Trane GP-155C Wiring

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  #1  
Old 10-08-18, 11:49 AM
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Trane GP-155C Wiring

Hello all, I searched the forum best I could to see if anyone had issues with this particular unit heater but no luck.

I live in northeastern michigan, so yes we have cold winters and I wanted to install a heat source for my garage during those cold winter months. So long story short, my wife's cousin gave me a Trane Model GP-155C Unit Heater that I have been trying to get running. I'm not sure how old it is but I'm guessing at least 20 years since I can't find info anywhere on the web for it. Supposedly it was ran on propane for a number of years.

Anyway, at first I couldn't even get the pilot to stay lit but I managed to figure that out after testing the thermocouple and cleaning it. Now my problem is that I can't seem to get the Basotrol solenoid to open and actually fire up the furnace. I assumed maybe I needed to wire in a thermostat but not sure where to even start with that because I can't find any info for this particular heater. I'm sure it's simple but I'd rather ask someone familiar with it than rely on guesswork. Currently the blower (fan) has a dedicated AC power chord attached and then there is another power chord that is wired in. The fan works when plugged in but nothing happens with the second plug providing power and the pilot lit. Sorry if I am not proving enough info or using improper terminology. I have attached a few pictures that hopefully will help.

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Last edited by aed2018; 10-08-18 at 12:04 PM.
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  #2  
Old 10-08-18, 12:32 PM
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I cannot find any information on that heater. It may be quite a bit older than 20 years.
In order for the pictures to be helpful they need to be full sized. The board will allow pictures up to 1000x1000 but only show 620x620. Yours are a third of that.
 
  #3  
Old 10-08-18, 03:29 PM
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I didn't realize they were such low resolution, I will upload higher quality ones when I get home.


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Last edited by PJmax; 10-08-18 at 05:00 PM. Reason: added labeled picture
  #4  
Old 10-08-18, 05:02 PM
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Ok. Your unit works strictly on 120vAC. No low voltage.... no 24vAC. That means you will need to use a 120v line voltage thermostat to run the unit.

Cable A = fan
Cable B = ?
Cable C = gas valve
Cable D = power ?
We need to identify the four cables in that 4" splice box.
 
  #5  
Old 10-09-18, 05:42 AM
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B and D are 120 AC power
 
  #6  
Old 10-09-18, 10:58 PM
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WHY..... are there two male plugs on BX on that heater ?
 
  #7  
Old 10-10-18, 05:09 AM
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No idea, that's the way I recieved it. Glad I'm not the only one perplexed by it. Should I simply unwire everything and begin from scratch?
 

Last edited by aed2018; 10-10-18 at 05:25 AM.
  #8  
Old 10-10-18, 08:40 AM
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One of the two plugs most likely went to a line voltage thermostat connection. Not right or safe.
 
  #9  
Old 10-11-18, 06:15 AM
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Let's assume that is the case, but when I have the pilot lit and I supply power to that line that would theoretically have been attached to a line voltage thermostat nothing happens.
 
  #10  
Old 10-11-18, 08:17 PM
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You would supply power to one of those plugs and short out the other one.

You don't have to re-wire..... just pull the wiring out of the box and snap another picture.
 
  #11  
Old 10-15-18, 04:55 PM
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Not sure how helpful this will be since wires don't really have much slack:
 
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Old 10-16-18, 12:14 AM
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I see more wires going out of the back of the box. Where do they go and how many wires are there ?
 
  #13  
Old 10-16-18, 10:09 AM
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Yes, there are 3 wires running through the rear of the box into the side of the unit. I didn't even notice them previously, but I can not tell where they are going inside the unit without further disassembly. The wires are colored blue, purple, and black. Here is a rough diagram of wiring:

 

Last edited by aed2018; 10-16-18 at 11:23 AM.
  #14  
Old 10-29-18, 01:40 PM
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Bump, do I need to provide more info?
 
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Old 10-29-18, 06:08 PM
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Yes.... there are too many variables here.

We see a 120v gas valve.
We see a 120v blower or fan.
We don't see an internal thermostat to cycle the fan based on heat.
We don't see any over heat safety sensors.

I suspect the missing items are at the end of those three wires but cannot guess.
 
  #16  
Old 10-30-18, 05:26 AM
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The wiring running out the back runs to this sensor I believe:
 
  #17  
Old 10-30-18, 11:19 AM
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Here's a very basic diagram of what you are trying to do. See if you can identify the limit/fan control on your unit. An ohm meter can help you to identify the normally open and closed contacts, no need to remove it. Get rid of the extra male plug for now, I suspect it was used for summer fan operation. If you want that option we can help later, first concentrate on the heating.


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  #18  
Old 10-30-18, 11:42 AM
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Close up of the fan/limit control. Important to identify switch position before wiring. Between 1 and 3 normally closed, high temperature limit. Between 1 and 2 normally open, fan on temp. control.
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  #19  
Old 10-31-18, 07:24 PM
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I appreciate your assistance very much, I will look into that as soon as possible. Happy Halloween as well!
 
  #20  
Old 10-31-18, 08:40 PM
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That last picture, is that a heat exchanger cell we are looking at? Is it split?
 
  #21  
Old 11-01-18, 04:50 PM
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No sir, that is just the lighting.
 
  #22  
Old 11-12-18, 12:48 PM
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Sorry for the delay, its bow season here in Michigan and the rut is ramping up. This is what I discovered with ohm test on the fan/limit control:

purple & black = 1
black & blue = 1
blue & purple = .5

Also, once I put the wiring back together to determine which plug powered the fan in order to remove it I can now here the solenoid valve opening when I plug in the one that does not power the fan. This didn't occur before so I assume there was a bad connection.
 
  #23  
Old 11-12-18, 02:25 PM
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Not sure that the ohm test is telling us anything. I think it would be easier if you pulled the fan/limit control out and took a decent close up of the switch and post it here, make note of any labels on the switch. Once you figure out what the terminals are ( common, normally open, normally closed) you can wire it like the diagram posted above. I think you are close to getting this thing operational.
 
  #24  
Old 11-13-18, 06:45 PM
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I am thinking the same, hopefully get that done this weekend. Thanks again.
 
  #25  
Old 11-27-18, 02:03 PM
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So I was trying to figure out how to get that thermal cutoff sensor out today and noticed what appears to be cracks in the heat cells. I assume this is not a good thing.
 
  #26  
Old 11-27-18, 03:06 PM
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Your unit heater is dead.
 
  #27  
Old 11-28-18, 08:41 AM
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Well, I wish I would have been more observant before wasting your guy's time. Thanks for all the help.
 
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