Calculating system Yields and GTI Inverter efficiency

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solaris3000
solaris3000 Registered Users Posts: 24 ✭✭
in Grid Tie and Grid Interactive Systems #1
Hello All
I have 455watt 4 panel system installed and I'm not seeing more that 340 watts exiting the inverter.
Using watts up meter, And a 24v configuration.
I made several changes over several months including the change from 12v to 24v and I can't seem to get past this 340watt threshold...

With a 600 watt Sun GTI rated 92% efficiency.

Specs:
25feet from array to Inverter
PV Cable - 2 types used at PV array
4 AWG cable from Panels to Load center
GTI connected to Load center via 40 amp Breaker.

Array configuration
2 X 120watt 12v >>> These 2 connected in series for 24v

1 x 85watt >>>>> These 2 connected in series for 24v
1x 130watt >>>>>

I have a 2 types of PV cable (one is a 6 foot jumper) into the PV combiner

Am I looking at inherent system related losses


Has anyone run into similar situation with their install.
Thanks Brian
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
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    Re: Calculating system Yields and GTI Inverter efficiency

    I don't see anything unusual about that.

    A 455 Watt array will not produce 455 Watts in normal operating conditions. More like 80% of that, or 364 Watts. Then the inverter is only 92% efficient, so the output power you'd expect would be a mere 335 Watts. You're reading 5 Watts more than that. Considering the number of variables (including meter accuracy) I'd say it's working as well as can be expected.

    And are you saying you have two strings at nominal 24 Volts paralleled with one 130 Watt 12 Volt panel? That is a waste of panel. The array strings need to all be at the same Voltage. Even minor difference in string Voltage will cause some reduction in power.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
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    Re: Calculating system Yields and GTI Inverter efficiency

    you are also being limited in your current output due to the 130w and 85w pvs in series. it will limit current to roughly that of the 85w pv so it's more like 2 85w pvs in series. find another 130w pv to put in series with the one you have and you will gain about 90w stc over what you are seeing now.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
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    Re: Calculating system Yields and GTI Inverter efficiency

    I didn't read that right the first time. You have one string of two 120 Watt panels and one string of one 85 Watt and one 130 Watt? As Niel said that one will perform like two 85 Watts effectively making your array only 410 Watts. Getting 340 Watts output from that is really good.
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  • solaris3000
    solaris3000 Registered Users Posts: 24 ✭✭
    #5
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    Re: Calculating system Yields and GTI Inverter efficiency

    Thanks for the feedback and advice everyone. I'm going pick up a 130watt panel immediately.
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