16A threshold for G83 - Array size or inverter output?

[SolarCity]

The saga continues. I was told today by an engineer at Central Networks that it is inverter output that is important when considering the G83 threshold.

Hopefully this will be the stance all DNOs take before long.

 

[TedM]

It is absolutely clear in the G83 document that it must refer to the inverter and it is the inverter - not pv panels - that are G83 type tested.

I'm still waiting for a reply from the ENA on my questions to them - that were written to persuade them to get all DNOs to agree to a consistent set of rules.

 

[SRE]

The saga continues. I was told today by an engineer at Central Networks that it is inverter output that is important when considering the G83 threshold.

Hopefully this will be the stance all DNOs take before long.

Not the amps??? The Fronius 3.6tl has max ac output of 3680 and 16 amps and will take a string of 17 x 235w panels ...

 

[mmccx]

Well you can work out the max output in amps if you know the max ac output of the inverter

 

[Blueflash]

Well you can work out the max output in amps if you know the max ac output of the inverter

A customer of ours has had a tripping fault, where by his 16amp mcb has been tripping on peak days. This was caused by the assumption that his ac supply was 240vac (we know what it is meant to be!), but he was at the edge of the network on a fellside. Because he was getting occasional ac volt drop to 230vac or slightly lower this tripped his breaker because the amps had risen over 17amps on peak days!
Food for thought when working in rural areas.

 

[liquidity]

And is the G83 limit 16 amps at the current operating voltage or at 230?

 

[mmccx]

A customer of ours has had a tripping fault, where by his 16amp mcb has been tripping on peak days. This was caused by the assumption that his ac supply was 240vac (we know what it is meant to be!), but he was at the edge of the network on a fellside. Because he was getting occasional ac volt drop to 230vac or slightly lower this tripped his breaker because the amps had risen over 17amps on peak days!
Food for thought when working in rural areas.

Could you not install a 20amp mcb? The mcb is just to protect the cable and not limit the output?

 

[Blueflash]

Could you not install a 20amp mcb? The mcb is just to protect the cable and not limit the output?

The thing is, you will not be limiting the export to 16amp/phase. You know and I know that this does not make much difference, but DNO would probably get upset if found out?If you left as 16amp though it would be a pain with nuisance tripping at peak, possibly system off during customers summer hols abroad?

 

[GaryM]

The thing is, you will not be limiting the export to 16amp/phase. You know and I know that this does not make much difference, but DNO would probably get upset if found out?If you left as 16amp though it would be a pain with nuisance tripping at peak, possibly system off during customers summer hols abroad?

The inverter should limit the current under G83, not the MCB!
There's nothing at all wrong with using a 20A MCB if the AC supply to the inverter is 2.5mm2 and above with installation conditions allowing. It's got nothing at all to do with the DNO.
Also, I'm gobsmacked that 17A is tripping a 16A MCB.

 

[BruceB]

And is the G83 limit 16 amps at the current operating voltage or at 230?

The legislation says:, "...the source of energy does not produce an electrical output exceeding 16 amperes per phase at low voltage;"

So it is defined in Amps in the legislation rather than Watts. That some DNO's produce an interpretation in Watts is just that.... an interpretation.

 

[MrBod]

Could you not install a 20amp mcb? The mcb is just to protect the cable and not limit the output?

When we got our system installed last October, the electrician installed a 16A MCB. We had a little chat about the potential output from a SMA 4000TL and then he swapped it for a 20A MCB. Everybody happy.

 

[SibertSolar]

As others have already said, the MCB is there purely to protect the AC cable run from the inverter. So long as it is sized correctly there's no harm in using a higher than 16A MCB.

 

[DomB]

I know UK Power Networks use 240V to work out the output current while Southern Electric use 230V. This means you can't install as big a system on an SE network as you can on a UK PN's!

 

[Earthstore]

Strange, every voltage that I have checked in SE has been 245v and I was informed by an employee that has over 30 service that they aim for 248v.
It would make the sums different if they worked on what they try to achieve.

 

[LightGEN]

I know UK Power Networks use 240V to work out the output current while Southern Electric use 230V. This means you can't install as big a system on an SE network as you can on a UK PN's!

Electricity NorthWest also uses 240V @ 16A (3840W) as their baseline for G83 solar installations.