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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 5648
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I am trying to wire a Reznor UA 100 overhead garage heater.

Customer Question

I am trying to wire a Reznor UA 100 overhead garage heater. I don't know where the hot wire should go into, common wire and the thermostat. I can't find any diagrams for this model at all. Any help is appreciated
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.

Hello.

Please attach a well focused, close up photo of the wiring diagram glued inside the service panel, the picture needs to be taken from straight on, in very good light.

You can use the paper clip- icon at the right end of thetool bar at the top of this dialog box to attach it here. ,Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If there is no paper clip-icon, look for the '+attach files' link at left of your send button.

I can mark it up with wiring instructions.

Customer: replied 1 year ago.
there is not an access panel with a wiring diagram- or any wiring diagram. I attached actual photos of the back of the unit
Expert:  Phil replied 1 year ago.

Hello again, it looks like the Black and red were the original power connections, nothing else is unattached. It is a bit of a risk. I can't recommend it. But some people would connect those two wires to 120 volts for one second and see what happens.

Customer: replied 1 year ago.
Ok- but what about the thermostat, where does that go? If I have a red and white coming off the thermostat and only one black wire coming off the unit that says "thermostat." what goes on there, the red or white wire? What is the thing called that is to the left of the junction box?
Expert:  Phil replied 1 year ago.

Hello again, without a diagram for the furnace, I suppose the thermostat is wired in series with the 120v power to the Red and Black wires. But first we need to see if 120v directly to the red and black wires runs the heater or not.

If it does, then either the red or the black goes through a line voltage thermostat on its way to the heater.

Set the thermostat on heat then put power to the red and black for 1 second, if it does not short out, try it for a longer period, if the furnace operates you have solved the problem.

If not, we can go way way off into the very tall weeds and attempt to figure out what the heck is going on without a diagram.

But first we need to do that test.

Customer: replied 1 year ago.
Ok- I have to take off; but you are saying hook the red or white wire to where on the unit? Which wire (red or white) goes on the black wire coming off the item hooked to the left side of the junction box? The thing will not turn on if I do not have the thermostat hooked up to turn it on- correct?
Expert:  Phil replied 1 year ago.

Hello again, I said Red and Black... look to be disconnected.

"it looks like the Black and red were the original power connections, nothing else is unattached. It is a bit of a risk. I can't recommend it. But some people would connect those two wires to 120 volts for one second and see what happens."

You would not connect them to anything on the unit.... you would run 120v to them as a brief test only.

You are undoubtedly 100% correct, if the thermostat is not connected it will not run.,, but that is something we can look into *later.

The wiring is completely messed up, and you do not have a wiring diagram... its a risky situation, do any tests at your own risk, and cautiously. ONE step at a time... not two or three steps at a time... just step at a time.

Customer: replied 1 year ago.
There is another wire unhooked. It is black, comes off the thing to the left of the junction box and has a tag that says "thermostat." That is the one i am asking if the red or white thermostat wire goes to. Why should I bother to hook up 120 volts to the other wires when it will not turn on unless the thermostat tells it to?