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Solar mark

Rising then decreasing pv output power cycles

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Solar mark

Has anyone come across a pv system (4kw kioto 2 x 8 strings) that is the majority of the time producing 1/2 the power, then momentarily the inverter (Eversolar) displays full power then steadily drops down again to roughly 1/2 the expected output.

at first I thought this was our first PID fault ? Or the other thought I had was  a faulty inverter ?

when I did I voltage Check on the Dc power coming into the isolator we were getting a steady voltage 

This was a system we were asked to re-fit after a new roof had been installed 

Any feedback would be welcome 

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binky

**** inverter and panels may be suffering from overheating. The other possibility is you have failed to make a proper connection on 1 string - should find it soon enough when connector burns out :^O

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Solar mark

Thanks for that I had thought it was potentially an inverter problem, as we have already been back to check one of the strings mc4 connections as they had a loss of power on them due to the poor MC4 connections they had been supplied with. So we carefully as we could made sure every MC4 connection was made as secure as possible. This was not as simple as it sounds as most cases I’ve ever been involved in fitting pv Pamela over the last 9 years, pushing together an MC4 connection is a simple matter of “push click” and the connection is made. And I can honestly say I’ve never been back to one of our jobs where one of the connectors failed, although I have been back to a couple of other peoples jobs where the MC4’s have failed and I guess arced and then burnt out.

my next step was going to be changing the inverter. What is making me think it was not a faulty connection was that the rise and fall of the power on the inverter is very consistent and time regular in time. It also tends to rise straight away after you turnover it back on after down powering it then back on again.

Then after a couple of times it can be 10 mins or so before it Rises in power on the inverter display, only for 3-4 secs then drains down again as if only one string is working. But at the same time when we check the 2 string voltages they stay on fairly fixed values.

from my experience this I think is more likely to be an electronic circuit fault with the inverted I think which is leading down that line.

unfortunately from the customers point of view he says it was ok until we reinstalled his Soakr panels and had never had a problem before !

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kerching

I don't do solar BUT.........don't assume that the customer is being 100% truthful EVER

 

long story short

carpet fitter mate of mine

finishing job on a monday

fixing thresholds

owner screams....there is water coming through ceiling

fitter thinks he has nailed a pipe

carpets up...nothing

head scratching

owners wife turns up

WTAF is going on here?

 

husband then fesses up to fitter that he nailed a pipe at weekend, turned water off, turned it back on when he heard banging

 

unpleasantness ensued

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Geoff1946

I suspect most users wouldn't even notice fluctuations in output. I rarely check mine, and only occasionally check that the green LED is on.

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binky

1/ OK so you have a voltage but have you checked ampage from panels for consistent energy flow? Need clamp ammeter and connect ends of string together.

2/ have you checked the AC side like the grid voltage and the cct in general?

3/ I am assuming a twin MPPT tracker inverter - swop strings between MPPT trackers and conect 1 string only.

has the customer got any form of inverter monitor, or is inverter stuck in attic where he never goes so hasn't a clue? 

 

Eversolar are rubbish inverters, but they generally fail the AC relay rather than mess around. Assuming inverter is actually working then I would suspect grid voltage is high or a fault with AC side such as high rsistance which is forcing inverter to derate itself. 

As for MC4s, they may be push and click, but that doesn't mean they are correctly fitted in the first place, though generally any issues are those from MC4s fitted to string cables rather than factory fitted connectors on the panels.

 

Trouble is you have taken on a piece of work you know little about, I suggest you avoid in future! :^O

 

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Solar mark

Just picked up the last feedback, thanks for that.

i must admit when I got the call letting me know their was a problem, I was a bit cynical there was a problem as I had told him the advantage of having a monitoring device when his inverter is tucked away I the lift, in order to at least see everything is working ok.

Anyway when I went round after finishing that days work it was about 5pm and the PV System is east facing and the irradiance level from the sun was going down as when I checke it was only about 200 wm and when I checked the inverter and the input from the panels the voltage was so steady, but I must admit I didn’t check the current and I could have swooped the strings over to see if the fault followed the string arrangement.

The only thing was it wasn’t a planned visit and I had another one to go to.

As far as the MC4 connections go, we were really careful pushing the mc4’s back together when we found the faulty connection, as we had the meter connected each time we re-connected each cable to check the connections we’re good, as you said just because you push the connectors in doesn’t mean you’ve got a good connection. Plus the Canadian Sokar MC4 convectors didnt make a clicking sound or feeling when you pushed them together.

So I’ll call round tomorrow if the clients in and swop the strings over and spend a bit more time with my ammeter and see how we get on with it TTFN

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