Tapping the Buss on a Substation

[steve66]

A client has an old Federal Pacific Substation: 4160 V primary, 208V secondary, 225 KVA.

The substation has an integral distribution panel (Federal Pacific again) with a 600 Amp main, and about 8 breakers.

The client would like to add more load to this substation, but the problem is the distribution panel is already full of 100 amp and 150A amp breakers.

Normally, I'd install a larger breaker and move some of the smaller feeds to a sub-distribution panel. But since its Federal Pacific, I can't get any new breakers for this substation.

Is it legal to tap the bus (load side of the main breaker) and run a feed to a new distribution panel? I can set a fused disconnect if necessary to comply with the tap rules, but I'm actually thinking about running full sized wire (600A) wire to the new panel.

This substation is in a school's corridor, so I want to make sure whatever I spec. is allowed.

Steve

 

[SteamDonkey]

Hi Steve, did you ever find an official answer to this? I was faced with the same predicament and my response was that a field installed tap would violate the listing of the equipment.

 

[zog]

What breaker do you need?

 

[mull982]

I do not see a problem with this as long as you follow the tap rules and located a fused disconnect switch within the proper distance from the tap as dictated by the tap rule. Feeders to sub-panl must also follow size requirement dictated by tap rule.

 

[mcclary's electrical]

I never saw thi spost until today. Not sure how.

But anyway, there are many dealers of old breakers.There is one here in Richmond that can get about anything you need

 

[dkidd]

From the UL White Book:

16. FIELD INSTALLATION OF DEVICES
The UL Mark applies to the switchboard as it is originally manufactured when shipped from the factory. Authorized use of the UL Mark is the manufacturer?s declaration that the switchboard was originally manufactured in accordance with the applicable requirements. UL does not know what the effect of a modification may have on the safety of the switchboard or the continued
validity of the UL certification mark unless the field modification(s) have been specifically investigated by UL. Unless UL investigates a modified switchboard, UL cannot indicate that the switchboard continues to meet UL?s safety requirements.
The only exception for a field modification authorized by UL is when the switchboard has specific markings regarding field-installation of equipment. A switchboard enclosure or section intended to accommodate a field installed device is marked to indicate the manufacturer and the catalog number or equivalent of the device to be installed.
Additions to switchboards not marked for the field installation of such devices can be investigated under UL?s Field Evaluation Service or Field Inspection Service.

Also, look at

http://www.ul.com/global/eng/pages/...ctrical/fieldcertification/fieldmodification/

which says the AHJ can make a determination. Otherwise, unless you find a spot on the bus labeled "tap", you can't.

Been there.