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Thermostat problems

Since I dont think the owner cares about automatic operation, this will due. rh/rc to air handler R term./ w1 on stat to energise a relay in addition to the on off switch at the pump. As far as the stat goes,..Change to a stat that will automatically energise the g term on a call for heat. This will save alot of rewiring. Digital stats have this common feature. Also your ac will be connected as follows: "Y" from stat, goes right to the cond./ 3 (or common of the air handler) make sure this is comm. to the other wire from cond. "G" from stat to g on A/H. Basically get rid of that existing stat and go with something like a Rob Shaw #9600.
I hope this helped....This is very basic control because you said they leave the boiler on all the time,.


  • Terry H.
    Terry H. Member Posts: 73

    I have an odd question, but it will take some thought.

    I have a customer who would like an answer to his problems. He has a Lenox air handler that was originally set up to cool their office. It is a model ecb18-12-5-3p or cbs18-41-3p. It is being controlled by a honeywell t87f thermostat. It may not be wired correctly but it does work for cooling. It is wired as follows: the air handler has four connectors labled R,WI,G,3. From the outdoor condenser to the unit is a two wire stat wire connected to terminals 3 & G. from the unit to the thermostat is a five wire stat wire. At the thermostat RC attaches to R at the unit, from the thermostat W goes to WI, also from the stat G & Y go to G at the Air Handler, Also at the Stat RH is connected but makes no connection to the air handler. I'm Not sure if this is correct but it does work.

    Now for the problem.

    A few years ago a contractor came in and added a hot water coil so they could heat the offices in the winter. He couldn't figure out the wiring so he added a second t87 thermostat to the system and instructed the guy on how to unwire the first thermostat and change it over when winter comes. He also installed a nice switch they have to go into the boiler room to turn on to turn the pump on(which wears out the pumps) to run continuously to keep the coil hot and the thermostat just cycles the fan. Now on days like this when we need heat in the morning and cooling in the afternoon this can be a problem especially if they forget to turn off the pump.

    I would like to know how we would wire this unit to be able to switch at one thermostat from heating to cooling. And be able to control the pump. The boiler does not need to be called because it is a waste oil boiler that the primary loop is always kep at temperature for the main shop's heating and hot water loads.


    Terry H.
  • Terry H.
    Terry H. Member Posts: 73
    Good call

    I think the problem he was faceing was a thermostat problem. I've done some testing with the RS 8400 and it will work as you said.


    Terry H.
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