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    solarboy's Avatar
    solarboy Posts: 9, Reputation: 1
    New Member

    Oct 8, 2005, 03:34 AM
    Trane Variable speed w/hot water coil/Ac wiring ?
    I've read many of the previous questions/answers, but haven't found what I need. Low voltage wiring is not my strong suit.
    My AHU has a hot water coil in it, that I plan to heat with a Voyager water heater. It has an A/C coil, and that works fine.
    Previous answers have said that I should find a transformer, which I do.. but the wiring makes no sense to me. There is a blue wire that is connected to ground from it, and a red to the panelboard. No other wiring other than line voltage to it.
    Wires from the stat are hooked to the AHU thus: G to G, Y to Y, R to R, W to W1 (ahu has w1, w2 and w3 terminals)
    Wires to A/C compressor are on terminals "B" and "Y".

    What I need: Fan runs on "fan", and on "auto" when in cooling. In heating, it doesn't run on auto. No combination of dip switch settings seems to matter.
    I need a set of contacts to run a relay for the hot water pump, and also for the fan to turn on at that time.

    Trane tech is not helpful, dealer who installed A/C and ahu admits lack of experience with this set up. I can take pics and scans of equipment and schematics if that is helpful.

    Great forum here!
    labman's Avatar
    labman Posts: 10,580, Reputation: 551
    Uber Member

    Oct 8, 2005, 07:42 AM
    I don't quite understand the set up. Most systems do not ground the secondary of the transformer. The blue is common to all the circuits, and functions like the ground in house wiring, but usually isn't grounded. There must be a return to it from anything controlled by the thermostat. Or do you mean it was connected to the control board ground?

    Usually in heating mode, the fan is controlled by a limit switch in addition to a relay so the heat does not come on until the air warms up. Also it may use a different relay connected to motor coil producing a lower fan speed. The current needs a path from the W1 terminal through the relay coil and limit switch, and then back to the blue on the thermostat. Try to identify and check the relay and limit switch. There should be a second limit switch that shuts off the gas if the blower doesn't start up.

    The W1 and B terminals should provide 24 volts to activate the relay for the pump when calling for heat.
    labman's Avatar
    labman Posts: 10,580, Reputation: 551
    Uber Member

    Oct 8, 2005, 01:32 PM
    I wasn't able to make out much in either the picture or the schemnatic. You simply must pick through the system and find how power was to get from W1 to the coil of the fan relay. The 2 black squares in the picture may be relays for low speed fan heating usually uses and the higher speed fan and A/C settings use. I didn't see any sign of the relays on the schematics.

    Likely you have it wired up right, and the problem is on the board.
    solarboy's Avatar
    solarboy Posts: 9, Reputation: 1
    New Member

    Oct 11, 2005, 01:05 PM
    How about this?
    I'm still trying to figure this thing out.
    I talked with a tech with Gus Larson, and he said to wire the t-stat like you would for electric heat.

    I look at my t-stat info, it's a LUX tx500. Says will handle electric heat (just not 110, which is fine) but all I see is diagrams for gas heat. He said "you wire it so G is energized on heat". Ok... so do I jumper G and W?
    What do you think?


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