On 14/04/2011 16:05, harry wrote:
On Apr 13, 10:36 pm,
wrote:
wrote:
In , ARWadsworth
writes
Arfa wrote:
We are in the process of taking some modern commercial premises, in
which the landlord is dividing down a 2k sq ft unit into two 1k sq
ft units, one of which will be ours. The electrical supply comes
into the unit that will not be ours, so the landlord is putting a
new supply into our bit for us as part of the deal. The currently
installed supply is three phase, with each phase company-fused at
100A, as far as I can see. We have approached NPower for a meter,
and one of the questions on the application form refers to the type
of meter required. The two three phase options given are "Three
Phase Whole Current" and "Three Phase CT".
I have not the slightest idea what the difference between these is,
or which it will be that we need ?? I have checked with the
landlord to make sure that it is a three phase supply that he is
bringing over to our unit, and he says that we will "need a three
phase meter for a 40kVA supply" First question then. If each phase
is currently fused at 100A, does that mean that the incoming supply
is 25kVA per phase i.e. 75kVA, and that by dividing it between the
two newly created premises, that is how he arrives at 40kVA ?
Our demand will be fairly high. There will be two electrical fryers,
each loading at 2 x 9kW, so I guess if they are all on and heating
up together, that would be a demand of 36kW. There is also a ceiling
mounted airco / heater unit that I don't know the specs for . It's
not very big - maybe 2 ft square. Other than that, the demand will
be moderately low - some fume extraction which is only a few amps, a
couple of small fridges and freezers, lights (not more than 1kW) and
small odds and sods for a normal ring main. So, given the
*potential* for everything being on together, does that mean that
the supply he is proposing giving us, is going to be adequate for
our needs ? Another question on the form is "Voltage - please delete"
The three
options given are 415V 11kV and 33kV. I assume that the correct
answer there is 415V as it's a three phase supply direct into the
premises ?

Have you got 3 phase appliances? It is worth noting that 3x100A
fuses on a 3 phase supply does not give you 300A of available power
for 230V appliances (no matter how well you share the load between
the fuses) as the neutral is only rated at 100A.

I have not done 3 phase for a while (other than just connect up a few
machines) but 40kVA sounds like he has just multiplied 400 (the
nominal voltage between phases) by the 100A fuse. ISTR that it
should be multiplied by sq rt of 3 to get the maximum power.

With a bit of (bad) luck Dennis should be along shortly to explain
everything as he is a f***ing know all.

You forgot Harry ...

No, I didn't.

And I was wrong. I offered my apologies to Harry. What more can you do? I
was wrong and I admitted it.

I will not try to make excuses, I will eat humble pie.

--
Adam- Hide quoted text -

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We all still love you :-)

But only in a manly, viking way....


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Dave - The Medway Handyman www.medwayhandyman.co.uk