thermostat question

[CRF8]

We have a standard electric central heat and air system in Florida. The current thermostat has 2 AA batteries, so I guess it doesn't have the 24v? or internal power? I would like to buy and install an internet thermostat so I can control it from my IPhone etc. I have looked at a few models but they all seem to need power. I have not pulled it off the wall yet to see what color wires I have. Am I correct that I need a powered thermostat because I have batteries in the old one? Does anyone know of any powered thermostats I can use?
thanks

 

[RECox286]

Consider that your T-stat is almost like a relay.

The batteries in the T-stat are there to work the

program, not to work the furnace. You will find

24vdc provided by a transformer that provides

the power to run the furnace components if you

stab the right wires hooked to the back of the

T-stat. You should have no trouble substituting

whatever you desire to replace the current one.

Just carefully follow the instructions, after making

sure that the new one is compatible with the system(s).

Uncle Bob

 

[Stuff]

There are a few wifi thermostats that are battery powered. There are others that use your existing wires and "steal" power from them but most are powered from the hvac unit. There are also devices that multiplex wires if you don't have enough to provide power.

You need to check what wires you have to know what your options are.

 

[ichabod]

I have not used a internet t-stat, but I would guess if you had a minimum of a 5 wire thermostat wire going to your HVAC equipment, you could make it work. this is assuming you have low voltage control. you would not need batteries then.

 

[CRF8]

OK thanks, let me pull off the wall and see what I have

 

[Richard Cranium]

The batteries are to run the functions of the therm. The furnace will have it's own power supplie

 

[going4speed]

Had old mercury thermostats when we moved in to the new to us house. The wiring had the required count and was just as stated in post 2. We just needed to hook up to the furnace and we had power to the electronic thermostats. Much better than changing batteries. Some internet searching with the furnace model number should get you the information you need.

 

[MrBalll]

I just recently put a 'Nest' in my house. Very happy I did it. So nice that it learns when you are home and helps save money by not running the HVAC all day when no one is there.
From what I remember I think I had five or six wires in my wall that went to my battery powered thermostat.
Just be sure when you pull your thermostat that you mark what each wire is plugged into. Should just be a series of letters and numbers.

 

[ctfjr]

Consider that your T-stat is almost like a relay.

The batteries in the T-stat are there to work the

program, not to work the furnace. You will find

24vdc provided by a transformer that provides

the power to run the furnace components if you

stab the right wires hooked to the back of the

T-stat. You should have no trouble substituting

whatever you desire to replace the current one.

Just carefully follow the instructions, after making

sure that the new one is compatible with the system(s).

Uncle Bob

Not the greatest advice. 1st its 24 volts AC that powers the equiment, not DC. It sounds as though the op has a battery powered thermostat. Most likely then the 'common' from the transformer is NOT brought up to the thermostat at all. Therefore 24 volts are probaly not there to power a wifi thermostat (almost all the wifi thermostats I know of require 24 volts for operation)
The op may be in luck if he has a spare wire coming up to the thermostat. That can be used to pick up the common down at the equipment & be used to power the new wifi. The 'R' terminal on the existing thermostat is most likely the other side of the 24 volt transformer.

 

[LS6 Tommy]

Most "Smart" stats require 24VAC to operate. Batteries or not, there are two basic types of T-stat- system powered and passive.
Pull your T-stat off the sub base and look at the terminals. If you have wires on "R" (or "Rc/Rh"), "Y", "W", "G" and "B" (or "C"), it's system powered and you're good to go. If there's no "B" (or "C") or there's no wire on that terminal, you have a passive T-stat and will have to either add a "C" wire or use a "Smart" T-stat that doesn't require it. The ecobee 3 has an adapter you wire into the furnace/air handler to allow use of a passive T-stat.

Tommy

 

[CRF8]

thanks, especially the last 2 posts. I have been busy with other projects but will get back to this.

 

[Ohmthis]

Being that his house is all electric there will be wires for back up/emergency heat and a wire for the reversing valve. OP in addition to what Tommy added you will probably have an orange (reversing valve) and either black or brown (back up/ emergency heat). Control wire typically has 2,4,5,7,8, or 9 wires in the cable. I'm betting you have enough wires to connect your new tstat.

 

[Denwood]

If you have two wires only, you can still use a powered stat using a "Fast Stat Common Maker" which uses your two wires to terminate in a three wire setup. The Ecobee 3 wiring kit essentially allows a 4 wire system to become a five so you have separate fan control and power for the stat if you only have four wires in the wall.

What you are doing with a C wire is providing a path for return current to power the stat. Normally that power (in a two wire system) has no return path when the stat is not calling for heat. We're running nine of the Ecobee 3 stats..highly recommended. My install was a combination of two wire/boiler and 5 wire with Heat/AC.

The link below applies to two wire, heat only, setups with the Ecobee 3:
https://ecobee.zendesk.com/entries/96808048-ecobee3-Heat-only-2-wire-boiler-furnace-installations