kva of new supply- query

[J.C.E]

Potential job for one of my builders I have done a smaller previous job for

turning office into 7x 1/2bed flats but no gas.
Load in flats is:

20 odd led downlights (2x 6amp)
15 d.sockets (2x 32a)
1x induction hob (1x 32a)
1x fan oven (1x 20a)
1x 3kw immersion (1x 16a)
5x heaters- assume <13amp oiled filled (split on the 2x 32amp rings)

so a max demand of around 57amps

so 7x flats on 60a supply =420a + communal lighting

safe to say 120kva TPN new supply would suffice?

Cheers guys

 

[telectrix]

120A TP-N. not120kVA

that's around 80Kva.

 

[The Ghost]

What no showers?
Kva depends on the PF x load surely. Anyway it is not as simple as even that. If you are being asked this by the DNO they actually want to know the peak demand. As a comparison; 66 Units all offices, communal areas and reception. Some electric heaters some semi industrial all rated at 80Kva. Is this installation going to be installed with HH meters?

 

[Gavin John Hyde]

Does this apartment building/ office building have lifts?
Also as @Vortigern has said what about showers? these will have to be electric if there is no gas or boilers in flats.
If you do have a 3 phase supply how are you going to separate it out to the flats? are you going to use a ryefield set up? It might pay you to have a chat with the dno to find out what they would be happy with. If you are going to connect all the flats on their own meter then you will get a better price from the electric firm / dno to do the work.

 

[J.C.E]

clients already said they have already ordered new 120kva supply
-not sure who done hes calcs (im new to him and only done a flat for him before (its still early for me- not even quoted yet)

shoot I did forget showers- so makes each of the 7x flats 73a max demand

was thinking Ryefeild route...

120KVA TPN NEW HEAD>> (as per client)
70mm singles in trunking (can these be tri-rated?)

200a Eaton TPN switch>>
70mm singles in trunking (can these be tri-rated?)

9way 80a Ryefeild>>
25mm double insulated in trunking

meter>>
25mm double insulated in trunking

80a SP isolator>>
16mm 3core SWA on tray

Consumer unit inside flats

 

[Ian1981]

Because there’s no gas to the flats doesn’t mean you need electric showers.
Numerous flats I’ve worked on the showers are a mixer ran off the unvented cylinder tank which contain On and off peak hot water thermostats.
The off peak being installed with DP switch via time clock set for say 1 am -8am for cheaper rates of electricity.

 

[Ian1981]

clients already said they have already ordered new 120kva supply
-not sure who done hes calcs (im new to him and only done a flat for him before (its still early for me- not even quoted yet)

shoot I did forget showers- so makes each of the 7x flats 73a max demand

was thinking Ryefeild route...

120KVA TPN NEW HEAD>> (as per client)
70mm singles in trunking (can these be tri-rated?)

200a Eaton TPN switch>>
70mm singles in trunking (can these be tri-rated?)

9way 80a Ryefeild>>
25mm double insulated in trunking

meter>>
25mm double insulated in trunking

80a SP isolator>>
16mm 3core SWA on tray

Consumer unit inside flats

Can’t the DNO connect their supply into the BEMCO then all you need to do is tails from the BEMCO fuse,into an isolator for each individual flat then your swa from the isolator to the flat consumer unit?
All flats metered of course.
Then if you ask they normally supply a 3ph and neutral isolator so you can connect into a 3 phase db for the communal areas and possibly a 3 phase lift supply.

 

[Gavin John Hyde]

Just make sure when running the cables from cutout to the flats via which ever method you have adequate fire stops to prevent spread of fire and plenty of fire rated sealant around cables when going through walls. Also ensure cables are correctly supported. the building control around here focus on that with eagle eyed vision, one of them is some sort of national fire safety expert on some advisory panel so really goes to task on the fire safety stuff, at same time hes great if you got queries about fire alarms systems and hmo's etc..

 

[bigspark17]

Why ryefield board and not control panel.?

 

[The Ghost]

cheaper

I see what you are saying, but electric shower is cheaper to run and more convenient in terms of taking a shower at anytime surely.

 

[J.C.E]

Why ryefield board and not control panel.?

doesnt DNO basically insist on you becoming the BNO and installing a Ryefeild

and 1 point of isolation- hence the 200a switch before the Ryefeild

 

[bigspark17]

Control panel has single point of isolation.

 

[davesparks]

Why ryefield board and not control panel.?

Control panel?

 

[J.C.E]

Control panel?

guessing he meant dis board? and surely discrimination wouldnt be correct if using a mcb as apposed to a 1361

 

[Ian1981]

Perhaps he means using mccb’s?

 

[bigspark17]

Perhaps he means using mccb’s?

Yes i did. I call it a control panel with mccb but may not be the correct grammer.

 

[Risteard]

Yes i did. I call it a control panel with mccb but may not be the correct grammer.

Panel board.

 

[J.C.E]

Yes i did. I call it a control panel with mccb but may not be the correct grammer.

Have a feeling they pretty much insist on a ryefeild setup or possibly a lucy

 

[EbolaSideRoom]

Sorry for back tracking a little, but personally I’d be planning to put the space heating onto separate circuits from the general power outlets, even if they are connected via plug tops.