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#90434 - 11/22/04 07:04 AM Fused Disconnect Ahead of Main Breaker
mustangelectric Offline
Member

Registered: 02/08/04
Posts: 496
Loc: Bentonville, AR
Hi,
When is a Fused Disconnect on the outside of a building required? This is a fueling station (gas station) kiosk.

Power is from the xfmr pad to a meter base on the Kiosk then to the Disco. This is feeding a manufactured panelboard with a MBO panel and a MLO panel fed from the MBO panel. The equipment as a whole or an assembly itself is NOT UL listed, the components are. The MB is a 200A. Why would this breaker not be SE rated?

I am guessing that you need a FUSED disconnect to meet the AIC rating required for SE Equipment.

Is this a NEC issue or NFPA 30 issue?

I am asking this question because I am designing the electrical plans for the Kiosk and the assembly is not UL listed.

I am a Licensed Electrical Contractor and an Electrical Field Engineer looking for advice and or comments.

Thanks for any replies.

-regards

Mustang



[This message has been edited by mustangelectric (edited 11-22-2004).]
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#90435 - 11/22/04 06:35 PM Re: Fused Disconnect Ahead of Main Breaker
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
Your problem may be a lot deeper than the disconnect. Where did this come from and is your AHJ going to accept non-listed panelboards?
We are probably not where you should be asking this question.
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#90436 - 11/22/04 06:49 PM Re: Fused Disconnect Ahead of Main Breaker
mustangelectric Offline
Member

Registered: 02/08/04
Posts: 496
Loc: Bentonville, AR
Hi,
Thanks for the reply.

" Is a FUSED DISCONNECT REQUIRED OUTSIDE and AHEAD OF A MB?"

The answer is:

If the Assembly as a whole is NOT a UL listed assembly the first OCPD has to be SE rated, to meet the AIC rating a fused disconnect with a high AIC rating is required.

Is this part of the NEC?

The panelboards are CUTLER HAMMER AND SO IS THE MB..THE TOTAL ASSEMBLY IS NOT UL LISTED.

1000AMP

-regards

Mustang



[This message has been edited by mustangelectric (edited 11-22-2004).]
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#90437 - 11/22/04 07:25 PM Re: Fused Disconnect Ahead of Main Breaker
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
You have the answer. The service disconnect/OCD needs to be listed as service equipment and must be sufficient to operate under the available fault current. Do you have any engineering on the AFC?
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#90438 - 11/22/04 07:31 PM Re: Fused Disconnect Ahead of Main Breaker
caselec Offline
Member

Registered: 04/14/02
Posts: 557
Loc: San Jose, CA
Typically the only difference between a panel that is service entrance rated and one that is not is the service entrance rated panel has a main bonding jumper. The service entrance rating doesn’t relate to the AIC rating. Do you know what the fault current will be at the lugs on the main breaker? What is the AIC rating of the panel? If the available fault current is greater than the rating of the panel installing a fusible disconnect before the panel will not automatically make the lower rating of the panel acceptable. Are you saying that the panel with main breaker is not UL listed or the fusible disconnect and panel are not UL listed as a unit?

Curt
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#90439 - 11/22/04 08:13 PM Re: Fused Disconnect Ahead of Main Breaker
mustangelectric Offline
Member

Registered: 02/08/04
Posts: 496
Loc: Bentonville, AR
Hi,
Thanks for the replies. This can get hairy so try to hang with me..

I have an assembly that is a pre fabbed power distribution center built for my client who is a MAJOR retailer. The system contains two panels.. a 200A MBO and a 100A MLO the panels are in a larger cabinet that makes up a few other devices used to pump gas. The panel is mounted inside the KIOSK. On the outside of the building is a 200A fused CH disconnect that is SE rated. DO I NEED THIS DISCO PER THE NEC?

The PDC as an assembly has no UL listing as SE equipment.

The 200A CH OCPD is SE rated itself. THE AIC rating is HIGHER than the FAULT CURRENT so there is no need for SE rating as I understand it.

Since the PDC is not UL listed as SE equipment is this a NEC requirement that there must bea FUSED disconnect or other OCPD that IS?

I will have to look at the drawing to see what the values are for the Fault current and the AIC rating.

If the SE rating doesnt relate to the AFC then what does it relate to? AMPS INTERRUPTING CAPACITY correct? SE rated means the capability to withstand se amperages and the afc available fault current is tied to this..If there is a fault the equipment must withstand that amount of current for a certain period of time..right?

I will follow up with some values tomorrow.

Thanks for the very helpful replies.

-regards

Mustang

[This message has been edited by mustangelectric (edited 11-22-2004).]

[This message has been edited by mustangelectric (edited 11-22-2004).]
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#90440 - 11/22/04 10:23 PM Re: Fused Disconnect Ahead of Main Breaker
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
I'm just a dumb assed inspector. If it don't say "suitable for service equipment" or words to that effect, somewhere on the label, it ain't suitable for the service disconnect.
The alternative is to get something in writing from the manufacturer that says it is suitable for service equipment.
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#90441 - 11/23/04 07:28 AM Re: Fused Disconnect Ahead of Main Breaker
mustangelectric Offline
Member

Registered: 02/08/04
Posts: 496
Loc: Bentonville, AR
Hi,
Here are some values for the equipment we have been discussing:

AFC=14,800A

The disconnect is Series rated to 22,000A.

Maybe this will help.

I have sent an e-mail to the manufacturer of the panels to see what the requiremnt is for the fused disconnect ahead of the main ocpd. I will let you all know what they say. This could get interesting.

Thanks for the replies.

-regards

Mustang

[This message has been edited by mustangelectric (edited 11-23-2004).]
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#90442 - 11/23/04 12:34 PM Re: Fused Disconnect Ahead of Main Breaker
rmiell Offline
Member

Registered: 11/09/00
Posts: 261
Loc: La Junta, Co. USA
The requirement for the disco to be outside is regulated by the utility and/or fire district, and as such there should be an ordinance adopted as such.

The code requires a main disconnect either directly inside or outside of the building, leaving the exact location up to the installer.

In Colorado, we are required to have an outside disconnect if the length of SE conductors from the meter to the panel are greater than 5', which means a back-to-back installation. If you can't install it back-to-back, use a disconnect outside.

Don't forget, these conductors, without OC protection, are unfused, and therefore a possible source of fire. You can limit that hazard by installing a disconnect outside of the building.

Of course, this doesn't address the AIC ratings, which need to be looked at in every installation.

Rick Miell

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#90443 - 11/23/04 03:22 PM Re: Fused Disconnect Ahead of Main Breaker
mustangelectric Offline
Member

Registered: 02/08/04
Posts: 496
Loc: Bentonville, AR
Hi,
Thanks for the great replies. Very helpful..

Happy Thanksgiving everybody.

-regards

Mustang
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