3 Phase Conection Cable

[Forkinhades]

How difficult will it be once completed to upgrade? either by parallel or new set of cables?

As you could do load test once finished, you can get an 100 amp clamp meter very cheap, then see how much you will be pulling in amps.

[Forkinhades]

Also I am quite sure that the 15/45 meter AND fuses can handle 1 and 1/2 times normal current loads, thus in effect giving 60 amps per phase

[Greenside]

How difficult will it be once completed to upgrade? either by parallel or new set of cables?

As you could do load test once finished, you can get an 100 amp clamp meter very cheap, then see how much you will be pulling in amps.

The cables are underground. Our present arrangement means I have to lay some anyway - see the attachment. The guy that wired our Studio (the one on the left, where we live now) misunderstood his instructions and instead of providing us with a single phase supply plus a spare 3 phase supply terminating in the junction box ready for the main house, he laid a 3 phase supply (in 25m² copper) and then used 1 phase of that to continue from the junction box to the studio.

The main house hadn't been designed at that point so we didn't really have much of an idea about how the loading would work out other than we'd need 3 phase, so if fact even if he'd done what we'd asked he'd probably have laid 25² cable which has turned out to be an issue in itself.

So at best we'll have to lay a couple of extra 25² cables to the JB and then four onward to the main house, but the worst case is a whole new set of 35mm² from the road to the main house.

The road is looking like it will turn out to be twice what we budgeted, and with the pound up and down like a yo-yo I'm trying not to spend any more than I possibly have to while doing a decent job.

[Forkinhades]

That junction box could prove be very handy indeed.

Are you going to keep the single phase to your current dwellings?

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[Greenside]

We'll (have to!) rent the Studio (that's our only current dwelling) out once we move into the main house. I'll leave its single phase supply in place and so the tenant will have his own meter.

[Forkinhades]

Will you be putting a pillar above the junction box?

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[Forkinhades]

If you had a pillar above the junction box, then that in turn could house a three phase sub mains board, which can then feed your 3 other boards. So your supply to your pillar could then be in parallel with another 25mm, to give a 50mm from the 30/100 supply which now seems inevitable. You can then do whatever you want from the pillar, and it will have nothing to do with the PEA.

From the pillar

1. 25mm supply fed via a 3 phase 50 amp MCB for board one in your house

2. 10mm supply fed via 3 phase 32 amp MCB for board two.

3. 16mm supply fed via 40 amp single phase MCB for your outhouse.

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[Greenside]

A pillar? You mean a pole to carry cables?

[Forkinhades]

No more like an enclosure.

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[Greenside]

Here is the Junction Box set up as it is now. The large one is the power in/out etc and the two smaller ones are for telephone, co-ax cable for video and power to a set of outside outlets and a side entrance.

If you meant something much bigger than this then I am reluctant to go that way having spent so much to keep the cables out of sight so far.

[jpeg]

3 phase is.for.factories et al. But the bigger the better huh? You shock 3 phase you dead. (Not as though shocks ever happen here ) Well. Natural selection and all that ....

Oh, good to see you doing your bit for the 'carbon footprint'

[Greenside]

The fact that I've got a lot of outlets and a/c's is both about convenience and saleability of the property and, had I the money and the roof aspects, I would have both solar power and water heating. What's a reasonable monthly electricity bill for a family of four in the summer?

[Crossy]

3 phase is.for.factories et al. But the bigger the better huh? You shock 3 phase you dead. (Not as though shocks ever happen here ) Well. Natural selection and all that ....

Oh, good to see you doing your bit for the 'carbon footprint'

Simply not true, a shock phase to ground (the common type) is the same whether you have a 1 or 3 phase installation.

[bankruatsteve]

Yah - so I think the main thing is that, given 3-phase, why you would need a 30/100 amp service for what you have given is just way over the top. You seem to need/want 3-phase but should be just fine with the 15/45 service and using the 25mm cable for that you already have for that. Maybe just tell your spark you are trying to save money (Thai's understand that) and just go with what you have. I doubt the PEA will give a crap in any case. As for the professor guy - his input was appreciated. Thank you very much.

[Crossy]

Yup ^^^

[Greenside]

The truth is that my understanding of the power supply part of this is very limited and I (mostly) go with what I am advised. I was told from the outset that 4 bedroom house with a pool would need a 3ph supply and that's why we tried to put one in the ground as far as the junction box when we built the Studio.

I would like to have two meters so that my future tenant has his own account.

Steve, you say I should be all right using the cable I already have and a 15/45 meter - do I take that to mean that the four incoming 25mm² wires will support two single phase installations (one of which you can see the size of and the other is pretty undemanding)? If so, that's what I'll aim for - I have absolutely no interest in having 3ph for the bragging rights!

[bankruatsteve]

I think that's what everyone is saying. YES.

You may/may not be surprised to know that, in the states, almost everybody has single phase (split phase) handling a lot more than you are showing so, the idea that 3-phase is required for large to really large homes is just not substantiated.

[Greenside]

Many thanks. I will be meeting with the main contractor and my architect tomorrow and put this to them. I'll let you know how it turns out!

