PV disconnect vs. DC breaker

[Devo1982]

Right now I don't have a dedicated PV disconnect between my panels and my AIO inverter. However, I do have a suitable DC breaker. But I know that I should have a proper switch for safe disconnection purposes if ever I need to do some maintenance.

My question (for my own understanding really) is why can't the breaker be used as a cut off switch? Isnt it designed, in theory, to cut current if it gets too high? So in that scenario wouldn't it risk arcing and not be a suitable safety device anyway?

Thanks in advance. Genuinely looking to increase my knowledge

 

[Brucey]

Only a few DC breakers are designed for multiple operations at load. Also it's often the case that a breaker is only configured on the positive, generally a code required disconnect will require disconnection of the positive and negative.

So if you have a fully rated DC breaker and its connected to both positive and negative PV that can double as a disconnect.

 

[Devo1982]

Thank you. No code involved where I am (Philippines) and my DC breaker is spec'd for my setup and handles + and -.

 

[little solar]

Ok I been using a breaker for a off / on PV main and seems to work but not the correct isolation switch to use
Myself keen to know . I got these on my 12v set up,1 for the PV main, 1 for the battery, 1 for the mppt , 1 for the inverter and turn system on and off in sequence instead of direct straight on, I just feel safe doin it like that,
Dont worry I got new one coming

 

[SeaGal]

I just feel safe doin it like that

... feel safe with the bare PV screw exposed like that? Those little plastic DIN covers are quite cheap

 

[little solar]

... feel safe with the bare PV screw exposed like that? Those little plastic DIN covers are quite cheap

Thanks never came with any but now you mention I shall fix that

 

[SeaGal]

... or a bit of insulating tape would work too !

 

[Devo1982]

Forgot to say that my breaker is DC1000v 16a. My PV array is 6x580w in series (about 260v and 11a) . Is my breaker okay to use as a disconnect switch?

 

[Q-Dog]

A lot of these breakers are polarized and can arc/melt if disconnected under load when connected backwards.

 

[Brucey]

Forgot to say that my breaker is DC1000v 16a. My PV array is 6x580w in series (about 260v and 11a) . Is my breaker okay to use as a disconnect switch?

Impossible to say without knowing more about the breaker specifics. There's a lot of garbage available online.

 

[Devo1982]

Impossible to say without knowing more about the breaker specifics. There's a lot of garbage available online.

I live in the Philippines mate. My breaker is the finest (or not) that China has to offer

 

[Devo1982]

This is the bad boy: https://ph.shp.ee/P7QYgyG

 

[Brucey]

Link requires login for me, proceed with extreme caution with a random breaker.

 

[littleharbor2]

This is from some Midnite Solar data sheets for their high voltage DC, PV circuit breakers. Note the endurance ratings with and without current flowing. I would not be comfortable using any CB without a spec regarding operation with current flowing

Product Type Circuit Breaker YA Ambient Operating Temperature-40 °C to +85 °C Mounting Options Dual (DIN and Mini rail), DIN rail mount Time Delay Curves Various Endurance 10000 operations; 1500 with current, 8500 without current (IEC 60947-2 Clause 7.2.4.2)

 

[Devo1982]

Link requires login for me, proceed with extreme caution with a random breaker.

 

[cdsolar]

I use a Midnite Solar 2-pole breaker as my disconnect. Midnite breakers are rated to break the full load and handle the full load continuously. UL too. The only brand I would trust.

Here is mine: (30A version):

Product - MidNite Solar

MidNite Solar Product Page.

www.midnitesolar.com

 

[robbob2112]

That physical size breaker makes me seriously doubt 1000v... maybe 300v if I was being generous. Were it me I would get a spare and drill out the rivets and check that it actually has an arc chutes and magnet.... you can check if it has a magnet just by holding a compas needle near it. There have been many pictures where the breaker had nothing but a bit of a solder blob and a spring. No arc chutes, no magnet, no nothing

 

[Devo1982]

That physical size breaker makes me seriously doubt 1000v... maybe 300v if I was being generous. Were it me I would get a spare and drill out the rivets and check that it actually has an arc chutes and magnet.... you can check if it has a magnet just by holding a compas needle near it. There have been many pictures where the breaker had nothing but a bit of a solder blob and a spring. No arc chutes, no magnet, no nothing

Thanks for the suggestion. I've just ordered another as they're so cheap, which I will dismantle and take a look. I'll post back with my findings.

 

[Devo1982]

Got my brother-in-law to dismantle one of the extremely cheap Chinese breakers. You can see what's inside in this video (starting at the 8.57 mark).

 

[robbob2112]

The one linked is a magnetic type with arc chutes and all the needed do-dads looks like it is polarized from the orientation of the chutes.
not all look that well made.

 

[Devo1982]

The one linked is a magnetic type with arc chutes and all the needed do-dads looks like it is polarized from the orientation of the chutes.
not all look that well made.

So are you saying it's not that bad?

 

[robbob2112]

The ones you linked looked well built. Assuming it is exactly the same as yours it is good. Just make sure to follow the polarization markings if there are any. The plus marks are to the most positive place. From mppt to battery the panels are most positive. For battery to inverter/charger you must use non-polarized breakers.