UK 3 Phase Supply

[mikehenson]

I have recently become involved with our local church when I became aware that the installation was 3 phase.

Looking at the meter I see that phase 1 is using 60%, phase 2 using 48% and phase 3 zero.

I was always under the impression that 3 phase supplies should be balanced?

 

[James]

Looking at the meter I see that phase 1 is using 60%, phase 2 using 48% and phase 3 zero.

I was always under the impression that 3 phase supplies should be balanced?

Ideally the phases would be roughly equal in current draw.
However, it only really becomes an issue when you are running out of capacity on one phase.
I am concerned that you might be reading the meter wrong.
It is not possible to draw 60% on phase 1 48% on phase 2 and 0% on phase 3
It adds up to 108% of your total load.

 

[Jock from the north]

I have recently become involved with our local church when I became aware that the installation was 3 phase.

Looking at the meter I see that phase 1 is using 60%, phase 2 using 48% and phase 3 zero.

I was always under the impression that 3 phase supplies should be balanced?

It also becomes an issue with current being diverted thru the neutral if the phases are extremely unbalanced .the neutral conductor would have to be suitably sized in that instance .it is a real challenge to balance a 3 phase installation especially when single phase loads are concerned and how and when they are being used .is there multiple distribution boards in church .

 

[Flanders]

Just a thought is phase 3 supplying storage heaters that only run over night

 

[James]

It also becomes an issue with current being diverted thru the neutral if the phases are extremely unbalanced .the neutral conductor would have to be suitably sized in that instance .it is a real challenge to balance a 3 phase installation especially when single phase loads are concerned and how and when they are being used .is there multiple distribution boards in church .

I was trying to keep it relevant, I have never seen a distribution circuit below 1Mwatt that has a reduced size N conductor.
Mostly but I can’t say always, N is the same size as the live conductors unless it is not there at all.

 

[Jock from the north]

Just a thought is phase 3 supplying storage heaters that only run over night

Yeh this is the problem.the designer might try there best to balance the phases /loads but if certain equipment say heaters are switched off or not being used you have the issue of unbalanced loads .there maybe parts of the building where the heaters are never on due to rooms not getting used .

 

[Jock from the north]

I was trying to keep it relevant, I have never seen a distribution circuit below 1Mwatt that has a reduced size N conductor.
Mostly but I can’t say always, N is the same size as the live conductors unless it is not there at all.

I completely agree .

 

[brianmoooore]

Places like churches rarely have any actual 3 phase loads. The 3 phase supply is installed mainly to meet maximum, usually heating, load.
You can use knowledge and experience to partly balance the loads, based on what you expect to be in use at the same time, but there's no guarantee that at times one phase with be under heavy load with none on the others, and this is what you have to design for.

 

[Simon47]

As said above, on this size of supply a reduced neutral is unlikely. Therefore, even with all the load on one phase there is no chance of overloading the neutral unless you also overload the line conductor.
So really don't worry about balancing loads - just make sure you don't overload any of the phases.

 

[Jock from the north]

Places like churches rarely have any actual 3 phase loads. The 3 phase supply is installed mainly to meet maximum, usually heating, load.
You can use knowledge and experience to partly balance the loads, based on what you expect to be in use at the same time, but there's no guarantee that at times one phase with be under heavy load with none on the others, and this is what you have to design for.

What I would say churches now come in all shapes and sizes.no longer can some churches be identified as a traditional gothic buildings ,but they could be large office buildings with even a cafe and warehouse .there are alot that Maybe running food Bank enterprises and hiring out office space .of course they have some sort of charity status as there run by buisness men/woman. Some even benefit from donations by large oil companies. So it could be feasible that with multiple sub distribution boards some parts of the installation may indeed have inadequate line and neutral conductors.of course unlikely to affect main incoming supply conductors .the op needs to elaborate on what kind of church this is and why he /she thinks the phases are so out of balance.it would seem to me that it would take some sort of electrical knowledge to even recognise the issue that is giving them cause for concern

 

[TheatreSparks]

I would ask is there an organ of the pipe variety? It is very likely that if there has been one at some point then a three phase supply would have been installed for the wind motor for it, but the rest of the building load was spread across two phases, say lighting on one phase and power on a second phase, with 2 single phase boards.

 

[Simon47]

I would ask is there an organ of the pipe variety? It is very likely that if there has been one at some point then a three phase supply would have been installed for the wind motor for it, ...

Unlikely unless it was a really massive organ - stop sniggering at the back. I haven't got at our blower yet (needs removing some shelves with a gazillion hymn books before I can take a side panel off) to look at the rating plate, but it runs off a 16A/1ph breaker. We only have a 63A 1ph supply.

Don't forget that they were hand blown originally - think Hattie Jaques charafter in Carry on Dick

 

[James]

Unlikely unless it was a really massive organ - stop sniggering at the back. I haven't got at our blower yet (needs removing some shelves with a gazillion hymn books before I can take a side panel off) to look at the rating plate, but it runs off a 16A/1ph breaker. We only have a 63A 1ph supply.

Don't forget that they were hand blown originally - think Hattie Jaques charafter in Carry on Dick

Again, guys please keep the sniggering down at the back of class.

I have come across many organs that have a 3Ph blower.

 

[Simon47]

Granted, if there is a 3ph supply then it makes sense to use a 3ph motor, but the organ blower wouldn't justify a 3ph supply.
Unless you've a 6,000 pipe theatre organ using 60hp of high pressure blower

 

[westward10]

Our church organ is three phase. The contactor is suspended on four springs within a soundproofed enclosure probably electrified in the 60s or earlier.

 

[Simon47]

Ours doesn't have a contactor - just a vintage bakelite bodied switch. Probably electrified in the 70s as well.
Apparently our oil boiler was second hand back then when lecky arrived. Before that, "the lad" would stoke up the coke boiler the day before a service.