Confused over output results

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Confused over output results

Postby justgotaknow » Sun Oct 08, 2017 1:20 pm

I picked up 4 230w panels

Specs from panels
Peak Power Watts-PMAX (Wp) 230
Maximum Power Voltage-VMP (V) 29.8
Maximum Power Current-iMPP (A) 7.72
open Circuit Voltage-VoC (V) 37.
Short Circuit Current-iSC (A) 8.26

I have wired them into two pairs in Parallel (2x2) that then comes down in two separate 6mmsq runs where these lines are then paralleled again into a single line.

this is then fed into a 1000w grid tie inverter that has the following specs MPPT voltage 24-38VDC to me this all seems to be matched OK

Voltage at inverter input actual 30v

Now this is where I am confused, with all 4 connected output is running at 540w, if I drop either of the two panels output is well above half at 350w
this is being measured with an hour watt meter.

Is there a logical reason that the system would lose efficiency as the available current increased?
I expected it to be better not worse?
where is the missing 160w ?
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Re: Confused over output results

Postby Gordon-Loomberah » Sun Oct 08, 2017 3:09 pm

Welcome to the Energy Matters Forums Justgotaknow :)

Did you know it was illegal, and potentially dangerous, for an unlicensed person to wire up and connect a grid tie inverter?

When you say 2X2, do you mean 2 in series and those 2 strings are then in parallel, or are all 4 in parallel? If the former, then by wiring 2 panels in series you have exceeded the MPPT voltage by a long way. What brand grid-connect inverter is it that has such a low MPPT voltage?

Are you sure that all panels have somewhere near their rated output? How old are they? Were they all face-on to the sun? If they aren't then you wont get near full output, and that would only occur in cold conditions anyway.

Typically you might expect 80% of rated output from new panels, so up to 750W. Even a small amount of shade on a panel can drastically reduce its output.
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Re: Confused over output results

Postby justgotaknow » Sun Oct 08, 2017 3:50 pm

you must have missed this line
"I have wired them into two pairs in Parallel (2x2) that then comes down in two separate 6mmsq runs where these lines are then paralleled again into a single line.

to make it clearer 2 in parallel plus 2 in parallel.

and this line "Voltage at inverter input actual 30v"

clearly nothing is in series


I also under stand the dangers, risks and have an understanding of electronics and electrical principals from DC to GHZ including high power RF
.
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Re: Confused over output results

Postby APR » Sun Oct 08, 2017 9:01 pm

Have you connected each panel individually to make sure they are all putting out around the same power, or checked the current from each panel with a DC clamp meter?
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Re: Confused over output results

Postby justgotaknow » Sun Oct 08, 2017 9:56 pm

Thanks APR either pair deliver very close to the same AC output from the inverter when connected, what has me confused is that the output does not equal the sum of both pairs.

I only have an AC clamp and not keen on using inline amp meters on the input.

I guess that would be the next step as the results dont make sense so far.
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Re: Confused over output results

Postby australsolarier » Mon Oct 09, 2017 2:52 pm

justgotaknow,
if you are in australia, it does not matter what knowledge you have, you can be an astronaut or a rocket scientist, it is still illegal to connect a gridfeed inverter. or the prime minister for that matter.
i suspect you have one of those cheap chinese gridfeed inverters. so when they say 1000w, that in reality means 500 watts . they might do 1000watts for a full nano second, but not much longer.
and consider, most chinese inverters have grossly optimistic specifications. so, you half them and you are right on your money.
and yes, i thought you are paralleling two in series too.
and, that cheap chinese gridfeed inverter might throw out a dirty sine wave that might damage your applications you have plugged in. they also can self destruct if you turn them off in the wrong sequence. they can trigger the rcd when turned off.
keep us posted.
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Re: Confused over output results

Postby davidg » Wed Oct 11, 2017 8:09 pm

Gordon-Loomberah wrote:Did you know it was illegal, and potentially dangerous, for an unlicensed person to wire up and connect a grid tie inverter?


Apparently in Asia, IP trace back would give a better idea of where .............. #just saying
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Re: Confused over output results

Postby Gordon-Loomberah » Wed Oct 11, 2017 8:23 pm

.au email address, IP # is in Oz too.
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Re: Confused over output results

Postby davidg » Thu Oct 12, 2017 10:44 am

Gordon-Loomberah wrote:.au email address, IP # is in Oz too.


Works for me :)
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Re: Confused over output results

Postby australsolarier » Thu Oct 12, 2017 12:22 pm

i have not the least idea what gordon and davidg are in about.
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