By the way, this is how the constructions is going with supposedly four months to go....

[IMHO]

Many thanks. I will be meeting with the main contractor and my architect tomorrow and put this to them. I'll let you know how it turns out!

By the way, this is how the constructions is going with supposedly four months to go....

If you have 4 guys doing roof tiling (where's the foil BTW?) and are using the dry-fit system, I'd say 14-18 days to go there including fascias (unless they use wood to attach fascia's which would be quicker). If you have a few guys doing cement rendering, I'd say maybe 8-10 days to go on that.

If you get the electricians in a pre-wiring as soon as the roof tiles are on, and you have two ceiling teams, I'd say around 2-3 weeks to get all ceilings in, electrical fitted off, and soffits finished.

After that you have wet areas to tile and fit off, which could take 4-5 days per each, and floor tiling which looks to be around 3-4 weeks for 2 teams (assuming nice big tiles here, and laid flat!).

Then you have door frames and hanging, windows, railings and trims, which could take a couple of weeks, then painting which I'd expect another couple of weeks on.

None of this accounts for rainy days, and crap work that needs to be re-done, and the 100 other things that could delay it.

4 Months is doable.

[Greenside]

Thanks for all the 3ph advice.

When I had the contractor ask the electrical sub-con if we could do this with a single phase supply and 25mm² cable this morning, he simply said "Yes" so really it turns out that all that headache was caused because they thought we wanted 3ph and that came from someone telling me at one point a couple of years ago that it was going to be needed. Moral: Ask the right questions and make no assumptions! Now we can save some money on the cable run, cable, meter and load centre which will be much needed for the road.

IMHO: The foil was offered but they said that they don't need it yet. Can't understand how they are going to do the fixing but will keep a careful eye on it to see that we get the best air gap possible. The project is 5 weeks behind the schedule but they keep saying they expect to recover some of that.

Those tile people work fast....

[Forkinhades]

ohms law is quite simple really.

P=V*I

so

I=P/V

I=60000/230

=260 Amp

For power factor we can use this : I_(A) = P_(W) / (PF × V_(V) ) so I = 60000/(0.86x230) = 303A

so your max demand is 303 Amp on single phase, and the PEA will supply you with a 30/100

well let us know how you get on with that buddy

[Greenside]

You've lost me. Do I take it from that post that you disagree with Bankruatsteve and Crossy (and apparently the electrical sub-contractor) or what?

[Forkinhades]

We was all debating on whether you needed a 45 amp 3 phase supply on 25mm cables, or an 100 amp 3 phase supply on 35mm cables. (3 phase = 3 x single phase)

and now you want to put it ALL on 1 phase. (1 supply)

As you can see from the previous max demand calc, you are at 303 Amps, so spread over 3 phases that is 100 Amp per phase (30/100 meter)

In my opinion you was very close to the limit with diversity put into the equation on whether you could 'get away with' an 15/45 meter.

This is done without the extra loading you will have on your 'studio' apartment, which again IMO would take you above the limits of a 15/45 meter, so then you would need a 30/100 meter

[Crossy]

OK, I think we've lost the plot somewhere.

This installation will need a 15/45 3-phase supply at the very minimum!

The best usage of your existing 4-wire 25mm² cable is to use it for 3-phase from the street (and the 15/45 3-phase meter) to the primary distribution box then split off one phase to the small rental via a local meter so you can charge your tenant appropriately. You'll need a 50A 3-phase breaker in that box to keep PEA happy that you're not going to fry their meter.

Divide your A/C and water heaters between the other two phases so things stay in reasonable balance and you're on a winner.

[Forkinhades]

^agreed

also during design stage, you shoiuld try and reduce the cicuitry on the phase, where your tenant will connect to. (just elaborating on crossy post)

You are building a lovely house, the last thing you want to do is have it burnt down by an electrical fire.

[Forkinhades]

When I had the contractor ask the electrical sub-con if we could do this with a single phase supply and 25mm² cable this morning, he simply said "Yes"

This installation will need a 15/45 3-phase supply at the very minimum!

with reference to post 54

I was trying to to say that you cannot have a single phase load of 300A (max demand) on a single phase meter, which your sparky was suggesting.

I hope tha conversation was lost in translation. Otherwise get rid of that sparky

[Greenside]

Thanks for the clarification. What worries me is that the electrical sub-contractor appears to have agreed to the apparently loony idea of putting the whole of the new house on single phase. OK, head spinning, I will dive into the fray again on Monday if I survive tomorrow's visit to the local rocket festival....

[Forkinhades]

Electrical Pillar box

Inside here you can house fuses, meters and your sub mains. Could work well next to your junction box.

[Forkinhades]

60KVA was taken from the load calcs previously posted

[Forkinhades]

Thanks for the clarification.  What worries me is that the electrical sub-contractor appears to have agreed to the apparently loony idea of putting the whole of the new house on single phase.  OK, head spinning, I will dive into the fray again on Monday if I survive tomorrow's visit to the local rocket festival....

Welcome my friend

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