[RE-wrenches] Point of connection

[Matt Lafferty]

Hi Keith,
 
Many of the mainlanders opt for a "supply-side" interconnection (tap service
conductors between meter and main breaker). There are a number of touchy
issues with this method if it's in a single box, and it certainly isn't a "1
size fits all" kinda thing. In case nobody has said it on the list yet, I'll
go ahead with the prediction that we are likely to see this method become a
lot more rare in the future... Unless of course, your local PV installer has
a UL Listed sticker in his back pocket... 
 
In most cases, my preferred option is to install a main breaker with a lower
rating... i.e. Replace the existing 200 Amp breaker with a 150 Amp breaker.
Be sure that the maximum continuous load of the residence does not exceed
80% of the new main breaker.  (80% x 150A = 120A max continous load) This
example gives you up to 90A of PV Breaker capacity on a 200A buss.
 
The vast majority of homes with 200A services don't come anywhere near 120A
continous. There are some that do, so make sure you understand their big
electric loads and how they use them. Otherwise, you can upgrade the
service, as you mentioned.
 
Aloha,
Matt Lafferty
gilligan06 at gmail.com
 
 

  _____  

From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Keith Cronin
Sent: Monday, February 09, 2009 2:41 PM
To: RE-Wrenches
Subject: [RE-wrenches] Point of connection


Hello

With the growth of the solar industry coupled with the generous incentives
now offered on fed part of the equation, we are seeing some trends here and
wondering what the approach has been in other areas. What kind of feedback
are you receiving from the AHJ?

There are some integrators who now are installing "systems" meaning,
multiple small inverters that are married to smaller arrays as opposed to
one large array with one large inverter. 

So, it is quite conceivable to have, for example, 3- 3000 W SMA inverters on
a customers home. So, the point of connection issues arise. When you look at
690.64B, it speaks to the 120% of the busbar rating.

What are folks doing in other areas, for this above example to address the
mechanical/electrical challenges associated with this situation, when if you
had 1- 200 amp residential service? There is alot of discussion, like
installing a 125 amp rated subpanel; interuppting the feeder from the
electric service and installing a 225 amp panel with a higher rated buss
(hard to find or custom made thru Cutler Hammer or others) etc.

We can also see a trend using the enphase products as well, but not as much
pronounced. It could be conceivable for a client to want to build their
system up over a few years and have 15, 175 watt panels on a circuit (2P15
amp) and grow the system up to lets say, 45, 175 watt panels (3-2P15 amp).
Same situation, different inverter manufacturer. My sense is this trend will
continue for the forseeable future, and alot of wrenches will find orphaned
systems out there and we should look at ways to address point of connection
issues that are bound to present themselves.

Thanks

Keith


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