Disconnect Ampacity

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tshephard

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Installing electric heat FCU's. 424.3B says wire and breaker must be 125%. Have to install pullout disconnect (not fused) because breaker is out of sight. Actual load is 55 amps. Is 60 amp ($11) pullout ok (are all considered continuous?) or must I go to higher rating (125% also) which ends up as a 100 amp disconnect switch at over $100?
Thanks for the help.
Also, please check 480/277 multi-wire question.
 
Re: Disconnect Ampacity

I see the disconnect as being part of the branch circuit conductors, and the same rules would apply. Is the 60 amp version listed for 100% of its rated current? If so, you could apply the Exception to 210.19(A)(1), and use the 60 amp disconnect. Otherwise, I think you need the next higher size.

I am not completely confident that I have this one right. Any other opinions?
 
Re: Disconnect Ampacity

If I understand the ratings properly, the 55A is the rating before the 125%. If so, you will need a 70A breaker, conductors and disconnect.

If the load is 44A and at 125% = 55A, then the 60A breaker, conductors and disconnect is good!
 
Re: Disconnect Ampacity

Isolation only devices are 100% rated.

Disconnecting devices intended to make or break motor currents must be horsepower rated.

But, non-fusible pullouts are listed for use with a specific overcurrent protective device. For example, Milbank 60A not fusible air conditioning disconnects have the note: "... Suitable for use ... when protected ... 60A or less."
 
Re: Disconnect Ampacity

CB, manufacturer lady did not know if rating was continuous.
Bennie, my 2002 424.3b declares must be 125% for conductors and OPD. I'm reading the 424 "not less than" to override the 210 "shall be permitted". I'm guessing heating is assumed to often be continuous.
WS, 55 is the load before the 125%, so 70 A OPD & conductors. I thought maybe a 60 A pullout might be ok.
JD, first line sounded great, last line means I still don't know 'til I go look at it(pullout).

Thanks all!!
 
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