Replacing old Mitsubishi panel

DanKegel

My 2008-era rooftop system, Xantrex GT 4.0 plus 22 Mitsubishi PV-UD175 panels, needs some love.
One panel shattered in the storm last month, and finding exact replacements is hard.  I found some of the 185 watt panels, though.
Any risks with that substitution?

BB.

It sounds like you may have 11 series * 2 parallel strings or is it (probably not) 22 series string * 1 string of panels?

Your panels are(?):

http://www.solardesigntool.com/components/module-panel-solar/Mitsubishi/PV-MF175UD4/specification-data-sheet.html

• STC Power Rating 175W
• PTC Power Rating 156.1W 1
• STC Power per unit of area 12.4W/ft2 (133.2W/m2)
• Peak Efficiency 12.7%
• Power Tolerances -5%/+10%
• Number of Cells 50
• Nominal Voltage not applicable
• Imp 7.32A
• Vmp 23.9V
• Isc 7.93A
• Voc 30.2V

Ideally, you want to "match" Vmp-panel within 10% (24 volts +/- 2.4 volts). And match Imp current +/- 10% if you have 2x parallel strings.

Can you tell us a bit more about your solar array configuration?

Your options appear to be:

• find a panel +/-10% on Vmp & Imp for replacement
• remove the "bad panel" electrically (and/or physically) and run a 20 panel array for now
• Find two new panels that "match" Imp (10%), remove one bad panel from string 1 and one good panel from string 2, and use the two new Imp matched panels (and keep the spare "good panel" as a replacement if ever needed).

One other option... Assuming 11 series x 2 parallel strings... the actual Vmp array needs to match Vmp-array:

• 23.9 volts Vmp * 11 = 262.9 volts Vmp-array-std
• 262.9 volts * +/- 10% = +/- 26.29 volts Vmp "new panel"

So, in theory, you can match a replacement panel with Imp=7.32 volts +/10% and Vmp=23.9 volts +/- 26.29 volts

In theory, you could simply bypass the broken panel and the array+GT inverter should be "OK" (albiet with the loss of 175 Watts of panel).

Or you can find a "reasonable match" 23.9 volts Vmp +/- a few volts and "match Imp" and the system will be pretty much good as new.

For example of a "sort of fix" here is a 140 Watt panel @ 12 volts (and some other single panel sort of  matches):

https://www.solar-electric.com/ameresco-bsp140-12-140-watt-12-volt-solar-panel.html

Electrical Specifications:

• Maximum Power (Pmax): 140W
• Voltage at Pmax (Vmp): 19.4V
• Current at Pmax (Imp): 7.21A
• Short-Circuit Current (Isc): 7.77A
• Open-Circuit Voltage (Voc): 23.1V

https://www.solar-electric.com/solarland-slp150-12-35mm-150-watt-12-volt-solar-panel.html

SLP150-12 Specifications:

• Has 35mm frame
• Maximum power (Pmax): 150 Watts
• Nominal voltage: 12 Volts DC
• Voltage at Pmax (Vmp): 18.5 Volts DC
• Current at Pmax (Imp): 8.11 Amps DC
• Open-circuit voltage (Voc): 22.2 Volts DC
• Short-circuit current (Isc): 8.68 Amps DC
• Power tolerance: +/- 5%
• Dimensions: 59.06" x 26.57" x 1.38"
• Weight: 26.68 pounds

https://www.solar-electric.com/solarland-slp200s-24u-200w-24v-solar-module.html

SLP200S-24U Specifications:

• Maximum power (Pmax): 200 Watts
• Nominal voltage: 24 Volts DC
• Module efficiency: 20%
• Voltage at Pmax (Vmp): 33.73 Volts DC
• Current at Pmax (Imp): 6.17 Amps DC
• Open-circuit voltage (Voc): 39.21 Volts DC
• Short-circuit current (Isc): 6.5 Amps DC
• Power tolerance: ± 5%
• Dimensions: 61.81" x 27.76" x 1.38" (35mm)
• Weight: 26.84 pound

The above are possible "close enough to function" matches that I could quickly find... You might find the shipping costs of larger format panels to be pretty high... Checking with local to you suppliers and see what they have that could match are options.

Replacing older panels is difficult. The available panels keep changing and can be difficult to find replacements for.

Another option would be took at replacing the entire array... New panels are in the $0.50 to $1.00 per Watt price range (not including labor and shipping). Much less expensive that my array from 20+ years ago....

-Bill

DanKegel

I think it's two strings of 11, as you suspected.

Dunno if they are literally connected in parallel, guess I should rtfm for the inverter.

Happy to just pull the old panel, I should check if there is enough slack in the cables to bypass the hole (assuming the strings aren't really jumpers in parallel?).

BB.

Assuming that your panels use MC4 connectors--You can get pre-made cable sets (and various "Y" adapters):

https://www.solar-electric.com/search/?q=mc4+cables

If you choose to jumper around the missing panel (or change to 10 series * 2 parallel) you are connecting the "missing panel" jumper (if needed).

-Bill