Low-Temperature Overvoltage Bypass switch

I ran across some 260W Ningbo modules, which seemed to be appropriate for one of our recent projects. I overlooked the o.c. voltage -- just assumed it would be in the vicinity of 35V a typical 230W module. Instead, the voltage is roughly 60! So, what I thought was easily well within range is now 11V over 600 in the coldest temperatures.

I thought the solution was going to be the Apollo Solar Low Temperature Overvoltage Bypass (LTOB) switch, which automatically switches one module out of the string in cold temps. However, that switch was discontinued in 2009. Its ghost still lingers on a few websites.

Anyone know of another solution? I found one micro inverter with a 65V input so far, but the LTOB switch would be a much quicker and cheaper fix. Also, I would really need a micro inverter with an absolute maximum of 70V+ to comply (not 65).

-AJ

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Low-Temperature Overvoltage Bypass switch

    I don't think I have any magic answers for you... Ouch.

    Removing one panel from each series string is the only other solution I can think of--And regarding the GT inverter, does it actually function up to 600 VDC input or does it shut down or go out of MPPT over 500 or 550 VDC?

    The only other option; are there currently any GT inverters that operate in the >600 VDC to 1,000 VDC range (Europe's max of 1,000 VAC?). That appears to be legal even in the US as NEC/NRTL usually use 600 VAC as the maximum working/rated voltage, so sqrt(2)*600VAC=848.5 volt VDC Max with 600 VAC rated wiring.

    Sorry I cannot offer anything else (that I can think of).
    -Bill

    PS: Your idea of placing the last couple panels on Micro Inverters really does sound like the best solution if you have to keep the array wattage as quoted (and the issue of extra 240 VAC branch circuit, any issues with monitoring can even cause problems there).
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset