Kent Osterberg wrote:
Thanks Robin. I've long been suspicious that the CBI circuit breakers
should not be run at 100% for a couple reasons:
1) I've seen too many 60-amp CBI breakers on charge controllers trip
habitually. But a replacement 60-amp breaker works fine.
2) Nothing in the CBI literature that is available on their web site
says the QY breakers are rated to operate at 100%.
The published trip curve shows that the breaker is supposed to hold at
less than 105% of rating and trip at more than 130% of rating.
The trip curve for a QO breaker shows that it is supposed to hold at
100% of rating and trip at 130% of rating too. Yet we know that it is
not intended for continuous operation at 100% of rating.
Kent Osterberg
Blue Mountain Solar, Inc.
HI Kent and Allan (isn't that the name of a TV show, a movie or
furniture store ?)....
More from Robin. I'm just relaying, but you can email him off list for
more info if you like
and take it from here unless there is something substantial to report.
Thanks,
boB
I have found enough information now from manufactures like CBI, Carling,
Heinemann and others that claim Hydraulic/magnetic breakers do not need to
be de-rated. It is not in the NEC, but Allan may be correct that if the
manufacturer says de-rating is not required, then it isn't required. Do a
Google search on "hydraulic/magnetic de-rating" You will find a lot of
information that substantiates the old myth. I was trying to find it in the
NEC, but it isn't there. I'm going back to my myth!
Robin Gudgel
boB Gudgel wrote:
Forwarding a message from Robin Gudgel...
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 <al...@positiveenergysolar.com>
Reply-To: al...@positiveenergysolar.com, RE-wrenches
<re-wrenches@lists.re-wrenches.org>
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.
*Allan** Sindelar*
al...@positiveenergysolar.com <mailto:al...@positiveenergysolar.com>
NABCEP Certified Photovoltaic Installer
EE98J Journeyman Electrician
*Positive Energy, Inc.*
3201 Calle Marie
Santa Fe, New Mexico 87507
*505 424-1112*
www.positiveenergysolar.com <http://www.positiveenergysolar.com/>
robert ellison wrote:
I believe that the breakers from CBI, Midnite and Outback are
hydraulic / magnetic and may be operated at 100% While the derating
applies to all others that are Thermal / magnetic,
Bob
On Fri, Apr 2, 2010 at 11:14 AM, Kent Osterberg
<k...@coveoregon.com <mailto:k...@coveoregon.com>> wrote:
Erika,
You should refer to NEC 690.8 this information. There are two
issues that contribute to the 1.56 factor. First is that the
maximum current from the PV array is considered the short circuit
current multiplied by 1.25 to account for higher than standard
irradiance such as cloud edge effect, high altitude, and high
operating temperature. The second multiplier of 1.25 is because
PV current is considered to be continuous. All conductors (and
breakers) operating continuously (over three hours I believe) that
are subject to NEC rules are limited to 80% of the ampacity in
Table 310.16. The two 1.25 factors equals 1.56.
For normal operation, wires selected under this criteria are
conservatively rated. But it is also the objective of the NEC to
design power systems in a manner that they will remain safe under
abnormal circumstances.
Kent Osterberg
Blue Mountain Solar, Inc.
Erika M. Weliczko wrote:
To my understanding the 156% on PV source and output circuits is
related to the ability of PV to deliver more than rated and be
continuous.
Therefore, the wire has to be able to carry this current, so now
the temperature and fill corrections are applied to find the wire
capable of the 156%.
I am in a debate where the question is why correct for temp and
fill on 156% of ISC and spend all that extra money when the
normal operating is at Imp. Or why correct the 156% but why not
correct the Isc or Imp.
I am going to stick to the fact that the circuit has to carry the
156% under all conditions.
Thoughts?
Erika
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
<mailto:RE-wrenches@lists.re-wrenches.org>
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
<http://www.re-wrenches.org/etiquette.htm>
Check out participant bios:
www.members.re-wrenches.org <http://www.members.re-wrenches.org/>
------------------------------------------------------------------------
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive:
http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
------------------------------------------------------------------------
No virus found in this incoming message.
Checked by AVG - www.avg.com
Version: 9.0.800 / Virus Database: 271.1.1/2787 - Release Date: 04/02/10 23:32:00
------------------------------------------------------------------------
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
_______________________________________________
List sponsored by Home Power magazine
List Address: RE-wrenches@lists.re-wrenches.org
Options & settings:
http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
List rules & etiquette:
www.re-wrenches.org/etiquette.htm
Check out participant bios:
www.members.re-wrenches.org
