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  1. #14
    Join Date
    Jul 2004
    Location
    Kent, WA
    Posts
    129
    Originally posted by rsmith46
    This is wrong, the 90*c column you looked that up in is to be used for deration corrections only. You can't go over the termination rating, which would be 75*c. But under 100 amps you have to use the 60*c column which is 70amps for #4 copper. That #4 from the main panel can only be protected by a 70amp breaker, and that's before you allow for voltage drop.
    You don't have to use the 60C column if the terminals are explicity rated at 75C, and most are now days. So you can have an 85A circuit with a 90A breaker if necessary. But there are many issues here we can't answer:

    Is this a branch circuit that has been tapped 60A and 30A? Or is it a feeder with feeder taps or a subpanel? What size breaker was used at the source of the #4 wire and was it sized for 125% of the heater load + the 125% of the fan load?

    If there is a junction box where the #4 has been tapped into two smaller wires (such as a #6 and a #10), I don't believe this is legal as you can't tap a branch circuit (only a feeder). But doing this tap inside the air handler right at the breaker may be legal if the instructions say you can do that.

    Many air handlers come with two ways of connecting them -- a lug for a huge circuit that is split inside the air handler to different heating elements or stages (usually a big lug bar that mounts into both breakers like a wire), or two separate branch circuits that terminate onto two breakers or switches in the airhandler one for each heating element or stage. If the instructions allow both methods, then this may be OK. Some others are quite picky and demand one way or the other. The key here is how the manufacturer listed the electrical section of the equipment, and you can only connect it via the way(s) it was listed.

  2. #15
    Join Date
    Jul 2000
    Location
    Louisiana , USA
    Posts
    3,280
    This is Turtle.

    Here is a view here.

    Two circuits as you stated with a 30 + a 60 amp breaker and two completely different circuits for the Air handler unit. [ The Best Way !

    1 -- # 4 circuit run to the outside of the furnace and then joined by a subpanal to have a 30 amp and a 60 amp breaker in the subpanal to run each a circuit to the Air handler. [ This is a very good way ! ]

    1 -- #4 circuit run to the air handler then double jump from one breasker to the other inside with the #4 wire tieing to each of the two breakers in the air handler. [ awwww well OK but just not as good as the others. ]

    1 -- # 4 circuit run to the outside of the air handler and then go into a gang box and then come out with a 30 amp circuit and a another 60 amp circuit going out of the gang box and not going through a 30 and a 60 amp breaker of any kind before going on to the air handler. You have now #10 wire hooked up to a 70 amp breaker which you could then put 70 amps on a #10 wire and burn the place down before the breaker will trip. [ You just broke the NEC Code for the sizing of wire verses the breaker size. ] You don't do that.

    TURTLE

  3. #16
    Join Date
    May 2001
    Location
    Kansas City
    Posts
    2,729
    Originally posted by suemarkp

    You don't have to use the 60C column if the terminals are explicity rated at 75C, and most are now days. So you can have an 85A circuit with a 90A breaker if necessary. But there are many issues here we can't answer:
    [/B]
    No you have to use 60C column under 100amps.
    Article 110.14 C 1a
    When making terminations of 100amps or less you are limited to using conductors rated 60C.
    70 amp breaker for #4
    And the 125% rule doesn't apply since this isn't a continous load.

    Turtle has it right. That's why he's Turtle.

    [Edited by rsmith46 on 02-21-2006 at 12:53 AM]

  4. #17
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    67,913
    Originally posted by rsmith46
    Originally posted by suemarkp

    You don't have to use the 60C column if the terminals are explicity rated at 75C, and most are now days. So you can have an 85A circuit with a 90A breaker if necessary. But there are many issues here we can't answer:
    No you have to use 60C column under 100amps.
    Article 110.14 C 1a
    When making terminations of 100amps or less you are limited to using conductors rated 60C.
    70 amp breaker for #4
    And the 125% rule doesn't apply since this isn't a continous load.

    Turtle has it right. That's why he's Turtle.

    [Edited by rsmith46 on 02-21-2006 at 12:53 AM] [/B]

    Since when are strip heaters not concidered a continuos load?
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  5. #18
    Join Date
    Feb 2003
    Location
    Huntsville,AL
    Posts
    4,125
    continuous load = one running for =>3h, unless the current NEC has changed that --

    overcurrent devices are rated at 80% for continuous load, so a 70a breaker should not have more than 56a! -- one gets the same results by 125% FLA.
    harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!

  6. #19
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,739
    Originally posted by hvac hero
    IMO its a new house, so the hvac guy is responsible for installing the system & the electrician is responsible for powering it. I dont see where the hvac guy has a right to tell the electrician how to power the units. If I was the electrician, I'd be tellin the hvac installer to just concentrate on his own stuff & quit meddlin in mine.


    if it is equipment being installed and warranted by me.it will be protected the way i want it or it will not be started up.

  7. #20
    Join Date
    Feb 2005
    Location
    Dothan, Al
    Posts
    3,453
    The way the electrician has it wired is not illegal as long as the #6 wire terminates on a 60 amp breaker and the #10 wire terminates on a 30 amp ( or less ) breaker, and the pigtails are not over 25ft. This is legal per the NEC. I would have no problem with this set up though I personally would use an 80 amp breaker for the #4 wire. I have ran many 15kw heaters on a 70 amp breaker with no problem - ever. It is not the perfect way, but it is code legal.

