William,
Just about a week ago I asked Greg Smith at SMA to confirm that it
would be appropriate to use THWN-2 in the buried PVC conduit for the DC run
from a pole mount array with it's DC disco to the SMA DC disco below their
inverter......Just to be sure you're not thinking you have to use PV wire all
the way back to the DC disco at the inverter. He confirmed that THWN-2 used
for the run from the array disco was AOK.
We have been using Midnight discos with touch-safe fuses and clear
signage to not disconnect under load.....authorized solar bozos only.
Bill
----- Original Message -----
From: William Miller
To: RE-wrenches
Sent: Monday, October 06, 2014 11:40 AM
Subject: [RE-wrenches] TL inverter with long DC Feeder
Wrenches:
We are getting up to speed on using transformer-less inverters. I have
advocated long for the additional safety offered by these inverters but I am
realizing the trade-offs with the new technology: The implementation gets more
complicated with the requirement for PV wire, OCPD and disconnecting means for
plus and minus and plus providing Arc Flash rated equipment.
I am currently designing a system that will locate the PV about 400 feet from
the residence. The system will utilize 2 Solectria 5200 watt inverters at the
residence. I would like to provide disconnecting means for the 4 strings at
the array, in case of any needed service or excavating. Preferably I'd like
the disconnecting means to be deployable by a lay person (i.e. the gardener).
Finding an 8 pole, arc flash, 600 VDC rated disconnect is not easy. I could
install an Outback 8 circuit combiner with 8 touch-safe fuse holders. The new
combiners have had dead-fronts for a while now. The gardener needs only to
have a Philips screw driver to open this cover. Any better ideas out there?
Thanks,
William
Lic 773985
millersolar.com
805-438-5600
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