DIY Home Improvement Forum banner

1 - 17 of 17 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter #1 (Edited)
I think I have my old 1980s furnace power/transformer wires crossed.
It calls for heat continuously regardless of having the thermostat connected to the transformer.
There are 2 white wires and 1 brown wire coming from the control board. And 1 white wire coming from the emergency switch.
The transformer has 3 terminals. Black, White and Red. The red is connected to the combustion blower.

I connected all 3 white wires together. The switch, transformer and controller wires.
I connected the black wire from the transformer to the brown.

Does anyone know what I did wrong? It seems I bypassed the thermostat call for heat because the furnace just keeps running even with the stat disconnected, set to off or low temp.

 

·
Registered
Joined
·
10 Posts
Discussion Starter #5

·
Registered
Joined
·
6,412 Posts
Why did the tech refuse to fix the unit?
Is there a safety concern with this furnace? When was the heat exchanger last inspected and confirmed ok?
Old doesn’t mean bad but we have to be certain the furnace is safe and able to be used.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #7
He said that the transformer would be impossible to find. And if they did order it in, it would be just as expensive as installing a new system. He suggested I get an estimate from his manager.
 

·
Registered
Joined
·
6,412 Posts
No, the heat exchanger is back above the blower. And should be inspected since your unit is so old. Often they are cracked, and if yours is then your furnace is unusable.
The wiring looks ok. Check the new transformer with your meter.
You could have a short that caused the old transformer to fail.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #10
I'll have to carefully select a technician who supports older models.
If the wiring is ok on the new transformer, then I'll need to find the short.
 

·
Registered
Joined
·
3,257 Posts
If you can post the circuit diagram from the furnace, we can help you wire the transformer properly. It's probably a simple fix.
 

·
Registered
Joined
·
10 Posts
Discussion Starter #12 (Edited)
If you can post the circuit diagram from the furnace, we can help you wire the transformer properly. It's probably a simple fix.
Boy am I an idiot. I spend hours up all night looking for a wiring diagram and it's right there inside the bottom cover. If ya'll can help guide me, my family will be relived.
So I do have a functioning transformer (C & R has 24v output). And a total of six wires need connected.


I have the following 3 wires connected transformer terminals:
1-Red connector wire coming from combustion blower pressure sensor to the Red transformer terminal.
2-Blue connector wire from the transformer to the controller connector T R Com to the Common transformer terminal.
3-White connector to White terminal going down to Relay 1R WHT.

I have the following 2 bare wires connected to the transformer neutral White Wire:
4- White wire connects to blower motor.
5- White (neutral) coming from emergency switch.

I have the common Black transformer wire connected to:
6- the Brown wire, which turns into Yellow (7) on the controller RS/RP.
http://rittenhousephotography.com/photos/IMG_9739.jpg
http://rittenhousephotography.com/photos/5.jpg
 

·
Registered
Joined
·
3,257 Posts
The red goes to the W terminal per the schematic and the white goes to the G terminal. You have the blue correctly connected to the C terminal. Try those changes and hope for relief.
 

·
Registered
Joined
·
3,257 Posts
If you check what the red wire is doing by following the schematic, you'll see that goes through all the safety switches and ends up at the ignitor control unit, which controls the ignition process including energizing the gas valve. The way you had it connected, it was getting straight control voltage directly from the transformer without any connection through the thermostat. That fits the symptoms you had so we're on the right trail.

You are correct by connecting the black transformer wire to the brown wire since that brown wire is the L1 120 vac power connection. The white transformer wire goes to the L2 white line connction. You have those correctly connected.

After correcting the red and white connections to the transformer, do you have other wires that aren't connected?
 

·
Registered
Joined
·
3,257 Posts
I see in one of your pictures that you have the white thermostat wire connected improperly as well. Move the white stat wire to the W terminal screw where the red factory supplied wire is also located.

Leave the red stat wire where you have it, under the R terminal screw.

Now you will have establishd a switch loop through the thermostat that will control the gas valve.
 
1 - 17 of 17 Posts
Top