Three phase incommers

[wade88]

Morning lads,

Having a bit of a moment and struggling to get my head around a few things (that are undoubtedly very straight forward).

Im trying to work out what available power i have to play with in anticipation of some heavy machinery coming into the warehouses in the next few weeks. We have three warehouses, side by side, but our main units power supply is well and truly maxed, so im looking to take some power from the neighbouring unit to supply these machines.

And so...The incomming live is broken down into three 100A fuses, then tailed into the meter. From the meter all three lives are then run to a seperate 100A isolator, and then split to supply various other DB's. Now im either being a total lemon, but i cant work out why three 100A supplies, giving a potential of 300A to be used where necessary, all consolidated into a single 100A supply - does this not remove the capacity for a further 200A?

That 100A isoltaor then feeds a DB powering warehouses lighting which are high pressure sodiums i belivew, around 400w each, and there are 11 of those, so no biggy, and then and office ring and lighting. again, nothing heavy. it is also split down to feed another DB with a single 63amp Type D breaker for two three phase motors next door which run large u-trough mixers. Im struggling to work out what i have available and where i can take it from. I understand without seeing the set up this post will probably be as useful as a chocolate dil*o but any input gratefully recieved.

I am also probably backing up to the firing squad wall a bit here but i need to ask these questions.

thanks chaps

 

[telectrix]

check the loading with a clamp meter on each phase with everything running. you have the potential of 300A, but this should be equally shared ( as close as poss, ) between the 3 phases. say for example you have 80A red, 75A yellow, 40A blue, you can add single phase loads of 40-50A to the blue. if it's more balanced, say 60A per phase, the you would split your sigle phase loads equally across the 3 phases. at approx. 30A per phase.

 

[wade88]

Well that i understand Tele, but i dont seem to have the option to seperate and use each phase individually as they have been consolidated into the one 100A breaker. All three lives enter that 100A switch?

 

[topquark]

If you are planning on using each phase individually? ... you probably want 3 single breakers after the main incomer; so you can isolate each sub DB independantly. You'll still need to be warry to keep those 3 phases usage as balanced as possible though (so as not to overload the neutral).

If you are puzzling over the rating on the breaker being 100A; that's still 100A per phase.

 

[wade88]

Ahhh yes Quark thats where i was getting hung up. In my naivity i was expecting to see three individual 100A switches on the end of each 100A supply so i could have organised them individualy. So even tho all three lives enter the one main switch, they are all still capable of supplying 100A. Not 33.3 etc

 

[Knobhead]

If your going to export power from one building to another that already has a supply be very careful segregating and clearly identifying them.
To be honest I don’t like the idea.
I would suggest having the existing supply upgraded.

 

[wade88]

Hi Tony,

thanks for reply. Well it has already been taken into another unit, Via a DB that was installed for that purpose. Allow me to demonstrate my immense drawing abilities...prepare to be dazzled.

 

[topquark]

If your going to export power from one building to another that already has a supply be very careful segregating and clearly identifying them.
To be honest I don’t like the idea.
I would suggest having the existing supply upgraded.

Good point Tony. It does open a rather large can of worms. Out of phase supplys adjacent to each other in unexpected areas (either different phases or may be supplied by separate substation), bonding/earth issues etc.

 

[wade88]

Does this monstrosity make sense?

 

[topquark]

Good enough to confirm my understanding of what you described. So you are already taking the phase loading unevenly (assuming the unit 12 mixers are three phase motor driver) by taking a feed from DB1 in unit 11. What is this supplying a commercial bakery? Just wondering what the mixers are

 

[wade88]

No they mix whole grain which is then coated in rodenticide...we formulate and manufacutre pest control products internationally. So we mix around 12-14 tonnes of rat poison a day..and thats only a small aspect of the business.

Yes DB3 in Unit 11 is an Eaton MEM board, with a 63amp type D breaker which feeds two, 3phase mixers, (very large, 2 tonne mixers) in unit 12. that MEM ONLY has that one breaker in. So there is a surplus there, as when the mixers are operating they are only running at about 20 amps each, they just have a huge in rush - hence the type D.

I did not install this set up, it was done some ago, no problems what so ever, so far...touch wood. I havnt got a clamp meter, cant afford a good one just yet, would like one with earth leakage etc on it. but they are about a tonne arent they?

 

[topquark]

No they mix whole grain which is then coated in rodenticide...we formulate and manufacutre pest control products internationally. So we mix around 12-14 tonnes of rat poison a day..and thats only a small aspect of the business.

Yes DB3 in Unit 11 is an Eaton MEM board, with a 63amp type D breaker which feeds two, 3phase mixers, (very large, 2 tonne mixers) in unit 12. that MEM ONLY has that one breaker in. So there is a surplus there, as when the mixers are operating they are only running at about 20 amps each, they just have a huge in rush - hence the type D.

I did not install this set up, it was done some ago, no problems what so ever, so far...touch wood. I havnt got a clamp meter, cant afford a good one just yet, would like one with earth leakage etc on it. but they are about a tonne arent they?

There was a nice cheap one that would do for earth leakage, well under £100 (Alphatek/Metrel 633) but they've stopped making it, which is a pity. May be worth spending a bit more and getting one with peak/max settings as well, if you need it.

Dilog do the Dilog DL6507 (Leakage & Resistance). Which is a reasonable spec machine.