80 amp main fuse

[skes]

Hi There

I'm about to fit a 8.5 kw shower (using 10mm2), at the moment i have a wired fuse Wylex(1x5a, 1x15a and 2x30a) i'm undecided at the moment whether to change the CU or fit a shower RCD (via a Henly) theres no problems pulling the service fuse as its a token meter, i'll wait till it runs out, lets hope it's during the day
The thing i'd like to know is the main fuse is a 80amp fuse, is this ok?

Thanks.

 

[ban-all-sheds]

Why might it not be?

 

[skes]

Just wondered if it was big enough for the job, because the other fuses add upto 80 and then there's 40+amps for the shower,

 

[dw3101]

Im not sure I would rely on a meter to isolate the supply, if thats what your suggesting?

It 'could' be wired wrong and isolate the neutral.. (god forbid..)

David

 

[plugwash]

and the switch may not have decent seperation

personally i would rather pull the fuse

 

[dw3101]

I agree with plugwash.. not that anybody would recommend breaking the tab on the ceramic.. as cutting the tag is naughty

 

[ban-all-sheds]

Just wondered if it was big enough for the job, because the other fuses add upto 80 and then there's 40+amps for the shower,

Individual fuses always add up to more than the service fuse.

You need to find out about diversity - see Appendix 1 in the OSG.

How many light fittings do you have on the lighting circuit, and what are the other 3 circuits used for?

 

[skes]

There are 9 light fittings including 2 wall lights, the other fuses are for 15A Water Heater, 30A Sockets and 30A Cooker(Oven).

 

[shaggy]

If the token meter is like the card meters then when it runs out there is a facility to get £5 credit by pressing a button. The question to ask is could anyone press the button while you were wiring the CU? Safer with the fuse out.

 

[securespark]

You're best off asking the REC for a 100A supply. Tell them you have X rings, an electric cooker & want an HP shower too

 

[skes]

Thanks for your reply's, i've arranged for my leccy company to come and change to meter to a billing one, so if i talk nicely to the spark he might do it for me and check the tails to see if there big enough.

Thanks.

 

[securespark]

You may find you need different departments to do different jobs.

I needed: a bigger fuse, a replacement meter, and a new intake, and needed to contact two seperate departments to get the work done.

 

[mildmanneredjanitor]

Tell them you have X rings

Surely a Doctor would be more appropriate!

 

[ban-all-sheds]

There are 9 light fittings including 2 wall lights, the other fuses are for 15A Water Heater, 30A Sockets and 30A Cooker(Oven).

11 light fittings x 100W x 66% = 3.2A
Water Heater = 15A (*)
Ring Main = 30A
Cooker = 10A + 30% of remainder = 16A (*)
Shower = 37A

Total = 101A (Actually less, as the * figures should be the based on the actual load, not the circuit protection, e.g. if water heater is 13A and oven is 20A, then the total becomes 96A).

It would seem reasonable to ask the DNO to upgrade you to 100A.

 

[plugwash]

yeah but it is commonly known that the guidelines routinely give figures far higher than the service fuse

yet such fuses very rarely blow domestically