Regarding the first part: yep, it let me keep the customer's system
working on a job in the middle of nowhere using what I had on the truck
(famous cop-out words, I know).
Regarding the 100% rating, Robin, isn't that provided by the
manufacturer, determined through the listing process? If CBI had it
tested and listed by a NRTL to 100%, that would qualify it, and the
Code would recognize it. If not, it's 80%. Can CBI simply provide a
thumbs-up (with documentation) or down?
Thanks, Allan
Robin Gudgel wrote:
The CBI QY series of DC breakers have an arc
shoot that is required to
quench a DC arc. This breaker would work just fine as an AC breaker
although
is not marked as such. I am not sure if the AC breakers (QL, QZ and QZD
series) have the arc shoot. I was told years ago by CBI that the AC and
DC
breakers are built the same, but I had never broke one open to see if
the
arc shoot is present on AC breakers until today. The AC breakers do in
fact
have the same arc shoot as the DC breakers. CBI just marks the outside
of
the breakers differently. You don't want to get called on the AC vs. DC
issue by an inspector because you are going to lose that battle. It
makes
things a bit confusing to have a DC breaker in an AC circuit even
though
they are identical inside. I believe Allan Sindelar was in the field
and had
a situation where it saved a bunch of time and hassle to use a QY
breaker
instead of a QL that he did not have on hand. I had told him that the
DC
breaker would function just fine as an AC breaker. That installation
was
safe, but an inspector would probably make you change to an AC breaker.
I remember years ago seeing in print that a Hydraulic/Magnetic breaker
could
be used at 100% duty rating where as a thermal breaker could only be
used at
80%. I have searched and searched to find this written explanation
again to
no avail. I thought it was in the NEC, but I now believe I was wrong.
If the
NEC does not allow the use of H/M breakers to be used at 100% duty
cycle,
then it just is not allowed. It is true that the H/M breakers are not
affected by temperature like thermal breakers are, but that in itself
doesn't overrule the NEC. I personally have been spreading this myth to
hundreds of installers for 10 years. I now believe I was wrong. Sure
wish I
could find that written explanation from years ago! Perhaps it came
from CBI
or some other circuit breaker manufacturer? (see below) Maybe an old
version of the NEC?
The NEC is the top authority, so please use the same de-rating
guidelines
for CBI as for thermal breakers.
Sorry for perpetuating this widely accepted myth.
PS. Robin found this and thinks that this may have been one of the
texts but still
does not override NEC requirements
From Heinamann:
Continuous operation at 100%current.
There
is no such assurance with a thermal device, which may
fail to carry rated current when subjected to above normal ambient
temperatures. A Heinemann breaker rated at 20 amperes, for example,
will sustain 20 amperes, even at elevated temperatures. Derating
and other forms of temperature compensation are unnecessary.
Robin Gudgel
MidNite Solar
-------- Original Message --------
Subject: Re: [RE-wrenches] DC wire sizing
Date: Fri, 02 Apr 2010 16:35:49 -0600
From: Allan Sindelar <[email protected]>
Reply-To: [email protected], RE-wrenches
<[email protected]>
Yes, they are 100% duty rated. Also, a little-known fact about the CBI
breakers used by Midnite and Outback, gleaned from conversations with
Robin Gudgel: because of this hydraulic/magnetic construction, all are
capable of controlling both AC and DC, even if not listed as both.
|
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