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Carrier 58GP, GS gas furnace IID pilot

Del Member Posts: 52
Tim, I've got a number of questions about the t-stat terminals on this unit.   There are R, Gh, W, Gc, Y and C.  #1) There is a jumper between R and Gh.  On the diagram, it looks like the Gh terminal is connected right to the heating fan relay.  Since there is a jumper R-Gh, would that cause continuous low speed fan operation?   What is the point of the jumper? If i was hooking up a typical T-stat for heating, would t-stat R go to this Gh terminal instead of R? It looks like during heating operation, the fan relay is energized through the gas valve and a time delay.  Does Gh  have something to do with continuous fan operation when t-stat is in heat mode, or is it used as 24V for heating instead of R? Where would my G from the t-stat go?

#2)  It looks like the Gc terminal controls the Cooling fan relay, but it doesn't look like Y is controlling anything.  Do I need a jumper between Y and Gc in order to control the condenser and the fan relay through the Y terminal of the T stat? 

What would a typical RC, RH, G, C, W and Y   thermostat hookup look like with this furnace for heating/cooling and fan control on or auto?  Thanks for your time!


<a href="http://www.xpedio.carrier.com/idc/groups/public/documents/.../58gp,gs-2si.pdf">www.xpedio.carrier.com/idc/groups/public/documents/.../58gp,gs-2si.pdf</a>



  • Tim McElwain
    Tim McElwain Member Posts: 4,621
    Mike is this

    a new system or has it been running? What is the make and model number of the thermostat? Is the thermostat wired to a control board, if so give me some numbers and make?
  • Del
    Del Member Posts: 52
    Older system

    Tim- this is an older system I went to service. The customer is a restaurant, and she had some handyman put in a new thermostat. I don't remember the brand, but it had the typical battery powered Rh, Rc, W, G, Y. It is hooked right to the unit PCB, and I put in a link to the wiring diagram in my first post. When I got there the unit was running the fan and not igniting, so I pulled the t stat wires off the unit, put in a call for heat and it worked fine.Started tracing the thermostat wires, and found a birdnest of sloppy splices with all different color wires, it was basically impossible to tell which color was which, so it being the middle of brunch hour, I wire nutted two wires at the thermostat, then went down to the unit and checked which were connected, and hooked those up to R-W at unit and thermostat and it worked fine. I told her I'd come back during regular business hours and pull new wire and hook it up so the ac would work next summer! I was looking over the diagram, and due to the Gh Gc terminals, jumper on R--Gh, I wasn't sure how to go about wiring it up, especially since they like to keep the fan on. I mean, I could take the thermostat down to the unit and figure it out, but I figured I'd ask here first ; ). Thanks again.
  • Del
    Del Member Posts: 52
    Ok, so

    I went back to this job and ran new thermostat wire from the thermostat to the unit.  Had 24V at R and Gh.  When I jumped R---Y, the fan did not turn on for the A/C, I had to jump R-Gc for that to happen, so I put a yellow jumper between Gc and Y to kick the condenser on, and things are working OK.  For the heat, I just used the typical R-W thermostat connections. Heat and A/C now function normally.  The only thing I wasn't sure about was where to hook the G from the thermostat so they can have fan only operation.  Should I cut the jumper(part of the circuit board) between R and Gh? I wonder why they designed the terminals this way? Shouldn't there be a separate terminal to switch fan relay? From the diagram, Gh appears to be it, but for some reason it is jumped to R.

    Anyone have any ideas? Thanks.

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