Over rated main cut out fuse or not?!

[ukpablo]

Ok, bear with me on this one!
got to customers house to do some work in bathroon, subcontracting to a local bathroom fitter for a 'homebase' contract.

bit of a drive out into the sticks, rcbo required to fit new whirlpool bath feed which i would be installing from board, and to also terminate a body dryer from old 10mm shower feed which was disconnected!
All this was info from bathroom contractor as i had not done a site survey myself.
Also this would be dependant on what i find at CU, however it had apparently been tested recently etc etc.

I turned up, removed cover from board but when i looked i informed them that there was not a spare way on board! (problem no 1)
All the kitchen was done about 3 months ago by a local contractor(the property is housing association by the way) and the main incomer has been changed from TT system to a PME TNCS upgrade

solution for (problem No 1) would be to fit bigger henley block and run whirlpool from a small new board, with new tails etc.

Looking at the CU in greater depth, and applying diversity to existing ccts (including the 9KW shower due to be replaced by a 9.5 KW body dryer) i calculated a total of 128 A.................................this does not take into account a seperate board running 5 storage heaters each on 16A breakers run from the same 16mm tails.

So here is my dilemma, Ze was good, Bonding in place, but the main switch on CU is only 80A and the main cutout fuse is only 60A!!!!!

Plus it all runs through a pay as u go meter which is sealed..................so looks a bit difficult to add a bigger henley block!

I have run all cables as contracted to do so and not terminated.

Crunch time..................was i right to inform customer that existing main fuse is not big enough? they need to contact DNO to clarify and get in writing?

Inform customer that this should have been picked up from previous electrician when kitchen was done..................and also that there are no copies of test results etc on any work done either?......so contact them too and ask why this is?

Any thoughts appreciated.................sorry if it is long winded...........just like my day yesterday really!!!

 

[Jay Sparks]

IMO, there should defo be test certs if it has been tested previously. I would also think the main cut out should be at least 100A, with a 100A isolater at the cu. I would guess that in winter at least 4 of the heaters would be on at the same time, so theres also some more ampage there! My house is only 3 bed with useuall 6 circuits and we have 100A cut out and 100A isolater. Of course this is only MY opinion but I would also have told the customer about the other sparks that "did/did not" do the test.

Hope this helps a bit

Jay

 

[ezzzekiel]

correct answer would be yes but short answer no, its highly unlikely that at anyone time you would go over (diversity is a queer old thing and should be replaced with a better method) assuming storage heaters are off peak, an upgrade to 80a would be a good idea, they tend not to like to fit 100a now for some reason.

you can
a: get dno to fit iso
b: fit it yourself and split tails.

wouldnt worry about fuse size not been picked up but missing certs suggest non-registered spark, a phone call would be in order.

 

[glynnis]

Surely if the property is housing association, it would be them (the landlord) who hold any certs for works carried out at the property?

 

[ukpablo]

dont know? thought a copy had to be left at property? so any spark like me coming along could see what state of play is?????

 

[glynnis]

maybe not at the top of thier "to do list" that year.
It also depends on who ordered the work and who paid for it?

 

[ezzzekiel]

hence the phonecall

 

[Baal]

Any certification should have been sent to the person ordering the work (probably the association)

It's good practice to leave a copy on-site but in my experience, pretty rare!

128A after diversity seems quite high even for a large domestic set-up!

 

[ukpablo]

hey, thanks for all ur input..................DNO are gonna upgrade to 100A fuse on main cutout, as to the rest of the board, im gonna fit new henley block, split some of the load into a new fuseboard.
thanks all

 

[malcolmsanford]

UKpablo an old DNO trick for diversity is add up your protection devices and multiply by 0.4 for domestic this is the rule of thumb the DNO boys work to.

It's 0.5 or 0.6 for offices/lightcommercial/ and 0.8 for industrial. Hope this might help in the future

 

[ukpablo]

cheers bud, did this but took off biggest fuse, multiplied the rest by 0.4 and added biggest fuse back on.
this is what the board had connected

6A lights
6A lights
32A radial for panel heaters
32A cooker(3KW)
32A hob (3KW)
32A ringmain
32A ringmain
16A water heater
16A skts radial
40A shower (9.5 KW)
16A whirlpool bath

total was 128A
main switch was 80A
main fuse was 60A.

thanks anyway

also connected was 6 x 16A mcb on seperate board for storage heaters........did not calc these.

 

[malcolmsanford]

Those 2 cooking units are interesting if they are 3KW they can be plugged into 2 x 13amp single sockets so those 2 X 32amp supplies are well over the designed.

You could change then to 2 x 16amp breakers to bring the installation right down

 

[ukpablo]

yea, but dont want to mess with ccts that im not getting paid to install etc! could open up a can of worms for myself, plus they are on opposite ends of the kitchen, which has just been done by somebody else!

plus thats only a guess, plugged clamp meter onto main incomer with only those two appliances on full............was drawing 30 ish amps.

6.9kw after calc