minor works cert help

[sinaloan]

cool ok sorry i got ya now thankyou all for the help i really appreciate it

 

[Guest123]

Have a read of this snippet BS 60439, Annexe Za.....


"Part 3 of the Standard, BS EN 60439-3, deals with the particular
requirements for low voltage switchgear and control gear
assemblies intended to be installed in places where unskilled
persons have access to their use. This covers the supplementary
requirements for enclosure distribution boards suitable for indoor
use containing protective devices intended for use either in
domestic applications or other locations where unskilled persons
have access. Control and/or signalling devices may also be
included.
These distribution assemblies are for use on AC supplies, with a
nominal voltage to earth not exceeding 300V. The outgoing
circuits include short circuit protective devices, each having a
rated current not exceeding 125A with a total incoming load
current not exceeding 250A.
In the UK, such equipment is referred to as a ‘Consumer Unit’
and as such is covered by this Standard. However, additional
requirements from annex ZA of the standard call for the
assembly to have an additional test; this is known as the
‘conditional withstand test’. The condition is that the consumer
unit must withstand a 16kA short circuit fault when protected by
a 100A HRC fuse to BS 1361 type II. Further requirements are
addressed by this annex:
• Means of isolation to be via a manual double pole switch
disconnector
• Rated current of consumer unit is determined by current
rating of incoming device.
• Outgoing protective devices can be MCB’s, Fuses and/or
RCBO’s."

 

[topquark]

Maximum is normally dictated by the DNO's fuse max rating. I believe that the maximum recommended for them is around 16.5 KA Most main switches 60947-3 are rated up to 6 KA (and it should be marked on each BS standard compliant device).

Ooops, that should be minimum!! I'd best fix that

 

[sinaloan]

so if not diversity factors are applicable to consumer units then how do i work out my maximum demand?

 

[sinaloan]

so if my pfc was over 6ka topquark then id have to upgrade them as this would exceed the breakers ssc?

 

[topquark]

so if not diversity factors are applicable to consumer units then how do i work out my maximum demand?

Diversity may be applied to all circuits that are supplied by that consumer unit.

 

[Guest123]

so if not diversity factors are applicable to consumer units then how do i work out my maximum demand?

Dont worry about that bit, circuits eminating from the consumer unit may have diversity applied. I'll edit it out to remove any confusion.

 

[topquark]

so if my pfc was over 6ka topquark then id have to upgrade them as this would exceed the breakers ssc?

No, as you are protected by the DNO's fuse breaking capacity, assuming that is large enough. As stated they must have a minimum of 16 KA for a 230V system (I think it's 33 KA for 3 phase).

You should not rely soley on the DNO fuse for overcurrent though, if that's what you are thinking, they don't very often fail that quickly at rated current capacity (an 80A fuse may supply current at 100A for some considerable time) and you wouldn't want to break the seal to replace it after testing would you now

 

[sinaloan]

ok cool so the best way to work out my maximum demand is to use the diversity factors in appendix 1 of osg. does everyone do it like this or is there an easier way to work it out, someone told me to just put down the rated current of the main fuse but thats wrong right?

 

[Des 56]

I think this thread is getting to be like that pantomime song

"There's a hole in my bucket dear Lisa, dear Lisa"

and finishes

"There's a hole in my bucket dear Lisa, dear Lisa a hole"

 

[sinaloan]

when i do the testing on my fuseboard i take it i cant pull the main fuse then? do i just turn the mains switch off to turn it off and start testing or take the tails out of the meter? how fussy will the nic inspector be

 

[topquark]

Just putting the rated current of the main fuse is wrong (well assuming the circuits load was designed correctly ). There are some "rules of thumb" that are often used. I'd suggest going though the exercise of doing it by the OSG though, coz it's useful to have that off the top of your head as well.

 

[topquark]

I think this thread is getting to be like that pantomime song

"There's a hole in my bucket dear Lisa, dear Lisa"

and finishes

"There's a hole in my bucket dear Lisa, dear Lisa a hole"

AaaRRRR! 'oles is what's left after an electron goes on sabatical

 

[Geoffsd]

when i do the testing on my fuseboard i take it i cant pull the main fuse then? do i just turn the mains switch off to turn it off and start testing or take the tails out of the meter? how fussy will the nic inspector be

Is this a wind-up?

 

[topquark]

when i do the testing on my fuseboard i take it i cant pull the main fuse then? do i just turn the mains switch off to turn it off and start testing or take the tails out of the meter? how fussy will the nic inspector be

No, you can't pull the main fuse (it'll be sealed anyway). You turn the main switch off then perform a safe isolation to prove that your circuits are dead.

 

[sinaloan]

when i changed the fuseboard i just taped the ends of the tails up

 

[sinaloan]

only joking by the way lol

 

[topquark]

only joking by the way lol

It helps to have a sense of humour 'round 'ere

 

[Des 56]

No, you can't pull the main fuse (it'll be sealed anyway). You turn the main switch off then perform a safe isolation to prove that your circuits are dead.

Stop trying to wind people up,you know its easier and a lot less bother pulling the fuse and taking the tails out

 

[Goody]

when i changed the fuseboard i just taped the ends of the tails up

Did you connect both the end of the live tails together before taping or taped them separately, LOL.