[RE-wrenches] box fill calcs
Jeff Blick
jeff.blick at sunlightsolar.com
Thu Nov 20 07:40:39 PST 2008
Hi wrenches,
In Reading 314.16(B)there is no mention of including polaris lugs or the
like in box fill calcs. Do any of you include such equipment in your box
fill calcs? If so how do you account for them (ie count it as two
conductors based on the size of the conductors that are landing in it)
Thanks wrenches!
Jeff Blick
PV installer
Sunlight Solar Inc.
4 NW Franklin
Bend, OR 97701
direct: 541-306-4196
fax: 541-322-1911
jeff.blick at sunlightsolar.com
www.sunlightsolar.com
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Today's Topics:
1. Re: grid-tie inverters & generators
(Jeff Clearwater, Village Power Design)
2. Re: utility EDS signage (Kent Osterberg)
3. Re: inverters/ generators and noise (robert ellison)
----------------------------------------------------------------------
Message: 1
Date: Thu, 20 Nov 2008 00:42:29 -0500
From: "Jeff Clearwater, Village Power Design" <jeffc at villagepower.com>
Subject: Re: [RE-wrenches] grid-tie inverters & generators
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Message-ID: <p06240806c54aa84bd6a8@[192.168.2.7]>
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Hi Folks,
We burnt up a gen set's voltage regulator on an off-grid system sunny
island/sunny boy system when we took the sunny island's off-line but
didn't shut off the sunny boy. So the SB backfed the genny and fried
the very expensive voltage regulator on a 30 KW system. SMA had us
install a relay to tell the SB to shut down as soon as the AC
reference from the SI was gone. Same situation as grid-tie really in
terms of your question.
Jeff
>Hi Kelly
>
>It is an interesting issue and was just dicussing this the other day.
>
>I think what happens if the inverter backfeeds the genny, the
>generator voltage will go up, if it goes up enough, it will go
>outside the window of the inverter and the inverter will drop out,
>voltage will them return to normal, inverter will reconnect and
>repeat.
>
>But I sure wouldn't want to fix the generator. A relay powered from
>the grid will take care of the problem.
>
>jay
>
>peltz power
>On Nov 19, 2008, at 5:24 PM, Kelly Keilwitz, Whidbey Sun & Wind wrote:
>
>>Wrenches,
>>I'm dredging up this subject again (previous postings 6/08) with a
>>simple question that doesn't seem to have been answered:
>>
>>Is there any issue connecting a batteryless grid-tie PV system to
>>the load side of a panel that is backed-up by a generator on an
>>automatic transfer switch, when the grid is down and the generator
>>running?
>>
>>In this case the PV is 5.7kW, the inverter an SMA 6000, the
>>generator unknown size/type, but propane, automatic start, and
>>backing up the entire main panel.
>>
>>SMA tech support first said it's OK, then that the generator will
>>blow up. I can imagine, if the inverter tries to sync with the
>>inverter, that the voltage could rise, causing the inverter to
>>disconnect, wait 5 minutes, repeat. Is there anything nasty that
>>could happen?
>>
>>Thanks,
>>-Kelly
>>
>>
>>Kelly Keilwitz, P.E.
>>Whidbey Sun & Wind, LLC
>>Renewable Energy Systems
>>NABCEP Certified PV Installer
>>987 Wanamaker Rd,
>>Coupeville, WA 98239
>>PH & FAX 360-678-7131
>><>sunwind at whidbeysunwind.com
>>
>>
>>
>>
>>
>>_______________________________________________
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--
~~~~~~~~~~~~~
Jeff Clearwater
Senior Design Engineer
NABCEP (tm) Certified Solar PV Installer
http://www.nabcep.org/
Village Power Design/NorthEast Solar Design
Turnkey Solar Design & Installation for the Commercial Sector
http://www.villagepower.com
gosolar at villagepower.com
Voice: 413-259-3750
Fax: 413-825-0703
65 Schoolhouse Rd
Amherst, MA 01002
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Message: 2
Date: Wed, 19 Nov 2008 23:24:59 -0800
From: Kent Osterberg <kent at coveoregon.com>
Subject: Re: [RE-wrenches] utility EDS signage
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Message-ID: <492510CB.1020708 at coveoregon.com>
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Phil,
NEC 690.17 says "Where all terminals of the disconnecting means may be
energized..." It would take a pretty rare malfunction of a grid
connected inverter to energize the load terminals of the utility
disconnect. But we have some AHJs that require this label on every ac
disconnect, all the way back to the utility meter, anyway. The warning
is appropriate on the dc disconnect of almost all inverters because the
capacitors in the inverter take a few minutes to bleed off.
To me, the bigger hassle are plaques required by 705.10. Can anyone
give me a reasonable explanation for their value in a utility
interactive system? I can understand if there is a grid backup system -
emergency personnel may need to know where to turn off the backup power;
but a grid interactive inverter shuts down when there service is shut
down. It seems to me that this plaque is likely to send an emergency
responder on a wild goose chase.
Kent Osterberg
Blue Mountain Solar
Phil Schneider wrote:
> Wrenches,
>
> Our utilities require an external AC disconnect between the inverter and
the
> point of interconnection, located next to the meter. In the past, we have
> marked this switch with the language in 690.17 (although no AHJ or utility
> has required it). Because we generally argue against the necessity of
this
> switch, I don't feel it is accurate to say that "terminals on both the
line
> AND load sides may be energized in the open position".
>
> Do other Wrenches post this plaque? Is there a way that both line AND
load
> terminals of this switch could be energized? (other than an inverter not
> paying attention to its UL listing?)
>
> Thanks again for your thoughts,
> P.
>
> Phil Schneider
> Creative Energies
>
>
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------------------------------
Message: 3
Date: Thu, 20 Nov 2008 06:38:45 -0500
From: "robert ellison" <reellison at gmail.com>
Subject: Re: [RE-wrenches] inverters/ generators and noise
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Message-ID:
<dae2914c0811200338t53f57516k77425841b255597 at mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Probably due to the load of the charger, try changing the rpm a little
(higher) if you can. Might help. I have had stoves that wouldn't light under
full charger load. They did better at a somewhat higher rmp (frequency)
Bob
On Thu, Nov 20, 2008 at 12:12 AM, jay peltz <jay at asis.com> wrote:
> Hi All,
>
> here is along those same lines a question about line noise.
>
>
> System 15kw diesel generator
>
> 4 stack outback at 24v 120v/240vac
>
> 3000 amp hr industrial batteries.
>
> when genny running, 59.5-60 hz
> voltage 122/244
>
>
> Symptoms.
>
> when charging there is some buzzing on some electrical equipment in the
> house. Stove pizeo won't lite, transformer on furnace runs hot, Fridge
> makes more noise.
> Seems to get worse at end of charge cycle.
>
>
> Now, with inverter only, no noise, humm, buzz etc.
>
> With Genny only no buzz, humm, etc.
>
>
> Any advice?
>
> thanks,
>
> jay
>
> peltz power
>
>
>
>
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