info on earthing the pv frame

dansk · Mar 16, 2011

Markc said:
Shouldn't use RCBO's as they aren't double pole from what I have read somewhere. You will not get a Class B RCBO anyway from my investigations and a Class B RCD will be 300mA. Unless anyone knows different?

OK - Just so i get this clear im my head - lets say i split the meter tails, install a small two board - were does the "class b" fit into this? If the radial upto the inverter needs 30ma RCD, how do i fit in a 300ma class b?

http://www05.abb.com/global/scot/sc...dc12576ba003c22bf/$file/solar cat lr v.06.pdf

Markc · Mar 16, 2011

dansk said:
OK - Just so i get this clear im my head - lets say i split the meter tails, install a small two board - were does the "class b" fit into this? If the radial upto the inverter needs 30ma RCD, how do i fit in a 300ma class b?

http://www05.abb.com/global/scot/sc...dc12576ba003c22bf/$file/solar cat lr v.06.pdf

Why does it need 30mA RCD protection. Is the AC embedded in a wall at less than 50mm depth? If so using SWA cable (Earthed metallic sheath) you do not need 30mA RCD protection.
The Class B can go in a module box with a MCB. Nothing stopping that. IF the inverter for any reason requires 30mA protection then a second RCD is required at 30mA (unless Fronius TL - They don't like 30mA, don't know if any issues with other makes). The Class B's only purpose is to prevent DC voltage being injected into the AC side nothing more.
Regarding the ABB link above. The F202 RCD is the correct item. The spec shows a range of 30, 300 and 500mA yet the device is 300mA.

dansk · Mar 16, 2011

ok - 300ma upstream, and 30ma downstream, its quite common to run the radial internally due to customer not wanting external cable run (dont ask it happens!), so to satisfy the big red book 30ma rcd is the easiest way to conform, and in this instance use the 300ma class b as the main switch in a seperate CU.

300ma RCD class B, 30ma RCD class A, then 16a MCB, phew what a mouthfull - shall be seeking a transformer inverter from now on.

TJLinks · Mar 16, 2011

Has anyone found a class b RCD for less than a 2nd mortgage??

Markc · Mar 16, 2011

TJLinks said:
Has anyone found a class b RCD for less than a 2nd mortgage??

NO......!

Markc · Mar 16, 2011

dansk said:
ok - 300ma upstream, and 30ma downstream, its quite common to run the radial internally due to customer not wanting external cable run (dont ask it happens!), so to satisfy the big red book 30ma rcd is the easiest way to conform, and in this instance use the 300ma class b as the main switch in a seperate CU.

300ma RCD class B, 30ma RCD class A, then 16a MCB, phew what a mouthfull - shall be seeking a transformer inverter from now on.

No problem with internal cable route but is it chased in? If it is you can still use SWA saves the issues of RCD protection.

As for TL's IF SMA have it right and I don't see why they don't then the Class B is included it's just the rest of them. Until they catch up with SMA then the Class B has to be fitted. And again with any TL bonding.

Neil Wright · Apr 14, 2011

Could you tell me where it specifies a 10mm earth and its calculation, because surely when we install large >50kw systems the earth fault current will be greater therefore the earth bond should be a larger size?

Markc · Apr 14, 2011

Neil Wright said:
Could you tell me where it specifies a 10mm earth and its calculation, because surely when we install large >50kw systems the earth fault current will be greater therefore the earth bond should be a larger size?

The OP started as a domestic system where by the the likely existing bonding conductors would be 10mm. As you say the larger the electrical system the larger the bonding conductors. I see it being very unlikely a >50kW system will be installed on a domestic property.

BS7671 requires us to calculate the bonding conductor cross sectional area.