Solar Supply Main Isolator tripping

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Solar Supply Main Isolator tripping

Postby gregstimewaster » Wed Feb 21, 2018 4:22 pm

My "solar supply main isolator" trips every so often. Its no too bad if I happen to be home but sometimes I am away. As a manual reset is required, I miss out on some days of power. I complained to the installer the first time it happened and he looked at it and said it should not happen. I have a 5kw Fronius system and the ac isolator is MOD6-1-25, 6kA C25. It has happened when I was importing power and exporting power. What is this actually doing. Is it faulty.
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Re: Solar Supply Main Isolator tripping

Postby Gordon-Loomberah » Thu Feb 22, 2018 6:36 am

Welcome to the Energy Matters Forums Greg :)

It is impossible to say from a distance whether or not it is faulty, someone needs to physically inspect it.

Does it get hot in the sun or other heat source?

What is the maximum output of your system?

5kW @230V is 22A, so it is conceivable that it could trip if it was exposed to external heat when the inverter was producing maximum output.
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Re: Solar Supply Main Isolator tripping

Postby gregstimewaster » Thu Feb 22, 2018 10:11 am

Its in the power box. The installer looked at the first time it happened and said it was OK but its intermittent. It has happened in the morning when the sun is on the other side.
I do have some trouble with the mains supply. I occasionally get spikes and flash outages.My inverter throttles back some times and I am told that's caused by over voltage. All my neighbours have large PV systems and I am on the end of the run (100m).
That's why the question on what the "switch actually is" Is it a circuit breaker (current) or is it also voltage impacted.

Thanks Greg
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Re: Solar Supply Main Isolator tripping

Postby Gordon-Loomberah » Thu Feb 22, 2018 1:37 pm

High grid voltage is a common problem where the mains cables are not large enough and the transformer taps are adjusted to a higher voltage to cover voltage sag under load. When the load changes to a source of power the voltage goes way too high. The electricity supplier may need to adjust the transformer tap to bring the voltage within a suitable range for your inverter to operate at its full potential.

The CB is probbaly rated to 500V, a grid voltage of, for example, 260V should not cause a trip.

You mention it tripping in the morning, was that late morning, or early morning? Early morning the inverter probably would not be producting anywhere near 5kW (unless your panels all face east), so it shouldnt be an overcurrent trip. Late morning on a hot day when 5kW was being produced, perhaps it could trip.

In the specifications, is the maximum output of the inverter 5kW?

Are you able to see from a system log what power was being produced, and the grid voltage at the times of the trips?
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Re: Solar Supply Main Isolator tripping

Postby gregstimewaster » Thu Feb 22, 2018 3:44 pm

In the specifications, is the maximum output of the inverter 5kW? *** Yes

Are you able to see from a system log what power was being produced, and the grid voltage at the times of the trips? ****
e.g. Reading the values just before it went off the air.
27/1/18 4758w and 236V 11:50 pm
15/2/18 4216w and 235.8V at 1:15 pm

example of not failing
6/2/18 4835w 243.2 volts
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Re: Solar Supply Main Isolator tripping

Postby Gordon-Loomberah » Thu Feb 22, 2018 4:13 pm

I assume you mean am...

>>27/1/18 4758w and 236V 11:50 pm

Those examples are all around 20A, which shouldn't trip the CB due to current, unless it is very warm, in which case it could thermally trip. Have you felt the temperature of it shortly after it trips?

It could get warm to hot if the cables are not securely fastened under the screw clamps in the CB- it doesnt take much to have a high resistance joint, and if that was the case, over time you'd expect the trips to happen increasingly often as the Copper oxidises. That is something that should be checked for ASAP.
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Re: Solar Supply Main Isolator tripping

Postby davidg » Sun Feb 25, 2018 6:00 am

Whats the current rating of the CB, whats the size of the cable ie 2.5mm2, whats the distance for the inverter to the switchboard?
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Re: Solar Supply Main Isolator tripping

Postby Gordon-Loomberah » Sun Feb 25, 2018 6:27 am

>>the ac isolator is MOD6-1-25, 6kA C25

= 25A
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Re: Solar Supply Main Isolator tripping

Postby davidg » Sun Feb 25, 2018 6:55 am

Gordon-Loomberah wrote:>>the ac isolator is MOD6-1-25, 6kA C25

= 25A

Um ..... I just include all by default always have.

It might be a bit more sensative than it should be, easier to replace it JIC and then see what happens, afterall there cheap enough.
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