Code for board chage

[Innominata]

Hi Alll,
Anybody suggest code for board change from old rewirable.
Thanks

 

[Spudnik]

Not sure i follow........

 

[jase]

code 2 - requires improvement
code 4 - does not comply with BS7671

although the latter might not be strictly true it could be said it doesnt comply with 17th edition

 

[Sintra]

You can not code a cu for having bs 3036 rewireable fuses if all tests prove satisfactory.

 

[Des 56]

Hi Alll,
Anybody suggest code for board change from old rewirable.
Thanks

If the trusty rewireable boards need a code
What about those mcb type things, that lots of people use,they are no better

can you justify why the rewireable board requires changing?

 

[nickblake]

right old wylex type board change well ,bs 7671 requires all circuits up 32 amps to disconnect in .4 of a second not easy with rewireabled to achive that infact only real way to do that is an RCD , the other thing is that if the board is the type that has the wooden frame at the back the its classed as a code 1 , reason is if a fault developes in the board and they do an awful lot burnt terminals etc etc , then the wood becomes a fire hazard ,so a code 1

 

[Sintra]

right old wylex type board change well ,bs 7671 requires all circuits up 32 amps to disconnect in .4

Why can you not achieve this with a BS 3036 fuse without RCD?

 

[pevvers]

Why can you not achieve this with a BS 3036 fuse without RCD?

Indeed...

How comes they still show disconnection times for both 0.4 and 5 seconds in BS7671:2008?

They are still current, and still can be used if RCD protection is not needed....

 

[nickblake]

they are in the regs and i accept they can be used but when you take into account the tripping current required to blow these fuses in the case of a low resistance fault not achieving the required current , the rcd will trip (well should do )having said that 60898 take a lot to trip ,ok ive dug a hole stick my head down it my error chaps

 

[pevvers]

they are in the regs and i accept they can be used but when you take into account the tripping current required to blow these fuses in the case of a low resistance fault not achieving the required current , the rcd will trip (well should do )having said that 60898 take a lot to trip

I think you mean a high resistance fault wouldn't achieve the required current. If the Zs is below 80% of the max stated in BS7671:2008, then the fuse will blow within the required time, which is exactly what the tables are in there for!

RCD's won't trip on a line to neutral fault, and they also aren't infallible. I've found many on a periodic that refuse to trip at all, let alone in 0.04 of a second!

ok ive dug a hole stick my head down it my error chaps

That's what these forums are for, to all learn off each other!

 

[nickblake]

Totaly agree think were all being led into a false sense of security there is a certain expensive make of RCB0/s ive never managed to test at the correct tripping times in fact the cheaper ones seam better

yep made an error

infact when you look at the real picture as electricians were told about RCD this that and the other ,all electric lawn mowers, trimmers,strimmer etc are class 2 and have no earth in the cables so an rcd to protect you when you cut the cable in half is useless !!

 

[Des 56]

right old wylex type board change well ,bs 7671 requires all circuits up 32 amps to disconnect in .4 of a second not easy with rewireabled to achive that infact only real way to do that is an RCD , the other thing is that if the board is the type that has the wooden frame at the back the its classed as a code 1 , reason is if a fault developes in the board and they do an awful lot burnt terminals etc etc , then the wood becomes a fire hazard ,so a code 1

Unfortunately there are sparks who see a rewirable board as a throwback to some distant unsafe era,then recomend.usually totally unjustified advise that they are somehow non compliant and/or dangerous

There is a big misunderstanding amongst our industry with regard to this, and sometimes un necessary cost to the customer based on this ill thought out advise

Rewirable boards often come with a bakelite rear plate for fire issues
Even where they are not fitted,more often than not they are mounted on stone or brick
Overheating or faults occuring have little or no more chance of burning than a plastic enclosure of the modern board
Obtaining readings that would render the circuit unsafe are few and far between
The most obvious case is where 1.0mm cpc on a ring with a 30 amp fuse and a long length of cable has been used
Test and calculation usually allows dis connection times to be met

To all who have this unjustified mis understood aversion to 3036 fuses I say
Get to know your enemy first,he might be much less of a threat than you were led to believe

Another point is that this mis understanding is also used by rip off merchants to gain un necessary work
Our job is to make and test installations for safety,not to advise wrongly on installs that are acceptable and mostly compliant