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Which Breaker?

LanduytG

Solar Enthusiast
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Apr 19, 2020
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Getting ready to mount PV panels and pull wire. I need a breaker for this but not sure what to use. Panels will be in series so the breaker will need to be rated for at least 75 volts DC. I like the breakers I have for everything else but they are only rated for 48 volts DC. I could use an inline fuse but not very handy if I want to shut off the panels.

Greg
 
I used these: https://www.amazon.com/gp/product/B07YDZ4GFB

Rated to 400v, in various amp ratings. None of the product specs call out AC or DC. But all the user Q/A says it's DC.

Well it says 50Hz right on the front so those are definitely AC for the Euro market. I wouldn’t use those for DC.

Try these, clearly marked DC:

 
I used these: https://www.amazon.com/gp/product/B07YDZ4GFB

Rated to 400v, in various amp ratings. None of the product specs call out AC or DC. But all the user Q/A says it's DC

If it’s AC, could burn, as in start a fire. There’s some good YouTube videos on this. If it’s AC/DC, sometimes the DC Amperage is nowhere close to the AC. I am by no means an expert, but I have not seen a AC/DC breaker rated the same amps for each.
 
The 400V is AC.

1602544476325.png

The tilde is for AC, and why would a breaker be rated for a Hz?
 
I have touch-safe fuse holder in my < 600VDC strings.
Outback breakers in a separate lower voltage setup. (pay attention to polarity, which matters for their magnetic trip)

Square-D QO panels and 2-pole branch breakers can also be used. UL listed to 48VDC, but with two poles interrupting the circuit, manufacturer says they're good up to 125VDC.

 
Circling around to close the case that the breakers I suggested and have installed are not DC rated breakers - Maybe.

While I don't have extensive knowledge about all things electrical, I can research things (eventually).

The 2 pole breakers I have are the DZ47-63. This is the generic model number that is available from many sources. The product listing for my breakers says they are, "Suitable for isolation in accordance with industry standards: IEC EC 60898-1/GB10963.1."

I looked up EC 60980-1. I'm having trouble finding the actual document for that standard. The link goes to the -2 standard. However, I did find this Schneider Electric blog entry that compares the -1 standard to another: https://blog.se.com/energy-regulations/2014/02/06/iec-60898-1-iec-60947-2-tale-two-standards/

The table in that blog explicitly lists the 60980-1 standard as addressing only AC breakers.
IEC-comparaison.png


There is also a 60980-2 standard (which my breaker does NOT reference) that has this in the summary:

Scope:​

Clause 1 of IEC 60898-1:2015 is applicable except as follows:

Addition at the end of the first paragraph:

This standard gives additional requirements for single- and two-pole circuit-breakers which, in addition to the above characteristics, are suitable for operation with direct current, and have a rated DC voltage not exceeding 220 V for single-pole and 440 V for two-pole circuit-breakers, a rated current not exceeding 125 A and a rated DC short-circuit capacity not exceeding 10 000 A.

NOTE This standard applies to circuit-breakers able to make and break both alternating current and direct current.

Delete the last two paragraphs.

This makes it sound like the -1 standard did address both DC and AC circuit breakers. This confuses me.

ZHIMING GROUP is a another manufacturer of the DZ47-63 series. However, they explicitly label their circuit breaker as DC. They also have a non-DC labeled product that has no mention of a DC rating and specifically references the IEC60898-1 standard. The one I bought does not have that DC designation in the label.

I'm still going with a different breaker, if for no other reason than I don't want to be in a gray area.
 
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Standards not withstanding, the specs on the breaker are clearly for VAC. No VAC breaker I've ever seen has a DC voltage rating the same as the AC voltage rating. The EM clamping force of DC is dramatically higher than VAC as it cycles to 0V 50-60 times per second.

IIRC, a typical 250VAC breaker has a 32VDC rating if dual rated.

Unless it's explicitly clear that a breaker has a specific DC rating, I wouldn't consider using it, and I'm the worst "that's probably close enough" kinda guy on the planet. :)
 
I like to read standards. I've noticed I can google some broad sentences about what a UL standard is, but if I want to find out what UL1178 standard is verbatim, its for sale for $700.

I don't like standards that much. I'd always assumed that would be public domain, I guess not.
 
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