Single Phase Vs. Triple Phase - Suggested Reading Please

[Orangutan]

Hello,

I am currently in the process of renovating a four story shop house, about 3400 sq.ft. I have plans that layout a three phase system, but I am now questioning if I really need it. I have read many references, but I have not found a simple convincing theory for what I need. This will be the primary home for my wife, son and myself. There is also an apartment rental included on the ground floor with mezzanine bedroom. Several TV sets, computers, 5-6 air-cons, two kitchens, 4 full bathrooms.

Is there an existing topic regarding "single phase and triple phase electrical systems" that someone could point me to.

Many thanks,

-O

[Crossy]

Your big draw items will be water heaters and aircons.

Let's assume 5kW heaters and 12,000 BTU aircons

Quick and dirty maximum demand calculation ;- 4 x 5kW + 6 x 2kW = 32 kW = 145A @ 220V = no way on a Thai single phase supply, biggest available is 100A.

I suggest a minimum of a 15/45 3-phase supply which should be adequate given diversity although a 30/100 3-phase may be better if your supply authority can provide (this supply is really intended for small industrial units).

[InterestedObserver]

It all depends on what the PEA can supply to you at the transformer secondary. 30(100) amps single-phase is perhaps the top of the line in most installations, from there the rating goes down in rural areas. Anything more than 30(100) amps will need a three-phase installation.

[Orangutan]

Thanks Crossy I will take your recommendations to my contractor, and see if my electrical layout reflects something close to what you suggested.

[gamini]

you must have three phase.

[Crossy]

I would wire it as if it was three single phase installations, possibly as 1 phase per floor.

Put the rental on a phase of its own, easier for metering and a fault in the rest of the home won't kill their power.

As an aside, don't forget to arrange a water meter for the rental.

[Orangutan]

I would wire it as if it was three single phase installations, possibly as 1 phase per floor.

Put the rental on a phase of its own, easier for metering and a fault in the rest of the home won't kill their power.

As an aside, don't forget to arrange a water meter for the rental.

I think (I have to check with the contractor) that each of the four floors will be on their own separate circuit. As I understand it I will have a after market meter that can be zeroed out for the rental unit. The rental unit will be available on a daily/weekly basis, but most of the time we will be using it.

What are the advantages for having three single phase installations as you suggested?

Thanks,

-O

[Crossy]

Running a single-phase sub-main from your main 3-phase panel to serve each floor and having a consumer unit (distribution board) on each floor is actually a good way of doing it and is easy to wire.

Something like this:-

If you have access to the proposed layout why not scan / photograph and post here for comment?

[Orangutan]

Running a single-phase sub-main from your main 3-phase panel to serve each floor and having a consumer unit (distribution board) on each floor is actually a good way of doing it and is easy to wire.

Something like this:-

shophouse1.jpg

If you have access to the proposed layout why not scan / photograph and post here for comment?

Crossy thank you for the hand holding .. here is a pdf file of the current layout. Your participation and opinion is greatly appreciated.

-O

electrical drawings.pdf

[Crossy]

A couple of quick comments, I'll have a proper look later but:-

How is the rental flat split out and metered, everything seems to be on one board?

The cable sizes for lighting (2.5mm²) and outlets (4mm²) seem excessive, I would normally specify 1.5mm² on lighting and 2.5mm² on outlets retaining the same breakers as in the current schedule.

I don't see much (any) RCD protection.

[sibelius]

I had a nice surprise too.

Our project is 500m from main road and they just made new electric line to pass our land with new electric poles.

First i hear that they will make a 3 phase line from main road but then i realize it will be just normal low power line, single phase line.

I going to need 3 phase line + big transformer. Because i going to have many houses and sauna building with pool too. I going to use a lot of electric.

I ask from electric company estimate price to make 3 phase line to my land and answer was around 1,3 million b with transformer.

Any one have experience of the prices to make own 3 phase line from main line????

[Orangutan]

A couple of quick comments, I'll have a proper look later but:-

How is the rental flat split out and metered, everything seems to be on one board?

The cable sizes for lighting (2.5mm²) and outlets (4mm²) seem excessive, I would normally specify 1.5mm² on lighting and 2.5mm² on outlets retaining the same breakers as in the current schedule.

I don't see much (any) RCD protection.

As the ground floor rental will not be for long term tenants there is no separate meter. Although I have seen separate meters (after market) that can be fitted to keep track of individual spaces/rooms. In my current apartment building the owner has such a meter for one of the units.. she unlocks the meter cover and sets it back to 000000.

I have added to my notes the cable size that you have pointed out, and I will discuss with my architect, so he can communicate with the electrical engineer about it.

As you pointed out I do not see any reference to RCD's, and have a message into the architect, so he can communicate with the electrical engineer about it.

Thanks,

-O

[Crossy]

I would still be tempted to meter the rental separately just in case you get a long term tenant, same with water.

It's easy to do at this stage

[Orangutan]

A couple of quick comments, I'll have a proper look later but:-

How is the rental flat split out and metered, everything seems to be on one board?

The cable sizes for lighting (2.5mm²) and outlets (4mm²) seem excessive, I would normally specify 1.5mm² on lighting and 2.5mm² on outlets retaining the same breakers as in the current schedule.

I don't see much (any) RCD protection.

Here is a pdf showing the ELCB's marked by the electrical contractor.

Regarding your earlier suggestion, and example of running a single-phase sub-main from the main 3-phase panel to serve each floor, and having a consumer unit (distribution board) on each floor .. what are the advantages of this compared to my existing electrical layout?

Thanks - O

EE-ELCB.pdf

[Crossy]

Having a panel per floor would reduce the amount of wiring in the shaft and may even reduce the cable cost if the sub-mains were sensibly sized.

It would also allow you to isolate a complete floor so you could work on it safely, or, in the case of the ground floor in the event of flooding it could be made safe with a single switch.

[Orangutan]

Having a panel per floor would reduce the amount of wiring in the shaft and may even reduce the cable cost if the sub-mains were sensibly sized.

It would also allow you to isolate a complete floor so you could work on it safely, or, in the case of the ground floor in the event of flooding it could be made safe with a single switch.

As I did not post my question in the "Do it yourself housing forum" you have provided me with an answer that even I can understand. The simplicity of your suggestion fits in with my request to my electrician for keeping each floor independent/separate, giving me the ability to shut down a specific floor.

Thank you,

-O

[Crossy]

Here is a pdf showing the ELCB's marked by the electrical contractor.

I would expect to see ALL outlets protected by RCBO (what sparky is calling ELCB).

EWH 1 and EWH 3 have RCD, EWH 2 does not.

I would also put outside lighting on an RCD.

EDIT Another possible advantage to the split by floor would be the ability to use RCDs rather than RCBOs (what sparky is calling ELCB) in a split board configuration, this would significantly reduce the cost of your distribution boards.