3 Phase Capacities

[chrisbyrd]

Hi All

This isnt really a DIY question, so dont get alarmed if it sounds like I'm going to be doing any of this myself... I'm not

Can anyone tell me what the standard 'starting' capacity of a 3phase mains supply is? We're looking to convert an office space into a reasonably substantial server room and I'm trying to work out if we'd need to upgrade the mains supply further than a basic 3-phase supply

What 'unit' do the distribution companies quote supply capacity in? Amps? KW? KVA?

In order to accomodate around 900 servers, i've worked out that we'll have about 600 'singe phase' amps of usage, including all the cooling (which is about 200A alone)

I know i'm going to need to speak to the distribution company (EDF I think) to get some proper figures etc, but I'd like to be clued up about the sorts of things I should be saying and listening for

I believe a standard single phase connection is 100a? so is a standard 3phase connection 300a?

What sorts of capacities are usually available without the need for a substation? Are we likely to be able to get this provisioned directly, without needing our own substation?

 

[plugwash]

Can anyone tell me what the standard 'starting' capacity of a 3phase mains supply is? We're looking to convert an office space into a reasonably substantial server room and I'm trying to work out if we'd need to upgrade the mains supply further than a basic 3-phase supply

usually its fused at 3x80A or 3x100A but the agreed max demand may be considerablly lower than that.

What 'unit' do the distribution companies quote supply capacity in? Amps? KW? KVA?

i think agreed max demand is generally measured in kilowatts but there may also be power factor stipulations in the deal especially as the incomer gets larger.

In order to accomodate around 900 servers, i've worked out that we'll have about 600 'singe phase' amps of usage, including all the cooling (which is about 200A alone)

so you are talking 200A per phase if you can get it well balanced, you probablly want a bit more to be safe. Probablly a CT meter setup would be used for an installation like that.

What sorts of capacities are usually available without the need for a substation? Are we likely to be able to get this provisioned directly, without needing our own substation?

ultimately you have to talk to them, if extra substation capacity is needed to support you then you will almost certainly have to pay for it to be built one way or the other (whether you decide to build and maintain it yourself or pay them to build it and have it on thier side), i'd imagine in a built-up area a 300A CT metered supply wouldn't be too much of a problem though.

 

[chrisbyrd]

thanks for that - all very useful

Whats a CT supply? :$

 

[plugwash]

CT reffers to the type of metering setup

for domestic supplies and small 3 phase supplies the meter comes as a single unit with input and output terminals.

for larger supplies things are done a bit differently, the main tails go straight from the DB to the service head but on the way are threaded through current transformers which allow the meter to measure the current flow. From the current measurements from the CTs and voltage measurements from a connection to a head the meter can then measure the electricity used.

your electrician should be able to sort that out but you would be well advised to plan for the migration to the new supply and get the new DB in place before the new supply is actually installed to ensure a smooth transition.

 

[Chri5]

Chris- You might want to add in the values for any standbye kit, batteries and UPS charging.

 

[ricicle]

You've been on here before about this havn't you?

 

[Lectrician]

In my experience you will be charged a monthly "availability charge" after agreeing your "maximum demand" with EDF. On larger supplies, this is standard.

If you take any more than your maximum demand, you are fined monthly. If you take less than your maximum demand you loose money, as you are paying for this agreed capacity.

You need to size your supply accuratly. You can pay to have a larger supply put in than you need, but agree a lower maximum demand to begin with.

 

[r.bartlett]

Make sure the air conditioning is spec'ed properly and includes things like floating head, heat recovery and free cooling which will greatly reduce energy consumption over the year

We are currently involved in such a project as yours ( heat load estimate 1.2mw) with the final spec being sorted out as we speak.

Cheers

Richard

 

[dw3101]

Personally I think you air con load sounds too small..

We have around 100 Servers and currently are using 190A for the aircon.

Even if its 200A per phase it sounds a bit small..

I was told to estimate at around a third of the total load, but have resorted to measuring it properly.

Also aircon suppliers quote the current at 27degrees outside temp iirc, so in cold weather they use less current (we are using around 50A per phase on cooling at the moment)

Then if your room isnt sealed properly you can have humidity problems and if the AC has a heater this can bump the supply up.

Also when building a data centre you need to consider harmonics and g5-4

 

[r.bartlett]

Floating the head pressure can reduce energy consumption by around a third for 70% of the year. However it's sophisticated and not many UK companies are up on it sufficient to incorporate it.

Plus there has been a woeful neglect to reuse the constant heat rejection which is a steady source of heat throughout the year which can offset energy consumption in other parts of the building etc

Cheers

Richard

 

[chrisbyrd]

Personally I think you air con load sounds too small..

We have around 100 Servers and currently are using 190A for the aircon.

Even if its 200A per phase it sounds a bit small..

hmm

our servers only use about 0.4a each - how does that compare to you?