Triple phase - do I need it for my planned building?

[TravelerEastWest]

Triple phase - do I need it for my planned building?

We will have zero heavy machinery.

We will have about 3 refrigerators and 12 air conditioners - new inverter style (split) ac used 12 hours on average per day.

Normal lights and about 10 computers (business use for the computers)

Vaccum cleaner and microwave.

Water heaters may be powered by solar energy but for this discusison lets say three 8000 watt water heaters.

Currently there is no 3 phase on the land but for around 30,000 baht we could get it. (actual cost 60,000 split with neighbors)

Any thoughts on pros and cons?

[Crossy]

A VERY quick-and-dirty maximum demand calculation says you will JUST squeeze on to a 30/100 single-phase supply, if one is available. But watch out for voltage drop on load (important with your technology).

Otherwise a 15/45 3-phase is the way to go.

Compare the costs, personally for 30k I'd go with 3-phase for the additional wriggle room it gives.

[sscsamui]

Go for the 3 Phase... You will be happy in the long run and peace of mind...

[TravelerEastWest]

A VERY quick-and-dirty maximum demand calculation says you will JUST squeeze on to a 30/100 single-phase supply, if one is available. But watch out for voltage drop on load (important with your technology).

Otherwise a 15/45 3-phase is the way to go.

Compare the costs, personally for 30k I'd go with 3-phase for the additional wriggle room it gives.

SSCsamui

"Go for the 3 Phase... You will be happy in the long run and peace of mind..."

Peace of mind and wiggle room sounds clear that I should get 15/45 3 phase.

1) Is 15/45 normal for 3 phase? Is the 45 amps?

2) Any safety issues with 3 phase?

3) Any downside such as some AC units computers etc won't work with it?

4) Is special cable needed? I ask as the building has not been started yet so I can plan ahead.

[Crossy]

1) Yes, 45 Amps per phase (usually on a 50A breaker)

2) No more so than single phase

3) Treat it as 3 single-phase boards (no actual 3-phase appliances), your normal supply is just 1/3 of 3-phase

4) No, just 4 wires coming in rather than 2.

[TravelerEastWest]

1) Yes, 45 Amps per phase (usually on a 50A breaker)

2) No more so than single phase

3) Treat it as 3 single-phase boards (no actual 3-phase appliances), your normal supply is just 1/3 of 3-phase

4) No, just 4 wires coming in rather than 2.

Crossy,

Thank you very much for your thoughtful answers.

This may be a myth but I have heard that if there is a power outage sometimes you amy still have power with 3 phase.

Also 3 phase can sometimes be cheaper to use?

[Crossy]

Often you lose one or two of the phases, this is death for a 3-phase appliance but means life to 30% of your installation if you only have single-phase appliances.

If you're careful about how you distribute your load between the phases you can survive if only one phase is still on

Doubtful that 3-phase will be cheaper to use for your loads, big industrial motors yes, domestic aircons, no.

[keeniau96]

I have 3-phase and during some of the power reductions (not total outages) some of the circuits will be working fine when others almost dead (dim yellow light with incandescents, fans very slowly turning).