Replacing Proteous MCB

[pca]

Hello all,

Hope someone can help. We have just had a new electric shower fitted (replacing an old electric shower). The new shower is 10.8 kW and after a few minutes (3 or 4) it keeps tripping the MCB. The MCB is rated at 32A - should it be more for the new shower ?

Also - we have already been looking for a supplier for a new MCB but they all say they do not stock Proteus. Is this now a defunct brand ? Does it mean we have to get the whole consumer unit replaced ?

We are at the point of thinking we will have to get an electrician in to check this out for us, but I'd like to at least understand the problem a bit more before getting someone in, so any advice is very much appreciated

Thanks,
Pete.

 

[plugwash]

Hello all,

Hope someone can help. We have just had a new electric shower fitted (replacing an old electric shower). The new shower is 10.8 kW and after a few minutes (3 or 4) it keeps tripping the MCB. The MCB is rated at 32A - should it be more for the new shower ?

yes but you also need to make sure the cable is suitable for the higher power its very likely that it isn't.

Also - we have already been looking for a supplier for a new MCB but they all say they do not stock Proteus. Is this now a defunct brand ? Does it mean we have to get the whole consumer unit replaced ?

iirc proteus is the own brand of city electrical factors (CEF). maplin used to stock thier breakers but i don't think they do anymore.
[/quote]

 

[Steve]

10.8KW shower needs a 50A MCB and 10mm T+E cable minimum.

 

[delmel]

Proteus is only available from City Electrical Factors, but note they as most manufacturers have changed the style and therefore old style are not compatable with new stlyle. How old is your board if older than 7 years i would say old style (old wylex mcbs are the same profile as Proteus old style and will interchange).
Also as mentioned you need to consider if your cable is correct for the new shower(Distance of the run is important)

 

[kai]

No! Don't even think of using Wyles MCB's in a Proteus Board - it can be highly dangerous especially in a shower circuit - the MCB's are precision devices, and the slightest misfit can cause poor contact and a fire risk.
The golden rule is Never Mix and Match different makes of MCB and board.

 

[plugwash]

yeah a mcb is a precision device internally but that isn't really what matters here.

what matters is getting a good contact between the MCB and bussbar yes you need to take care if mixing brands but as long as you make sure the contact is good it doesn't really make any difference if the brands are the same or not

btw wylex don't even seem to be able to keep the exact position of the contacts all that consistant even on breakers with the same part number! So you always need to take care to get a good contact even if the brand matches.

 

[ban-all-sheds]

The new shower is 10.8 kW and after a few minutes (3 or 4) it keeps tripping the MCB. The MCB is rated at 32A - should it be more for the new shower ?

Have you tried dividing 10800 by 240, and seeing what the result is?

 

[delmel]

Note wylex and proteus were the same mcb, not similar exact the same made by same company also Proteus used to make them under license. They are different now. Also I believe wylex now use two different manufacturers for the mcbs

 

[ninebob]

Have you tried dividing 10800 by 240, and seeing what the result is?

The calculation should be done using 230, no?

 

[plugwash]

the headline power figures of showers sold here are usually based on 240V (read the small print if you must)

its totally stupid to devide a power figure thats given at 240V by 230V

what you should really do if you want to be totally correct and assume a mains supply of 230V is

10800/240/240*230

which will give a lower figure than just deviding by 240

ofc in reality we all know british mains is 240V despite what the beurocrats say so its best to design the cuircuits with sufficiant capacity for 240V running.

 

[mapj1]

To save you the sum, the smallest breaker you should consider using is a 45A for a 10.8KW shower.
However, unless the original installers were in generous mood, it is likely the cable will be as under sized as the original breaker. You need to check that, before upgrading the breaker alone. If there is no way of getting a 45A breaker into the existing board, and that may well turn out to be true, then a new mini CU should be added along side the existing one, many makers do a dedicated 'shower CU' with one large breaker in it for just this purpose. However to connect it will probably require henley blocks in the meter tails (to split the supply to the two CUs) and this is not an amateur job, although the wiring is easy, the price of failure is high.

 

[dabaldie]

henley blocks

what are these?
can you not just connect the small CU to a MCB in the main CU?


oops just read the post above more accurately.

cant get a 45MCB into the existing CU

sorry.

 

[mapj1]

Henley Blocks are the giant's junction boxes used for connecting meter tail thickness of wire together.
Sometimes called service cable connectors
see here - for a picturehttp://www.tlc-direct.co.uk/Main_In...ector_Block_Index/Connector_Blocks/index.html

Not normally an amateur thing to be meddling with, but often found near meters supplying more than one CU, or economy 7 heating or similar...
Occasionally seen in boat battery wiring, as the currents are high enough to warrant it.

 

[jondiy]

Somebody said that the Old Wylex MCB's and the Proteus M6 MCB's were exactly the same fitting.

Does anybody know exactly what type I need to specify on the Old Wylex Ones, ie is there a code number for them, as I'm finding it hard to get a 40Amp Proteus M6 MCB, for my new 8.5kW shower (cable run in 10mm).

There are so many Wylex MCB's out there, its confusing.

 

[Spark123]

Try googling for "wylex nb"