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kltsin · Apr 25, 2005, 10:17 PM

Wanting my new digital thermostat to run off the 'C' 24 vac common instead of batteries I opened my Thermal Zone (#ah368-1s) electric furnace door panel.
I have been unable to find any details online about that specific unit, but there is a wiring diagram inside.
The low voltage for the thermostat appears to wired improperly.
Here are the labels on the exterior of above.

This isn't a common way to label so I am a bit confused, but here's my real problem.
The wiring from the thermostat was prewired like this
Furnace ------ Thermostat, (wire color) - properties
R --------- (R or RH) - HEATER TRANSFORMER
C --------- (Y) - COOLING COMPRESSOR
G --------- (G) - FAN RELAY
W2 ------- (W) - HEATING CONTROL
E --------- unused
W3 ------- unused
W4 ------- unused
Of course the wiring in between has the(Y) COOLING COMPRESSOR goes to outside compressor and then returns to 'C' and there are two unused wires, brown and blue.
Shouldn't the stat (Y) COOLING COMPRESSOR be connected to E not C.

Anyway I connected the thermostat to 'C' but haven't touched (Y)

At first I was quite thrown by the labeling and spent hours trying to figure out what E, W3 & W4 were and thought they might be the common.
Should I rewire it?
Thanks for your time

tkrussell · Apr 26, 2005, 03:27 PM

Appears the wiring diagram in the furnace is only for the blower motor, I don't see any connection for heat or cooling in the furnace wiring. Terminals E, W2,W3, & W4 are doing nothing.

Is there another wiring diagram in the furnace? Or is there a piece missing?

Y on on a thermostat is typically a switch leg to energize the compressor, however I do not see any connection in the furnace diagram for compressor.

All I see the thermostat doing is turning on the blower motor.

The "AH" in the model number tells me the unit you are looking at is only an air handler, which makes sense with the diagram. There must be additional components to your system.

How old is this furnace? I can only find one website, energystar.gov,that mentions this brand. All model numbers begin with G.

Is there any manufacturer info on the unit,such as phone number or address, to try contacting them directly? Try some local heating suppliers to see if they are dealers of this brand, or know how to contact the manufacturer.

Installing a thermostat should not be this difficult, and most manufacturers use a standard for wiring.

Not sure if this is any help. If you come up with any additional info, get back here with it and I should be able to help further.

labman · Apr 26, 2005, 08:09 PM

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. It may be wired to have the AC control wires return to the furnace and its controls and then a second pair of wires goes to the A/C unit.

Your system seems to have labeled the other side of the transformer C. I couldn't read some of the diagram. You must have a second wire, blue or brown, running out to the AC relay. Connect the blue or brown wire to the same terminal at the furnace, and to the "C" common at the thermostat. The W2, W3, etc. may be for furnaces that have different firing rates.

kltsin · Apr 27, 2005, 12:24 AM

Originally Posted by tkrussell

Appears the wiring diagram in the furnace is only for the blower motor, I dont see any connection for heat or cooling in the furnace wiring. Terminals E, W2,W3, & W4 are doing nothing.

Is there another wiring diagram in the furnace? Or is there a piece missing?

Is there any manufacturer info on the unit,such as phone number or address, to try contacting them directly? Try some local heating suppliers to see if they are dealers of this brand, or know how to contact the manufacturer.

You are correct that is the blower diagram only, as it doesn't come with a heating kit.
The one installed has zero info except a model number h1h something, I looked it up and found nothing.
This unit is very very old although the wiring for the heating unit looks very new.
Only other info is a location of the state the company is in .

Originally Posted by labman

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. It may be wired to have the AC control wires return to the furnace and its controls and then a second pair of wires goes to the A/C unit.

Your system seems to have labeled the other side of the transformer C. I couldn't read some of the diagram. You must have a second wire, blue or brown, running out to the AC relay. Connect the blue or brown wire to the same terminal at the furnace, and to the "C" common at the thermostat. The W2, W3, etc. may be for furnaces that have different firing rates.

Ok I didn't understand a word of that. :)

Its not a gas furnace but electric, as the previous poster stated it just the air handler diagram. The actually diagram of the heating unit is MIA and I can't find any info about it.

Would some pics help showing all of the wiring to the heating unit?

Overall everything works, I just believe its wired incorrectly from the stat to the unit.

PS: From a admin and moderator of several PC tech sites/forums to you guys, thanks for your time. If you ever need any help in the PC department especially with proprietary equipment or security issues just pop in to the forum in my profile.
Thank you

tkrussell · Apr 27, 2005, 02:44 AM

Lets work this backwards, there are two wires that go out to the compressor. Where are these located at the central unit inside?

This is where the wire from the Y terminal will connect to one (red) wire going out to the comp unit, the other wire (white) will need to connect to the C terminal, being common or return back to the 24 volt transfomer.

The thermostat is only a switch, with a common going out to the relay coil on the comp unit, and the other providing power from the transformer, through the switch in the stat, and out to the other wire on the relay coil.

Lowering the stat when its warm will close the switch in the stat, sending power out to the comp uint relay coil ,energizing the relay and start the compressor.

Hope this makes sense.

labman · Apr 27, 2005, 07:44 AM

I think this is much less complicated than you are making it. Sorry about the gas comment. The thermostat will still be wired the same for a furnace with electrical resistance heating. Somewhere there is a 24 volt transformer. The thermostat turns on various relays by switching one side of the transformer, usually a red wire to usually white, yellow, and green wires for heat, AC, and fan only. Each relay must be connected to the other side or terminal of the thermostat. Often the only wiring from that terminal outside the furnace is the one going to the AC relay outside at the compressor. To power the thermostat with power from the transformer, both sides of the transformer circuit must be connected to the thermostat, one to the red, and one apparently in yours, the C.

kltsin · May 4, 2005, 01:48 AM

Sorry for the delay in replying..
I haven't had time to check the wiring as of yet per your advice.

Well it works and always has, I just don't like the 24v common being used for the AC as well..

Also this unit poors water all over the floor during the hot months here in FL, I have cleaned the system many times with no luck at all.
When running the AC hard and it stops it seems like there is a floodgate, maybe I need to clean better.

labman · May 4, 2005, 07:05 AM

Using the common for the A/C too isn't a problem. It is always in use for the relay for air handler on heat, cool, and fan only. On heat or cool, it is also in use for the proper relay, but only that relay and the fan relay. The transformer and wiring usually is sized to handle the loads.

A/C drains are a frequent problem. Too often they are run with too small of pipe, and too many bends and too short of bends. Then they plug up and water goes all over. Make sure it is at least 3/4'' pipe, and not too many bends. Try to find the longer radius drain elbows. They give less resistance to flow and are less likely to plug up.