New DB (additional)

[westward10]

That is the problem with the higher rated Memshield 1 stuff a 63A second hand breaker could be £50-60.

 

[TheReturnOfHightower]

That is the problem with the higher rated Memshield 1 stuff a 63A second hand breaker could be £50-60.

I'll have a more thorough look at the board tomorrow and see exactly what it is I'm working with and let you all know

 

[TheReturnOfHightower]

Okay, so it's a 6-way MEM1, and about 4 of the MCBs are the double-width RCBO type that are eating in to space. None of the current breakers are redundant.

Best I can think of is to try and pick up a 63A MCB for a distro circuit, moving a circuit for it to the new DB. I can see a 45A single-pole breaker on ebay which I think I would be alright with, but a 63A would be better if anybody had one lying about?

EDIT: There is this: MEM MCB Type 3 63 Amp M6 Single Pole 63A Memshield Circuit Breaker 631MC 631MB3 - Willrose Electrical - Discontinued & Obsolete Circuit Breakers - https://willrose-electrical.co.uk/product/mem-mcb-type-3-63-amp-m6-single-pole-63a-memshield-circuit-breaker-631mc-631mb3/

 

[happysteve]

Eh up, good to hear from you again.

Quick thought: are you going to be ok selectivity-wise?

If all the circuits in your new board are RCBOs, then you'll probably be alright, but worth checking.

 

[TheReturnOfHightower]

Hi Steve, yeah, that was a question on my mind - any distro circuit fed off a standard breaker is going to provide an issue really though, so I don't see what other options I have. All the new circuits will be RCBO.

 

[westward10]

I wouldn't lose too much sleep over selectivity you can only play with what you have.

 

[TheReturnOfHightower]

Okay, so I think I've made my mind up and wouldn't mind a sanity check. There's a couple lighting circuits that don't pull much so I'm going to join them in to the same breaker, creating a spare way. Then, C63 MCB as a distro circuit, running in SWA to a little 2-way DB in the room where the new circuits are going, running 2 x B32 RCBOs - they won't be anywhere near 32A at full load, but need 2 circuits as it's computer equipment and would likely trip the RCBO if all lumped together.

Should get away with 10mm SWA for CCC, but was going to install 16mm just to keep the Zsdb as low as possible. Run will be around 8m for SWA from the upstream DB, and then the 2 circuits are RFCs ran in 4mm (again, to keep that Zs down).

All sound tickety boo?

 

[Deleted account]

If your using C type breakers I think I would change this to B type then you’d get away with 10 mm SWA. Probably.

That’s if you where going to use C type.

 

[davesparks]

Should get away with 10mm SWA for CCC, but was going to install 16mm just to keep the Zsdb as low as possible. Run will be around 8m for SWA from the upstream DB, and then the 2 circuits are RFCs ran in 4mm (again, to keep that Zs down).

If there is a problem with the Zs of the existing submain then that needs to be sorted out rather than oversizing new cables to try and achieve compliance.

 

[TheReturnOfHightower]

If there is a problem with the Zs of the existing submain then that needs to be sorted out rather than oversizing new cables to try and achieve compliance.

If there was a problem with the Zs of the existing submain, I wouldn't be able to get that Zs down no matter what I did. The Zs is fine - I'm just conscious I'm extending on to a long submain anyway. However, it is only a half dozen metres so I'm probably overthinking it with 16mm. I'm going to take some readings this afternoon and then I will do my cable calculations properly to ensure that circuit Zs's will be compliant.