1 and a gas furnace as stage 2. The thermostat used is the White-Rodgers 1F82-261 which supports 2 stages of heat. When using regular ...
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2answers
2k views

Why my baseboard heater won’t turn with new thermostat?

I have a pair of electromod basement heater. The label on each of them show them show 750/1000W. Power supply to this is 240V I am trying to replace the old manual thermostat with a progrmabale one. ...
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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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25 views

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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40 views

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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67 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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39 views

Connect “C” wire on boiler model number 1135-601

I've read several threads here and on the other websites but still can't figure out how to add C wire to my boiler wiring. I would like to replace my old mercury thermostat with Nest E or any other ...
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72 views

Can I calibrate this thermostat? (Cadet brand, 240V)

My thermostat operates but seems to be badly calibrated. It will hold temperature, and you can adjust that temperature, but its not the temperature it says on the dial! It goes much higher than the ...
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186 views

Honeywell RTH5160D Thermostat Wiring w/ Heat Pump

I have installed a Goodman heat pump and a Honeywell RTH5160D thermostat. I chose that thermostat because it is supposed to switch automatically between cooling and heat modes. The system has been ...
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31 views

New thermostat turns fan off when set to on, never turns off on auto

My oil heat furnace was functioning normally on an old mercury switch thermostat, but I wanted to replace it with a programmable Honeywell 5+2 one. There were Y, W, G, R, and B wires screwed in on the ...
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1answer
155 views

Another “How do I add ”c" wire to boiler for Nest

I have tried searching this forum and others, but I could not find anyone with a situation like mine. I thought it better to ask here, rather than damage something. I have a Lennox wall mounted ...
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45 views

Thermostat wiring for ac

I recently installed a nest thermostat for our AC system. Unfortunately I was short sighted and just assumed all the wires were the color I needed. Since installing the thermostat our system won’t ...
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48 views

Will the existing wiring work with the new thermostat?

I am looking to upgrade my line voltage thermostat from a Dimplex mechanical thermostat to a Honeywell digital thermostat. Both thermostat has 2 wires on its back. Would the new thermostat work if I ...
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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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615 views

C-wire on Weil-McLain CGA Series 2

I have an old thermostat with only 2 wires connected to my Weil-McLain CGA Series 2 boiler. I would like to replace it with a Nest thermostat. I need to add a C-Wire in order for it to work. Luckily, ...
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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
518 views

Installing a Hive Thermostat

I purchased a HIVE thermostat and want some assurance before I go about installing this. First of all i was wondering where to put the receiver as I thought it would just replace one of the ...
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965 views

Honeywell WiFi thermostat jumper loop separate ac and gas furnace

I need to validate my understanding for the installation of a WiFi thermostat that requires 24volt continuous power to operate in a constant state. I am DIYer who is computer literate. Like a number ...
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2answers
139 views

Misbehaving/inaccurate thermostat?

I have a portable air conditioner/hvac and I'm having issues with it in heating mode. It's actually summer where I live but it was somewhat chilly as a storm passed over so I wanted to test heating on ...
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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
584 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 ...
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104 views

Why are certain radiators hot during the night when the thermostat is very low?

We have a gas central heating system and we have set the thermostat to come on at different temperatures during the day. Generally between 7.00 and 22.00 it is set between 19 to 22 centigrade. From 22....
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1answer
857 views

How to install a 4-wire a/c & fan thermostat with only 3 wires

My home currently has a central a/c unit which is controlled from an 3-wire old mercury switch thermostat. I want to replace it with a newer Honeywell that requires 4 wires. The existing thermostat ...
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1k views

Are w1 and w2 both energized during a second stage heat call from the thermostat?

Short version: does two-stage thermostat always close W1 circuit when it closes W2 circuit, or they might be closed independently? Long version: I have two-stage furnace, currently connected to older ...
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1answer
128 views

New thermostat: How to wire it?

