# DC shut-off / breaker / switch...

#### Externet

Joined Nov 29, 2005
1,847
Hi.
From what I know, DC should not use AC circuit breakers because their distance between contacts is not wide enough when trips and may not extinguish arcing.
There is some auxiliary panels for HVAC that use a pull tab to disconnect. Yes, DC breakers do exist too.

Would those be suitable for a 250 VDC / 15 A solar array ?

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#### schmitt trigger

Joined Jul 12, 2010
497
Your assessment is correct in regards with the regular AC rated breakers for DC. They should not be used.

Now, whether the pull plug you show is suitable, I sincerely do not know.

#### LowQCab

Joined Nov 6, 2012
2,055
As a general "Rule-of-Thumb" for stopping a DC Arc,
you need ~1.5-inches of separation for every ~100-VDC.
2.5 X 1.5 = 3.75 inches of Air space between Terminals.
This Air-Conditioner Disconnect aint gonna get it.

With proper DC rated Fuses BEFORE the disconnect,
you can probably get away with it,
but you will be personally exposed to a potentially serious Plasma-Arc.

Don't play games with High-Voltage-DC.
You could easily burn-down your House.
Use ONLY standard, Commercially available, Switch-Gear rated for your DC Voltage.
.
.
.

#### Externet

Joined Nov 29, 2005
1,847
That is a well chosen demonstration video, thanks.

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#### Lo_volt

Joined Apr 3, 2014
267
The specs on the pull tab disconnect should tell you whether it's allowed for use as a DC disconnect. If you can't find it contact the seller or the manufacturer.

Don't assume anything and don't take the word of anonymous forum users when it comes to your safety.

#### AnalogKid

Joined Aug 1, 2013
10,062

#### Lo_volt

Joined Apr 3, 2014
267
Externet it sounds like you're putting together a solar array. When I installed my own, I took a course on designing and building solar arrays. It helped a lot. Here in Maryland, when I installed my array, I was not required to be certified to design my own array. Maryland has since changed their rules and the system designer must provide proof of NABCEP certification.

Fortunately, the distributor that I purchased my system from also has a NABCEP certified engineer on staff. For arrays that I've worked on for other people, I've leaned on them to help with the designs. I'd suggest you talk to whomever you are buying your equipment from to see if they've got someone qualified available on staff.

As for your DC disconnect, here's what I used:

https://www.se.com/us/en/product/HU...ible,-30a,-3-poles,-30-hp,-600-vac-dc,-nema1/

Schneider's list price is currently $279, but it's available for under$150 at other sellers.

#### Externet

Joined Nov 29, 2005
1,847
Thanks, Lo_volt. Yes, installing photovoltaic system.
The seller of the equipment with apparent good experience and knowledge suggested a method that prompted asking at this forum. Seems uncomplicated, basic, less cost and less parts. Am reading and learning on my side too.

Panel array(DC)-------------Gridtieinverter(AC)-----------AC60Adisconnect*----------30A breaker in main panel

Blue is outside the house, * for firemen to disable the system. Can be of the pull tab image on post 1 or AC breakers (below)

The inverter is ----> https://www.energysage.com/solar-inverters/solarcity/2613/h6/

Will find out at some point what color is the smoke...

#### Lo_volt

Joined Apr 3, 2014
267
Will find out at some point what color is the smoke...
Cool stuff. The best part is turning it on for the first time!

Good luck and keep us apprised of your progress.