board change questions

[ExArmy]

theoretical question:

if the main fuse is a 80A BS88 type IIb, tails are 25mm with 16mm earth, can i install a 10 way dual rcd board with a 100A main switch?

how is the total load calculated? all the MCB'sin your average 10 way bpard add up to way over 100A?

 

[Grants]

With domestic, don't worry about the load, in practice you never come close to max demand. In theory even with diversity it always seems too much.

 

[ExArmy]

the thing i was worrying about is what about the potential to overload the tails and fuse by someone coming along and adding extra circuits.

say for example theres an old 4 way wyllex 3036 board with 80A BS88 IIb and 16mm tails, the house get rewired and theres now 6 circuits as you split the lights onto 2 seperate breakers, and you install a ring in the kitchen, now theres 4 spare ways in the board, what if some DIY cowboy just uses all the spare ways and then overloads the tails and fuse?
sort of along the same lines as you can't install a GU10 downlight into a ceiling thats rammed full of insulation with no space around or above it and say it's ok cos theres a CFL or LED lamp in there!?
i realise i might be worrying too much about this as i'm typing it, but what do you guys think?
also , is there anything to say you can't leave unused MCB's in the spare ways? i did once as i didn't have any modular blanks and the customer (who was supplying the materials) wouldn't buy any and said i've paid for those MCBs leave them in as blanks... i do need to start finding some customers with money to be honest they are all tight as ****!

 

[Guest55]

Perfectly fine to put spare mcbs into unused modules.
Customer pays for them so may as well fit them
And you worry too much.

 

[Guest55]

And its handy to have spares already there for emergencies.

 

[ExArmy]

good to know, thanks

 

[Guitarist]

The point of the fuse is to prevent the tails from being overloaded. Now if you had 16mm tails with a 100A fuse, then you could be concerned.

 

[Grants]

You can't worry about what may happen in the future, you can only certify that the work you did at that was at a standard of the current regulations.
if you see anything that is not up to current regs you state so in the part of the certificate for existing installation. You point it out to the customer who has a choice to act on it or not. If the installation is unsafe, and you have told the customer and he will not sanction the work then you fill out a dangerous situation report and get him to sign it. Then it's up to him as you have done everything in your power to make the installation safe.

 

[Guitarist]

It can be really soul-destroying when you see something which you would put right in a heartbeat, yet a customer gives you the usual "it's worked like that for years" speech, then gets into their brand new car.