trane thermostat question - Contractor Talk - Professional Construction and Remodeling Forum

NCSteve · 02-02-2007, 11:51 PM

I am trying to figure out trane thermostats on a typical trane heat pump is

R has 24 v
G has 24 v
B is common
Y is compressor
O is reversing valve and is energiezed in cool
W2 is second stage heat
E is emergency heat

is this right please advise

#CARRIERMAN · 02-03-2007, 01:28 AM

Hi NCSteve

The thermostat nomenclature you have is partially correct. This is how most thermostats for heat pumps operate. You need to first understand the input and output terminals.

R= 24 volts power
Y= 24 volts output either cool or W1
G= 24 volts output to blower
O= 24 volts output reversing valve
W2= 24 volts output auxillary heat
E= 24 volts ouput auxillary heat
X= 24 volts common or neutral
B= 24 volts output heating mode only
Hope this helps to answer your question, if you need any further help one of us on here can help.

Good luck
Rusty

AirPro · 02-03-2007, 02:16 AM

Rusty, pretty good explaination, but I need to correct one thing...I hope you don't mind. There is NO neutral in a 24vac circuit, it is referred to as common, being the coil return to the secondary transformer winding. This winding is sometimes grounded which would make it appear like a 110v circuit, but it does not complete the circuit with the ground like a 110v neutral does. Just a clarification.

mdshunk · 02-03-2007, 02:21 AM

Quote:

Originally Posted by AirPro

This winding is sometimes grounded which would make it appear like a 110v circuit, but it does not complete the circuit with the ground like a 110v neutral does. Just a clarification.

Actually, on large RTU 24v transformers, it does. Normally over about 1000va.

"neutral" is a meaningless term, in reality anyhow. Probably not worth fussing over rhetoric, I suppose.

AirPro · 02-03-2007, 02:32 AM

Quote:

Originally Posted by mdshunk

Actually, on large RTU 24v transformers, it does. Normally over about 1000va.

"neutral" is a meaningless term, in reality anyhow. Probably not worth fussing over rhetoric, I suppose.

I have never worked on a unit with a 1000va xfrmr, that would have to be 600 volt or 480v 3 phase,correct? I have worked on some big stuff....but I have never seen or heard of a 1000VA xfrmr, The biggest I have seen were 400VA and were only wired for 230 volts on the primary....where would the neutral (or ground) come into play in completing that circuit on a step down transformer?

mdshunk · 02-03-2007, 02:34 AM

Quote:

Originally Posted by AirPro

....where would the neutral (or ground) come into play in completing that circuit on a step down transformer?

One lead of a transformer's secondary is required to be bonded to ground over a certain transformer size. It escapes my memory at the moment what that "certain size" is, but I can look it up. It's a code thing.

AirPro · 02-03-2007, 02:38 AM

Quote:

Originally Posted by mdshunk

One lead of a transformer's secondary is required to be bonded to ground over a certain transformer size. It escapes my memory at the moment what that "certain size" is, but I can look it up. It's a code thing.

That would be the common lead.

I can understand that, but looking at what a step down transformer does and how it works, it has nothing to do with completing the circuit....correct?

And it is still not considered or referred to as a neutral.....right?

mdshunk · 02-03-2007, 02:50 AM

Quote:

Originally Posted by AirPro

That would be the common lead.

I can understand that, but looking at what a step down transformer does and how it works, it has nothing to do with completing the circuit....correct?

And it is still not considered or referred to as a neutral.....right?

It seems you and I have a totally different definition of "neutral", so I'll stop right here if that's okay with you. "Neutral" is a meaningless term. We might just be saying the same thing in different ways.

AirPro · 02-03-2007, 03:10 AM

Quote:

Originally Posted by mdshunk

It seems you and I have a totally different definition of "neutral", so I'll stop right here if that's okay with you. "Neutral" is a meaningless term. We might just be saying the same thing in different ways.

My interpretation(sp?) of "neutral" is the leg that completes a 110 volt circuit to ground, and in no way comes into play in a 230 volt single phase or any 3 phase circuit. Let me know if I am wrong, I never claimed to be an electrician.

#CARRIERMAN · 02-03-2007, 02:40 PM

Hi Air Pro

Not a problem, the way I see it this sight is for each proffesional on here to be able to help another with a problem. Just to clarify my use of the word, Md was right neutral is kind of a relevant term used loosely. However in this case I was referring to it as a non voltage carring line in the open state. However it has the potential to carry voltage when hooked into series with a device, thermostat, relay, etc. This was why I put that in the post. I have even heard it called a return line. Not exactly sure that thats a better term for it, just wanted to make sure he had the possible needed information. Besides, the day we quit teaching one another, boy is this world going to be in trouble. Who will take care of their comfort?

Rusty

FemaleAstarCO · 02-05-2007, 01:16 PM

Agreed that we are all professionals Carrierman yet we all knew what you were talking about. Frankly I was thinking if they do not know they should be calling one of us.

Trane partial

Cindy

TheBigDog · 02-06-2007, 11:33 PM

NCSTEVE,
Be careful where you hook up the common wire. Some of the older Trane stats use the "B" terminal for common, typically these will not have a "C" terminal. Some of their stats also use "X" for common. If you hook up to the "B" terminal on some stats when you turn the mode switch to heat you now have a dead short, and if you do not have an inline fuse you will let the smoke out of the transformer and we all know how hard it is to get it all the smoke back into the transformer

. If you do not have the install litature let me know the model # and I can email one to you.

John