Stand Alone PV system volt / amp problem [RE-wrenches]
Matt Lafferty
mlafferty at universalenergies.com
Fri Apr 8 02:15:25 PDT 2005
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Chris,
RE: Trailer Inspector
Since this is specifically a "manufactured home", I recommend a pair of
tickets to the Jerry Springer Show for the Inspector and the guest of
his/her choice, instead of the usual "donuts & coffee" for the Inspector.
(Bonus Question: Does anybody remember the ratio of Jellies to "regular"
donuts?) My guess is that you are wishing you had stayed a little closer to
town about now. Just kidding.
There are a couple of key things to keep in mind when dealing with
"manufactured homes", at least in California. (I understand that similar
things are also the case in other states as well.)
#1. They are regulated by the HCD (Housing and Community Development),
which used to be the DMV. Yep. Wheels or no wheels. New or old. The
applicable rules and regulations are handed down by the state. The HCD
(Housing and Community Development) may or may not adopt the relevant
sections of the NEC in its entirety, at the sole discretion & pleasure of
the HCD. I'll leave the UBC "maybe maybe-nots" out of this conversation....
The bottom line is that, unless the HCD has adopted the NEC in its entirety,
that trusty old Bibble of Ours is only one part of the puzzle. Before
picking a fight with the Inspector, you might find it worth your time to
find out "what parts and how much" of the NEC has been adopted, or better
yet, get a copy of the current adopted standard relating to manufactured
homes directly from them. Sigh!
#2. One of the "generally understood" aspects of getting Building
Inspections is that the HCD basically "assigns" a conditional and limited
amount of agency jurisdiction to the local AHJ to "act on behalf of" the HCD
for the purposes of administering the regulations related to various
building, electrical, and mechanical aspects of these Manufactured Homes.
Some Building Inspectors know this, and some don't. Kinda funny how that
"works".
#3. I don't have a copy of the current standards & regulations relating to
this particular mattter, but.... You can find out more at:
http://www.hcd.ca.gov/codes/mhp/ . I would click on the link to the RH
side of the page that says: Program Law and Regulations... Or, you can just
click on http://www.hcd.ca.gov/codes/mhp/lawregs.html to get closer the the
old statutory rigamarole.
#4. As if all that wasn't enough, there is the element of HUD, which
establishes most of the "baseline minimum" standards and regulations
regarding these things, from the Feds down, for everything built since the
mid '80s if I remember correctly.
#5. Unless you double-lugged inappropriately when you did the jumper at the
100 Amp Main Breaker on the coach distribution panel, your description of
what you did is NEC Compliant.... Mostly. It sounds safe and functional,
with the possible exception of making sure that there are no three-wire
branch circuits and any electric dryers and ranges have the grounds and
neutrals isolated, if they aren't / weren't already.
#6. Jerry C was right on with the 550 & and "he's the AHJ" reference, but
he didn't quite take it far enough for the purrposes of "getting inside" the
inspector's head. My guess is that you have sized the AC Feeder for your
Inverter (50 Amps) and that there are only three conductors feeding the
Distribution Panel. (Hot, Neutral, and Dirt) Oh, by the way. Your main
feeder "dirt" wire cannot be bare, per the NEC. Here's another scrap to
chew on from the 2002 NEC, related to all this:
550.33 Feeder.
(A) Feeder Conductors. Feeder conductors shall consist of either a listed
cord, factory installed in accordance with 550.10(B), or a permanently
installed feeder consisting of four, insulated, color-coded conductors that
shall be identified by the factory or field marking of the conductors in
compliance with 310.12. Equipment grounding conductors shall not be
identified by stripping the insulation.
Exception: Where a feeder is installed between service equipment and a
disconnecting means as covered in 550.32(A), it shall be permitted to omit
the equipment grounding conductor where the grounded circuit conductor is
grounded at the disconnecting means as required in 250.32(B).
(B) Adequate Feeder Capacity. Mobile home and manufactured home lot feeder
circuit conductors shall have adequate capacity for the loads supplied and
shall be rated at not less than 100 amperes at 120/240 volts.
Not that any of that matters, really.... Since, as Phil U said, "The final
trump card is 690.3, which states that wherever the requirements of other
articles of the Code and 690 differ, the requirements of 690 win." Which
leads to Phil's other reference....
#7. 690.10(A)&(C). The good old, "As long as there are no multi-wire
branch circuits or 240 Volt appliances / loads, you can feed the panel with
less amps than it is rated at and lower volts, too" passage.
#8. Be sure to review and understand #1 - #4.
I hope this stuff helps you out in some way on this one and helps you and
anybody else veturing into the Trailer PV field for the future.
Peace and Palm Trees!
Matt Lafferty
mlafferty at universalenergies.com
(415) 252-0343
(415) 748-6010 Cell
(916) 914-2247 Fax
-----Original Message-----
From: Chris Anderson [mailto:chris at borregosolar.com]
Sent: Thursday, April 07, 2005 10:25 AM
To: RE-wrenches at topica.com
Subject: Stand Alone PV system volt / amp problem [RE-wrenches]
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Any help on this one would be appreciated.
We have an off grid home, where we have installed 12 Shell 160's 6x2 on an
Outback VFX 2548 with 8 6v Concorde Batteries. The system is feeding a 100
amp Square D main distribution center. Given the inverter output is only 120
volt, we fed inverter output L1 to one leg of the 100 amp main breaker at
the top of the main distribution panel and jumpered over to the second
bus/lug on the main breaker in order to electrify both bus' in the panel
with 120v power. There is a 50amp breaker on the AC output circuit of the
inverter.
I have two problems.
1. I have got an inspector who is saying that manufactured homes MUST be fed
by 240V power. He is adamant that the main distribution panel must be fed by
240v. We have jumpered the bus in grid tie battery back-up systems like this
before, but never on an off grid. Anyone have any thoughts here or can point
me to a code section that either confirms or negates what we have done?
2. The inspector is also saying that panel must be fed with the amps
indicated on the main breaker. In this case, the main breaker is 100amps,
therefore it must be fed with 100A. Either that or the main can be replaced
if a load calc is done and the home is "de-amped". He has taken issue with
the 100 amp main being fed by the inverter given the 50 amp breaker on the
AC output side of the inverter.
Any help/insight on these two issues would be greatly appreciated.
Thanks in advance.
Chris Anderson
Borrego Solar Systems, Inc.
727 Allston Way, Suite B
Berkeley, CA 94710
Tel. - 510-843-1113 x 105
Fax - 510-843-1116
Cell - 510-501-7062
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