Asked to supply a log cabin

Is the supply to the house up to the job?  It sounds like this cabin is going to be a complete new dwelling, so it will need a decent supply. Especially if heating and cooking is electric.

Maybe what they need is a complete new supply from the DNO, but I doubt they will want to pay for that.

J Harrison said:

Turns out there is 56 circuits within the house and out buildings.

Is it a palace, or just a mess?

The addition of a supply with a small CU in the cabin will require you to I & T the installation from the origin to wherever you tap into it because in effect, you accept responsibility for it when you do the work and issue the EIC.

I suggest that you quote for that separately on the basis that it the work would have to be done (and charged) either way.

Unless you are desperate for work, I'd make it a hefty quote and keep my fingers crossed. :-)

More questions than answers I think.

Is this a single phase 100A supply ? Is there an obvious 'origin' CU feeding the others - so really it is 'container supply' or 'garage supply' or whatever that are 30A sub mains  feeding final circuit sub-boards at the  locations. or is it lots of boards on Henley splitters only fused at the meter tails level of protection ? 
The former would sound like an industrial spark used to big factories but working on domestics, and  may be OK if the final circuits have RCD cover, that latter would be a someone too tight to pay for a larger main board ;-) 

Agree, a quick tot-up of total loads to see if an upgrade is recommended, but there are plenty of flats with showers sharing fuses that give no issue, so it may be alright.
Does it look like things have been overheating or damaged ?

are there heavy loads ?

Do you want the aggro ?

Mike.
PS cheapest if slightly dishonourable  is to do your bit as another small CU, split at the meter  tails and say ' I'm leaving all that alone and not testing it ' to the existing rest of it.

Yes 100a fuse and cut out in good working order.

Yeah was thinking a 16mm supply but wasn't sure on where to come off, hence why i said to the client to test prior.

Its like a large cottage/farm house out in the sticks.

I just didn't want to add/alter anything without testing first - which will also lead the client in to fork out an additional cost for remedials.

Yes 100a main fuse supplying the property. 

There is a main cu withing the property which supplies other boards, but im sure it was like a cu will feed another one then that one would feed another one and so on.

Kind of dont want to get involved with testing 

In my view, a new all electric habitable home, whether in a log cabin or otherwise needs at least a 60 amp supply

32 amps for a shower

20 amps actual loading for a cooker

10 amps for electric heating

5 amps in total estimated for lighting and small appliances. Is of course a total of 67 amps, would probably get away with a 60 amp supply and a bit of short term overloading. Though it is poor practice to design on that basis.

LPG for cooking and water heating could reduce electricity demand substantially. An automatic load control device that isolates the space heating and hot water cylinder when the shower is used would help a bit.

Most park homes, in effect a caravan for 2 folk have a 32A supply, though most have gas for space and water heating, just the shower is electric. Unlike a shower, space heating may be on for hours at a time...

But I am aware of more than one block of flats with storage heaters where there is a 100A 3 phase feed teeing off to supply many meters and flats, where the ADMD must be a lot less than 30A per flat as the no of flats per 100A incoming phase range from 5 to 7 but the DNO seem happy enough.

Mind you I'm very glad I'm a flat lease holder and not the freeholder whose kit that actually is.

I agree its not to the best practice or future proof, but in practice loading like that seems to work, and I've seen a few 'granny annex' type set ups that are similar.

Mike.

 it was like a cu will feed another one then that one would feed another one and so on

Yep. that is someone used to industrial work, stick another DB instead of run more than one cable all the way back !

Mind you I can't really be too disapproving, I have a CU in the house one way of which is a 32A sub main that feeds a small DB in the garage, that in turn has RCBOs doing garage lights and power, and one more MCB way in that feeds an SWA submain that goes to the two sheds, each of which has small DB that splits the supply over separate power and lights RCBOs . It minimises the walk to reset things, and in practice has never tripped on anything that was not a real fault.
So I can sympathise. (quick sanity check is an IR test over the whole lot from the house CU end and R2 wander to verify as many far point earths as can  sensibly be reached and note the highest ... )

Mike.

J Harrison said:

Wondering what other sparks would do here.

Make the connection to as close to the origin as reasonable practical and ignore the rest (at most a few choice words in the 'comments on the existing installation' box)!

The shower need not be of the instantaneous electric type. Most French homes seem to survive on a 32A single phase supply even when all the hot water (and cooking and likely a bit of space heating) is electric. It's sobering to see they can do - an immersion in a pressurised cylinder, careful use of off-peak tariffs and if needs be a little load shedding - and it all seems to fit!

   - Andy.