RCD Tripping at night and morning? Help!

[Jie]

Got a call from a client saying that the RCD on the garage unit I installed is tripping in the morning and at night time, but the system is working perfectly during the day and doesnt trip its a 17 panel system Schott Poly 235W and a Fronius IG 3.6. Reasons for the 3.6 is that the DNO's dont like 4000W inverters but this bypasses it. Wired in 6mm to the gen meter then the DP switch then into a GarageUnit with a 60A RCD and then wired into a 40A Breaker in the house board, had to re-route the lights to the garage unit as ther was no space in house board. Any ideas?

 

[beefheart]

hi jie, did you see my earlier post regarding ig3.6 tl, on these inverters certain brand of rcd make it trip out when it trys to connect to the grid, volex was responsible in my case a quick call to fronius technical will usually give you an answer, might be related in my case i uprated to 100ma no issue then ,, jope this helps

 

[Jie]

ahhh brilliant mate! ill give a bell in the morning! cheers

 

[Jie]

what types of RCD do people use if they install transformerless inverters? been told to use 100mA RCD's.

 

[Markc]

what types of RCD do people use if they install transformerless inverters? been told to use 100mA RCD's.

I think we need a sticky on this subject.

Its a Class B RCD for TL's as in the BRB. A standard 100mA isn't compliant.

 

[smiffy_99_uk]

hi jie, did you see my earlier post regarding ig3.6 tl, on these inverters certain brand of rcd make it trip out when it trys to connect to the grid, volex was responsible in my case a quick call to fronius technical will usually give you an answer, might be related in my case i uprated to 100ma no issue then ,, jope this helps

Is a 100mA Compliant to Regs rather than a 30mA?

 

[BruceB]

Is a 100mA Compliant to Regs rather than a 30mA?

There is no simple answer to that. It depends on why you are installing an rcd and which reg you are trying to comply with.

Regards
Bruce

 

[smiffy_99_uk]

Thanks for your reply, I have wired the PV into a separate garage board next to the meter and have come out of the Henley block. I Have used a 100amp RCD 100mA main switch and a 16amp MCB. The reason I have used an RCD Is to comply with 17th ed. and protect the AC Side of the install. I was advised to use a 100mA but now wondering if i should switch to a 30mA. Any help would be most grateful as this ones being inspected.

 

[BruceB]

Yes, but WHY have you put an rcd in the circuit? The 17th edition does not require them for everything just some particular circumstances. You would only need to protect the ac side of the install with an rcd in the circumstances you describe if:
- it is a TT system, or
- there are cables buried less than 50mm deep in a wall, or
- it is for fire protection in an agricultural location, or
- it is a transformerless inverter which does not fall within the exemption in 712.411.3.2.1.2, or
- Zs too high, or
etc etc

Some inverters cannot take a 30mA rcd so beware. The installation instructions will say. What sort of inverter is it? A 100mA rcd will probably do no harm, albeit might not be required.

Regards
Bruce

 

[smiffy_99_uk]

Thanks for your info Bruce , I am using A SUNNY BOY 3300 so no need for a type b RCD. There are no cables buried in the wall and it is a TNCS. I Think that you are right, I did not need to fit an RCD although Cant do much harm. Because its my first one I tend to go over the top with things.