I have a question on inverter "phasing". By that, I mean connecting multiple
240 volt inverters to a common single phase sub panel or service panel and the
need (or not) of making sure that L1 -L2 correspond on each inverter to the L1
- L2 buss bar in the panel. I recall issues in the early day
August - we've been using 1/2" emt between arrays with plastic bushings to
protect wires and a dual "minerallac" clamps (
http://minerallac.thomasnet.com/viewitems/pipe-fasteners/ll-categories-cully-pipe-fasteners-conduit-hangers?&bc=100|1006|1281&forward=1)
to tie the conduits to the riser on t
Colleagues:
I have acquired a few SW conduit boxes and DC disconnects with all the
trimmings that I'd like to get out of my shop. Contact me off list if you
are interested.
William Miller
Please note new e-mail address and domain:
William Miller
Miller Solar
Voice :805-438-5600 Fax: 8
August and Max,
If all you are doing in supporting the conductors, PVC conduit is sufficient
with protective bushings on each end. Once you go to EMT, then grounding
bushings must be installed at both ends and the EGC needs to pick up those
bushings. More expensive and time consuming, but it
August:
I suggest the use of EMT with proper fittings to protect high voltage, high
amperage DC Wiring on rooftops. Sure it is time consuming, but high
quality, reliable craftsmanship will always be thus.
William Miller
At 11:07 AM 10/8/2009, you wrote:
Hi Wrenches,
I'm looking for
Except for coastal installations where EMT is NOT recommended
outdoors, PVC browns out and warps, and we should therefore use
product X???
R. Walters
r...@solarray.com
Solar Engineer
On Oct 9, 2009, at 11:38 AM, William Miller wrote:
August:
I suggest the use of EMT with proper f
This link to galvanic compatibility is puzzling to me, it indicates that you
should not connect copper wire to a gold plated terminal, or tin/lead solder on
copper or connect a copper wire to a AL lug. However, all of these combo's are
commonly done and most AL lugs are listed and rated for CU.
Ray:
Good question. We do use PVC in coastal zones to avoid corrosion. We try
to keep it in the shade, paint it where exposed to UV and support it in
close intervals.
William
At 10:57 AM 10/9/2009, you wrote:
Except for coastal installations where EMT is NOT recommended
outdoors, P
All -
PVC doesn't hold up well in the Bay Area - Here's a photo of some ~4 year old
PVC browned PVC from Marin County:
[cid:image002.jpg@01CA48DF.F8EAE150]
You can see that the straps melted resulting in the conduit sliding down. Thank
goodness we didn't install this. PCV seems like a good op
August:
As discussed, PVC is sometimes the best solution in a corrosive
environment. I would never recommend supporting PVC as depicted in the
photos. Shooting a screw through comp roofing is questionable at
best. Better methods of installing PVC are available, including better
straps and
Thanks August... these images of PVC strapped to the roof, with a joint
totally failing after only 4 years, are a great reminder to follow the code
(some of this is new for 2008):
NEC 352.20 (fasten PVC such that movement from thermal effects is permitted)
NEC 352.44 (use expansion fittings to com
August,
Home Depot now sells bonding bushings for EMT down to ½, which should solve
the availability issue. I was very surprised to see them last trip to the HD
money pit.
Bill.
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Hey Folks,
I don't want to dicourage anyone from doing good work that meets or exceeds
Code requirements. But I am a little quizzical about the how we all seem to
be ignoring what the Code actual says about this.
"250.97 Bonding for Over 250V Volts
Exception: Where oversized, concentric,
Mark,
Although this exception is allowed, I think it is bad practice in the field.
We will probably see the NEC revoke this exception within the next few
cycles, and it may be revoked for PV systems much sooner. Relying on box
connections to carry the low fault currents inherent in PV systems i
EMT needs to be "pickled" with vinegar or acid, to get the paint to
hold. I love it for inland work, but near the ocean, it'll rust
through in 5 years. I'm not sure how much more time paint would buy you.
Anybody use other plastic materials HDPE? Supposed to not have the
expansion problems o
Colleagues:
I think the correct answer is: there are no short cuts to good
workmanship. It requires intelligent design, a judicious selection of
materials and careful installation. EMT is appropriate in low corrosion
environments, PVC if you can control UV damage and accommodate
expansion.
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