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Thread: Aux. Heat for Heat Pump not working

  1. #1

    Unhappy Aux. Heat for Heat Pump not working

    I have a Hiel Forced Air furnace with Heat Pump/AC and Electrical Auxhillary Heat - 11 yrs old.

    Situation: Aux Heat not kicking in in auto mode to assist Heat Pump (LED on thermostat not lighting as I believe it should). Heat Pump barely brings the house up to 64 deg F and runs continuously 24/7 - my electrical bill is setting all time records.

    Blower and thermostat LED function when Aux Heat is manually called for. The Heat Pump shuts off and the air from the floor vents is very cool as are the sides of furnace near the heating element. Aux. Heat will not bring the house up above 60 deg F.

    I found a small pigtail wire on top of the furnace unit (washer type connection on one end, female spade type on the other) so I opened the wiring panel to inspect. There were four ceramic insulators with two leads each with wires connected to what I think are relays - each of the relays had two wires, except one. I connected the wire (nothing blew up and the house didn't burn down) but it had no effect on the performance of the system.

    Could it be that I have a faulty relay or two? Could it be something worse? Any suggestions are greatly appreciated.

  2. #2

    Default

    Open the furnace, with a screw driver push in that contactors one at a time for a few seconds. If the heat elements turn red then they are good. If one or more do not turn red when its contactor is made in contact then may be a burnt out heating element. YOu should have a bank of more than one separately controlled heating elements in that furnace.

    If none turn red when you close the contactors then check for 220 volts at each contact. May be a blown fuse in the furnace or feeding the furnace.

    If the elements all turn red then suspect the wiring to the termostat or the thermostat itself.

    Just some ideas

    Wg

  3. #3

    Question Thanks - I think I'm getting closer to a resolution.

    Well, I got brave and brought out the multimeter and pulled the heating coil unit out of the chamber above the blower. There are six heating coils that "snake" through a series of ceramic insulators in a metal cube-shaped cage. I checked each coil with the meter and I got similar resistance readings (12.5 - 13.0) on three of the coils: I'll call them numbers 1,5 & 6. I received no reading on numbers 2,3 & 4.

    I placed the unit back in the blower chamber with enough of the coils exposed so I could view them, turned the unit back on, turned out the lights and waited. The #1 coil glowed after about 15 seconds, right after I heard a few soft clicks. I gathered this was the sequencer. Several soft clicks and a minute or so later, #5 glowed. A few more clicks and nothing else came on. I expected #6 to do something but it didn't. I only had #1 & #5 glowing.

    A few minutes later, after a loud click, number one went out. After about 20 seconds and another loud click, it came back on. I gathered that the loud click was the high temp. limit switch. After a few more minutes, it went out and later back on. Eventually, the same thing happened to #5 but only once and it remained on until I flipped the breaker. With the unit back in the blower chamber, they remained on. I suspect that the coils weren't getting enough air from the blower chamber to cool them.

    I checked voltage across each the coils and it shows 240 for each. With the meter readings and the visual inspection, it would seem that I have four faulty coils. Am I right to think this or am I missing something else?

    Also, the entire coil setup looks like a complete unit. Can the idividual coils be restrung through the cube-shaped metal cage?

    Any thoughts are greatly apppreciated - it's getting down to about -4 F overnight these days and the dogs are anxious to be able to sleep in their own beds.
    Last edited by eduke; January 31st, 2004 at 10:43 AM. Reason: I did some more digging - dumb or brave? I'm not sure.

  4. #4

    Default

    Yes, there are kits to restring the resistance heat coils. You can buy the NiChrome wire, high temp splicers, and even the ceramic insulators if you need. They are available at national HVAC supply houses such as United Refrigeration, Johnstone Supply, Sid Harvey's, and R.E. Michaels.

  5. #5

    Smile Does my furnace's KW rating mean anything?

    Quote Originally Posted by mdshunk
    Yes, there are kits to restring the resistance heat coils. You can buy the NiChrome wire, high temp splicers, and even the ceramic insulators if you need. They are available at national HVAC supply houses such as United Refrigeration, Johnstone Supply, Sid Harvey's, and R.E. Michaels.
    Then it sounds like I've likely found the problem. Woohoo!

    I'll look into restringing the unit myself. The furnace is rated at 30.0 KW. Dose that mean each of the six coils is 5KW? I remember seeing coils for clothes dryers once and they were packaged by KW rating. I want to make sure I get the right things.

    Thanks

  6. #6

    Default

    Take the heating unit with you when you buy the repair kit or replacements. You are correct the elements are progressive. If each unit is a separte unit and not having to restring the elements but just move the separate units then you may be able to quickly move 5 and 6 over to 2 and 3 and get your heat up and running. If you have to restring do not do this the heating coils once they have operated are stiffened and probable breakage or that coil if trying to restring will happen.

    By the way your limit tripped because you had the cover off. The cover has to be closed to get the air flowing across the coils. Cover off blower blows into the room not across the coils.

    Let us know how you come out.

    Wg

  7. #7

    Default Looks like I'm on the way!

    Quote Originally Posted by Wgoodrich
    Take the heating unit with you when you buy the repair kit or replacements. You are correct the elements are progressive. If each unit is a separte unit and not having to restring the elements but just move the separate units then you may be able to quickly move 5 and 6 over to 2 and 3 and get your heat up and running. If you have to restring do not do this the heating coils once they have operated are stiffened and probable breakage or that coil if trying to restring will happen.

    By the way your limit tripped because you had the cover off. The cover has to be closed to get the air flowing across the coils. Cover off blower blows into the room not across the coils.

    Let us know how you come out.

    Wg
    Unfortunately, the coils aren't separate and I'll have to wait until I have the new coils installed before I have full heat. I'm going to go ahead and restring all six. Now I just need to find someone in town who sells the coils I need. I'll give you an update once I get things going again.

  8. #8

    Default

    Well if you are having trouble finding the repair kits for your elements you have one more chance for quick fix heat to your cold home. YOu should be able to move the wires connected to the burned out element of heater 2 to heater 6 and switch the wires from heater six to heater 2. This would give you one more bank of heat till you get the repair parts.

    Just trying to get you more heat till you can repair it right.

    Wg

  9. #9

    Smile

    Quote Originally Posted by Wgoodrich
    Well if you are having trouble finding the repair kits for your elements you have one more chance for quick fix heat to your cold home. YOu should be able to move the wires connected to the burned out element of heater 2 to heater 6 and switch the wires from heater six to heater 2. This would give you one more bank of heat till you get the repair parts.

    Just trying to get you more heat till you can repair it right.

    Wg

    That's a great idea. I really only need to switch the hot wires from the sequencers because the wires from the common side of the high limits all go to the same place - common post of the 240 power source, right?

  10. #10

    Default

    The heating elements are 220 volt not using a neutral wire. The control wiring stays the same. You move the two wires going to one element to the other element then again move those loose wires you removed from that element back to the empty element.

    Good Luck

    Wg

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