CU upgrade - which of these issues need sorting ?

[GaryMo]

The main earth conductor (from the PME cable head to the earth terminal) should be 16mm, and use all of the cores!

Even if it's been sized using the adiabatic equation (543.1.1(i) / 543.1.3)?

 

[ColJack]

nevermind, I got MPBC's confused with CPC's again.. the main earth is just a CPC for the supply circuit..

 

[mikej2005]

I based my reply on this paragraph from your original post:

NB. Main fuse is 60A. The two separate 40A RCDs serve two electric showers - 10.8kW via 10mm2 cable & 9.5kW via 6mm2 (the latter of which will be removed when the bathroom is renovated). In the meantime, we never run both showers at the same time !

Yes, sorry - I do make sure the showers aren't run at the same time and do indeed intend to remove one of the showers, so perhaps I shouldn't worry - I'm just trying to cover all angles, mainly so that I can get as much of this done at once as possible.

 

[Adam_151]

It won't be 60 hours coljack

I can tell you now without even looking at the graph that 90A will cause it to go within an hour (and probably much uicker than that), though you could probably draw 100A for long enough for a bloke to take a shower

 

[ColJack]

I've looked at the graph, I've got it right here in front of me.. 3600 seconds is when the graph "tops out" and at that point the line for the 60A fuse is a little further than the 100A line, so about 110A... that's the start point of the curve..

at 200A it will blow in 80 seconds
at 150A it will blow in 400 seconds.. it's logarithmic..