Barrie

Can you help with this, I need to specify to a landlord the power req's for an industrial unit.

Overall there is approx 30 kw req for lighting / ventilation in the storage area of the unit and then the electrical load for a office area (approx 200m2, 50 sockets, electric convection heaters, lights, internal ventilation fans, etc)

I need to convert this load to a KVA power requirement, the supply is 3 phase.

Do you need any more info?

Can anyone do a quick calc, I have had some conflicting advice so far hence the question here!

Thanks

Barrie

logiclee

If you haven't got any power factor information which you won't have for domestic equipment the nearest you are going to get is a direct KW to KVA conversion.

ie 1KW = 1KVA.

Some of your equipment is going to be single phase such as lighting, computers etc. Is your storage area equipment 3 phase?

Is your landlord asking for load per phase or total load? You can use discrimination to a certain extent ie- you will not have everything on at once but ensure you have enough maximum demand capacity. You may have an electricity contract where you are charged extra for going over you maximum demand so check the small print.

Lee

edited to add..
Not 100% sure what is required for domestic/small industrial 240v 3 phase supplies. Our little unit runs oun nine 4000KVA supplies at 11000V Most of the load is inductive so Power Factor is a big issue.

matt.bowey

agree, power factor is needed to work out total kVA.

kVA = kW/pf

hedgehog

A lot of that gear looks like it is going to be mostly resistive so as Lee says a direct conversion might get pretty close. It doesn't look like there is a lot of highly inductive gear in there, nearly impossible to tell though.

I'm no good at this power stuff anyhow but do the supply companies not like you to put in big caps if you are running lots of very inductive gear?

matt.bowey

They love you for putting it big caps!! They call it local pf correction. It saves the grid havign to supply loads of reactive power (kVAr).........which they dont like doing, as it drops the system voltage.

logiclee

We run a few large 11kV capacitors to try and correct the power factor a little.
As a by product we produce Methane as waste, we've just installed two 2.4MegaWatt generators that burn the methane and that also helps with the Leccy bill, The V20 Turbo engines look beasts as well.
Leccy bill can still run at £1million a quarter though.

Lee

matt.bowey

Just re-read the question..............provide more info (why, etc) and you are bound to get an answer.......!

30kW is bugger all really, so if u r looking to buy some plant, just over rate it a little!!!

The only time when kW does not almost = kVA is when you have induciton motors running fans, machinery etc, so i would be inclined not to worry about the pf.

Make sure you get the 3 phase kVA correct though. You may need to get a 1.41 (root 2) in there somewhere, so be careful!!

Cheers,

Matt.

Barrie

Hmmm, that will be why I did chemical eng and not electrical stuff then, and here was me thinking that all I had to do was plug it in and it would work

Have been advised that 35 kva per phase should provide plenty of power.

Anyone care to disagree?

Thanks

David_Wallis

Depends what you want to 'plug' in as you put it!

matt.bowey

u could be over-rated by 3......! But who cares, it aint your cash!!

If you install an overrated transformer, you need to up rate the bus as it will have more short circuit capacity.........!

logiclee

If you have a base load of 30KW in the storage area then 5KVA/5KW per phase should be ample for the office area providing you are not going to install electric heating or air conditioning in the office area.
Some big Photocopiers can require their own 5KW supply so be carefull if you are going to need one.
Ensure you get the pro's in to install the correct dis-board and protection systems. You will need to do a plan of what equipment you are having and where it is going to be sited.

Cheers
Lee