point of connection [RE-wrenches]

Mon May 5 14:05:12 PDT 2008

Dick,

I'm not sure I see the reason a UI inverter can't be viewed as a parallel
power production system and be eligible for the allowance under 230.2(A)(6).
The definition of a utility interactive inverter is "an inverter intended
for use in parallel with an electric utility to supply common loads that may
deliver power to the utility." This is the exact reference I have used to
connect a PV system on the supply side of a MDP that had 6 service
disconnects in it already.

705.12 actually uses the language "interconnected electric power source" not
"parallel power production system" (this is probably splitting hairs
though). I don't see how 70512(B) and (C) preclude a PV system to be
included in the 230.2(A)(6) allowance. Am I understanding you correctly?

I am also confused by " The much more common situation permitted by
705.12(A)
is ONE service." Wouldn't the new PV connection constitute a new service
disconnect?

This is a great thread, thanks to all.

Ryan Mayfield

-----Original Message-----
From: Dick Ratico [mailto:Richard.L.Ratico at VALLEY.NET] 
Sent: Saturday, May 03, 2008 5:24 PM
To: RE-wrenches at topica.com
Subject: RE: point of connection [RE-wrenches]

Bill,

It is, but mostly it isn't:

I think this is a case of the exception proving the rule, the general rule
in
this case being, "A building or other structure
served shall be supplied by only one service."

Article 705.12 specifies where a "parallel power production system" shall be
permitted to be connected:
 "705.12(A) An electric power production source shall be permitted to be
interconnected to the supply side of the service disconnecting means as
permitted in 230.82(6)."

705.12(B) and 705.12(C) permit interconnection of specific types of systems
at
different locations elsewhere on the premises. These are the different
services
permitted by 230.2(A)(5). The much more common situation permitted by
705.12(A)
is ONE service.

The situation William described is covered by 705.12(A). It is to be
considered
one service. And, yes, service conductors can be tapped, see article 230.46.

It would be wonderful if the NEC was more user friendly. I attended your
workshop in Burlington ,VT and greatly admire your work. 

Dick

You wrote:
Dick,

It is:

230.2(A)(5) Parallel power production systems

Also a battery-backup system could also be classified as a separate service,
depending on how it is connected under #4 "Optional Standby Systems"
(Article 702).

Bill.

-----Original Message-----
From: Dick Ratico [mailto:Richard.- at VALLEY.NET] 
Sent: Saturday, May 03, 2008 1:05 PM
To: RE-wre- at topica.com
Subject: RE: point of connection [RE-wrenches]

Bill,

I'm not sure I understand. I think you are saying a grid-tied PV system with
no battery backup is considered by the code (as allowed by Article 230.2(A)
Special Conditions) to be a separate service. It is not among the six
Special
Conditions listed.

Dick

You wrote:
In general you are correct, (with few exceptions, e.g. a PV system) but the
NEC permits multiple services under 230.2(A) Special Conditions.

230.2 Number of Services. A building or other structure
served shall be supplied by only one service unless permitted
in 230.2(A) through (D). For the purpose of 230.40, Exception
No. 2 only, underground sets of conductors, 1/0 AWG and
larger, running to the same location and connected together at
their supply end but not connected together at their load end
shall be considered to be supplying one service.
(A) Special Conditions. Additional services shall be permitted
to supply the following:
(1) Fire pumps
(2) Emergency systems
(3) Legally required standby systems
(4) Optional standby systems
(5) Parallel power production systems
(6) Systems designed for connection to multiple sources of
supply for the purpose of enhanced reliability

Bill.

William,

My understanding is that the "tap rule" does not apply to supply side
service connections. There is a limitation on the supply side and that is
the service conductor size on the high side and 60-amps on the low side if
the supply is connected to a building. I try be careful to not use the term
"tap" when referring to anything on the Supply side of the service
disconnect. The NEC considers this connection a new service.

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