Memera 2000 AD MCB

shaky1105 · 12 Jun 2010

Hi guys, my mate has one of the aforementioned boards and needs to find a 45A Type B mcb for it. Are these actually available because we've searched quite a bit and only been able to find a 40 or a 50 amp version.

TIA - Shaky

jaysean1 · 12 Jun 2010

I think mem do a 40a mcb dont think they do a 45a

BigJon · 12 Jun 2010

I'm 99.9% sure they're not available in 45A.
Can he not use a 50A?
Whats he supplying, cable size, length & route?

shaky1105 · 13 Jun 2010

It's for a 10.5KW shower. It's fed via 6mm cable clipped direct over a run of about 5M. IF I think correctly a 40A mcb is too small ( 43.75A draw from shower ) and a 50A would be too big for the cable rating ( 47A according to tlc's calculator ).

Basically, he's asked me to find out for him to see if he can avoid having to run a fresh cable ( 10mm² ) for the new shower.

I'm trying to find out as much as I can because he's a tight git ( doesn't want to spend about ten quid or so on some cable !! ) and one of those lads that will do it regardless of safety, rules etc etc !!

I've already told him about the regs about diy etc and his attitude was basically I don't give a toss. So if he's going to go ahead and do it anyway, I would rather it be done as safe as possible. I know the best thing to do would be for me to not get involved and just walk away but he's got a young kid in the house and I couldn't live with myself if I just left him to his own devices.

Any help would be appreciated.

OwainDIYer · 13 Jun 2010

A 50A might be acceptable.

An electric shower is unlikely to have an overload, so the MCB only has to protect the cable against short circuit, you would have to calculate that a 50A MCB would clear the fault quickly enough that the cable wasn't damaged.

Or maybe you could 'find' some 10mm cable 'left over from a job' that he could have.

londonboy · 13 Jun 2010

Without looking through the books a 40a would probably be ok (as the showers only used for a few minutes at a time).

Although Id strongly suggest changing that cable to 10mm and using a 50amp breaker.

I hope this circuit has RCD protection too.

shaky1105 · 13 Jun 2010

londonboy said:
Without looking through the books a 40a would probably be ok (as the showers only used for a few minutes at a time).

Although Id strongly suggest changing that cable to 10mm and using a 50amp breaker.

I hope this circuit has RCD protection too.

It is fed off the rcd side of the board atm via the existing 40A mcb. The existing shower is only an 8.5KW unit. I wondered if the 40A would be OK for use but as I'm not a spark, I haven't got access to the usage characteristics of mcb's.

ban-all-sheds · 14 Jun 2010

londonboy said:
Without looking through the books a 40a would probably be ok (as the showers only used for a few minutes at a time.

Without looking through you might not be able to quote the actual regulation number, but you are sure, are you, that somewhere there is a regulation which allows an undersized breaker to be used if the load is only on for "a few minutes at a time"?

londonboy · 14 Jun 2010

ban-all-sheds said:
londonboy said:

Without looking through the books a 40a would probably be ok (as the showers only used for a few minutes at a time.

Click to expand...

Without looking through you might not be able to quote the actual regulation number, but you are sure, are you, that somewhere there is a regulation which allows an undersized breaker to be used if the load is only on for "a few minutes at a time"?

No but as the blokes obviously not going to pay any attention its better a 6mm being on a 40amp ocpd than a 50.

shaky1105 · 14 Jun 2010

londonboy said:
ban-all-sheds said:

londonboy said:

Without looking through the books a 40a would probably be ok (as the showers only used for a few minutes at a time.

Click to expand...

Without looking through you might not be able to quote the actual regulation number, but you are sure, are you, that somewhere there is a regulation which allows an undersized breaker to be used if the load is only on for "a few minutes at a time"?

Click to expand...

No but as the blokes obviously not going to pay any attention its better a 6mm being on a 40amp ocpd than a 50.

I can probably get him to wait a couple of weeks or so before he'll just "dive in" and try to do it himself, so if anyone can confirm any of the above it would be really appreciated. In the meantime, I'm going to see if I can scrounge some cable of any of the sites I visit, I might even just go and get some and tell him I got it for nowt

PS to londonboy, sorry if you get a message saying that I've added you to my ignore list, I hit the wrong button when I tried to quote your post

All sorted now though.

diynot

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Memera 2000 AD MCB

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