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Thread: Multiple circuits in raceway without upsize

  1. #1
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    Multiple circuits in raceway without upsize

    Sorry to keep bugging you guys but I have another one for you. Tomorrow I have a job at a house that is going from a gas package system to a split electric heat pump. The panelboard does not have additional space (slam full 20/40 homeline) to add the 2 240v circuits for the e-heat and the booster heat. Currently there is a 40 amp circuit that feeds the package system and we need (according to the nameplate data) an outdoor 40 amp and indoor 30 and 60 amp circuits.

    My foreman's plan thus far:
    Use the spaces for the existing circuit, add a 100 amp breaker to a sub panel. Feed with #4. Install 60, 40 and 30 amp breakers to sub panel.

    Only 2 of the 3 circuits will be in use at one time.
    -If the heat pump fails, the e heat takes over, using the 60 and 30
    -In normal AC mode, the 40 is in use and the 30 should only have a few amps on it for the blower

    My question:
    All 3 circuits will be in the same 1-1/4" conduit. #8 for both 30 and 40 and #6 for the 60. Run is ~10 feet. Is this ok?
    -I would prefer to upsize each circuit one size and use either 1-1/2" or 2" conduit.
    -Again, not all 3 circuits will ever be used at the same time.
    -There really is not a way to use multiple raceways. (Stucco house)

    Again, sorry to keep bugging you guys. Im not all that code savvy but having that many circuits in one conduit just seems like a lot.

  2. #2
    Join Date
    Aug 2004
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    11,834
    you only have 4 CCC. If you are using 90C wire, you have plenty of derating available. even if all of them were on at the same time it is only 6 CCC, which would still work.
    Bob

  3. #3
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    Jul 2003
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    #4 is not big enough to feed the sub panel on a 100 amp breaker.
    If you are using NM to feed then it would need to be#2.
    If you are using a nipple or raceway and THHN then you need to use #3.
    Tim
    Master Electrician
    New England
    Yesterday's Technology at Tomorrow's Prices

    Answers based on 2011 NEC

  4. #4
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    Feb 2003
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    Alabama
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    Quote Originally Posted by stevephillips View Post
    add the 2 240v circuits for the e-heat and the booster heat. Currently there is a 40 amp circuit that feeds the package system and we need (according to the nameplate data) an outdoor 40 amp and indoor 30 and 60 amp circuits.

    My foreman's plan thus far:
    Use the spaces for the existing circuit, add a 100 amp breaker to a sub panel. Feed with #4. Install 60, 40 and 30 amp breakers to sub panel.

    Only 2 of the 3 circuits will be in use at one time.
    -If the heat pump fails, the e heat takes over, using the 60 and 30
    -In normal AC mode, the 40 is in use and the 30 should only have a few amps on it for the blower

    My question:
    All 3 circuits will be in the same 1-1/4" conduit. #8 for both 30 and 40 and #6 for the 60. Run is ~10 feet. Is this ok?
    -I would prefer to upsize each circuit one size and use either 1-1/2" or 2" conduit.
    -Again, not all 3 circuits will ever be used at the same time.
    -There really is not a way to use multiple raceways. (Stucco house)

    .
    You have 4 or more conductors so you will need to derate the conductor. My question is are there 4 or 6 conductors.
    You say that only 2 of the 3 ckts will be used at a time. Typical heat pump installation has the compressor running at the same time as the electric heat on very cold days. If so, then you derate using the 6 conductors. Big question. What size is the main panel? I hope 200 amps or more. Please give the FLA of the compressor and the kw of the heat package. Question is the 100 amp large enough?
    Posted after Bob and Tim.
    Last edited by bob; 07-29-12 at 05:53 PM.

  5. #5
    Join Date
    Dec 2006
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    Chapel Hill, NC
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    Quote Originally Posted by stevephillips View Post
    Sorry to keep bugging you guys but I have another one for you. Tomorrow I have a job at a house that is going from a gas package system to a split electric heat pump. The panelboard does not have additional space (slam full 20/40 homeline) to add the 2 240v circuits for the e-heat and the booster heat. Currently there is a 40 amp circuit that feeds the package system and we need (according to the nameplate data) an outdoor 40 amp and indoor 30 and 60 amp circuits.

