[RE-wrenches] Tranformless inverter

[Bill Brooks]

Hans,

It is not correct that you will have twice the disconnects necessarily. Most
switches require passing through the disconnect twice. This must be done on
the one ungrounded conductor for grounded systems, or the two ungrounded
conductors with ungrounded systems. It is a circuit and it simply must be
broken twice in series simultaneously to reduce the arc voltage on each
switch opening to exactly half.

All 600V disconnect combiners use multiple poles so there would be no
difference at all with these devices--only twice as many fuses--not a really
big deal considering the huge safety advantages of ungrounded arrays.

Bill.


-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Hans
Frederickson
Sent: Monday, October 04, 2010 9:16 AM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] Tranformless inverter

Ryan,
Yes, there are twice the number of ungrounded conductors, so twice as many
fuses and switches are required. I haven't seen much in the way of combiners
for ungrounded systems... A combiner for an ungrounded system has two fused
ungrounded sections instead of the typical combiner of today which has fuses
on the ungrounded input conductors and just a terminal block for all the
grounded conductors.

-Hans

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Ryan LeBlanc
Sent: Saturday, October 02, 2010 10:52 AM
To: re-wrenches at lists.re-wrenches.org
Subject: Re: [RE-wrenches] Tranformless inverter

Bill, 

Specifically, the additional fusing and disconnect requirement you mentions.
Is that each positive and negative PV Source and Output Circuit must have
OCPD and go through switched?  Twice the combiner boxes, fuses and switches?

Thanks,

Ryan J. LeBlanc
NABCEPT Certified Solar PV Installer
Cell: 707.591.1950
Direct: 707.536.9839
ryan at NaturalEnergyWorks.com
http://www.NaturalEnergyWorks.com


Ungrounding the array requires additional fusing and disconnects, but the
most significant difference is that the module wiring and all external cable
must be PV Wire/Cable. Therefore only modules with PV Wire/Cable can be used
in these systems. You must confirm from the manufacturer that they have made
the switch. Hopefully all manufacturers will be installing PV Wire/Cable
soon so that this will not be a problem anymore.

 


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