Combing two incoming municipal electricity supplies

[Theo.vogel]

I've an interesting problem.
I've got an potential client. It is a commercial property that used to be two separate businesses each with a separate 60 Amp single phase electricity municipal electricity supplies to the same building. The one company has gone bust while the other one has grown. The remaining company's electricity demand has grown to the point where 60 Amp is not enough.

Is it possible to combine the two incoming 220v single phase supplies into one to supply peak loads. The 2 main dbs are relatively close to each other so adding cabling to combine will be easy and relatively cheap.

The Company does not mind getting two electricity bills.

Any recommendations will be appreciated.

Regards

 

[westward10]

Is this applicable to South Africa or the UK.

 

[Theo.vogel]

Yes, we've 220v 50hz supply

 

[telectrix]

maybe transter some of the load onto the other (unused) supply

 

[westward10]

In the UK there are requirements to bond the earthing systems together but not sure it this would apply there. As far as I know our only member in your neck of the world is @Marvo so maybe he can advise more clearly.

 

[Theo.vogel]

They are trying to run a 80amp pottery kiln, so nether one of the existing supplies would cope on its own.

 

[davesparks]

No you can't just join the two supplies together, unless the electricity supplier does it for you, but I highly doubt they would.

It's quite likely that the two supplies will be on different phases, so you will create a phase to phase short circuit when you join them, this will be sure to remove your eyebrows, possibly your eyesight and maybe your life.

 

[westward10]

I think the intention is to combine and not join.

 

[Marvo]

I'm not understanding exactly what they're thinking about doing but under the SA regs you're not allowed to supply a machine from more than one DB and you can't run cables between two DB's to achieve some kinda two-phase supply.

Each DB and the final circuits run from it is classed as an 'Electrical Installation' and there should be only one electrical installation per premises or property or per 'Erf'. If two separate premises are combined to become a single larger premise you must contact Eskom or whoever the local council supply authority are to have one of the DB's removed and the other one upgraded if necessary.

Each electrical installation should have a single point of isolation, having more than one DB in a premises is the kinda thing that kills electricians.

edit not sure why my post needs moderator approval....??

 

[davesparks]

I think the intention is to combine and not join.

The OP says they have an 80A kiln which cannot be supplied by either supply on its own, that says to me they want to join them.

 

[davesparks]

edit not sure why my post needs moderator approval....??

It's not just me then, I just assumed I'd upset someone again.

 

[westward10]

The OP says they have an 80A kiln which cannot be supplied by either supply on its own, that says to me they want to join them.

Yeah I have not fully combined and understood all posts. The moderation thing is forum wide at the moment so it is nothing personal.

 

[davesparks]

Each electrical installation should have a single point of isolation, having more than one DB in a premises is the kinda thing that kills electricians.

What exactly do you mean by DB here? This statement makes no sense to me at the moment as a DB here is a distribution board of which it's normal to have many in an installation.

 

[DPG]

What exactly do you mean by DB here? This statement makes no sense to me at the moment as a DB here is a distribution board of which it's normal to have many in an installation.

Pretty sure he means DBs fed from different supplies but in the same building.

 

[Marvo]

What exactly do you mean by DB here? This statement makes no sense to me at the moment as a DB here is a distribution board of which it's normal to have many in an installation.

What you might refer to as a consumer unit or CU in the UK is termed a DB in South Africa. You can have other distribution boards fed from the main DB, these would be 'sub DB's but they would be isolated via the main circuit breaker in the DB which is referred to as the 'point of control' in the SA regs.

The OP is referring to a scenario that would have two separate electrical supplies which would have two points of control within the same premises. This is not legal. I understand why he's thinking about this because there would be costs involved to have the supply authority upgrade the supply at his original DB which he thinks he could avoid by such an arrangement.

 

[davesparks]

What you might refer to as a consumer unit or CU in the UK is termed a DB in South Africa. You can have other distribution boards fed from the main DB, these would be 'sub DB's but they would be isolated via the main circuit breaker in the DB which is referred to as the 'point of control' in the SA regs.

The OP is referring to a scenario that would have two separate electrical supplies which would have two points of control within the same premises. This is not legal. I understand why he's thinking about this because there would be costs involved to have the supply authority upgrade the supply at his original DB which he thinks he could avoid by such an arrangement.

We call them DBs too, it would only be a CU usually if its in a house.
We tend to refer to all DBs just as DBs rather than making the distinction between main and sub DBs hence my confusion.

It is permissable in the UK to have multiple incoming supplies to a building.
Most of the theatres I work in have at least two, sometimes more, incoming supplies, one for the domestic installation and one for the stage lighting/production power.

 

[Theo.vogel]

I am pretty sure both incoming supplies are on the same phase as the the minisub 20 meters down the road where both originate only seen to have three cables. How would I confirm that both are the same phase?

 

[davesparks]

I am pretty sure both incoming supplies are on the same phase as the the minisub 20 meters down the road where both originate only seen to have three cables. How would I confirm that both are the same phase?

Even if they are on the same phase you cannot just join the two together to create a bigger supply, this will create a dangerous situation.

If there are three cables coming in to a substation then it is almost certainly three phase as the incoming HV will be 3 phase delta.

If you need a larger supply capacity then your only option is to contact the supply company and get the correct size supply installed.