Thermostat

[radhak]

I have the Honeywell Thermostat



It has been giving me problems for some time, and today I am totally unable to read it despite all efforts (change battery, slap it around), and am ready to replace it.

Question is - do I need to replace with the same unit, or can I 'upgrade'? I see the connections at the back look easy to remove and re-attach, but are these standard connections? And do they have electricity surging thru them?

[Mr__Bill]

No, yes, yes and yes.

Unless you have a controller for a computerized heating system the thermostat is just a fancy switch. Wires should be color coded and you just follow the code on the new one...... better to note what color goes to what terminal and what that terminal is for and then attach to new one at terminal that is the same..... There is power from the furnace/boiler to power the thing and for signal back. Probably 12 to 24 v. Just turn off the unit when it's not in a heating cycle and change the thermostat. The hardest part will be figuring out how to program the new one.


Bill

[LCHIEN]

most thermostats are interchageable if they are the heat only or cool only type (not control simultaneous heating and cooling). They use 24V (AC, i think) from a transformer located in your attic or basement near the furnace so they're not dangerous but you should probably turn off the 24V when you change it out. The 24V is used to control contactors in the compressor or furnace.

[TheChief]

You should be able to easily replace any existing 'stat with a new one of just about any model, unless this 'stat is being remotely controlled for automation purposes in which case you should stick with the same make and model.

The number of wires will depend on whether your HVAC system is single- or multi-stage and whether or not the 'stat is powered by the HVAC system, with local 12v or 24v power, or by batteries.

Most HVAC systems only use wires labeled R, G, Y1 and W1. Multi-stage systems may also use Y2 and W2. Some 'stats may need signals labeled RC and RH shorted together (but that will be in the instructions).

Once you identify/label the wiring to the existing 'stat, just pay close attention to the setup instructions on the new 'stat. Many new ones have different jumpers or switches that need to be set if you have a heat pump and/or if you use oil/gas vs. electric heating. These are more important than may be obvious as they affect start and run times for various equipment to help prevent damage.

I've been pretty impressed with Braeburn 'stats and recently installed a 5300 series. They are a touch spendy from retailers, but the last two I've bought were found on eBay, barely used, for less than 50% of street price.

Good luck!

[billwmeyer]

Replace quickly!

If you have trouble with a thermostat, replace it quickly. My wife and I came home around 8PM last winter, and it was about 90 in the house. My programable thermostat somehow stuck. I shut off the furnace and went to Home Depot and bought another one. It was a cold night, but it was still hot in my house when I got home. I live about 25 minutes away from the store. I don't know what would have happened if I was out of town.

Bill

[master53yoda]

The thermostat you show is a battery powered generic stat.

Shut off the power to the furnace or boiler so that the inadvertent touching of wires won't either blow the fuse in the heater or burn out the transformer.

If the thermostat you are replacing has a battery it MUST be replaced by one with a battery because there is not a common wire coming up from the heating system so the system 24 VAC isn't available to the thermostat.

wiring ID

RH 24 VAC power heating
RC 24 Vac Power Cooling ( jump to the RH in most systems some Lenox equipment has a separate transformer in the ac Unit.
W or W1 first stage heat other Ws are for other stages of heat
Y or Y1 first stage of cooling
G Furnace fan operation
X or C is 24 VAC common
Other would be identified in the t-stat instructions.

The switches in the stat will set the delay timing on the switch points in relationship to each other and to the actual temperature settings.

This should give you what you need. Read the installation instructions as well.

[herb fellows]

Once again, I am amazed at how many people know how much stuff on this forum! If we all lived together, we could form a coop that would be so knowledgeable, you would never have to pay for help!
Of course, we might kill each other under those circumstances, but it would be good for awhile! :-)

[radhak]

Wow - I log out for a couple of hours and now I have all this info!

I agree with Herb - would have made an impressive family; I salivate at the prospect of borrowing some tools; but cringe that I might have to lend out mine !

Thanks guys. Shall get to HD this evening.

This one runs on 2 alk batteries, running either cool or heat at any given moment. Lemme now hunt for the power supply to it.

[master53yoda]

the batteries are the power supply

[Mr__Bill]

the batteries are the power supply

Ah, the batteries power it when there is no power from the furnace but there is power from the furnace to the unit. Do turn off the power to the furnace prior to removing the wires. Just to prove it lick your fingers and touch them. When you get a tingle that's the hot lead from the furnace. Ok don't do that use a VOM.

Bill

[Kristofor]

If the thermostat you are replacing has a battery it MUST be replaced by one with a battery because there is not a common wire coming up from the heating system so the system 24 VAC isn't available to the thermostat.

Maybe.... Mine has a battery, but it will work just fine without having it installed or when it's dead (ask me how I know , replacing it 6 years after moving in...). I assumed it was just a backup power source like in a clock radio...