thoughts on this 3ph commercial unit

jammiedodger

hi all..

can i get some opinions on how best to approach this..

commercial unit divided into 3 I.T units 9mx 5m with a common canteen area..

3ph 80a supply in canteen
24 skts in each IT room
5A of HF lighting each IT room
8kw 1ph aircon in each IT room

customer wants separate board in each room with metering facility so that rooms may be leased out separately..

originally the idea was to put each room on its own phase but i dont really think that this is an option as the rooms may not be used at the same times.. conceivably 1 room may use 50A while the others nothing..

this is going to make things quite a bit more expensive for him but i dont see any other option atm..:(

anyway any of your thoughts, views or comments would be appreciated...;)

DublinDilbert

What's wrong with putting each on a seperate phase? 3 phase loads don't always have to be balanced, that's what the neutral is for

I work in a shared office set up and each office is on its own single phase supply, with consumer unit with meter in each office.

M cebee

try to calculate the 'demand' first -see if it's within 12-16kva limits


what's the IT load and diversity ? could be tight

workstations about 3-500w afaik
SP metering should be fine if load allows

if you need to up the capacity to '3-phase wholecurrent' the air-con will prob be 3-phase

jammiedodger

thanks for your replies guys..

10 workstations at 350w (only reference i found was to allow 300w for a computer)
1 aircon @ 8000w
lighting at 1000w

total 12,500w

jammiedodger

guys one last question.. the above mentioned rooms, the owner has his data unit near the door and has suggested putting the switchboard beside it..
as that door is the only exit, am i right in thinking that this is an escape route and i should then place it well away from it??

M cebee

in this case i reckon 25sq tails 16kva SP metering should just do it

if you're saying supply is 80amp 3-phase-options are limited with the multi-metering required





'isolating switch' normally close to entrance assuming board isn't impeding exit

not aware of any particular precautions?

jammiedodger

whats happening is the distribution board is being fed from cts in 25mm to a 3ph 80a sw fuse.. off that i intend running a 16mm from each phase to feed a 63a sp sub board in each room..

??

cheers for helping me with this by the way

M cebee

it's a sub-main then and the SP meters are 'landlord's meters' so to speak

not esb meters


are you not using 80a tp+n switchfuse on the supply side and and isolator on the sub-main side

that's the way i see it done usually -or are stepping down from 100 to 80

jammiedodger

yeap the meters are for his benefit so he can see what each is using..

what is in place at the distribution atm is a 100a 3 pole isolater switch which feeds into an 80A 3p sw fuse.

my intention, to take a supply from each phase through a 63 sw to a consumer board in each room which will go through a 63A neozed sw fuse..

is this ok do you think??

jammiedodger

sorry.. i am talking about the sub-main

M cebee

you have a 'distribution circuit' feeding a 3-phase 'sub-main board' in the canteen

normally switchfuses on supply side of 'distribution circuits' and 'isolating switch' at sub-board if you get me

you are putting the 63amp switches and switch-fuses in the wrong sequence for the units



anyway you're options are limited with the supply available and the requirement for local 'landlord's metering'

jammiedodger

i really wonder sometimes if i should have been that guy who turns the light around and around in a lighthouse all night..

yea i got mixed up there when i said db i meant sb..

anyway tbh i think i was getting a bit jumpy as its my first job as my own boss. i'm certain it will be done up to scratch.. just maybe not the way normal people would do it

HighlyCooL

jammiedodger wrote: »

hi all..

can i get some opinions on how best to approach this..

commercial unit divided into 3 I.T units 9mx 5m with a common canteen area..

3ph 80a supply in canteen
24 skts in each IT room
5A of HF lighting each IT room
8kw 1ph aircon in each IT room

customer wants separate board in each room with metering facility so that rooms may be leased out separately..

originally the idea was to put each room on its own phase but i dont really think that this is an option as the rooms may not be used at the same times.. conceivably 1 room may use 50A while the others nothing..

this is going to make things quite a bit more expensive for him but i dont see any other option atm..:(

anyway any of your thoughts, views or comments would be appreciated...;)

just my two cents

Load:
sockets 3 circuits at 40A (100% first, 50% remanding)
Lighting: 5A have you taken into consideration PF and the power used by the ballist? (multiplying by 1.1) say 6 to be sure.
HVAC: 8000watts 35a

Each unit will need a supply of about 81Amps so good with 100amp fuse this giving room for expansion. each unit might what to add there own servers UPS,Laser printers ect.

what i would do is pick up my tails where they enter the building, put in my 4 check meters 3 single ph 100amp HCRs and 1 3ph 80amp HCR for the canteen take a single phase supply to each room with a sub board, and a 3ph+N to the canteen. then put an isolator on each board in the 4 rooms. i would leave room for circuits in the main DB, for the likes of emergency lighting and fire alarm, intruder alarm, cctv and general lighting and power , out door lighting.

as for sizing the supply form the esb, take it your going to need a minimum of 80amp per phase by my (rough)calculations, but you will need to know what going in the canteen.


best of luck its not easy out on your own, but needs must