PV Voltage Goes to Zero When Closing Breaker

Discussion about the Power System PV Combiner (PSPV)

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Bajaloha
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PV Voltage Goes to Zero When Closing Breaker

Post by Bajaloha » Tue Mar 24, 2020 10:30 pm

I've got 117 volts coming from a series of panels into a Midnight PV Combiner box. The voltmeter shows the 117 volts when the breaker is open but these volts go to zero on both sides of the breaker once it's closed. The PV terminals inside the charge controller show zero, as well. The charge controller display also reads zero PV volts. I've checked the polarity of the circuit. In the words of Marvin Gaye, "What's Goin' On?"

fcwlp
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Re: PV Voltage Goes to Zero When Closing Breaker

Post by fcwlp » Wed Mar 25, 2020 9:20 am

You appear to have a short between your positive and negative/ground somewhere in or past the combiner box.
To start the debug process:
  • Shutoff PV breakers,
  • Measure resistance between the positive bus plate and the negative terminal block,
  • I expect it will be ~0, if so you are going to have to move the next interface which could be the CC or an intermediate wiring box,
  • With the PV breakers off and inverter and CC(s) shut down, remove the PV+ input wire at the CC or intermediate wiring box and measure resistance between PV+ and PV-,
  • If reading is ~0 there is a short somewhere between your combiner box and this point.
  • Continue to progress in a methodical fashion through the system.

Bajaloha
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Posts: 5
Joined: Tue Mar 24, 2020 5:14 pm
My RE system: 48V VFXR3648A Inverter
FLEXmax 80 Charge Controller
Samsung Mega 3.3 Kw Rack Batteries
Mate 3s
Midnight 175 Amp Epanel

Re: PV Voltage Goes to Zero When Closing Breaker

Post by Bajaloha » Thu Mar 26, 2020 11:17 am

Thanks for your reply. I followed your directions, but I'm getting zero resistance from the PV panels through the combiner box and into the charge controller. The bare PV+ wire in the charge controller shows 117 volts, as well, with the PV combiner panel breaker closed. Does this mean that the short is somewhere in the epanel? Are there any common wiring errors to be aware of inside the epanel? Nothing is jumping out at me. I appreciate your time!

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Greg T Fordan
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Re: PV Voltage Goes to Zero When Closing Breaker

Post by Greg T Fordan » Thu Mar 26, 2020 11:23 am

1. Turn off PV breaker, but leave battery breaker on
2. On the CC main screen, observe the IN and OUT voltage. The OUT voltage is the battery breaker. The In Voltage is the PV input (breaker is off). It will not be at zero if CC is ok. Due to capacitor action it will build up to about 75% of battery voltage. If it stays at zero, CC is bad. If it is = to battery voltage, CC is still bad. Time to call Tech support.
Greg T Fordan
EngTech
Outback Power Technologies

Bajaloha
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Joined: Tue Mar 24, 2020 5:14 pm
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Mate 3s
Midnight 175 Amp Epanel

Re: PV Voltage Goes to Zero When Closing Breaker

Post by Bajaloha » Thu Mar 26, 2020 2:17 pm

Thanks for weighing in, Greg. I followed your directions and the "PV In" is indeed zero--in fact, every value listed on the CC screen other than the "Out" is displayed as zero. And the "out" value reflects the battery voltage as tested at purchase.

The only other tidbit I wanted to mention that I tried after running through your directives, is that per the other fellow's response, I followed the battery wires from the CC into the epanel and disconnected them, testing each end with the voltmeter. There was 9.5 ohms of resistance with the PV breaker open between each end (+ and - battery wires coming from the CC into the epanel); the resistance increased to around double when I closed the PV breaker, with zero voltage displayed. *But these wires were secured when I followed your directions (Greg's). I don't know if this info sheds any more light on the situation or if the CC is a dud either way... If so...by "calling tech support," does that mean I'll need to arrange an exchange for a working charger--or is there a possibility that they'll be able to direct me as to how to fix the one I have... Just wondering. I appreciate your time on this! All the best.

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Greg T Fordan
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Re: PV Voltage Goes to Zero When Closing Breaker

Post by Greg T Fordan » Thu Mar 26, 2020 4:12 pm

You have a bad CC, most probably shorted FETs, and there is not much else you can do for troubleshooting or repair. If your CC is still under warranty, you can arrange for an RMA to have your CC shipped and repaired at the Phoenix facility.
Greg T Fordan
EngTech
Outback Power Technologies

Bajaloha
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Posts: 5
Joined: Tue Mar 24, 2020 5:14 pm
My RE system: 48V VFXR3648A Inverter
FLEXmax 80 Charge Controller
Samsung Mega 3.3 Kw Rack Batteries
Mate 3s
Midnight 175 Amp Epanel

Re: PV Voltage Goes to Zero When Closing Breaker

Post by Bajaloha » Fri Mar 27, 2020 1:12 pm

Boy, is that a bummer. I'm living in southern Baja, Mexico, at the moment, "holding in place" for the foreseeable future... Oh well, I'll contact Outback and at least let them know the situation, maybe get a dated confirmation that I can use for a return at some point in the future. I don't know how long the warranty lasts. I bought all of the equipment a month ago. In any case, I really appreciate your help on this, Greg, and how quickly you picked up this thread. All the best. Be safe!

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Greg T Fordan
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My RE system: Radian, FM80, FNDC, 48V batt bank

Re: PV Voltage Goes to Zero When Closing Breaker

Post by Greg T Fordan » Fri Mar 27, 2020 1:22 pm

Bajaloha,
Hope you'll work out something in your situation.
I am working at home myself, but still trying to keep up with what's going on in this forum, so that I can jump in when I can confidently put in my opinion.
Good luck in contacting the OB Technical Support.
Greg T Fordan
EngTech
Outback Power Technologies

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