[BlaineBug]

Hello. I have an older furnace with an Ark-Les transformer inside.

I need help distinguishing what the various terminals on the transformer are for. I will be wiring up a newer wireless thermostat in the future that requires a common power source. Luckily, my thermostat harness already contains 4 wires. I just need to ensure that these wires are hooked up properly. My current thermostat works fine, but I just want to be sure as well as educate myself along the way.

In the furnace, there are 5 terminals on the transformer. "F" terminal hosts the green thermostat wire. "V" terminal hosts the red thermostat wire. "H" hosts the white thermostat wire. "T" and "V" both host the wires coming out of the actual transformer. And finally, "C" hosts the orange thermostat wire.

I would just like some assistance relating to the actual purposes of the F, V, H, T, and C terminals.

Thanks in advance!

 

[supers05]

Picture of the wiring would help. But my educated guess is :
F=fan
V=24v power
H=heat
C=24v common

I am assuming that you mean some kind of terminal strip or control board, because the thermostat wouldn't be connected to a transformer like that.

On the thermostat side:
R= 24v power (usually red)
G= fan (usually green)
W (w1) = heat (usually white)
C = 24v common (any colour not already used, on your case b orange)

Do you have a/c? What type of heat do you have?

Cheers!

 

[Bitters]

I have never seen a transformer with those letters. Are you talking about the control board?

 

[BlaineBug]

I have never seen a transformer with those letters. Are you talking about the control board?

Yes, it is the control board. I can see the transformer sitting on top......I just wasn't sure what to call it. Because it's a box, you can't see the internals. I doubt that there is a circuit board in there!

This is an OLD furnace, but it works fine. 1973. With a new gas valve in 2011.

 

[BlaineBug]

Picture of the wiring would help. But my educated guess is :
F=fan
V=24v power
H=heat
C=24v common

I am assuming that you mean some kind of terminal strip or control board, because the thermostat wouldn't be connected to a transformer like that.

On the thermostat side:
R= 24v power (usually red)
G= fan (usually green)
W (w1) = heat (usually white)
C = 24v common (any colour not already used, on your case b orange)

Do you have a/c? What type of heat do you have?

Cheers!

I will grab some photographs. This is a 24 volt system with central heat (gas) and A/C. Old systems, though. Climatrol furnace from 1973 and Janitrol A/C condenser from 1990. I have no idea if the evaporator unit is matched or not. Everything works fine, though.

 

[BlaineBug]

The electrical tape harness is there because much of the original insulation was so old and coming off, and some of the wires were developing cracks due to heat. I ended up splicing out the cracked wire and then wrapping it for added protection for the years to come. But then it is more difficult for you to see the wire colors hidden beneath the tape...

 

[BlaineBug]

So, since I have an air conditioner, is the orange wire "Y" for the air conditioner, or is this my common wire?

 

[BlaineBug]

Upon further investigation, I discovered that the orange wire (formerly hooked to the "Y" terminal on the thermostat) was hooked up properly, and was indeed the trigger wire for my air conditioner.

I pulled the thermostat off the wall to check how many wires were in the harness. I was thinking that I would have to replace it in order to add that 5th wire, but behold, this harness had a 5th black wire un-used at both ends. THIS is the common wire.

I ended up hooking this same black wire to the "C" terminal on my thermostat, and then to the "T" terminal on the furnace control "board" beneath the transformer.

Now I show a steady 27 volts between the "R" and "C" terminals on my thermostat backing plate.

I believe that once my wifi thermostat arrives in the mail, I should be all set. What do you guys think? Is everything wired properly now with the addition of connecting this black wire as the 5th common wire?

To recap:

Inside furnace, on control "board":

"F" terminal hosts the green thermostat wire (and fan wire)
"V" terminal hosts the red thermostat wire and one wire to the transformer
"H" hosts the white thermostat wire and one wire to the gas valve
"T" hosts the black thermostat wire, one wire to the a/c condenser, one wire to the gas valve, and one wire to the transformer
"C" hosts the orange thermostat wire and one wire to the a/c condenser

Thermostat upstairs:
W = White
G = Green
Y = Orange
R = Red
C = Black

Thanks.

 

[roughneck]

Has the heat exchanger been checked in that old beast lately? Not normal to have rollout strong enough to start affecting the wiring harness. And there appears to be a lot of rust around the burner area.

