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diy solar

Replaced panel array with existing inverter now PAC reading "0"

pretzelboy said:
took DMM reading at pv disconnect red lead zero black lead fluctuating up to high 400's (neg polarity)
close breaker at disconnect, go to basement turn on/reconnect Sunny Boy
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pretzelboy said:
Definitely positive grounded.
Click to expand...

Find out if your new panels are best off positive grounded (negative biased) or negative grounded (positive biased) to avoid PID.

Manufacturer may claim "PID free" (I didn't see mention on data sheet), but that just means reduced degradation.

Ask them which grounding configuration is better. Ask them about P vs. N type silicon (doping of wafers) and implant (to make P-N junction). From that should be able to figure it out even if they don't clarify grounding.

Grounding in the better polarity should eliminate PID, one less thing to reduce output over time.
 
Hello

Wanted to give an update on the solar panel replacement project I undertook with help and advice from many here.

I had a 2009/2010 grid tied roof mounted solar system that was professionally installed by a contractor that has merged changed many times since 2010. They did a very good professional installation with all codes and permits met, including a straight net metering 100% excess production buyback that continues to this day.

I had a 4.2 kw hour system that at its highest functioning with lots of good sunny days kicked out about 400kwh per month. My usage as it was a weekend and summer home at time was usually 300-400 kwh per month.

I'd have months with only the $20 hookup fee and even get a rebate of 100-150 at end of year.

fast forward to last couple years and im averaging 200-250 kw per month generation due to a combination panel degradation, shading and then in 2023 a panel failure that took out one of the 2100 watt strings ( 0x 210 watt sunpower modules)

I wanted to somehow just replace/upgrade the modules without ripping out and starting over with new inverter etc, ie keep the project simple and straightforward. i started with a major tree trimming ( me on a 60 ft cherry picker with a chainsaw) I can be a very stubborn "do it yourself" person.

went with canadian solar 390 watt panels 14 of which would fit on the existing rails i had by array length--I only had to move the top rail up the roof a few inches to accommodate the taller panels then the same with the bottom rail of the bottom row.

As forum members know I had an issue with the new panels being at a significantly lower rated voltage (Vmp) than the originals the Sunpower 210w rated at 40 volts and the Canadian Solar 390w panels only at 31 volts.

the Sunpower 4000M string inverter (rebranded Sunnyboy 4000us) has an operating voltage of 250-600v; My new array was 2 strings of 7 modules each, producing about 225 volts, which was not enough to put the inverter into operating mode (It would register "waiting")

The solution arrived at was to run all 14 panels as one string, decommissioning, weatherproofing the MC4 connectors no longer used.

Did that last weekend finishing on Monday.
have checked throughout week to see how things are going including sleet crusting and snow yesterday. Everything running beautifully.
Today as of 2 pm ( clear cold sunny day) system has already produced 20kwh humming along at full output (4060w Pac)

Q: I know that the 5460w total module output is higher than the recommended input for the inverter (4800 w); is that going to significantly stress the inverter to the point of lessening its lifespan? I'm trying to get the most out of what I already have, but understand that 15 years is about the lifespan of some of these older string inverters.

Thanks everyone for putting up with me ;-)

G
 
pretzelboy said:
Q: I know that the 5460w total module output is higher than the recommended input for the inverter (4800 w); is that going to significantly stress the inverter to the point of lessening its lifespan?
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You are fine, excess power will not be captured, and you’ll run your system at full power more often, which will reduce it’s reliability somewhat. However, you are long past the infant failure part of your reliability curve, so I’d say you’re good.
 
pretzelboy said:
Q: I know that the 5460w total module output is higher than the recommended input for the inverter (4800 w); is that going to significantly stress the inverter to the point of lessening its lifespan? I'm trying to get the most out of what I already have, but understand that 15 years is about the lifespan of some of these older string inverters.
Click to expand...

It is fine to overpanel Sunny Boys in terms of PV watts.
Panels normally put out less than rating, and Sunny Boy will only draw up to 100% of what it can deliver.

Never go over Voc limit, including when voltage is higher cold.

OK to go over max operating current, inverter won't draw more.

Best not to go over max short circuit current. Especially if you accidentally connect string backwards, the reverse polarity diode would burn up. So connect one string first and confirm operation before connecting all strings if you want to push that.

Heat is one thing that shortens inverter life. Look up efficiency chart vs. PV voltage and AC voltage.
98% vs. 99% doesn't sound like much, but 2% turned into heat is twice the temperature rise of 1% loss.

Avoid direct sun on inverter, shade it if sun hits it middle of day.
Make sure there is space for ventilation.
Check and clean grills. Note if a fan fails and replace it.
 
Hedges said:
It is fine to overpanel Sunny Boys in terms of PV watts.
Panels normally put out less than rating, and Sunny Boy will only draw up to 100% of what it can deliver.

Never go over Voc limit, including when voltage is higher cold.

OK to go over max operating current, inverter won't draw more.

Best not to go over max short circuit current. Especially if you accidentally connect string backwards, the reverse polarity diode would burn up. So connect one string first and confirm operation before connecting all strings ifyou want to push that.

Heat is one thing that shortens inverter life. Look up efficiency chart vs. PV voltage and AC voltage.
98% vs. 99% doesn't sound like much, but 2% turned into heat is twice the temperature rise of 1% loss.

Avoid direct sun on inverter, shade it if sun hits it middle of day.
Make sure there is space for ventilation.
Check and clean grills. Note if a fan fails and replace it.
Click to expand...
Hi i
s Voc limit on inverter the "DC input voltage range"? My new panels Voc is/are 36.4 volts each so about 510v for the string.

inverter input voltage range is 250-600v

"peak power tracking range" is 250-480V

G
 
Nice-- 30kwh of output today and sunset isn't for another 1/2 hour.
My average usage is about 20Kwh a day, this is a harbinger of a close to $ net zero utility bill going forward.

(smiles a very independent satisfied smile)
(nods a humble nod to good folks at DIYsolarforum)

G
 
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