Hmmmm....Square D QO and QOB circuit breakers

Jim Burrow

Solar Addict
In my circuit breaker panel/box, I have one 50 amp main, one 30 amp 240vac (for air conditioner), and a bunch of 15amp and 20 amp breakers for the house. All are from Square D. After I retired, I worked part-time for a hardware store in the electrical department. I could be wrong since it been over 15 years since I worked in that store, but I don't recall Square D making a distinction between AC and DC.

I too have a lot to learn as I'm new to the Solar stuff and working with DC components.
 

apctjb

Solar Addict
Yes, QO breakers used to have a 48V 5ka AIC rating, not sure if they still do however.
 

Rich Palmisano

Just a fiddler at heart...
In my circuit breaker panel/box, I have one 50 amp main, one 30 amp 240vac (for air conditioner), and a bunch of 15amp and 20 amp breakers for the house. All are from Square D. After I retired, I worked part-time for a hardware store in the electrical department. I could be wrong since it been over 15 years since I worked in that store, but I don't recall Square D making a distinction between AC and DC.

I too have a lot to learn as I'm new to the Solar stuff and working with DC components.

Yes they are not stated DC compliant on the breaker itself. This data is 2008, so...yes, take with grain of salt and some research.

A little research: Straight from their current website:

 

mopat

Solar Addict
Refer to Square D Data Bulletin 0601DB0401 for additional information on dc-rated circuit breakers :

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Steve_S

Offgrid Cabineer, N.E. Ontario, Canada
I use Square-D on my AC side. Some of their breakers have a DC rating but generally, that is much smaller than what we are dealing with and they are not recommended. DC will weld contacts without a blink. Square-D also makes special application breakers which are not normally stocked items but can be ordered from their shipping dept at very reasonable prices as well. For example, I needed a Single Pole 45A which isn't stocked anywhere (homedepot etc) but ordered online, it came out to the same as a QO-30A. Best part of Square-D, is you can get them anywhere if needed and they are not expensive but high quality.

There is no substitute for good quality DC Breakers. Midnite Solar, for example, uses Carling Technologie DC Breakers: https://www.carlingtech.com/renewable-energy

Eaton Energy now owns Bussman & Cooper (great quality DC goodies) They are now listed under Eaton/Cooper/Bussman. Many of the BlueSea products are Bussman or Cooper as well.
 

apctjb

Solar Addict
Pay attention to the AIC rating for the breaker. Others on this forum have suggested AIC of >15kA is needed when used with larger LiFePO4 batteries. I was able to grab some Fuji Electric breakers on Ebay for my main battery and PV disconnect which have a 250VDC 15kA rating.
 

mopat

Solar Addict
Are QO load centers suitable for use on a 125V DC application?
The QO single Phase Main Lug Load Centers are SQUARE D CERTIFIED for use on 125 V DC systems. The load centers listed ARE NOT MARKED for use on this voltage system, however are suitable for the application. The positive (+) conductor should be connected to one phase lug, while the negative (-) conductor should be connected to the other phase lug. USE QO 2-POLE BRANCH BREAKERS ONLY. QO branch breakers, 10-70 ampere, are also SQUARE D CERTIFIED for use on 125V dc systems. Short circuit current rating is limited to 4,000 amperes (10-30 ampere) or 10,000 amperes (35-70 ampere) when used on 125V dc. https://www.se.com/us/en/faqs/FA95999/
 

PHoganDive

Solar Addict
This video gives a good demonstration why AC only rated breakers are not acceptable for DC use, and why DC rated breakers have much better arc supression incorporated in their design.

 
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