 

[BlaineBug]

Furnace was looked over in 2011 when gas valve was replaced. Rust was noted on the heat exchanger, but nothing else significant. Furnace also has a newer limit switch and blower. It may be an inefficient beast but it is still a beast nonetheless. I have insurance through my local utility company that will cover expenses for repairs and/or replacement of the furnace. Hoping that this is one insurance that I'll actually put to good use!:wink2:

PS, this furnace is not experiencing roll-out. The insulation on the wiring was brittle due to 40 years of heat cycling, though. It wasn't burnt, but it was hard and cracking in some spots. Old wire + heat. Even my old thermostat wire uses plastic insulation on each strand, but all five strands are enclosed in some sort of cloth-like insulation as well.

 

[BlaineBug]

I should update you all that this furnace is still working strong this fall, nearing its 46th year in this home and that the thermostat/transformer wiring is all good being used with two different wireless thermostats thus far. Now I am using a Nest thermostat in place of the Honeywell wireless thermostat that I installed when I created this thread back in February of 2016.

I should note that I cleaned the heat exchanger a few months back and experienced very little filth and carbon build up. Seems to be burning rather clean!

As I mentioned over two years ago, there is no roll out from this furnace, but a long time ago someone had removed the shield above the burners because apparently the pilot light used to go out from time to time with the old gas valve and needed re-lighting. They probably were using a short match instead of a long stem butane lighter and needed the access. Not everyone is perfect or OCD...

I have since re-installed the shield. That is where some of the discoloration of the wiring was from, I believe. Excess heat making its way out in to the front of the furnace area, which is normally shielded when the plate is installed correctly.

 

[user_12345a]

nest has a horrible reputation.

i'm betting the entire heat exchanger isn't visible so it can't be fully inspected.

you would save a lot of fuel by getting rid of it, plus if it's oversized as many were back then a new one would provide much more comfortable heat, especially if 2-stage or modulating.

 

[BlaineBug]

nest has a horrible reputation.

i'm betting the entire heat exchanger isn't visible so it can't be fully inspected.

you would save a lot of fuel by getting rid of it, plus if it's oversized as many were back then a new one would provide much more comfortable heat, especially if 2-stage or modulating.

Not getting any carbon monoxide readings in the home. Yes, two stage or modulating would be exceptional. Adding electronic dampers would also be great but unfortunately that would be impossible without breaking out walls, as with an early 1970s quad level home, the supply trunk for the second to lowest level and the highest level of the home is all the same coming out of the air handler. 2,214 square feet on three levels plus the fourth level, an unfinished sub-basement.

At the same time, we have loved our third generation Nest thermostat. The automatic home/away ability controlled with our phones' geo-fencing as well as a motion sensor, and additionally the ability to add a battery operated wireless temperature sensor on our upper most floor where the bedrooms are has improved comfort in an older home without zones or automatic dampers.

My Honeywell wireless thermostat was great for altering the temperature while on the go via the phone app, but that was about it. It lacked many of the other great features that Nest brings.

 

[user_12345a]

Ecobee 3/4 probably more comparable to nest than what most retail honeywells are - more features, can use sensors easily occupancy detection too I believe.

To be able to use sensors you need the professional grade honeywell product vs nest and ecobee that sell fully featured products at retail stores.

Generally carbon monoxide alarms won't go off until you're at near life threatening levels, far higher than what's in the exhaust. Cracks can cause combustion issues you may not notice, flame rollout which you would notice, and can pose a latent safety hazard - small cracks can open up at any time.

Adding electronic dampers would also be great but unfortunately that would be impossible without breaking out walls, as with an early 1970s quad level home, the supply trunk for the second to lowest level and the highest level of the home is all the same coming out of the air handler. 2,214 square feet on three levels plus the fourth level, an unfinished sub-basement.

To do zoning, you have to re-do the ducts, not just put dampers.

Plus if the duct system is designed properly to begin with, zoning is not required to keep things balanced.

Zoning is good for areas with a very different load profile than the rest of the house that has different sun exposure, attic exposure, insulation level.

 

[BlaineBug]

I do keep a regular eye on it, and my CO detectors do have a digital display to show less than lethal levels, as well.