Single phase or 3 phase supply

[johnbc]

Hello,

I currently have single phase supply to my house and the meter is 5/15 . I am renovating my house an I will add a lot of appliances so I will need to order a new meter and to rewire the cables and buy a new breaker box.
After calculation it seems that maximum power draw if all appliances will work concurrently is about 160 Amps. What does the meter 5/15 or 15/45 actually means, how much continuous current it can provide? Do I need a single phase or 3 phase supply and what type of meter should I order?

Thanks

[impulse]

I know it's tempting to DIY once we escape the nanny state most of us left behind.

But I sense something seriously wrong with your math if you're expecting 160 amps at 220V in a household install.

While I'm sure you could buy all the kit you need to get 160 amps, my question would lean towards what's going to catch fire first if you actually use 160 amps.

I suggest you hire someone to do some cyphering for you and design the system, including wire sizes as well as breaker needs. The small amount you'd pay for the consult would probably save you tons of money (and potential disaster) in the long haul. And if you actually need 160 amps, and can afford to power all that, you can afford a few hundred bucks for a consult.

[johnbc]

Thank you for your reply. It is actually 181 Amps. Here is my rough estimation of maximum current per all my appliances...

It might be lower but I put a margin of about 20-25% for each.

3 Air Con 18,000 BTU = 2000 * 3 = 6000
3 Water Heaters = 6000 * 3 = 18000
Washing machine = 1000
2 Refrigerators = 1000 * 2 = 2000
oven = 3000
Misc. max 1500+1500+2000= 5000

total 40000 Watts = 181 Amps

Is there a mistake I did in this calculation?

[Crossy]

The second figure on the meter rating is the rated current 45A for a 15/45. In reality these things are incredibly robust and can handle a 100% overload without blinking.

To your supply requirements.

Forget the fridges, washer and oven etc. for now, these are intermittent loads and don't really affect things.

Big draw kit:

3 x 18k A/Cs @ 2,000W = 6,000W

3 x 6k water heaters @ 6,000W = @ 18,000W

With all that on you're at 24,000W about 110A

But you are highly unlikely to be running all your water heating and A/C together, applying diversity we can get you down to:

A/C = 4,000W

Water = 9,000W

Total 15,000W or 68A

As to what supply you need, that's down to what's available.

You could get a 30/100 single-phase supply, which would meet your needs easily, but it's not available everywhere. You need to ask your supply authority.

If you can't get 30/100 then you are looking at 3-phase, a 15/45 would be more than adequate.

Alternative solution: Get tank type water heaters, they're about 3,000W each, but even with 3 we can get the water heating load down to 3000W using diversity. That would get you 7,000W, 30A well within the capability of a single-phase 15/45.

It depends on your lifestyle, but in reality, a single-phase 15/45 would likely be just fine, we have a similar sized home on a 15/45, our (measured) peak load is about 10kW but only for a few minutes each morning.

[johnbc]

Thank you Crossy for you help. I think that in my place they don't have a single phase 30/100 meters. I would like to be on the safe side because I may one day add another AC, so I think I would go with a 15/45 3 phase system. I have been to an electricity shop and was looking at a 3 phase distribution box. They have a Square-D box. I also would like to have an RCD to protect agains ground fault. They offered me a an expenssive separate ELCB SafetyCut box that should be connected before the main DU. They said that there are no RCD's that are part of the Sqare-D system. Are they right or it is possible to have the RCD as an integrated part of the three phase load balancing consumer unit?

Thanks

The second figure on the meter rating is the rated current 45A for a 15/45. In reality these things are incredibly robust and can handle a 100% overload without blinking.

To your supply requirements.

Forget the fridges, washer and oven etc. for now, these are intermittent loads and don't really affect things.

Big draw kit:

3 x 18k A/Cs @ 2,000W = 6,000W

3 x 6k water heaters @ 6,000W = @ 18,000W

With all that on you're at 24,000W about 110A

But you are highly unlikely to be running all your water heating and A/C together, applying diversity we can get you down to:

A/C = 4,000W

Water = 9,000W

Total 15,000W or 68A

As to what supply you need, that's down to what's available.

You could get a 30/100 single-phase supply, which would meet your needs easily, but it's not available everywhere. You need to ask your supply authority.

If you can't get 30/100 then you are looking at 3-phase, a 15/45 would be more than adequate.

