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Fan not working when Fan Auto is set

rrabihrrabih Posts: 32Member
Believe it or not; I still have 2 Glowcore FCU (Fan Coil Unit), I don't know what year is this thing, but didn't find any information about it ! I bought the house 3 years later and both worked well up to now.
My issue is this: The glowcore fan of the Attic does not start when FAN auto and heat mode is set in the thermostat. When FAN only is set, it works.

the boiler is in the basement, it is a separate unit from the FAN unit which is in Attic; the unit is essentially an air handler, with a fan motor and is compatible with source of hot water not exceeding 180F.

any idea what this can be? may be a relay issue? this is only thing I can think about.

Thank you


  • HVACNUTHVACNUT Posts: 2,172Member
    The blower motor has a different speed for heat thats not powered through the thermostat.
    At the A/H, the fan control for heat speed will be either an aquastat or temp sensor on the hydro coil or by a time delay relay.
    Leave the fan on for now.
    The system should be wired so both sets of motor windings cant be powered at the same time.
  • rrabihrrabih Posts: 32Member
    edited January 4
    thank you, I am on fan On, it is running all time, hope it will not get exhausted soon and stop working.
    In the meantime, I'll change the relay (no aquastat or temp sensor in this very old AH) hoping this to fix the issue for the winter.
    any good suggestion to change that old Glowcore thing? (Glowcore 48VDX-4HW) it should really be old (more than 20 years) and will surely break soon...
  • DZoroDZoro Posts: 760Member
    Did you recently change the thermostat?
  • rrabihrrabih Posts: 32Member
    no, the thermostat is also an old carrier one..
  • SuperTechSuperTech Posts: 938Member
    48VDX-4HW? That sounds an awful lot like a model number of a First Co. Hydro air unit, maybe glowcore is a re-badged unit.

    Anyway, I see a lot of hydro air units and the older First Co units used a sequencer relay for the heating fan speed which is notorious for failure. I usually recommend ripping out all of the old relays and installing a modern circuit board, CB201V to be exact. You can really clean up and simplify the wiring.
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