Advice please on correct MCB – might not have correct unit!

[zappastix]

Hi

Around 2 years ago I upgraded an electric shower to a Triton 8.5kW

It required a higher rated fuse/breaker: 40A MCB.

I used the cable already in place – 6mm clipped to roof joists
(above insulation) around 10 metres to CU.

My CU is a Crabtree Starbreaker fitted with RCD MAIN SWITCH / 80 amp 30ma

We’ve been here 9 years, so it is at least that old.

The consumer unit does not have a clear plastic cover – but a hard plastic off
white cover attached with two screws.

I took the redundant MCB to B&Q and found a match, inasmuch as the DIN Rail Mounting
guides were exact, and the measurements APART FROM the “trip lever” which extended
out more and the trip lever is lower than the original.

Looking at Screwfix the new MCB is called: Crabtree 40A SP Type B Curve MCB

The original MCB I think is called: Crabtree Starbreaker 61 RANGE TYPE B MCB

I took a chance, and the MCB fitted perfectly, and has not tripped once.

BUT IT HAS JUST DAWNED ON ME – just because it has not tripped I have no way of
knowing if it would trip if there was a problem.

I know that the CU works because if a light bulb blows it trips that circuit, and sometimes
other bulbs have gone and they have tripped the main switch. And a dodgy appliance
once tripped the main switch.

There is a yellow TEST button.

So my question, should I worry about this “not being an exact match MCB (bit late I know)?

Or would it be advisable to try and find original MCB’s?

Also, could someone explain how to use this yellow test button.
Do I have to turn all the other MCB’s off – and test the shower/40 MCB on its own?

Any help or advice welcome.

Thanks in advance.

Stephen

 

[Taylortwocities]

You mean you installed it without testing it?


This yellow test button, is it on the "MCB" itself?
If so then you may not have an MCB, it may be an RCBO.

This may help you identify what you have put in there

Untitled

• Taylortwocities
• 27 Mar 2010
• 43

Can we see a picture of it?

 

[PrenticeBoyofDerry]

It is always advisable to use the MCB of the manufacturer of the consumer unit, as they are type tested to that model of board and other brands are not.
Look here
http://rbstaronline.co.uk/acatalog/Crabtree_Starbreaker_range.html
As far as whether MCB is actual function as it should, would be hard to say without shorting the circuit out!

 

[zappastix]

Thanks all.

The yellow test button is near the main on/off switch on the CU. Not on th MCB itself.

 

[ericmark]

Years ago I would cringe at a yellow test button as it meant a ELCB-v rather than ELCB-c but today many RCD's have yellow test buttons.

The ELCB (or RCB if current operated) come as many types. The old voltage type are outlawed but even the current type come as 10, 30, 100, 300, and 500 mA with 100 mA being used for TT supplies but 30 mA is required for a shower.

There are also passive and active but that is unlikely to be a problem.

6mm sq cable does have a host of power ratings according to type and how installed. Reference Method 100# (above a plasterboard ceiling covered by thermal insulation not exceeding 100 mm in thickness) for 70oC thermoplastic insulated is 34A so likely your 6mm is not good for 40A.

The yellow button tests the mechanics of the trip. It needs a special meter to test a RCD 6 tests are the norm. 2 (Pos and Neg) to show it will not trip too soon, 2 (Pos and Neg) to show it will trip at 30 mA, and 2 (Pos and Neg) to show it will trip within 40 mS at 5 times rated value.

If you want to be sure then only way is get some one to do an electrical installation condition report. They were called PIR's.

 

[ban-all-sheds]

As far as whether MCB is actual function as it should, would be hard to say without shorting the circuit out!

Not so.

Here's one way:

http://www.eurosmc.com/pdffile/GAMA_EMU ing screen.pdf

Other makes are available.

 

[PrenticeBoyofDerry]

eric, It's the MCB's function that the op is concerned about not the RCD or RCBO.

 

[PrenticeBoyofDerry]

As far as whether MCB is actual function as it should, would be hard to say without shorting the circuit out!

Not so.

Here's one way:

http://www.eurosmc.com/pdffile/GAMA_EMU ing screen.pdf

Other makes are available.

Available where?

 

[ban-all-sheds]

Here: http://www.google.co.uk/search?q="primary+injection+tester"

 

[PrenticeBoyofDerry]

So wont find one at CEF then, will they order me one in?

 

[ban-all-sheds]

I'm sure they will.

 

[flameport]

Looking at Screwfix the new MCB is called: Crabtree 40A SP Type B Curve MCB

The original MCB I think is called: Crabtree Starbreaker 61 RANGE TYPE B MCB

They are the same item in a different style casing.
The design was changed in an attempt to distance the products from the recall mess.
No problem with using a mix of those types in the same unit, other than the appearance.