tails, floorboards and over stuff

[solo2771]

Hi all I am doing rewire for part P assesment ( was just a cu but no earths in lighting ect)
Anyway its tncs and its on 16mm tails with a switch fuse before the cu as it is about 3.5 M away from meter , am I right in thinking as long as it is fused for 16mm it will be ok?
also i believe I would need a smaller value fuse in the switch fuse than in the main fuse?
another problem is none of the switch back boxes have earthing points do they need them? and if so could I use thefixing screw with a crimped ring on it?
Is it ok to use the earthing bar for MET? and finally for now cross bonding on the new gas boiler (mounted on the wall in the loft)?
Thanks in advance
paul

 

[Sintra]

Hi all I am doing rewire for part P assesment ( was just a cu but no earths in lighting ect)
Anyway its tncs and its on 16mm tails with a switch fuse before the cu as it is about 3.5 M away from meter , am I right in thinking as long as it is fused for 16mm it will be ok?
IMO yes thats fine but others may disagree.
also i believe I would need a smaller value fuse in the switch fuse than in the main fuse?
Again yes need discrimination between fuse in switch fuse and service fuse.
another problem is none of the switch back boxes have earthing points do they need them?
Not if you have one fixed lug in back box and are using a core in a cable as the cpc.
and if so could I use thefixing screw with a crimped ring on it?
Is it ok to use the earthing bar for MET?
Yes as long as it complies with section 542
and finally for now cross bonding on the new gas boiler (mounted on the wall in the loft)?
Thanks in advance
paul

My responses in blue.

 

[Des 56]

I dont think you need disrimination between the suppliers fuse and your own
Either one goes and supply is lost,so a bit pointless
As long as the fuse is rated for the cable its protecting you could have a 60 amp supply fuse and your own 80 or 100 amp on 25mm tails