Shower circuit design.

We seem to be drifting slightly, but the type testing could be interesting.

There are only two or three sets of dimensions used for busbar and terminal positions among the various makes of MCBs, and the overall outline is very similar. They are almost all made in China from unknown manufacturers, and looking inside there is very little variation either. This is unsurprising as the function is identical as is the specification. The brand and labelling are printed on the outside, but all (presumably) have been type-tested to the same specification.

As many of you probably know, I am fairly cynical about many things, but with very good reason and as much understanding as I can achieve. I wonder how many factories these devices actually come from? I suggest that it may be only one or two, backed up by the noticeable fact that certain components get more difficult to source at the same time for several brands at once! Very curious.

As all of these devices have the same type-test, I cannot see what parameter could be different between brands to cause any problem. Mike says “eject metal” above, but this would surely happen whatever the containment, bus bar exact shape, and outer box material were used? They can all break the test 6kA (or 10kA) satisfactorily without failure, my question, therefore, is “what is the difference which prevents intermixing of brands, on the basis of product failure”? My cynic says “this is to keep the customer from buying spares from another source”, and that it is in BS7671 under manufacturer pressure. Trying to stop aftermarket parts for vehicles has been tested as illegal, surely the risk here is actually less, or potentially zero following above?

mapj1: 
 

Presumably the potential for  coming to grief is very Zs and PSSC dependent, as it should relate to how much the MCB comes to bits or ejects flames and hot metal drops during normal breaking operation - which really should not be that often . (cheese cloth tests)

 

Mike.

So I think that's the point. At the origin, the full prospective fault current is there. For single-phase supplies up to 100 A, you have 6 kA OCPDs that have been tested for 16 kA conditional short circuit rating by the manufacturer.

Elsewhere in the installation, you select the device with an appropriate prospective fault current rating and things are hunky-dorey.

Hmm. always ? 

How much worse is an MK breaker in a generic DIN rail box than say an MK light switch or fused  spur on a pattress or back box manufactured by AN-Other ? 

In the latter case we mix manufacturers and adopt responsibility at the drop of a hat.

Presumably the potential for  coming to grief is very Zs and PSSC dependent, as it should relate to how much the MCB comes to bits or ejects flames and hot metal drops during normal breaking operation - which really should not be that often . (cheese cloth tests)

I'd not condone the cropping of  bus-bar teeth, however  a short link of suitably rated cable should be perfectly OK if it can be done so it is making good contact at both ends. As an aside, it has often occurred to me that the DIN rail is a great mechanical standard, and what is really needed is  a second standard to define the plane of contact of the things  attached to it, but sadly that co-operation between makers is lacking.

Mike.

Zoomup: 
 
 That is a purely academic point. Reality varies with theory in many cases. We are talking about Chint here not Rolls Royce. This is a way to ensure makers' profits. Use our stuff only. I am sure that we are aware of that.

 

We can put our stuff into an empty enclosure or existing low Voltage assembly competently, so why not competently modify an existing assembly. 536.4.203 para 1. It is only a simple consumer unit so this is easily achieved.

 

Note 2. “Incorporated components inside the assembly can be from different manufacturers.”

Z.

Not really.

I would recommend you complete your reading of NOTE 2, because it goes on to say (my bold):

It is essential that all incorporated components should have had their compatibility for the final enclosed arrangements verified by the original manufacturer of the assembly and be assembled in accordance with their instructions e.g. the consumer unit, distribution board manufacturer. The original manufacturer is the organization that carried out the original design and the associated verification of the low voltage switchgear and controlgear assembly to the relevant part of the BS EN 61439 series. If an assembly deviates from its original manufacturer’s instructions, or includes components not included in the original verification, the person introducing the deviation becomes the original manufacturer with the corresponding obligations.

In other words, if you fit someone else's breaker, and the original manufacturer does not endorse it, you become the manufacturer of the assembly. Does your insurance cover for that outcome?

Jaymack: 
 

Zoomup: 
 

So what is really wrong with fitting a different make of M.C.B. and slightly adjusting a bus-bar finger to suit? Or putting the new device at the end of a shorter bus-bar and linking it by a short wire tail/link? Isn't that just site engineering?  A better quality make of M.C.B. than Chint would be a benefit.

Sorry, I have to ask: are you a registered electrician ?

Jaymack

Sorry, but I have to ask. Are you an agent provocateur in sheep's clothing.

Z.

Zoomup: 
 

So what is really wrong with fitting a different make of M.C.B. and slightly adjusting a bus-bar finger to suit? Or putting the new device at the end of a shorter bus-bar and linking it by a short wire tail/link? Isn't that just site engineering?  A better quality make of M.C.B. than Chint would be a benefit.

Sorry, I have to ask: are you a registered electrician ?

Jaymack

Maybe the fact you couldn't get a Chint breaker locally has answered the question why the correct MCB wasn't installed in the first place? The previous electrician could just have been told to go and run the circuit in, then found that the client had the shower ready to go and wanted it running, so had to fit the biggest breaker he had in his van and make it work?

gkenyon: 
 

Zoomup: 
 

Sparkingchip: 
 

My only issue with Chint is that I could not find a wholesaler who keep their MCBs in stock, Screwfix supply them, but they don’t keep them in stock with them only being available after 24-48 hours.

If Chint and Screwfix ensured there was stock in each branch I would have completely resolved all the issues on Friday and there would not now be unresolved issues to deal with.

I actually have a better stock of 40 amp circuit protective devices in my van than any wholesaler in the United Kingdom have in their warehouse, except a some of the specialist second hand suppliers such as Willrose, but I didn’t have Chint so I have ordered three as  “just in case” van stock.

 

So what is really wrong with fitting a different make of M.C.B. and slightly adjusting a bus-bar finger to suit? Or putting the new device at the end of a shorter bus-bar and linking it by a short wire tail/link? Isn't that just site engineering?  A better quality make of M.C.B. than Chint would be a benefit.

 

Z.

Regulation 536.4.203 (2nd para)?

That is a purely academic point. Reality varies with theory in many cases. We are talking about Chint here not Rolls Royce. This is a way to ensure makers' profits. Use our stuff only. I am sure that we are aware of that.

We can put our stuff into an empty enclosure or existing low Voltage assembly competently, so why not competently modify an existing assembly. 536.4.203 para 1. It is only a simple consumer unit so this is easily achieved.

Note 2. “Incorporated components inside the assembly can be from different manufacturers.”

Z.

I have personal experiences with Chint. Chris are you saying that everything made in China is top quality?

Petrol lawn mowers and leaf blowers are annoying noisy smelly things.

Z.

It also becomes an interesting sounding board of what seems to be deemed acceptable and why when you cannot understand how some people think things through.

I knew what to expect, so I was not actually surprised when I got it, even though I think I should be ?

Presumably applying the same logic it is okay to install a supply to Electric Vehicle Supply Equipment and hook up an electric car charging point with an ill fitting, under rated MCB that was not designed to fit the consumer unit?