    Richard

  8. #21
    Join Date
    Jul 2004
    Location
    midwest
    Posts
    2,868
    Originally posted by bornriding
    The way the electrician has it wired is not illegal as long as the #6 wire terminates on a 60 amp breaker and the #10 wire terminates on a 30 amp ( or less ) breaker, and the pigtails are not over 25ft. This is legal per the NEC. I would have no problem with this set up though I personally would use an 80 amp breaker for the #4 wire. I have ran many 15kw heaters on a 70 amp breaker with no problem - ever. It is not the perfect way, but it is code legal.

    Richard
    I am not going to look it up but you will not find any #10 wire I ran fused at 80 amps. This includes even 1 foot of wire.

  9. #22
    Join Date
    May 2001
    Location
    Kansas City
    Posts
    2,729
    Originally posted by beenthere
    Originally posted by rsmith46
    Originally posted by suemarkp

    You don't have to use the 60C column if the terminals are explicity rated at 75C, and most are now days. So you can have an 85A circuit with a 90A breaker if necessary. But there are many issues here we can't answer:
    No you have to use 60C column under 100amps.
    Article 110.14 C 1a
    When making terminations of 100amps or less you are limited to using conductors rated 60C.
    70 amp breaker for #4
    And the 125% rule doesn't apply since this isn't a continous load.

    Turtle has it right. That's why he's Turtle.

    [Edited by rsmith46 on 02-21-2006 at 12:53 AM]

    Since when are strip heaters not concidered a continuos load? [/B]
    Since when is central electric space heating considered a continuous load by the NEC? Check 230.20 C and you'll see why the NEC doesn't consider the heat strips to be continuous.

    If your running all 3 strips more than 3 hours straight I think you need more.

  10. #23
    Join Date
    Nov 2005
    Location
    Shreveport, Louisiana
    Posts
    2,329
    Originally posted by trane
    Originally posted by bornriding
    The way the electrician has it wired is not illegal as long as the #6 wire terminates on a 60 amp breaker and the #10 wire terminates on a 30 amp ( or less ) breaker, and the pigtails are not over 25ft. This is legal per the NEC. I would have no problem with this set up though I personally would use an 80 amp breaker for the #4 wire. I have ran many 15kw heaters on a 70 amp breaker with no problem - ever. It is not the perfect way, but it is code legal.

    Richard
    I am not going to look it up but you will not find any #10 wire I ran fused at 80 amps. This includes even 1 foot of wire.
    I do not see in the above quotes were anyone says that a #10 wire is fused with an 80 amps breaker.

  11. #24
    Join Date
    Jun 2003
    Location
    Florida
    Posts
    9,548
    Originally posted by bornriding
    The way the electrician has it wired is not illegal as long as the #6 wire terminates on a 60 amp breaker and the #10 wire terminates on a 30 amp ( or less ) breaker, and the pigtails are not over 25ft. This is legal per the NEC. I would have no problem with this set up though I personally would use an 80 amp breaker for the #4 wire. I have ran many 15kw heaters on a 70 amp breaker with no problem - ever. It is not the perfect way, but it is code legal.

    Richard

    I agree with you, but question the legality on a 70 amp breaker.At 240 volts, you're at 62.5 amps on the heatstrips,plus fan amperage. I know this is actually lower as a 15kw is really less,the combination of two strips.But if you size the breaker at 70,yes it will work,but is it legal per code,which I believe is 125% of circuit rating.
    If everything was always done "by the book"....the book would never change.

  12. #25
    Join Date
    May 2001
    Location
    Kansas City
    Posts
    2,729
    Central electric space heating is not considered a continuous load by the NEC. Check 230.20 C and you'll see why the NEC doesn't consider the heat strips to be continuous. So you don't apply the 125% overcurent protection rule.

    You need a 70amp breaker for the #4 going to a subpanel. The #4 needs to be 4 conductor as its feeding a subpanel.
    The subpanel needs 30amp and 60amp breakers for the #10 & #6 wires going to the heat strips.
    Go ask Wolfdog.

    Bornriding, its not cord and plug connected so the NM going to the air handler can be over 25'.

  13. #26
    Join Date
    Jul 2004
    Location
    midwest
    Posts
    2,868
    Originally posted by berg2666
    Originally posted by trane
    Originally posted by bornriding
    The way the electrician has it wired is not illegal as long as the #6 wire terminates on a 60 amp breaker and the #10 wire terminates on a 30 amp ( or less ) breaker, and the pigtails are not over 25ft. This is legal per the NEC. I would have no problem with this set up though I personally would use an 80 amp breaker for the #4 wire. I have ran many 15kw heaters on a 70 amp breaker with no problem - ever. It is not the perfect way, but it is code legal.

    Richard
    I am not going to look it up but you will not find any #10 wire I ran fused at 80 amps. This includes even 1 foot of wire.
    I do not see in the above quotes were anyone says that a #10 wire is fused with an 80 amps breaker.
    Read it again
    It says terminates at a 30 amp breaker

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