Airhandler

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silverromex

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I saw in an airhandler today where the previous "electrician" had run a 4/2 romex to an airhandler that had a 15Kw heat strip in it. The airhandler had a 2 pole 60A and a 2 pole 30A breaker in it with the #4 wire landed at the 60A breaker. Then they had taken a #10 wire and used it to jumper the 2 breakers together. How many code rules do you think were violated? Thanks.


"If we used silver romex we could cut the worlds electric use by 33.333333%"

[ August 26, 2004, 03:43 PM: Message edited by: silverromex ]
 
Re: Airhandler

There is no answer to this one.
There's not enough information. What's the voltage? What's the HP of the airhandler? What type of construction? What type of insulation is on the wire?
 
Re: Airhandler

Originally posted by jerryb:
There is no answer to this one.
There's not enough information. What's the voltage? What's the HP of the airhandler? What type of construction? What type of insulation is on the wire?
Click to expand...
240V, 1/3 HP, single familly dweling, THHN.
 
Re: Airhandler

The key is the listed max breaker required.A 10 kw ahu electric strip requires a 60 but to use 6/2 nm is a violation.Use 6/2 se and its allowed.The ampacity has to come from the correct table.
 
Re: Airhandler

Allen, why do you say 6/2 nm can't be protected at 60 amps? See 240.6

Roger
 
Re: Airhandler

Roger
Doesnt NM have to be protected at it's 60?C ampacity which for No. 6 is 55A? Where is it permitted to go up from 50A to 60A?

[ August 26, 2004, 09:07 PM: Message edited by: electricman2 ]
 
Re: Airhandler

Hello John, My earlier post was a little incomplete I guess, as a companion to 240.6 I should have pointed out 240.4(B).

With the 60 deg column allowing 55 amps which is not a standard size breaker, we would be permitted to go to a 60 amp breaker.

Roger
 
Re: Airhandler

Right. In this case all 3 conditions of 240.4(B) are met. Condition (1) would not allow it for ordinary muli-outlet branch circuits.
 
Re: Airhandler

Silverromex, there's a problem with the factory 60 amp breaker and the 15kw heat strip if we are talking single phase 240 volts. Are you sure this is the case?

As far as the #10 jumper between the breakers, probably fine as well as the 4/2 NM feeder.

Now, please answer this question, what formula are you using to come up with silver providing a 33.33333% reduction of the worlds electic use?

Roger

[ August 26, 2004, 09:51 PM: Message edited by: roger ]
 
Re: Airhandler

Roger, the A.H. is indeed a 240V single phase unit. One 10Kw heat strip is protected by a 60A breaker and the 5Kw heat strip is protected by a 30A breaker. I didnt know you could run 1 circuit that would have the ampacity to supply power to 2 different breakers/heat strips. I allways ran a 6/2 and a 10/2 romex to feed the 60 and 30 amp breakers, but If I can get away with just pulling 1 romex to the unit instaed of 2 then I like that idea. The breaker isnt listed for 2 conductors under its terminals so I fail to see how the #10 jumper is code compliant.
As for the silver romex I actually dont have a formula, but I read that silver is THE best conductor of electricity because of its molecular structure so this got me to thinking what would be the savings (if any) of wiring a house with silver romex?

[ August 26, 2004, 10:18 PM: Message edited by: silverromex ]
 
Re: Airhandler

With the 60 deg column allowing 55 amps which is not a standard size breaker, we would be permitted to go to a 60 amp breaker.

Roger that would be overfusing the wire that is rated at 55 amps.IMO and the AHJ here has tagged finals for just that use of 6-2 nm when max breaker size listed is 60 amps.had to remove the NM and to to 6 se.
 
Re: Airhandler

Allen,
Roger that would be overfusing the wire that is rated at 55 amps.IMO and the AHJ here has tagged finals for just that use of 6-2 nm when max breaker size listed is 60 amps.had to remove the NM and to to 6 se.
Click to expand...
your inspector was wrong and cost you money.

Did you read 240.4(B) and 240.6?

As long as the calculated load does not exceed the conductors ampacity, 240.4(B) and 240.6 allow the 60 amp breaker.

Silverromex, I should have said it before, Welcome to the forum.

If the breaker isn't listed for the multi conductors, then you are right that this is a violation. You could still use a terminal strip or some means to land the #4 (or the proper sized conductor) and tap to both breakers from here.

On commercial projects where the heat strips are not part of a factory AHU, we do virtually the same thing by running one feeder to a 6 circuit panel mounted on the duct or close to it, and distribute the loads from two breakers here.

Silver is a good conductor, but man would it be expensive to buy ;)

Roger

[ August 27, 2004, 06:22 AM: Message edited by: roger ]
 
Re: Airhandler

Allen, 240.4(B) Devices Rated 800 Amps or Less. The Next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following are met:[/b] I'll let you read the rest from a code book.

If you still want to believe protecting 6/2 NM at 60 amps is a violation then thats your prerogative.

Roger
 
Re: Airhandler

Roger thanks for the lesson,You gave me some ammo.I was using the degree table and as you have shown these articles allows 6/2 nm.on a 60a brkr. I can`t wait to bring this up to the AHJ here.BTW
we have a code thing going on glad I found this site a few years ago ;)
 
Re: Airhandler

Allen, you're welcome.
icon14.gif


Roger
 
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