My old air conditioner thermostat broke down, so I bought a new one. But when it arrived, I was horrified to discover that the terminal of the wires were not named the same. Both thermostats have ...
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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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19 views

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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23 views

Upstairs is getting frigid at night during cool nights

I have a dual zone Lennox system, and it cools well, but for the past few weeks it seems to run away at random cooling the upstairs to several degrees lower than requested. We have EcoBee thermostats ...
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50 views

C Wire doesn’t work

Trying to swap an old Honeywell thermostat for new with Wi-Fi. Old thermostat doesn’t need C wire, but I have an unused blue wire in the wall. I installed the new thermostat correctly with the C wire, ...
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32 views

Are 8-Zone Wiring Centers Compatible With Smart Thermostats?

I'm looking at various wiring centers for gas boiler heating and I'm wondering if they're compatible with the major smart thermostats, such as Nest, Hive, and Honeywell. Wiring Centers: Reliance:...
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1answer
23 views

furnace thermostat problem

Thermostat is reading crazy high temps when it is really 67. Furnace won't deliver heat. Fan works. Is it the thermostat (batteries replaced already) or the furnace?
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1answer
68 views

wiring hrv in a confusing house

some beautiful pictures first time posting apologies if my placement is off Buying HRV. I am debating between two units, venmar evo5-700 which doesn’t support furnace interlock or lifebreath rnc205, ...
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29 views

No Y wire to thermostat

I am trying to install a Honeywell rth6580wf thermostat. I have located all the wires except Y. It is a gas powered heat and central AC system. At the system there is a Y wire going outside to unit, ...
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1answer
80 views

How do I wire a/c if furnace wiring compartment has no y terminal?

I have been trying to figure this out for more than a year. All was running until HVAC company came to replace 2 thermostats with nest and rewired 2 HVAC units (a front of house and a back of house ...
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32 views

2 humidistats for 1 humidifier

I have two zones in my house with a damper system and want to move away from using my humidistat to control the solonoid valve on my humidifier and instead use my Nest thermostats. My zone control ...
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61 views

Thermostats with or without variable temperature differential (swing)

I am looking at replacing my thermostat, and don't really need or want one with geosync. I am thinking of the honeywell RTH9585wf. Currently I have a lux that is not wifi but programmable. It ...
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38 views

Very Old thermostat with TR wires

I want to buy a new smart thermostat, but am confused on the old wiring. I have single zone 120year old gas boiler (converted from coal, then oil, now gas). No cooling. The old honeywell thermostat is ...
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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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21 views

PTAC heat troubleshooting

I own a condo with two Islandaire EZ09EBMXH8N10AA PTACs, one of which is acting weird. They have self-contained A/C mechanisms, but the rooms are heated by pumping hot water from the building through ...
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24 views

Pretty basic Honeywell Wireless Thermostat Questions

I thought I knew at least the basics of how the Honeywell Thermostat worked, but testing with a multi-meter dashed those presumptions. I have another question posted, but until I get the basics ...
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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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315 views

Only getting 15-16 volts from Furnace R and C

I recently purchased a smart thermostat. Because it needed a common wire and I only had a 3 wire setup, I ran a new thermostat wire to my furnace. However, I now get only 15 volts (inconsistently, ...
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979 views

Carrier Furnace (6-wire) to Honeywell thermostat --> no cooling :-(

Carrier Furnace w/ Honeywell WiFi Thermostat I have a Carrier furnace with the cheapest programmable thermostat (TB-PHP01) that came with my house. The thermostat uses six wires: Y, C, R, G, W, and O. ...
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38 views

Separate Thermostats for Heating and A/C

I recently purchased a vacation home that has two thermostats for a forced hot air gas furnace and a separate A/C unit that shares ductwork. The A/C also cools better when both the A/C and furnace fan ...
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1answer
65 views

Plz help me, connect a common wire for smart thermostat in furnace

I bought a 3rd generation Nest. It doesn’t turn on after I hooked it up. I did research saying I need a common wire as power supply. I have closely look all the wires in my system and drew a diagram....
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71 views

AC unit not turning on

My A/C doesn't come on when I set the temperature on the Braeburn thermostat very low. Also, the recirculation fan doesn't come on when I set the thermostats fan setting to 'on', as though the indoor ...

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