Application for new electrical supply (eg.northern power grid)

[franki]

Has anyone completed an application for a new electrical power supply?
I have been asked to complete the form for a new small office 9x6m.

When calculating the max load it states that a single phase can provide a capacity of 20kVA, and a 3 phase supply can provide up to 60kVA.

Will a single phase be adequate for the office? I have done some calculations but they are coming out at 36kVA, yet this is a small single storey office.

Thanks

 

[Engineer54]

A single phase supply will be more than adequate for your limited needs. Your estimations are way over the top, but then your not an electrical trained person, so your excused in this case!! :seeya:...lol!!!

 

[Darkwood]

Has anyone completed an application for a new electrical power supply?
I have been asked to complete the form for a new small office 9x6m.

When calculating the max load it states that a single phase can provide a capacity of 20kVA, and a 3 phase supply can provide up to 60kVA.

Will a single phase be adequate for the office? I have done some calculations but they are coming out at 36kVA, yet this is a small single storey office.

Thanks

Hi Franki.
Just done one for a 400kva supply and a pain in the arse believe me, i cant comment as you tell me whats available and what you have estimated but the vital thing is how you arrived at your answer, you sound over the top for such a small office as 20kva is approx 80amp cutout fuse, the 3ph 60kva again will give 3x 80amp (approx) cutout fuses.

 

[franki]

Thanks for comments
i've done my calc's and applied diversity from osg found results to be 29kW then divided by 0.8 to find a reading of 36kva

My circuits are
Bugular alarm 6A,
Fire alarm 6A,
Lighting 6A (19x50w) not discharge lighting
Lighting 6A (18x50w) not discharge lighting
O/s lighting (2x400w)
Server 16A
Office heater 16A, 3000w
Conference heater 16A ,3000w
Kitchen water heater 20A,3500w
Ring main 32A
Ring main 32A
Ring main 32A

Id be grateful if someone could let me know if these final figures/calcs are ok
Thanks!

 

[Jimmyb]

your looking at about 85amp max demand so 20kA single phase is what your looking for.

 

[Engineer54]

Franki,

Believe me when i tell you, you won't see anywhere near that 29KW or anywhere near the DNO cut-out fuse rating of 80A. I would hazard a guess, that you'll be lucky to see a 1/3rd of that 80A

As a little exercise for you, add up all the circuit ratings of your home, you'll find that even after the diversity factors you apply, (according to BS7671) the rating will be well above your cut out fuse rating. Has your home main cut-out fuse ever blown?? Nope !! In the real world, you are not using those circuits to full capacity, and even if you did, on one or two or more of those circuits, it would be for very short periods of time. If you don't believe me, get an electrician to put an Amp Clamp on the main live tail from the meter, i think you'll be very surprised, maybe shocked even!! lol!!!

To carry out a an ''Precise/Accurate'' demand load assessment, you need to be an experienced Electrical Design Engineer, and even they are not infallible when it comes maximum demand assessments either... But they will be a hell of a lot closer than you'll ever be!! lol!!!

 

[Darkwood]

A tip in future for you, i assume you are adding the alarms and server together as mcb ratings where in reality the alarms power consumption is neglegible and the server been a fixed item to that circuit wont be taking 16amps but possible a small fraction of that (enquiry needed to confirm), then i assume you applying diversity to said 6+6+16 to arrive at a your sum, this will over-rate you needs alot as your probably allowing 20-25amp for circuits whos total wont be pulling 2-5amps between them

 

[franki]

Thanks for your help everyone, i'll think i'll go with the single phase supply!