Need Help Urgently please..

[infinity]

i was going to install new ccu, with 30mA main switch. + 16A mcb

 

[Sparkydan]

I think this would be your best option, install a 100A DP service block and feed from the meter reconnect the existing db and connect the new db.

 

[moggy1968]

doesn't get around the need for a type B RCD though

 

[infinity]

the feeding of its not a problem. As Moggy said it the rcd thats my problem.

 

[Sparkydan]

Type B RCD? as long as the circuit is protected by a 30mA RCD and a 16A type B MCB it will comply with regulations, what is a type B RCD?

 

[moggy1968]

no it won't for the reasons gone into in some detail elsewhere on this forum.
a type A RCD will not disconnect within the required time and may not trip at all.
Installing PV circuits requiring RCDs opens up a whole can of worms better left unopened if at all possible

 

[infinity]

Are you a solar installer? type B also detects DC residual.

 

[Sparkydan]

Yes just started, didn't know transformer less inverters needed type b rcd's though have learned something tonight.

 

[BruceB]

Its mainly because the cable s buried in the wall now at customer request so no avoiding the rcd. I thought RCD protection was required on TL inverter regardless unless manufacturer stated otherwise if it incorporated some form of protection against DC leaking back down the circuit?
Do you always surface mount or use SWA then?

I have been away for a couple of hours, but it looks like you have most of the answers since you made this post. TLs do not require an rcd unless there is a reason to put one in. Burying in a wall less than 50mm deep is of course a good reason for an rcd and you have no option but a 30mA one. So you could try it and take the risk of nuisance tripping or go for SWA or trunking etc. I find conduit/trunking beside inverters is usually acceptable as they are not works of art.

Regards
Bruce

 

[JulianC]

TLs do not require an rcd unless there is a reason to put one in.

The very fact it is a TL is usually the reason it needs an RCD in the first place, and a type B at that....unless by design it can't inject DC onto the AC side in the event of a fault or whatever it states in 7671.

As far as I'm concerned, burying cables less than 50mm so that a 30mA is required is a no no if the inverter continues to deliver a hefty shock for several seconds after you've bashed a nail through the cable. The RCD is not providing the additional protection for which it is required.

 

[BruceB]

The very fact it is a TL is usually the reason it needs an RCD in the first place

I cannot think of a regulation or guidance that implies this................?

 

[JulianC]

712.411.3.2.1.2?

 

[infinity]

The very fact it is a TL is usually the reason it needs an RCD in the first place, and a type B at that....unless by design it can't inject DC onto the AC side in the event of a fault or whatever it states in 7671.

As far as I'm concerned, burying cables less than 50mm so that a 30mA is required is a no no if the inverter continues to deliver a hefty shock for several seconds after you've bashed a nail through the cable. The RCD is not providing the additional protection for which it is required.

I Called the Napit technical team who informed me additional protection is provided by the RCD. The disconnection time of the inverter is how long it takes to shut down not how long it keeps providing power. As soon as AC is lost, the AC from the inverter is also lost.
This is what i was told today because i thought the exact same thing which is why i called them.

 

[JulianC]

As soon as AC is lost, the AC from the inverter is also lost.

I'd like to see where they got this information from. If that's the case then we can happily connect PV circuits onto shared RCDs, which I believe NECEIC frown upon because.......the inverter can continue generating for up to 5 seconds!

Not that I'm an expert (far from it), but I'd be sceptical of any PV related advice provided by the trade bodies, unless they'd be prepared to put it in writing.

 

[moggy1968]

I think connecting to a shared RCD is still an issue because of nuisance tripping.
Also the overunning of the inverter is not the only problem. there is a problem with the nature of the currents set up by the inverter which may delay or even prevent tripping.
I don't pretend to understand the technicalities of this but there is some good info on Sibberts website