Multi-Contact parallel connectors [RE-wrenches]

jberdner at sma-america.com jberdner at sma-america.com
Mon May 20 06:39:01 PDT 2002


Bill:

I am sorry I missed seeing the retraction to the blanket statement.
I agree that many of the pre engineered solutions out there still need
some work. Until recently there were no pre engineered solutions so at
least we are headed in the right direction.  I also feel strongly that
connector based wiring solutions are necessary. Without them I do not
believe we can reduce the installation costs to where they need to be.
Connectors also minimize exposure to hazardous voltages and reduce the
number of "in the field" operations needed to wire a PV system.  This is
not to say that the MC Y connector is the solution but it is a start. We
are seeing a migration toward larger "24 volt" modules with MC
connectors. With our product this commonly means 2 Strings of modules.
I think a connector based paralleling solution for two strings has a
place in the market. 

Yes, Some people will apply them incorrectly.
These same people could just as easily use the wrong wire or fuse size. 
The complexity of a PV system is similar or less than the wiring of the
building on which it is attached.  The electrical trade seems to be able
to cope with wiring buildings and I expect they will easily handle PV as
our industry matures and PV becomes more commonplace.   

I don't think we can throw the baby out with the bath water because
someone might make a mistake.  We have seen 2 installers who have wired
arrays for Sunny Boys at ca 1000 Vdc.  In both cases the inverters
failed and no one was injured. At $750 a pop to repair the inverters I
think the lesson was learned well and quickly. When I look at the number
of installations out there it seems reasonable to expect some mistakes.
You simply can't teach everything form a book.  At some point installers
need to put wrench to nut and they will make mistakes. This does not
mean they are not qualified to wire up PV systems. 

I agree that more training is needed in our industry.
The California grid tied market is expanding rapidly and many new
players are entering the market. This includes manufacturers like
ourselves, installers who are new to PV, and inspectors who have never
seen a pv system before.  Lack of infrastructure was one of the key
items DOE identified as a key barrier to widespread adoption of PV.
This is one of the reasons Kent and I are constantly visiting our
distributors and conducting training seminars for new installers.  When
I am in the office I spend the majority of my day on the telephone
answering tech support questions from new installers.  Forums like this
and the exchange we are having now are another important vehicle for
disseminating experience.  Thanks for the opportunity to participate.  

If you have any questions, or if I can be of further assistance, please
do not hesitate to contact me.

Best Regards,

John Berdner
Phone: 530.273.4595
Fax: 530.274.7271


-----Original Message-----
From: Bill Brooks [mailto:billb at endecon.com] 
Sent: Sunday, May 19, 2002 10:26 PM
To: RE-wrenches at topica.com
Cc: Chuck Whitaker
Subject: RE: Multi-Contact parallel connectors [RE-wrenches]

John,

I actually wrote a retraction to my blanket statement that never made it
through my email server on Friday night. It still concerns me that many
people will misapply the connector. It takes something that is
straightforward and makes it less straightforward. It also requires very
detailed instructions on how it can and cannot be applied in the field.
Ilsco terminal blocks are fairly straightforward and are based on
current
ratings. However, you still must observe bending radii and other issues
which is why some local jurisdictions require that they be assembled by
a
508A shop.

I'm 100% in favor of straightforward, fully engineered, system designs.
But
manufacturers routinely supply partially designed systems with partially
designed components and then throw them at the installer and say
"here--wire
this according to the code." The devil is in the details of all this
stuff
and my main concern is that the suppliers and manufacturers using this
equipment is not providing the level of training and instruction
necessary
to have their products safely and properly applied in the field. Would
you
not agree with that statement?

Bill.



-----Original Message-----
From: jberdner at sma-america.com [mailto:jberdner at sma-america.com]
Sent: Sunday, May 19, 2002 6:43 AM
To: RE-wrenches at topica.com
Subject: RE: Multi-Contact parallel connectors [RE-wrenches]


Bill:

I do not understand why you say this assembly can not ever be UL Listed.
You can certainly make code approved, parallel connections with a number
of UL Listed Products.
Ilsco power distribution blocks come to mind for one.
Several other companies make UL recognized (RU) terminal blocks as well
but I am pretty sure the Ilsco's are UL Listed.
Listing versus RU is a big deal for 508A shops and when I was at Pulse
we had to have the Gould blocks tested by UL so we could use them in our
508A combiner boxes.  This testing was required because they were only
RU not UL Listed.  Split bolts, wire nuts, etc. also qualify as ways to
make parallel connections.  Over current protection does not necessarily
have to be included in a product for it to be Listed.

Also, I think the assumption that there are few places where this
product can be used is incorrect.  They can be used with most
crystalline modules and Sunny Boys for example.  They could also be used
in conjunction with inline fuse holders with any modules and any
inverter or battery combination.  Some modules have a high UL series
fuse rating compared to their Isc rating. In that case you can certainly
make a parallel connection without any over current device.  I agree
that this is usually higher voltage thin film but I think it is better
to do the calculation than to make a untrue blanket statement that a
parallel connection is strictly prohibited.

IMHO, parallel connections always add cost and complexity to a system
but there is nothing in the code that prohibits parallel connections.

One other thing to consider: Once you make a parallel connection you
have created a PV output circuit on the side away from the modules. Now
you have to consider the code requirements for that as well.  Some of
the exceptions the code allows for PV source circuits (one series
string) do not apply to output circuits (more than one series string).

If you have any questions, or if I can be of further assistance, please
do not hesitate to contact me.

Best Regards,

John Berdner
Phone: 530.273.45595
Fax: 530.274.7271


-----Original Message-----
From: Bill Brooks [mailto:billb at endecon.com]
Sent: Friday, May 17, 2002 11:57 AM
To: RE-wrenches at topica.com
Cc: Chuck Whitaker
Subject: RE: Multi-Contact parallel connectors [RE-wrenches]

Ryan,

This is precisely why that assembly is not, nor ever can be, a UL-listed
item. It could be a UL-recognized item that becomes part of a fully
UL-listed system package, but that is a very different situation. There
are
a few places where that assembly can be used in a code-approved fashion
and
will not void the UL listing of the modules (max series fuse rating for
amorphous silicon modules). But in most applications (crystalline
silicon) a
parallel connector is absolutely prohibited.

Bill.

-----Original Message-----
From: Ryan Mayfield [mailto:ryan at energyoutfitters.com]
Sent: Friday, May 17, 2002 7:45 AM
To: RE-wrenches at topica.com
Subject: Multi-Contact parallel connectors [RE-wrenches]


Wrenches,

I have a sample from Multi-Contact of their "branch plugs and sockets"
for
parallel connections of modules but there is no UL listing on them. I am
hesitant to use a non listed product and was curious what others are
doing
to get around this problem. Do you only bring down conductors off series
connected panels? Is there another product out there that has a listing
for
parallel connections? Thanks in advance.


Ryan

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