600 VDC switches [RE-wrenches]

[matthew tritt]

William,

The SQ D switches in question are definitely rated 600 VDC on the inside
switch cover. These are just disconnects and have no breakers. I was asleep
at the keyboard when I trans-mogrified breaker for switch.
My error, not yours. I've got'ta stop composing messages at 11:00 PM!

Matt
----- Original Message -----
From: "William Miller" <wrmiller at slonet.org>
To: <RE-wrenches at topica.com>
Sent: Thursday, October 10, 2002 9:50 PM
Subject: Re: 600 VDC switches [RE-wrenches]


> Matt:
>
> I believe you missed the thread some months ago (or maybe a year or so?)
in
> which I shared some research on Square D breakers.  They are UL rated for
> 45 VDC and factory certified for 125VDC.  As it was put so succinctly by,
I
> believe, Bill Brooks UL trumps factory certification, so you can't argue
> the 125 VDC rating to the inspector.  This is all regarding single pole
> breakers.  I doubt that one could extrapolate a 600 VDC rating on any
> number of poles for Square D breakers given the 45 VDC limits on 1 pole.
>
> My original post that started the discussion on 600 VDC switches referred
> to a Siemens catalog page in which a two pole breaker was wired in series
> to achieve some higher voltage rating.  I don't know the breaker or the
> rating, but I'm curious now and I will try to find out more.
>
> I hope this clears up any confusion I may have caused.
>
> William
>
>
> At 09:21 AM 9/18/02 -0700, you wrote:
> >William,
> >
> >Your questions bring up some very interesting points. I did an install
> >yesterday using a Sq D 3 pole breaker which has no jumper and no mention
> >anywhere of a decreased rating. I'm going to check with the distributor
and
> >see if I can get an answer on the need to add a 3rd breaker to the
system,
> >or if these switches are actually rated @ 600 volts per contact.
> >Also, I regularly used to switch both DC inputs until I was admonished by
an
> >electrician who insisted it was illegal to break the negative lead. I
> >believe that he said this because of his assumption that the neutral in
AC
> >is grounded and it would be somehow interrupting the ground to break the
> >neutral on the DC circuit as well. Why not switch both?
> >
> >Matt
> >----- Original Message -----
> >From: "William Miller" <wrmiller at slonet.org>
> >To: <RE-wrenches at topica.com>; "John Berdner" <jberdner at sma-america.com>
> >Sent: Tuesday, September 17, 2002 9:42 PM
> >Subject: 600 VDC switches [RE-wrenches]
> >
> >
> >> Colleagues:
> >>
> >> Those of you who have installed the Sunny Boy inverters have used the
600
> >> VDC rated switches, such as the Siemens HNF261.  It is interesting how
the
> >> manufacturers achieve the 600 volt rating:  They use a 3 pole
disconnect
> >> and put two of the poles in series.   This way, the contacts break two
> >> times at the same moment.
> >>
> >> A few months ago I was unable to obtain a 2 pole 600 VDC disconnect in
> >> short order, so at the same price I was able to purchase a three pole
> >unit.
> >>  Lo and behold, the series jumper was missing and the cover showed a
> >rating
> >> of only 250VDC.  I since learned that because only three pole devices
are
> >> commonly manufactured, if you need to use all three poles separately,
you
> >> can not occupy two of them in series, therefore you can not achieve the
> >600
> >> volt rating.
> >>
> >> Should we switch the positive lead?  I submit that there may be a
safety
> >> advantage to switching the negative.  The Sunny Boy takes the negative
to
> >> ground.  If the negative is left connected, the array still has
potential
> >> to ground.  If the negative is switched, the array is floating,
therefore
> >> no (or less) shock hazard.  We know this because my helper got zapped
> >> today.  We are still discussing the ramifications so as to avoid this
in
> >> the future.
> >>
> >> Here's another idea:  Why not switch both leads?  Siemens has a circuit
> >> breaker that does the same trick, and the Siemens catalog contains a
> >> drawing that shows one side of DC going through the two series poles
and
> >> the other side going through the one pole.  Is this how I should be
wiring
> >> the DC disconnects for Sunny Boys?
> >>
> >> (BTW, the drawing on the cut sheet for the SB1800 shows only the
positive
> >> switched through one pole.)
> >>
> >> Thanks for considering these nit picky, nerdy questions.  I believe it
is
> >> in considering these details that safety is achieved.
> >>
> >>
> >> William Miller
> >>
>
> __________________________________________________________________
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