3phase dis inb domestic setup

[J.C.E]

looked at a rewire of a 4storey property today (lower,ground,1st,2nd)
they is a 100a 3ph head on lower floor- and there is 2x seperate SP c/u (think there use to be 2x flats)

but is now going to be one house

best option?... to install something like a 8way 3ph amd3 dis board by the head on lower floor and have all my circuits off rcbo's off that (balancing the load evening across the phases)

probaly do circuit wise:

lower floor lighting 6a 1.5
ground lighting 6a 1.5
1st+2nd floor lighting 6a 1.5
lower ground power 32a 4mm radial
ground power 32a 4mm radial
1st floor power 32a 4mm radial(with 2x 3m2 UHF kits)
2nd floor power 32a 4mm radial (with 1x 3m2 UHF kits)
kitchen ring 32a ring/radial
Indcution Hob 32a 6mm
Oven 20a 2.5mm
MW 20a 2.5mm
I.H 16a 2.5mm
Boiler 16a 2.5mm
Alarm 6a 1.5mm
Smokes 6a 1.5mm

no 'building' work is being undertaken as in extensions etc- so no building inspector- would I need a system grade A fire system as a large house or will I be fine will LD3 (smokes in 4x halls and heat in kitchen- all interlinked)

 

[J.C.E]

Never seen a gas boiler which needs a 16A supply!

likely 6a mate- just poss allow for a 16a radial for another spur or 2 for the plumber.....

 

[davesparks]

Smokes have batteries, so you don't lose them- I never put smokes on their own circuit.

Why 16A for the boiler?

Because a 16A radial is the smallest standard power circuit and it is the most common circuit to be installed to feed a single small load appliance.

 

[Richard Burns]

any advise on what fire grading is needed for a large 4storey house?
exisiting building just having a rewire- no structual alterations

You need a fire risk assessment to properly decide on what grade of FDAS you should install.
If the house is old and not being renovated then the risk may be greater and consequentially need a more robust system. If the house is of conventional high quality build then a grade D LD3 should be acceptable, unless the plan is to use the house for multiple occupancy.

 

[willy fixit]

Because a 16A radial is the smallest standard power circuit and it is the most common circuit to be installed to feed a single small load appliance.

Could use the unused 1.5mm you bought for the lighting as long as it's ref B, C, 100 or 102.

 

[Gavin John Hyde]

with a property like that (over 2 stories)the people who mortgage/insure it and maybe even local council may insist on certain types of fire alarm, sound out the local fire brigade, they all have somebody driving round to offer advice and it is less aggro than the council and free aswell.
Having done quite a bit of work on multi storey town houses, most of them listed then we have had to ensure the cabling was all fire protected, fire blocks between floors, interconnected smokes/heats as a minimum and if more than 4 floors install emergency lights in the event of power failure, as if you are on 4th or 5th floor its a bit of a trek in the dark to get to basement to reset things. Always had another firm install the fancy fire alarm system when required as the firm I sub contracted for had lots of people on call.
Also you might want to check with the local building control as changing 2 flats back into 1 dwelling can come under a lot of different areas, regardless of what it is now, you are in effect creating a new dwelling as far as council are concerned. without the certificates from building control showing its up to standard and complies the property could be non-mortgageable and find insurance firms wont touch it.

 

[J.C.E]

learn today a bit more..

so 100a 3ph head coming in >> 100a 3ph isolator
then they only used 1 phase into sp meter and henley blocked into 2x sp fuse boards

for a 4storey house (with gas for heating) would you tend to keep simular setup and just use 1 ph into a hager stacked consumer unit with rcbos

or get the client to get a 3phase meter and put a 3ph dis board with rcbo's in?

cheers for help

 

[Andy78]

I'd look at the demand taking into account current measurements and go from there. Seems to be fine for the current usage ?

 

[J.C.E]

I'd look at the demand taking into account current measurements and go from there. Seems to be fine for the current usage ?

nothing heavy

all LED lighting (was going to have 1x circuit circuit per 4 floors)
4mm 32a radials for sockets per 4 floor (normal ammount of points)
32a ring for kitchen
32a for ind hob
2x 20a radials for MW+fan oven
1x 16a for immersion
1x 16a for 2x boilers
on the 1st floor 32a raidal (there will be 2x 3m2 elec ufh in bathrooms)
on the 2nd floor 32a raidal (there will be 1x 3m2 elec ufh in bathroom)

so if I was to calc max demand adding up circuits and x0.4 -that will obviously be >100a

but i am thinking 100a will be ample..

 

[Timbo]

Why 4mm radials? 2.5mm is cheaper and easier to work with.

 

[Spoon]

Why 4mm radials? 2.5mm is cheaper and easier to work with.

Could be cause radial is safer than ring.

 

[J.C.E]

this is the current setup before rewire

3phases from head >> MEM isolator

L3 goes into a henley in the trunking >>which feeds the SWA and that SP meter

the SWA then feeds another meter which supplys a c/u for one part of the house

and the SP meter in the picture feeds another c/u which does the rest of the house (via the orange pyro)

so the old 2x c/u are both on L3 100a

The house is now one- and the client wants one consumer unit in one place- nice and organised

I was thinking to start from scratch

take head tails (only from 1 phase)>> SP meter >> new 100a SP isolator

then a SWA from new 100a SP isolator>> a new hager 20+20 stacked consumer unit with rcbo on the ajacent wall (as the curved ceiling will look craap with trunking/cables

then just leave the other 2 phases unused at the head

thoughts