grid tie DC breaker went off

[PoPoShoo]

Our grid tie system is 32 - 400w, 10 amp panels tied together in 4 - 8 panel strings. The DC produced first goes through a DC breaker box with 4 - 16 amp breakers, then to the Inverter. No combiner box....each string has it's own breaker

The other day, I noticed that string #3's breaker was off. Reset it and everything fine. I had been gone for 2 days and know all breakers were functioning before I left.

I have had this setup running since late January of this year and it's the first time a breaker went off. Any ideas what may have caused this? The 2 days we were gone, I do know my area had several lightning storms. It doesn't appear that we had the grid go down (no resetting dig. clocks, etc.)at any time.

 

[Solar Guppy]

Partial shading could do it, dumping 3 strings into one is bad.

Typically with grid-tie and with ~13Kw of PV, you would have a multi mppt channel inverter or multiple inverters so none of the strings are in parallel.

Also, solar panels have maximum current specifications, at most two strings in parallel, never more.

 

[John.DS99]

I don't see why anyone would care if their 3 cents of extra solar power is wasted by dumping it into the "Grid". A lot of fuss for no reason.

 

[PoPoShoo]

neither of you are making any sense. again, what might cause a DC breaker to flip off?

 

[Solar Guppy]

Partial shading causes panels to not generate energy so then that string becomes a load and the remaining strings will push current into the shaded string of solar panels. Three strings into the remaining one could trip the breaker.

Your system is not designed correctly, no more than one string can be in parallel with another without over current events happening if some panels are shaded, and you are also losing energy by having 4 strings in parallel, each should be independent to the grid-tie inverter ( a mppt for each string ) which is how almost all grid-tie inverters are.

What inverter(s) do to have to sell the energy to the grid?

As an example, I would expect you have a pair of inverters at this power level ( ~13Kw ) that would each have at least 2 independent mppt channels

 

[PoPoShoo]

no string(s) are parallel with each other. 4 separate strings are fed to the Inverter, a Fronius Primo with 4 inputs

 

[Solar Guppy]

no string(s) are parallel with each other. 4 separate strings are fed to the Inverter, a Fronius Primo with 4 inputs

I misread your first post. apologies.

That leaves a weak breaker or they are getting hot as a trip event. Check all the breaker connection screws and verify they are tight as a loose wire would be common issue.