MidNite Solar / CBi Breaker Ratings

[solardad]

Planning on expanding my PV array and the total voltage of the series based on VOC could be as high as 330v when "cloud edge effect" takes place.
I use a MidNite breaker today (rebadged CBi), MIDEPV15-300, which is rated for 300v limit. Majority of the time the expected voltage will be in the 280-290 range.

https://www.midnitesolar.com/produc...BREAKERS&productCat_ID=16&sortOrder=20&act=pl

I came across this study done by Midnite where they were testing their breakers at 25% above there rating capacity 125v breakers tested at 165v: http://www.midnitesolar.com/pdfs/MidNite_165vdc_ETLtest.pdf

The 2p breaker that I have is stamped with a 250v limit but they added a ETL sticker that ups the limit to 300v.

Any thoughts on the tested vs. rated capacities of the breakers? If I go by their test rating (165v) then I am at the 330v rating (two poles in series).
Wondering though if these could safely handle a higher voltage? Anyone using these in a similar setup?

MidNite's next inline offering is rated at to 600v 4p which would require an extensive redo of my current shutdown and breaker box setup so would like to stay in a 2p scenario.

I could go the mini din rail route and get a breaker rated at 400v or 500v but they don't seem as well built:
https://www.ebay.com/itm/MCB-50A-El...aker-PV-Solar-Energy-Air-Switch-/113277763760

Thanks

 

[tictag]

Nobody is going to reply saying, "Yes, totally fine to exceed your manufacturer's specification ... go for it!" so if that's what you were hoping for then I think you may be disappointed.

That being said, the voltage being applied to such a breaker would effect two aspects:

1. Resistance. Are the materials making up the breaker capable of insulating that much potential?
2. Arc. Maintenance, or rather cessation, of any disconnection arc.

In terms of the first, I can't imagine a manufacturer using a material that would be sensitive to a <10% increase in any one specification. I mean apply 300V and you're fine, apply 330V and all of sudden you get tracking? I doubt it.

In terms of the second, the likelihood of you either manually disconnecting or the breaker activating during a 'cloud effect' event is marginal at best. The breaker is only there should a catastrophic failure occur and, assuming you have built your PV system to code, your cable and ancillary equipment would be rated for more way more than than the array could even theoretically generate e.g. Isc + multipliers.

And with that said, I would recommend that you stay within the ratings and specifications your manufacturer has determined as safe!!

 

[solardad]

Nobody is going to reply saying, "Yes, totally fine to exceed your manufacturer's specification ... go for it!" so if that's what you were hoping for then I think you may be disappointed.

That being said, the voltage being applied to such a breaker would effect two aspects:

1. Resistance. Are the materials making up the breaker capable of insulating that much potential?
2. Arc. Maintenance, or rather cessation, of any disconnection arc.

In terms of the first, I can't imagine a manufacturer using a material that would be sensitive to a <10% increase in any one specification. I mean apply 300V and you're fine, apply 330V and all of sudden you get tracking? I doubt it.

In terms of the second, the likelihood of you either manually disconnecting or the breaker activating during a 'cloud effect' event is marginal at best. The breaker is only there should a catastrophic failure occur and, assuming you have built your PV system to code, your cable and ancillary equipment would be rated for more way more than than the array could even theoretically generate e.g. Isc + multipliers.

And with that said, I would recommend that you stay within the ratings and specifications your manufacturer has determined as safe!!

Thanks for the comments.

 

[Robin Gudgel]

The MidNite breaker will be fine. Don't lose any sleep over it.