    My foreman's plan thus far:
    Use the spaces for the existing circuit, add a 100 amp breaker to a sub panel. Feed with #4. Install 60, 40 and 30 amp breakers to sub panel.

    Only 2 of the 3 circuits will be in use at one time.
    -If the heat pump fails, the e heat takes over, using the 60 and 30
    -In normal AC mode, the 40 is in use and the 30 should only have a few amps on it for the blower

    My question:
    All 3 circuits will be in the same 1-1/4" conduit. #8 for both 30 and 40 and #6 for the 60. Run is ~10 feet. Is this ok?
    -I would prefer to upsize each circuit one size and use either 1-1/2" or 2" conduit.
    -Again, not all 3 circuits will ever be used at the same time.
    -There really is not a way to use multiple raceways. (Stucco house)

    Again, sorry to keep bugging you guys. Im not all that code savvy but having that many circuits in one conduit just seems like a lot.
    I am very confused. The blower will run on the circuits that are provided for the heat. I have never seen a unit require 3 circuits. One for the outside heat pump and either one or two for the heat strips and motor. Somehow you have 4 circuits.

  6. #6
    Join Date
    Jul 2012
    Location
    knoxville tn
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    46
    Bob,
    Main is 200 amp.

    According to nameplate data @240V:
    FLA of comp = 18 amps
    E Heat amps = 45 amps
    Boost amps = 20 amps

    tkb,
    The #4 to the sub was a type, its going to be #2. All wire is THHN.

    Dennis,
    There are only 3 circuits.
    60 amp Inside E Heat coils
    30 amp Inside booster coils, condensate pump, blower, and control system
    40 amp Outside compressor unit

    Possible modes:
    Normal cooling - 40 amp running the compressor and 30 amp running condensate pump, blower, and control system.
    Normal heating - 40 amp running the compressor and 30 amp running condensate pump, blower, and control system.
    Heating when very cold - 40 amp running the compressor and 30 amp running condensate pump, blower, control system and boost coils.
    Heating with failed compressor - 60 amp running E Heat coils and 30 amp running booster coils, condensate pump, blower, and control system.

  7. #7
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    Dec 2006
    Location
    Chapel Hill, NC
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    My confusion was that the existing a/c wire is there and that 3 circuits were being pull in the conduit. If the conductors are 90C rated in conduit and the service can handle the load then you should be fine as the de-rating should not affect it when using 90C wire in this scenario.

  8. #8
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    Olathe, Kansas 338 mi SE of Wingedhorses
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    I would put the new A/C load along with E Heat in the existing panel, then you could use

    smaller wire to feed the sub panel which would have lighting & recptacle loads.
    Electricity is Color Blind
    Leave the shirt pocket rules in your pocket.

  9. #9
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    Jul 2012
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    knoxville tn
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    Quote Originally Posted by John120/240 View Post
    I would put the new A/C load along with E Heat in the existing panel, then you could use

    smaller wire to feed the sub panel which would have lighting & recptacle loads.
    Thats what I wanted to do but the HO would rather have all the HVAC stuff on the sub panel.

  10. #10
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    Apr 2009
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    Olathe, Kansas 338 mi SE of Wingedhorses
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    Quote Originally Posted by John120/240 View Post
    I would put the new A/C load along with E Heat in the existing panel, then you could use

    smaller wire to feed the sub panel which would have lighting & recptacle loads.
    Quote Originally Posted by stevephillips View Post
    Thats what I wanted to do but the HO would rather have all the HVAC stuff on the sub panel.
    Either set up will likely give satisfactory performance. It is the electricians job to state the

    benifits of this way as opposed to that way. Cost, realiabilty, ease of installation etc
    Electricity is Color Blind
    Leave the shirt pocket rules in your pocket.

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