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  1. #1
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    Staging/Operation of electric heat strips

    I have a 15 kw electric heat strip kit (HKR-15C) in my Goodman air handler (ARUF374316).

    The Product Specs for the heat kit notes "Sequencers for better temperature control". What are sequencers and what does this mean?

    The Product Specs also state "Control circuitry arranged to readily permit staging". I'm assuming that the staging is a function of the t-stat and it has to be capable of calling for staged aux heat. Yes/No?

    I have been taking temps in the air handler with a Fluke meter w/thermocouple wire to check heat pump output temps on days of different outdoor temps. I have noticed that, when aux heat is called because I am bumping up the t-stat, sometimes I'll get a reading of 117F and sometimes I'll read 130F. The 117 makes sense - 93F heat pump air temp plus 24F from the 10 kw aux heat strips. The 130F would be the heat pump plus all 3 strips (15kw). My t-stat is a Honeywell 7500 (not a VisionPro). Is it staging the aux heat by going from 10 kw to 15 kw based on setpoint temp versus room temp?

    I always thought, in a 15kw electric heat kit, that 10 kw was for auxillary (or defrost cycle) and 15 kw was for emergency heat.

    Please educate me.

    Thanx.

  2. #2
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    What you have is two sets of heatstrips, a 10kw and a 5kw(not exactly, more like 14.6 kw combined). How they come on is all dependent on the control wiring. They might be wired through one control, when the stat calls for aux heat the first bank energises, then a delay before the second bank comes on. The emergency and auxilary are the same sets of heatstrips, although they can be wired in a variety of different ways, including use of outdoor t-stats. Sequencers are a high voltage time delay that delays the voltage being sent heatstrips, so that they are staged(first bank on,delay, second bank).
    If everything was always done "by the book"....the book would never change.

  3. #3
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    Thank you for replying, smokin'.

    I understand that the heat strips are used in both a call for aux heat as well as running in emerg heat.

    My question is will I get all 15kw (all 3 strips) energized on a call for aux as well as running in emerg heat (there is no special wiring to the t-stat and no outdoor sensor)?

    They are wired for one 10kw and one 5 kw bank - what does this do for me?

    Are there any conditiions that only 10 kw will be energized and not all 15 kw?

    I always thought I got only 10 kw on aux and the full 15 kw on emerg heat. I think I'm wrong on this but I'd have to meter it to be sure.

    Take care.

  4. #4
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    Nov 2007
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    Sequencers are a high voltage time delay that delays the voltage being sent heat strips, so that they are staged(first bank on,delay, second bank).[/QUOTE]


    Most 15KW heaters consist of 3 5KW elements each with its own contactor
    (actuation relay). The 15's are usually wired in two separate HV circuits: as a 10KW with a 60AMP BRKR (which usually turns on first and includes the blower amperage), and a 5KW with a 30AMP BRKR (which usually turns on second) to give the full Monty of resistance heat. I have never understood the logic or desirability of having 10KW on first (seems very uneconomical) but I am very interested in knowing if there is a way to effectively stage the bank of 2 two 5's with a sequencing delay. Are there Hi-Tec Stats that can do this?

  5. #5
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    Quote Originally Posted by gary_g View Post
    Thank you for replying, smokin'.

    I understand that the heat strips are used in both a call for aux heat as well as running in emerg heat.

    My question is will I get all 15kw (all 3 strips) energized on a call for aux as well as running in emerg heat (there is no special wiring to the t-stat and no outdoor sensor)?

    They are wired for one 10kw and one 5 kw bank - what does this do for me?

    Are there any conditiions that only 10 kw will be energized and not all 15 kw?

    I always thought I got only 10 kw on aux and the full 15 kw on emerg heat. I think I'm wrong on this but I'd have to meter it to be sure.

    Take care.

    Without seeing the wiring, I can't answer your question. Like I said, there are many different ways to wire them, usually (from what I've seen) if you have 15 kw heatstrips, it's 15 kw for all applications (aux,defrost,emergency). However, you can wire them up different and add controls to do certain things(like only 5kw during defrost).
    If everything was always done "by the book"....the book would never change.

  6. #6
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    OK - thanx.

    I have a call into Goodman to get a copy of the wiring diagram for the air handler and heat strip kit combination. The wiring diagram is on a large sticker inside the air handler on a shelf so it's tough to read.

    I have no problem with aux heat and I think I am getting all 15 kw like was stated.

    When I switch from heat pump to emerg heat, I think I get all 15 kw but it shuts of prematurely before the t-stat setpoint. If a bump it up more than 2 degrees, aux heat runs the same strips to setpoint. I have to look into this a little further. Not sure what's going on, if there is a time delay somewhere when running in emerg heat.

    Take care.

  7. #7
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    From making temperature measurements of the air after the air handler, looks like I am getting all 15kw on a call for aux heat (measured 113F = 70 room + 43 from strips).

    When I switch to emergency heat, the t-stat is calling for heat (the blower fan runs and the t-stat says "heat"), but the strips are not being energized. If I bump the setpoint up by more than 2 degrees while in emerg, the strips come on, but then cycle off once setpoint vs actual is less than 2 degrees.

    There is no special wiring. The strip heat kit came with a plug that is connected to a mating plug in the air handler.

    The t-stat is wired correctly. I have to check for loose wires or maybe a bad relay. Not sure why aux works but emerg doesn't if they are the same strips for both functions.

  8. #8
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    Your t stat is not wired correctly.
    If it was, when you switched it to emergency, the heat would stay on until set point was reached.
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  9. #9
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    There are 2 separate wires at the stat for aux and emerg. W2 (white wire) goes to aux terminal, E (black wire) goes to E terminal. I will check them out more thoroughly.

    Thanx.

  10. #10
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    Its a common mistake to think of it the way you are.

    Also, your stat doesn't have the ability to control 2 stages of electric strip when it is used as a heat pump stat.

    I'm not allowed to tell you what is not wired right.
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  11. #11
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    BeenThere:

    Thank you for taking the time to reply to my post.

    I re-checked the t-stat wiring and reviewed the Honeywell install manual and it is wired correctly. There is a note stating to wire the Aux and E terminals together if there are not separate Aux and E wires.

    I looked inside the air handler and found my problem. There are 3 low voltage wires and 2 high voltage wires tied together with a wire nut. The black (emerg) wire had worked loose and was not making a connection. I re-connected the wires using a larger wire nut and everthing is now kosher.

    Take care.

  12. #12
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    See if it still shuts off 2* before set point.
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  13. #13
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    Quote Originally Posted by beenthere View Post
    See if it still shuts off 2* before set point.
    Good to go - it runs to setpoint. The reason it was turning off 2 degrees before setpoint was that the aux was kicking off and the emerg wire was not connected.

    Thanx for your input.

    Happy New Year to you and yours.

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