IET logo
 
IET
Decrease font size
Increase font size
Topic Title: Uprating of circuit breakers
Topic Summary: When is an MWC required?
Created On: 30 September 2013 02:30 PM
Status: Post and Reply
Linear : Threading : Single : Branch
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 30 September 2013 02:30 PM
User is offline View Users Profile Print this message



mazzy2000

Posts: 18
Joined: 25 June 2013

I recently submitted a post regarding our in-house electricians not carrying out an EIC for a replacement distribution board, something which was corrected and they have now carried out said inspection & tests.

However, I recently learned that following the DB change, one of the circuit breakers for a lighting circuit was repeatedly tripping. The electrician's solution to this problem was to uprate the circuit breaker from a 6 amp to a 10 amp.

When I asked for a copy of the Minor Works Certificate, they looked at me as though I was mad and claimed that it did not require one. In my opinion, even derating a circuit breaker is classed as an alteration and should have an MWC to document what was done, why it was done, who done it and records of any relevant tests carried out.

Any comments on this subject from others within the industry would be greatly appreciated.

Incidentally, the 10 amp breaker also started to trip. On further investigation they found a faulty cable, which was replaced and the circuit has been ok ever since.
 30 September 2013 02:41 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11269
Joined: 13 August 2003

When I asked for a copy of the Minor Works Certificate, they looked at me as though I was mad and claimed that it did not require one. In my opinion, even derating a circuit breaker is classed as an alteration and should have an MWC to document what was done, why it was done, who done it and records of any relevant tests carried out.

I agree - you'd want some evidence at the very least that someone had checked circuit's max Zs was suitable for the uprated device - even if replacing with one of the same ampare rating but different type (e.g. 6A B type with a 6A C type).

I think OMS used to have a phase something like 'if you can't change the people, change the people' - which for some reason has come to my mind...

- Andy.
 30 September 2013 03:28 PM
User is offline View Users Profile Print this message


Avatar for Parsley.
Parsley

Posts: 960
Joined: 04 November 2004

This may help see Q2.20

http://www.esc.org.uk/industry...and-similar-premises/


If the MCB's are being upsized or different tripping characteristics installed then a re-valuation (design) is definitely required.

Regards
 30 September 2013 05:43 PM
User is offline View Users Profile Print this message


Avatar for OMS.
OMS

Posts: 19455
Joined: 23 March 2004

I think OMS used to have a phase something like 'if you can't change the people, change the people' - which for some reason has come to my mind...


LoL - for sure, Andy

Never mind the paperwork, what maniac decided that the cure for intermittent tripping was to bang in a bigger breaker.

First you need a diagnosis - then you come up with a solution, and as that solution is effectively design, then you need a method of recording it - a MWC would appear reasonable, if not actually designed for the job (technically it's only for an alteration where the circuit protection characteristics remain unchanged - ie the definition of a circuit)

Regards

OMS

-------------------------
Failure is always an option
 30 September 2013 09:51 PM
User is offline View Users Profile Print this message



keylevel

Posts: 456
Joined: 31 October 2003

Indeed. Mine detector on: La! La! La! Stomp! Stomp! Stomp!
 01 October 2013 02:11 PM
User is offline View Users Profile Print this message



normcall

Posts: 8111
Joined: 15 January 2005

That's why they used to use a lot of 15A fusewire (or even 30A).
Commonest reason round my way is the sudden finding out that 'low energy' 12v lighting seems to cause the problem with 6A.
Nuffink strange about finding 20 'low energy' fittings in one room in some of the flats. Theory and practice!

-------------------------
Norman
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.