Author Topic: New non-polarized 100A @ 150 VDC MNEPV breaker  (Read 763 times)


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New non-polarized 100A @ 150 VDC MNEPV breaker
« on: December 11, 2020, 05:21:38 AM »
The new BREAKERS wall chart shows the MNEPV100-150-2PNP, a non-polarized version of the soon-to-be-discontinued MNEPV100.

Is this new breaker available yet?
I'm not seeing it at any reseller sites, nor even in the products section of the MidNite Solar site.

The reason I'm interested is that I'm getting closer to permitting and installing my new system, and though I already bought the polarized MNEPV100 breakers to use as OCPD and Photovoltaic System Disconnecting Means per 2017 NEC 690.13, as I further study the code (and Bill Brooks' "PV and the NEC"), I've come across 690.13(F)(2), which states that devices marked line and load (i.e., polarized) are not permitted for reverse current.

As discussed in the Classic installation manual, a breaker between the battery and the Classic should have its + terminal connected to the battery, since a failure in the Classic is likely to be a short at its output terminals.
However the "normal" direction of current flow is in the opposite direction, TOWARDS the battery, and so operating the breaker as a disconnect would interrupt current going the opposite direction of how it was designed.

Finally, I think I would actually need a 4-pole version of this breaker, to be able to simultaneously disconnect both the + and - conductors between the Classic and the battery, based on the use of GFP within the Classic, which causes its negative terminal to NOT be "solidly grounded". Because the ground fault jumper causes the negative terminal to be connected to ground through a fuse. In 2017 NEC 690.15(D) it states that a PV Equipment Disconnecting Means must simultaneously open current-carrying conductors that are not solidly grounded. It would seem this must also apply to the 690.13 PV System Disconnecting Means.

[I guess this also means I won't be grounding the negative terminal of the battery bank.]

Brooks extensively discusses how the 2017 code considers the PV system to end between the charge controller and the battery bank (or ESS). So the 690.13 PV disconnect must clearly go here.

Any opinions on this from folks actively complying with the 2017 NEC in their installations?


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Need for two-pole non-polarized 100A @ 150 VDC MNEPV breaker
« Reply #1 on: December 20, 2020, 02:33:55 PM »
The more I study the 2017 NEC and Brooks' book, the more I'm convinced the code requires the PV System Disconnect (per 690.13), in a DC-coupled system using charge controllers, to be between the ESS (battery bank) and the Classic(s). Further, the code requires GFP [690.41(B)] for the DC PV arrays installed on buildings; this is provided by the current models of the MidNite Solar Classic charge controllers. The Classic implements GFP by inserting a fuse between the negative array conductor and the Equipment Grounding Conductor. Therefore, if GFP is enabled via the little jumper inside, the negative conductors at both input and output sides of the Classic are only "functionally grounded", definitely not "solidly grounded", per NEC definitions. Therefore the required PV System Disconnect must break both positive and negative conductors between the battery bank and the charge controller(s).

I guess the OCPD may be allowed to open only the positive conductor from the battery bank; the requirement would be in 240.15(A) and (B), which require opening all ungrounded conductors. Before 2017, the term "grounded conductors" (I believe) included what are now called "functionally grounded" conductors. So my understanding is that under the 2017 NEC we still only need OCPD in the positive conductor.

However if we want to use a circuit breaker as BOTH the required OCPD and as the PV System Disconnect, then it would appear to me that it must open both conductors simultaneously, that is, it must be a two-pole breaker.
Also as I stated above, the CB here must be non-polarized.

As far as I can see, MidNite's circuit breaker offerings do not include such an animal for V >= 125 volts and A >= 80 amps.
Maybe there are other 2-pole DC-rated disconnect switches that can be used, in addition to the single-pole circuit breaker?


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Re: New non-polarized 100A @ 150 VDC MNEPV breaker
« Reply #2 on: May 23, 2021, 10:09:37 PM »
Any luck finding/buying the new non-polarized 150V PV breakers?


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Re: New non-polarized 100A @ 150 VDC MNEPV breaker
« Reply #3 on: May 23, 2021, 11:10:56 PM »

I seem to remember asking that question a couple of weeks ago and I *thought* that the answer was yes...

Let's find out !

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