MCB Selection

[johndevin]

Having a discussion at work ..

We are installing a 9.8 KW Shower.

If my calculations are correct this will draw just above 40A

The distribution board we are using does not fit a 45A breaker.

I think it would be safer to use a 40A than jump to a 50A.

I highly doubt the current would ever reach anywhere near 40A.

Whats your thoughts ?

P.S I know i could change the board but trying to avoid this ....

 

[telectrix]

it's partly because the CU is type tested by the manufacturer with their own brand innards. alter the spec. then i could invalidate the CU's compliance. also, if there were a fire or similar mishap, the manufacturers could wriggle out of a claim.

 

[uksparks]

Yes I can understand that and thought you would say that, other than that would you say it's quite ok to do it if it fits properly but do it at your own risk of invalidating your enclosure or whatever.

just to look at this another way then, how does this sit if you buy a metal enclosure of no particular brand, say one that doesn't actually manufacture switchgear and then put a selection of different brands into it? I suppose it's designed for "any brand".

 

[davesparks]

I'm not one for mixing and matching but can you explain why it's wrong to mix and match? Let's take for example a Hager MCB and a MK MCB, let's just pretend they are the same shape and fit nicely in one another's board, please explain what is so wrong about doing this other that the fact it will look different.

im bot wanting an argument just interested to hear your explanation,

A CU and it's accessories is type tested and given a CE mark/declared compliant with the low voltage directive by the manufacturers as a complete range of parts which are designed to work together. Using another manufacturers parts has not been tested or approved by the manufacturer.

By bringing together parts from two different manufacturers you may be, legally speaking, manufacturing a new product for which you are the manufacturer and so have to accept liability and carry out laboratory testing etc on the newly manufactured equipment.

 

[davesparks]

just to look at this another way then, how does this sit if you buy a metal enclosure of no particular brand, say one that doesn't actually manufacture switchgear and then put a selection of different brands into it? I suppose it's designed for "any brand".

This is what panel builders do on a daily basis, just on a bigger scale. And they have a legal obligation to build that panel to certain standards and must make the declaration of conformity and CE mark the product themselves.

 

[Dave OCD]

That's a good point, many a time I've bought a 4 module enclosure [empty] to make up a small CU for an outbuilding or shower for example using a spare RCD and MCB/s accumulated over time - normally all of the same brand though.

 

[newtothis]

I the the vital specs were in the BS number, and the rest was protectionism. :thinking:

 

[uksparks]

Dave, so would you not use a generic enclosure to house different brands of switchgear then?

 

[davesparks]

Dave, so would you not use a generic enclosure to house different brands of switchgear then?

Depends what I'm doing really.

I would never recommend that anyone do it on an open forum.
I only do it for temporary repairs or connections as far as installations go.

 

[ElectroChem]

Guess I've got it lucky over here, all domestic switchgear has to comply to the same set of standards, one manufacturer can't forbid using another's product. We can buy a Hager enclosure, fill it with Clipsal and NHP breakers and all's well. Different in industry where chassis and faceplates need to line up so best to match breaker to enclosure.

 

[Andy78]

Best one I saw recently was a flat that had had a few minor works done and a DB swap. As it was only a few circuits the guy had opted for a main switch enclosure of one brand and 4 RCBOs of another brand. The upright portion of the RCBOs were not accommodated by the enclosure, so the idiot had chopped out a smoke packet sized piece out of the front of the enclosure so they could stick out of the front, exposing the terminal screws of course.