[RE-wrenches] AC breakers used in DC applications

[R Ray Walters]

My understanding was that the din mountable QOU breakers were rated to 125 vDC, and are internally the same as the QO. The difference was the connectors, and the mounting method.
I've used the QOUs reliably at 120 v nom on an EV, (but don't try this at home, kids)
We still use the QOs sometimes based on cost and availability, but I don't use them on anything over 24 v nominal anymore. 
They were handiest in that one breaker line could cover AC and low volt DC.
With MPPT high voltage arrays, and some of Midnite Solar's new products (Mini DC & Baby DC boxes), though, we've found less and less of a place for the venerable QO line.

R. Walters
ray at solarray.com
Solar Engineer




On May 16, 2010, at 2:25 PM, Kurt Albershardt wrote:

> Square-D tells me they have tested the breakers to a higher voltage (can't recall now whether it was 80V or 125 VDC) but the listing is indeed for 48 Volts.  24V battery systems are useful for a lot of applications, but the unfortunate lack of a 5A breaker means we can not use them to derive a Class 2 supply, which would make them about 10x as useful to me.
> 
> 
> 
> On May 15, 2010, at 9:22 , jay peltz wrote:
> 
>> Hi Rebekah,
>> 
>> The 48v is a max rating not a nominal rating.
>> So yes only good for 12 and 24v systems.
>> 
>> However with CBI breakers I don't understand why the need for QO for DC anymore?
>> 
>> jay
>> 
>> peltz power
>> On May 15, 2010, at 6:28 AM, Rebekah Hren wrote:
>> 
>>> Hi,
>>> One thing to be clear about is whether these are listed for "48 volt systems," or for max 48 volts?
>>> I was under the impression that they were max 48 volts, meaning you really shouldn't use them on a system >24volts nominal.
>>> 
>>> Rebekah Hren
>>> North Carolina
>>>  
>>> 
>>> 
>>> http://thecarbonfreehome.com/
>>> 
>>> --- On Sat, 5/15/10, Kurt Albershardt <info at es-ee.com> wrote:
>>> 
>>> From: Kurt Albershardt <info at es-ee.com>
>>> Subject: Re: [RE-wrenches] AC breakers used in DC applications
>>> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
>>> Date: Saturday, May 15, 2010, 12:59 AM
>>> 
>>> The Square-D catalogs are marginally clear on which breakers are listed for DC and for what voltages, but when I tried to select an appropriate load center for a DC application earlier this year I quickly ran into a number of conflicts in their catalogs.  Here is the response from Schneider tech support (Case# 4845778 on 1/19/10 in case anyone runs into problems with an inspector):
>>> 
>>> 
>>> 
>>> The load center catalog numbers listed below are UL LISTED, File E6294, for use on 48 V dc systems. The load centers listed ARE NOT MARKED for use on this voltage system, however are suitable for the application. QO branch breakers, 10-70 ampere (1 and 2 pole) are also UL LISTED for use on 48V dc systems. Short circuit current rating is limited to 5,000 amperes when used on 48V dc.
>>> QO24L70F, S or RB QO612L100F, S, DF, DS, DFCU, DSCU, RB, TRB or RBCU QO816L100F, S, DF, DS, DFCU, DSCU, RB or RBCU
>>> QO112L125G or QO11224L125G QO116L125G QO11624L125G QO120L125G QO12024L125G QO124L125G or QO12030L150G QO124L150G QO130L150G or QO112L200G or QO130L200G or QO13040L200G QO142L225G or
>>> GRB or GRB
>>> or GRB
>>> GRB
>>> GRB GRB GRB or GRB QO142L225GRB
>>> 
>>> 
>>> I can email the PDF to anyone who needs a copy.
>>> 
>>>  
>> 
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