[RE-wrenches] Supply Side Tap Overcurrent Protection

[August Goers]

Hi All,

I think it is clear that a fused disconnect is required next to the service tap. But I have one other thought.

When we install line side taps we always run the wire between the disconnect and service panel in rigid conduit and bond both sides of the conduit just like we would do with service wires. This is a requirement in San Francisco and come to think of it I haven't looked deep enough into the code to see if it is an actual NEC requirement or not. Thoughts?

-August

August Goers


Luminalt Energy Corporation
O: 415.564.7652
M: 415.559.1525
F: 650.244.9167
www.luminalt.com<http://www.luminalt.com/>

________________________________
From: re-wrenches-bounces at lists.re-wrenches.org [re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Bill Brooks [billbrooks7 at yahoo.com]
Sent: Sunday, March 28, 2010 10:04 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Supply Side Tap Overcurrent Protection

Dave,

All line side connections must have overcurrent protection (230.91) at the disconnecting means. Article 230.70 through 230.95 is what generally governs these connections. Without rewriting John Wiles’ articles on this subject, here are a few quick pointers.

The basic rule to remember, since you don’t have your code book, is to install a disconnecting means with overcurrent protection adjacent to the existing service. No specific distance is given, but the implication, and the field experience is as close as physically possible to the existing service disconnecting means. Circuit breakers or fused disconnects are allowed if they are listed as service equipment. Fused disconnects are used more often than circuit breakers since many utilities require a visible-break switch.

To give Xantrex the benefit of the doubt, their manual probably was not intended to address line side connections. If it is intended to cover these, there statement may be accepted by some jurisdictions, but it quite unlikely that a jurisdiction would ever allow it. To have line side conductors, with no disconnecting means, installed into a PV inverter wiring center just doesn’t make sense. Always install a service disconnect with overcurrent protection on every connection to service conductors—that seems like a logical and simple rule that can never go wrong.

Bill.

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Dave Palumbo
Sent: Sunday, March 28, 2010 10:53 AM
To: 'Wrench List'
Subject: Re: [RE-wrenches] Supply Side Tap Overcurrent Protection

Wrenches,

I am tasked with reviewing an installation by a licensed electrician in Vermont and would like help with the following:

Grid-tied PV system with battery back-up. AC point of connection is a supply side tap (done on customer side of utility meter ) then traveling 5 feet of #2 THHWN in 1” EMT to the 60 Amp 240vac Lockable Utility Disconnect (unfused) and continuing 15 feet #2 THHWN 1” EMT to Xantrex XW 60 Amp breaker.

I had said that the 60amp 240vac lockable disconnect needed to be fused, and received the following reply from the installing electrician.

<< “The Xantrex XW Power Distribution Panel contains the required over current protection (60 amp
double pole circuit breaker) negating the need for a redundant fuse at the Utility Disconnect switch.” >>

I am on a short trip in Florida and away from my code books. Can someone provide guidance and code reference please? I am concerned about the 20 foot distance of the un-protected circuit from the supply side tap and also the interrupt rating of the 60 Amp breaker in the Xantrex distribution panel.

David Palumbo
Independent Power LLC
Offices in Lamoille and the Champlain Valley
802.888.7194
www.independentpowerllc.com

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