fuse board change advice please

[James sparks]

Hey all,

Looked at changing a fuse board the other evening but am not quite sure on a couple of things so wanted to gain some opinions please.

It's the top flat (victorian two storey house converted into two flats), meter cupboard externally at ground level. A armoured is run to both flats (one to each), each is a 3core looked like 25mm. The SWA enters the meter cupboard through a form of plastic ducting, it has a gland on the end but is floating in mid air. The cores then go into the meter and earth block. SWA isn't earthed at this end. The armoured run is 4-5meters approx and there is no isolator in the meter cupboard.

Questions:

1 - Should the SWA be earthed at the meter end or can it be done at either end so long as it is done at one or the other.

2 - The cores are single insulated pretty much straight after the gland. Does the meter cupboard count as a enclosure? It's the usual triangle key to access it but the cupboard door has taken a beating at some point. If not then is heat shrink countable as a second insulation?

3 - There physically isn't enough room to fit an isolator in the meter cupboard to comply with the 3m rule. Is it ok to change the DB and note on the cert' that there is no isolator present?

4 - The other end of the armoured is terminated into a metal clad rewireable board. Curretly the earth core in the armoured goes straight into the earth bar within the DB and then they've taken one from the DB to the external (beside the DB) earth block where the gas and water run from. Is this ok to do? Or would you terminate the armoured into a enclosure first, split the earth from there to the block?

Thanks for any comments!

 

[Engineer54]

1/ I would always earth the SWA at the source, so yes add a flying lead from the gland to the earth connection in the cabinet...
2/ I would say that the cabinet is an enclosure...
3/ That's not a problem, you can say the CU earth bar is an EMT which is connected to the installations MET outside of the CU, so i would say it's fine as it stands. No problem however, if you want to change the set up as you suggested...
ie ... Flying lead to the CU earth bar (EMT) and the main earth core direct to the MET...

As for double insulated tails, you can if you wish use heat shrink tubeing. But normal meter tails are not double insulated, they are in fact insulated and sheathed....

Not sure what you can do if there isn't the physical room to fit a switch fuse, i'll let others advise on that one!! lol!!!

 

[malcolmsanford]

It is so difficult to argue against regulation 433.2.2 and 434.2.1 with regards to position of protection for respectively overload and fault protection.

Both these regs allow you to site the protection along the run but where a change in reduction of current carrying capacity, be that size of conductor, method of installation, type of cable or conductor or environmental conditions.

So if you assess that you have met all these conditions, then you can site the switch fuse where convenient.