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#96038 - 11/01/05 09:59 AM 380-2(b) Disconnect  
rad74ss  Offline
Member
Joined: Apr 2004
Posts: 156
Pryor, OK USA
I have a job where the heat trace cable for some water piping and a convenience outlet have a seperate disconnect from the rest of the HVAC unit.

It is 115VAC running from the residence on a 20 amp circuit. This enters our disconnect which is a 230VAC 30A non fused disconnect. From the bottom of this disconnect the conductors run to a terminal block and then split off into two circuits. One for the heat and one for the outlet. Each is individually fused.

The question I have is whether I should open only the ungrounded conductor per 380-2(b), or open both per the exception to that rule? Both conductors if ran through the two poles of the disconnect would be broken at the same time.

I am a proponent of breaking both lines since the heat tape is wrapped around water lines (3" copper, or black steel at the pumps), but others at my company do not think the exception should apply.

I would appreciate any knowledge that could be offered.


2017 / 2014 NEC & Related Books and Study Guides

#96039 - 11/01/05 11:05 AM Re: 380-2(b) Disconnect  
raider1  Offline
Member
Joined: Jul 2005
Posts: 46
north logan, utah, US
If you simultaneously disconnect the ungrounded and the grounded conductors of the circuit then you can use the exception to 380-2(b)

There is nothing wrong with this pratice if done according to the NEC.

Chris


#96040 - 11/04/05 09:15 AM Re: 380-2(b) Disconnect  
rad74ss  Offline
Member
Joined: Apr 2004
Posts: 156
Pryor, OK USA
Here is the current state of this pickle. Article 424 states that disconnects shall disconnect all ungrounded conductors.

I think that is the minimum for safe operation. Per the article on switches if you can break all leads simultaneously that is acceptable.

I like the idea of having no electrical connection to the pipe when changing a pump out.

Does 380-2(b) supplement article 424 or should 424 be the sole condideration when dealing with heating cable?

Any ideas? Am I missing an obscure code article that would nail this down?


#96041 - 11/04/05 11:07 AM Re: 380-2(b) Disconnect  
raider1  Offline
Member
Joined: Jul 2005
Posts: 46
north logan, utah, US
You need to use section 426-Fixed Outdoor Electric Deicing and Snow-melting Equipment, instead of 424, that is for space heating equipment.

420-50 (a) of the 99 NEC talks about the disconnect for tracer cable. This section talks about switches being used for the disconnect. So if you use a switch, then 380-2(b) can be used.

I am assumming you are using the 99 code?

Anyway I hope this helps. [Linked Image]

Chris


#96042 - 11/05/05 06:22 AM Re: 380-2(b) Disconnect  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
radSS, I agree that what you propose is perfectly code compliant.

Regardless of what you are installing the code requires a disconnect that "shall" disconnect all the ungrounded conductors, that in no way prevents you from disconnecting all the conductors at the same time.

As a matter of fact the disconnection of the grounded conductor is actually required when dealing with fuel pumps. 2002 514.11(A)

In your case I do not see the need to disconnect the grounded conductor but you certainly can if you want.

If this heat trace was cord and plug connected the grounded and grounding conductors are all disconnected simultaneously, doing the same with a switch is fine.

Bob


Bob Badger
Construction & Maintenance Electrician
Massachusetts


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