TL inverters and TT earthing systems?

[Ross Harvey]

HI

Im after a bit of advise.

Im a suby for british gas wiring heating systems. When a salesman goes to quote a job they have to do a "socket and see" test on a circuit to see if the main earth is sufficient. (not a great way to test it by hay-ho). Anyway this installation fails the test. so they send me in to do a proper inspection. It turns out that it needs the main earth upgrading. In this case we sell them an earth rod pack. This is where it gets interesting. The main cut out fuse for this installation is in a neighbours house (great!).Also he has a Sunnyboy 4000TL already installed. As this is a TL inverter i cant put the whole installation on a 30mA RCD.

So my question is can i put a 100mA RCD in instead?

I know some might say just get them to upgrade there earth through the DNO, but i would rather the work myself (selfish i know, but work is work).

Any advise would be appreciated.

Thanks

 

[Marvo]

What is the existing earthing arrangement at the head?

 

[Ross Harvey]

The existing earth is tns but it has corroded badly.

 

[Marvo]

I would request the DNO to come and sort it out TBH. What's the Ze reading at the moment?

 

[Ross Harvey]

Ze was over 20ohms

 

[Richo77]

I'd get the DNO out to sort the Earth out as Marvo said. And I would split the supply so that you got the house on its consumer unit and then install a 2 way consumer unit for the PV. That way you would have a 30ma on each consumer unit. It's recommended to install PV on it's own RCD to avoid nuisance tripping with all the combined Earth leakage of the house and PV

 

[Unregistered]

The pv circuit is already on its own consumer unit. But not on an rcd. TL inverters are not supposed to be protected by a 30 mA rcd. I new that getting the DNO to re new the earth would be best solution. I was just wondering if I could use a 100mA rcd instead of a 30mA.

 

[SolarCity]

Is there any reason why the TL inverter needs to be on an RCD? Such as how the array is installed or the route of the AC cable? If not, then what's the issue?

ETA Ah, now that I've read the thread properly, I see what you mean.

Surely getting the DNO out is the right thing to do. If a TNS is achievable then surely it is desirable over a TT setup?

 

[Richo77]

Yes 100 ma RCD will be fine. You may actually find the Inverter manufacturers instructions state that it should be protected by 100ma RCD protection.

 

[Richo77]

100ma for the PV. Make sure the houses final circuits are on 30ma.

 

[Worcester]

Yes 100 ma RCD will be fine. You may actually find the Inverter manufacturers instructions state that it should be protected by 100ma RCD protection.

Don't see how you can say that, one of the issues is DC leakage and thus holding the RCD closed. Sibert will post you the appropriate technical documents from Doepke in Germany if you like.

100mA Type B I'd agree with, have you seen the prices of one of those though - Andy at Sibert will sell you one quite happily

 

[SibertSolar]

Oi, don't drag me into this thread Worcester, I'm not commenting....

 

[Eco Chap]

Don't see how you can say that, one of the issues is DC leakage and thus holding the RCD closed. Sibert will post you the appropriate technical documents from Doepke in Germany if you like.

100mA Type B I'd agree with, have you seen the prices of one of those though - Andy at Sibert will sell you one quite happily

I was aware that as the sunny boys AC/dc inputs are electrically separated there wasn't as issue with reverse dc currents??

High ze is DNOs problem. Call them out to sort the issue IMO