Balancing a 3 phase load

[gerard]

I have a question on balancing a load. We have 3 cabins with the following loads: 10kW, 8kW and 3kW, supplied by a three phase supply. Each cabin will have it's own supply. Is there a simple way of balancing these loads, or is it possible?

 

[nickblake]

Is that total load or can you apply diversity to it

 

[gerard]

Total Load

 

[davesparks]

Anything is possible, but how far you go will depend on how necessary it is.

If this is going to be fed by a DNO supply then your loads will be a drop in the ocean compared to everything else fed from the same Tx

If however you have a small generator supply you will want the total load to be no more than 30% out of balance.

If you need to balance it then you need to look at the nature of the loads/ load profiles aswell as their power ratings.

 

[gerard]

Loads will be supplied by DNO. I can't really change loads so I was just thinking of leaving it as it is - unless someone had another idea?

 

[Darkwood]

Balancing loads from our side of the supply is purely to allow for better scope for future additional circuits especially 3ph ones... of course this cannot always be achieved but do it as best you can.
The problems arise when you have a scenario like a 100amp 3ph supply and you have

L1-85% loaded
L2 60% loaded
L3 15% loaded ----and someone wants to wire a load of say 20% capacity per phase so clearly L1 would overload, thus a better balancing by previous installers would have not made this an expensive addition with either the extra work swapping circuits about or an increased supply application.

In your case I don't have enough info to say you can/can't balance it better even with additional costs, would need a lot of info about the existing supply, balancing, peak KVA demand per phase etc etc... getting this wrong can be costly to the customer in the future, depends whether you act as a proffesional or a sod it and just wire it type... a chat with the customer about the balancing and consequences of taking a possible cheaper option may be needed to give your customer the choice and also to explain a higher quote you may have against another company.


EDIT ... to note balancing of phases with effectively reduce the N current and may in some circumstances like older systems with reduced sizes on N cables need to be factored when making load additions or even modern systems with Harmonic issues that can cause many issues with the Neutrals been overloaded if excessive imbalances occur.

 

[Pete999]

Can't see how you are going to balance these loads, you have 3 cabins each with a SP supply @230v 10A, 8A and 3A respectively, is that correct? if you have any peripheral loads such security lighting etc, which you could take from the phase supplying the cabin with 3 amps.

 

[Darkwood]

Can't see how you are going to balance these loads, you have 3 cabins each with a SP supply @230v 10A, 8A and 3A respectively, is that correct? if you have any peripheral loads such security lighting etc, which you could take from the phase supplying the cabin with 3 amps.

If it was 10A, 8A and 3A I'd be telling the OP to stop been silly and install it and forget.... Think the KW he expresses makes this a worthy query!

 

[benji]

stick 2x3kw heaters in 3rd container

 

[Pete999]

Can't see how you are going to balance these loads, you have 3 cabins each with a SP supply @230v 10A, 8A and 3A respectively, is that correct? if you have any peripheral loads such security lighting etc, which you could take from the phase supplying the cabin with 3 amps.

Correct my mistake, confused KWs with Amps duuuu:6:

 

[Darkwood]

Correct my mistake, confused KWs with Amps duuuu:6:

I gathered it was a Typo but best to let you know straight away

 

[nickblake]

Agree with dave here

 

[davesparks]

If that is the load before diversity I'd say you are probably on a hiding to nothing, once diversity has come in to play you'll probably have naff all load to balance.

Give us the breakdown of the loads for each unit and maybe we can give a better idea.

 

[guest119]

Correct my mistake, confused KWs with Amps duuuu:6:

Time for another 5 weeks at the skill centre for you Pete ...

Boydy

 

[gerard]

I have found out that the phases are not balanced throughout the building. All I can do is wire new loads to the phases with smallest loads