Gary,
I thought most inverters share power. So if the inverter has a 60A
transfer switch and all of that is needed for loads then none for
charging and as load demand decreases, charging increases.
Larry Liesner
Elektron Solar
On Feb 28, 2013 11:33 AM, <g...@icarussolarservices.com
<mailto:g...@icarussolarservices.com>> wrote:
Garrison, et al:
Another consideration when sizing the POCC OCPD (either load side
or supply side) is charging current when the grid power returns
and the battery bank is near the LBCO voltage.
Bulk charging current and AC pass-through current both must be
considered when sizing the POCC OCPD.
Regards,
Gary Willett
Icarus Solar
On Thu, 28 Feb 2013 10:04:51 -0600, Garrison Riegel
<garri...@solarserviceinc.com
<mailto:garri...@solarserviceinc.com>> wrote:
Great point Dave. It crossed my mind that it was technically
possible, but figured since I would be removing loads off the
main panel it was highly unlikely. Thanks for the code
reference. I'll go load side, and be prepared for some
discussion.
Thanks,
Garrison
*From:*re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>
[mailto:re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>] *On Behalf
Of *Dave Click
*Sent:* Thursday, February 28, 2013 9:21 AM
*To:* re-wrenches@lists.re-wrenches.org
<mailto:re-wrenches@lists.re-wrenches.org>
*Subject:* Re: [RE-wrenches] Conductor Sizing for Supply Side
Connection
As a note, supply side connections have an extra complication
with battery backup systems. With a regular GT inverter you're
just pushing current into that interconnection point and you
can work out easily that you won't have any overcurrent issues
unless you made a big mistake and your inverter output exceeds
the rating of your service conductors. However, with a battery
system you're also potentially pulling current from that
point. Before the battery inverter is installed your main
breaker protects your service conductors, but if the inverter
is pulling in 60A and the main breaker is also operating near
its capacity, you could have >240A running over 200A service
conductors with no breakers tripping. You would overwhelm the
capacity of the service [230.23(A)] and no breakers would
trip. You could fix this by replacing your service conductors
back to the transformer (I'm just saying that it's an option)
or downsizing the main breaker, and at that point you're
probably better off just making it a load side connection. I'd
go load side and argue with the AHJ to use the 2011 update
mentioned earlier.
Dave
On 2013/2/28 9:55, Garrison Riegel wrote:
Allen,
The benefit I see would be to allow for a code compliant
load side connection on a 200A panel with a 200A MB, where
the AHJ is on the 2008 NEC or older and will not listen to
your good logic. I don't think this would always be the
best option, but if backup loads and inverter output were
less than 32A then a 40A OCPD in the main panel should be
fine? Since it sounds like the 60A breaker in the main
panel is not a safety issue, but a design consideration, I
suppose I would just prefer flexibility when possible.
That said, this AHJ is on the 2008, and the loads will be
less than 30A, but based on this conversation I plan to go
with a 60A and try to convince the AHJ that it will be
code compliant in their future!
Thanks,
Garrison
*From:*re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>
[mailto:re-wrenches-boun...@lists.re-wrenches.org] *On
Behalf Of *Allan Sindelar
*Sent:* Thursday, February 28, 2013 8:14 AM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] Conductor Sizing for Supply
Side Connection
Garrison,
I don't know why it's not listed as 60A max, but my own
internal logic would ask why it should be. The only
benefit I could see for using smaller than a 60A breaker
would be to allow use of #8 conductors (allowed with a 40A
or 50A breaker) instead of the #6 necessary with a 60A
breaker. And of course, you could use a 40A breaker with
#6 conductors, so theoretically it would be fine. I just
fail to see any benefit to doing so.
Allan
*Allan Sindelar*
al...@positiveenergysolar.com
<mailto:al...@positiveenergysolar.com>
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
*Positive Energy, Inc.*
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
*505 424-1112 <tel:505%20424-1112>*
www.positiveenergysolar.com
<http://www.positiveenergysolar.com/>
On 2/28/2013 6:27 AM, Garrison Riegel wrote:
Thanks Allen for clarifying why a 60A is required. I
was wondering. The spec does list a surge current of
9000W so I thought that may be the rationale, but even
that would only require a 50A, and since this surge
occurs during 'stand-alone mode' it didn't seem to
apply to the OCPD at the main panel. Your explanation
makes more sense, but I wonder why then they don't
list the AC input breaker size as 60A /max/. If you
have few backup loads, and are not on the 2011 NEC, a
40A could theoretically be fine?
Thanks all for your thoughts, much appreciated.
Garrison
*From:*re-wrenches-boun...@lists.re-wrenches.org
<mailto:re-wrenches-boun...@lists.re-wrenches.org>
[mailto:re-wrenches-boun...@lists.re-wrenches.org] *On
Behalf Of *Allan Sindelar
*Sent:* Wednesday, February 27, 2013 6:08 PM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] Conductor Sizing for
Supply Side Connection
August,
The 60A breaker is intended to allow grid power to
pass through to the loads in excess of the inverter's
stand-alone output. The point of 705.12 (moved in the
2011 NEC from 690.64 (B)(2)) is to differentiate
between load pass-through current and sell current.
The amount of current fed into the grid is (4500/230
=) 19.56A, while the amount that can be taken from the
grid and passed through to the load is much greater.
If you were limited to a 40A breaker in order to
maintain 120% of a 200A main bus, you'd be prone to
nuisance trips under large cumulative loads.
Allan
*Allan Sindelar*
al...@positiveenergysolar.com
<mailto:al...@positiveenergysolar.com>
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
*Positive Energy, Inc.*
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
*505 424-1112 <tel:505%20424-1112>*
www.positiveenergysolar.com
<http://www.positiveenergysolar.com/>
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