[RE-wrenches] backfeeding "six disconnect" panel

Mon Nov 1 22:01:07 PDT 2010

Dana,
I'll echo Scott's earlier comment: connecting to an empty 'main' breaker
position that is on the top bus will be a supply-side connection. From Code
Corner #126:
*
*
*Some dwellings have main-lug-only panels. There is no *
*single main breaker feeding the panel, but up to six main *
*breakers are allowed. Empty breaker positions can be used *
*as supply-side connections. The basic restriction (which *
*will be in the  2011 NEC) that would apply to this type *
*of main service panel is that the sum of the overcurrent *
*devices from the PV inverter(s) should not exceed the *
*rating of the panel bus bar or the rating of the service *
*entrance cables.*

-Phil Boutelle
Real Goods Solar

On Mon, Nov 1, 2010 at 6:55 PM, Dana Brandt <dana at ecotechenergy.com> wrote:

> Hi everyone,
>
> I just noticed my last email didn't go through because I'd attached
> pictures of the panel. If you're interested in the pics of the panel please
> contact me off-list.
>
> Thanks for the feedback. To clarify, the upper part of the bus is lug-fed
> directly from the service meter - no overcurrent protection. I have this
> same situation in two homes - one has a Bryant panel, not sure about the
> other.
>
> It seems possible connecting to the top bus could be considered a supply
> side connection. It's done through a panel bus, though, which seems like
> maybe it wouldn't qualify.
>
> It's true that the 60A breaker feeding the 100A bus fulfills the
> calculation requirements. However, the calculation has to follow upstream to
> the bus supplying that 60A breaker, so again we have a potential problem
> since there's no overcurrent protection for that bus.
>
> So, it seems the real question is about that top bus. Can we consider a
> connection there a supply side tap? If not, who do we do the 690.64 (B) (2)
> calculation without a main breaker?
>
> Thanks!
>
> Dana
>
> Dana Brandt
> Ecotech Energy Systems, LLC
> www.ecotechenergy.com
> dana at ecotechenergy.com
> 360.510.0433
>
>
> On Thu, Oct 28, 2010 at 6:37 PM, Matt Lafferty <gilligan06 at gmail.com>wrote:
>
>>  Hi Dana,
>>
>> "Sounds like" you have a lower-bus rated at 100A being fed by a 60A
>> breaker... Yes?
>>
>> If so, technically speaking but not necessarily the right thing to do, you
>> have a SWEET SETUP! In 690.64 terms, you are legally allowed 120A to feed
>> that bus. Which converts to a maximum 60A PV interconnection breaker located
>> at the opposite end of the bus from the 60A supply breaker. This is a panel
>> configuration that I have wished was still made for many years.
>>
>> The downside is... It's probably older than me. With really wimpy buses.
>> And really bad options for replacement breakers. And is full of 2-wire
>> homerun circuits.
>>
>> If it doesn't have a perfect-in-every-way bus, it's time for a new panel.
>> You also need to be able to buy real... Modern.... And New UL Listed
>> breakers. Those gray looking replacement breakers in the home improvement
>> store? They're NOT OK. In any way.
>>
>> Wadsworth? FPE? Bulldog? &...??? These panels are NOT OK for
>> interconnection at this point. Time to upgrade. Yes, really. Zinsco?
>> Depends. Any panel with signs of arcing around the bus anywhere? Better have
>> a damned good explanation before I'd be tying in some PV. I know of a
>> couple. Warped breakers? Change it!
>>
>> I just got done doing a 90% rewire on a friend's house and it tore my
>> heart out sending the panel to the recycler.* (This friend is into
>> long-term thinking and sustainable everything. I would have left it if I
>> could and so would they.) *The bus was pristine. It is rumored that Al
>> Capone used to stay in this place when he was in the area. The panel was
>> giant, with lots of room. This panel had a coolness factor off the
>> charts. But... I couldn't reliably get trustworthy breakers. And it was
>> my friend's house. Somebody I care about. I couldn't leave it in there. I
>> use the same judgement whether my customer is a friend or not.
>>
>> If what you have is a modern panel, share! I know I would personally
>> appreciate it if you were able to share mfr, model, pictures, etc. Whenever
>> we are upgrading/swapping/moving a service panel, we need to be installing
>> something that provides the best opportunity for interconnection of
>> distributed resources. We don't have those at this point. And we need them.
>> A split-distribution *(not just split-bus)* service panel is one way to
>> accomplish this. The trick is to limit the possible size of the breaker
>> feeding the "2nd" bus *(the lower bus in this case).* It's not rocket
>> science.
>>
>> I'd be happy to use and publicize a product that a mainstream manufacturer
>> came up with to deal with this. How about you?
>>
>> $0.02001,
>>
>> Solar Janitor
>>
>> PS - Home rewiring for friends only. I love doing it, but I do it for
>> love. There ain't no amount of money that makes me want to do it just for
>> money!
>> ------------------------------
>> *From:* re-wrenches-bounces at lists.re-wrenches.org [mailto:
>> re-wrenches-bounces at lists.re-wrenches.org] *On Behalf Of *Dana Brandt
>> *Sent:* Thursday, October 28, 2010 5:19 PM
>> *To:* RE-wrenches
>> *Subject:* [RE-wrenches] backfeeding "six disconnect" panel
>>
>> Hi everyone,
>>
>> I'm working on two systems for homes that have the old style breaker
>> panels with no single main breaker. Instead, they have six breakers in the
>> upper part of the panel each labeled "main breaker," which satisfies the six
>> disconnect rule. The bus bar is split, with one of the six upper breakers
>> (60A) feeding a separate bus in the lower half of the panel. It appears that
>> the upper bus is rated for 200A, and the lower at 100A.  The sum of the main
>> breakers does not exceed the 200A rating of the upper bus. There are spare
>> breaker slots on both the top and bottom buses. How do I deal with 690.64
>> (B) (2) when there's no main breaker?
>>
>> Thanks!
>>
>> Dana
>>
>> Dana Brandt
>> Ecotech Energy Systems, LLC
>> www.ecotechenergy.com
>> dana at ecotechenergy.com
>> 360.510.0433
>>
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