[RE-wrenches] AC Combiner with main breaker as system disconnect

[Glenn Burt]

Bill,

 

I have never seen a main breaker in a residential main load center (say 200A) that has a rating of less than 20k AIC. Is there somewhere else in the panel that changes this?

 

Glenn

 

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Bill Brooks
Sent: Wednesday, March 12, 2014 7:24 PM
To: 'RE-wrenches'
Subject: Re: [RE-wrenches] AC Combiner with main breaker as system disconnect

 

Glenn,

 

The vast majority of service equipment for residences is rated 10k AIC. Although utilities may say they have some residential services that exceed 10k short circuit availability, it is still pretty rare. 

 

Using single phase gear on a 3-phase commercial installation is a different story. Perhaps this is what you were referring to when talking about 10k AIC being too low. 

 

I don’t people to get the idea that you have to check the fault current of every PV installation. You should only have to check fault current on a new service. Simply checking the ratings of the exist service equipment at an installation is sufficient to know what the minimum AIC rating of the equipment must be. The utility is not legally allowed to increase the fault current on a service above the service equipment ratings unless it is part of a service upgrade and the service equipment is being replaced.

 

Bill.

 

 

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Glenn Burt
Sent: Wednesday, March 12, 2014 3:13 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] AC Combiner with main breaker as system disconnect

 

Beware of breakers used as service disconnects. Most in the range suitable for a supply side connections for PV are really branch circuit rated with 10k AIC which is generally too low for the utility fault current they may be exposed to.
If you can get a statement from the utility with available fault current at the install site you might sneak one in. If you don't want to go to this trouble, use the rating of the exiting main breaker as a minimum value. Usually 20-25k AIC.

  _____  

From: Brian Teitelbaum <mailto:bteitelbaum at aeesolar.com> 
Sent: ‎3/‎12/‎2014 17:32
To: RE-wrenches <mailto:re-wrenches at lists.re-wrenches.org> 
Subject: Re: [RE-wrenches] AC Combiner with main breaker as system disconnect

One big omission, in the otherwise fine Soligent white paper, is that the 60A minimum disconnect has to be rated as “Service Equipment”. Generally this means a “Heavy-Duty” safety switch or Service-rated load center with Main breaker. 

 

I don’t see why an AC breaker panel, with a Main breaker, couldn’t act as the PV system disconnect, as long as it’s Service-rated, a minimum of 60A, and the utility does not require an external-handle disconnect, lockable in the off position. Many utility companies still do.

 

Brian Teitelbaum

AEE Solar

 

 

 

From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jason Szumlanski
Sent: Wednesday, March 12, 2014 2:14 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] AC Combiner with main breaker as system disconnect

 

Don't utter the word tap. :)

 

See:

http://www.soligent.net/documents/HappyLandings_v3.pdf

 

We usually specify a fusible disconnect for overcurrent protection when grouping the PV AC combiner with the main premises disconnect is not practical.

 

Jason Szumlanski

Fafco Solar


 

  <https://wisestamp.appspot.com/pixview.gif?p=chrome&v=3.31.0&t=1394658190268&u=eb875d38140ce271> 

 

On Wed, Mar 12, 2014 at 1:31 PM, <kevin at renovusenergy.com> wrote:

I am trying to determine whether an AC combiner panel (for multiple inverter outputs) with main breaker can be also used as the PV system disconnect? 

This is for a line tap situation.  I am accustomed to doing these systems with an AC combiner, and separate enclosure for a breaker style, line tap over current protection.

Any thoughts/comments would be appreciated.  

Thanks,

Kevin


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