Electrical - Three Phase House Wiring

[carlyai]

Hope I'm not breaking any rules but I've posted this on the Issan forum but no replies as yet and my Thai electrician is pushing me for some action.

I've inherited a 3 phase 15(45) meter from my brother in law's old rice mill that is no more. I have read all the forum pages about electrics and Crossy's pages too. Thanks very much. I am building a house outside Kuchinarai and am up to the electrical installation stage. Reading what has been written before I have come up with a plan for the consumer unit, cabling etc for the house. The 3 phases will feed a main 100A 3 pole breaker. The red, blue and yellow phases will feed separate 63A breaker, 63A RCD and then 10 other breakers ranging from 32A to 16A. I have tried to apply the correct formulas to get the correct rated cables and breakers.

i had to make a quick trip back to Pattaya for some skin checks and put into practice something that Crossy said. I had an electrician put a correct SafteyCut in out house and upgrade the earths and some cable sizes. Lucky we did as the electrician drilled through a live wire with his metal drill and sweaty hand on the wall with the ensuing 'pop' and brown smell and the safetycut working 'clack'. One thankful electrician, and unsued house owner.

While talking to the electrian I went over my plan and we did some more load phase current calculations and he said my loads were not balanced enough. He also said that electricians would try and wire the house in sections, ie the living room, kitchen, tv room and second bedroom etc.

I am back in Kuchinarari and trying to balance the phase loads and change the wiring plans to separate the house in sections like suggested. So my questions are: as I am not using three phase equipment or motors, why can't I look at my three phases as 3 different houses (like I can see the houses in the street are hooked to a single phase, but the 3 phases are used), so the red, yellow and blue phases can be 3 separate identities but in the one house? i will try and get the phases balanced, but if I end up with say a maximum demand on the red phase of 72A and the yellow of 60A and the blue 65A is that OK?

[Robroona]

What is the 3 phase voltage? Is it 220v 3 phase or is it 415v 3 phase and neutral?

Whatever it is, you must have a helluva big load for these sort of currents.

[Neeranam]

If Crossy can't answer your questions, nobody can.

[nopmypomplem]

Yes that will be fine. Just balance as best you can it does not have to be perfect obviously don't load one phase to the hilt,your protection device will let you know if you have.

[Rooo]

Moved but leaving link in general.

[Crossy]

@Robroona - Thailand is 3-phase 4-wire with a phase-neutral voltage of 220V. There are still a few remote villages with 3-phase 3-wire and 220V phase-phase but these are now very much the exception.

I would wire it a three single-phase installations, even going so far as to have three consumer units (one on each phase) fed from a single 3-phase incoming breaker.

Are you having a 30/100 3-phase supply? If not that 100A incomer may be rejected by PEA as oversized, check with the supply authority.

You can't use an 'inherited' meter unless it's still on the PEA pole and being supplied and as a 15/45 should not be fused at >50A (some PEA offices will let you have a 63A incomer).

So long as each circuit is wired correctly with its own L and N (no borrowing neutrals) you can mix and match phases as you wish, lights on one phase outlets on another.

I would not however, have lighting in the same room on separate phases, simply because the temptation to borrow the neutral would be too great and you would never get your RCD to stay on.

Don't be overly worried about phase balance, at the power levels we are dealing with even a moderately sized village supply won't notice.

[carlyai]

@Robroona - Thailand is 3-phase 4-wire with a phase-neutral voltage of 220V. There are still a few remote villages with 3-phase 3-wire and 220V phase-phase but these are now very much the exception.

I would wire it a three single-phase installations, even going so far as to have three consumer units (one on each phase) fed from a single 3-phase incoming breaker.

Are you having a 30/100 3-phase supply? If not that 100A incomer may be rejected by PEA as oversized, check with the supply authority.

You can't use an 'inherited' meter unless it's still on the PEA pole and being supplied and as a 15/45 should not be fused at >50A (some PEA offices will let you have a 63A incomer).

So long as each circuit is wired correctly with its own L and N (no borrowing neutrals) you can mix and match phases as you wish, lights on one phase outlets on another.

I would not however, have lighting in the same room on separate phases, simply because the temptation to borrow the neutral would be too great and you would never get your RCD to stay on.

Don't be overly worried about phase balance, at the power levels we are dealing with even a moderately sized village supply won't notice.

[carlyai]

The 15(45) A meter is still on a pole (we are using a phase for the building site), and I had the PEA guy around awhile ago to see if I could move the meter about 100 m to a new location and use it. He said OK, so that's how I inherited the meter. I will change the plan and make the main breaker 63A and see how I go with PEA. I read before that Crossy had to change his to a 50A by PEA so this may happen. I originally had it drawn at 63A but the Pattaya electrician said to change it, so I did.

What made me panic yesterday on my return to the building site in Kuchinarai was my electrician has purchased a few rolls of 4 mm and no earth cable.

I had the room ceiling fans on a separate breaker (7 fans), but the Pattaya electrican said to wire them with the (room they are in) power outlets. Is this OK if I use the correct cable/breakers etc?

Also when you say "borrowed neutrals" do you mean that an active is run to say the power outlets in the kitchen and another active is run to the lights in the kitchen (two cct breakers) but they use the same neutral return to both cct breakers?

Not sure if 'big thank you's' are ok on the forum but again a big thanks to Crossy and the other informed Electrical contributors. About 12 years ago on one of our trips to Kuchinarari my Brother in law's son was cleaning his car (water, concrete, bare feet) at the house and bent down to look under the car and put his hand on the house wall right into the exposed power knife switch for the bore pump. The knife switch cover had been broken for at least the last 20 odd years I can remember. Exit one productive young Thai, exit one young wife to Pattaya and enter two young kids that the grandparents are still looking after. So am now getting SafteyCuts installed in the houses here. Thanks again

[Crossy]

Ah, I now understand the 'inherited' meter situation

Ceiling fans are usually put on the lighting circuit as it's easiest to wire.

Yes, your interpretation of 'borrowed' neutrals is correct, they should be avoided at all costs (Thai sparks will pick up any available neutral). If you have multiple RCDs in your installation you'll never get the RCDs to stay on if there's a neutral serving two circuits.

[carlyai]

I have just had a good talk with the electrician/builder and we agree on: no split neutrals, earthing and everything. Wonderful. I've just got to write the wire size, phase and breaker on the plan (R6 etc) and all good. Thank you to all the answers. Not sure how to cancel this post at the moment but have all the answers at the moment.