Alternative solution: Get tank type water heaters, they're about 3,000W each, but even with 3 we can get the water heating load down to 3000W using diversity. That would get you 7,000W, 30A well within the capability of a single-phase 15/45.

It depends on your lifestyle, but in reality, a single-phase 15/45 would likely be just fine, we have a similar sized home on a 15/45, our (measured) peak load is about 10kW but only for a few minutes each morning.

[h90]

If you can get 3 Phase easily go with it. You never know what you may need it later.

But if they make some problems (they did for us) than just stick to the 220 Volt.

At:

3 Air Con 18,000 BTU = 2000 * 3 = 6000
3 Water Heaters = 6000 * 3 = 18000
Washing machine = 1000
2 Refrigerators = 1000 * 2 = 2000
oven = 3000
Misc. max 1500+1500+2000= 5000

total 40000 Watts = 181 Amps

It is complete improbable that everything runs on full speed at the same time. I would think half of it will do the job.

[Crossy]

In a way they are correct, the locally available Square-D range is sadly lacking in 3-phase RCD/RCBO units. They do have individual RCBOs that replace each circuit's MCB, but if you have a lot of circuits they can get expensive. As a minimum you need to protect your water heaters as well as downstairs and wet room outlets. No real need to RCBO aircons or lighting.

Assuming you will be having all single-phase appliances (sensible) you could treat the installation as three single-phase systems and have a 3-phase incoming breaker feeding three small single-phase boxes.

This would allow you to use three of the ABB series of DIN rail consumer units which are infinitely customisable. We have several of these CUs with various timers, contactors and breakers to manage our whole house UPS and generator as well as the security lighting.

If you want to stick with Square-D use three of their single phase CUs, they do make 2-pole RCBOs that replace the main switches in these boxes.

[impulse]

Crossy, what size pole mount transformer and cabling would the utilities typically provide if they were feeding his 5/15 inlet panel? Would it typically be one single phase, 3x single phase or a 3 phase transformer in a residential situation?

What's the customary procedure to have the system on the other side of his panel upgraded to meet his upcoming needs? Is it easy?

I'm asking because I don't know, and I'm curious.

Edited September 14, 2013 by impulse

[kamalabob2]

You could bring your electrical plans to the local PEA office with a copy of your current electrical bill. They can see exactly where you are located, and what type of electrical service level would be possible currently at your location. They can recommend which meter and what size Square D breaker boxes you should consider. Pricing including all fees and taxes and deposits of new or upgraded electrical service is NOT a mystery. The price is on the wall of the PEA offices. However your specific location might not have PEA power lines in front or at the rear or the side of your parcel. Or the existing utility poles might not support the 3 phase service you were considering. You probably have some sort of security deposit already with the PEA, so the upgrade to a higher capacity meter will entail more money (minus your existing deposit) to be placed on deposit with the PEA.

Decent experienced electricians are in every province in Thailand. Just ask the Thai business men who own significant hotels, significant shopping centers which firms they used for the electrical work on the shopping center or their large personal homes. Same deal with plumbers, it is not Somchai who does electrical work when they build the Big C in the town near you. It is not some random guy who hooks up water supply or water filter tanks at the shopping centers. The general contractor hires real licensed electrical contractors who work on commercial buildings, government buildings and better homes. To have 3 phase installed by a private electrical contractor at your residence, the license numbers of the electrical contractor must be documented on the application and plans submitted to the PEA. But in my experience, the private licensed electrical contractor gave us a lower price and better documented work than the PEA would for the same installation. The moonlighting electricians who did the electrical installations at my home on the weekends also worked for the electrical contractor who did all the electrical work at the Big C center nearby. You can ask the plant manager of the local Government Hospital what firms they hire to maintain or improve electrical supply at the hospital or the water supply at the hospital. It is NOT hospital staff doing the heavy duty plumbing or electrical work at hospitals, even up country, it is the "go to" electricians or "go to" plumbers.

When the PEA refer to a 3 phase transformer, it is quite a bit more than just the cost of the actual transformer. The "bits and pieces" all itemized do add up.

[Crossy]

Crossy, what size pole mount transformer and cabling would the utilities typically provide if they were feeding his 5/15 inlet panel? Would it typically be one single phase, 3x single phase or a 3 phase transformer in a residential situation?

What's the customary procedure to have the system on the other side of his panel upgraded to meet his upcoming needs? Is it easy?

He's unlikely to have a private transformer for a 5/15, supply will be from a village transformer. If it's anything other than a tiny village the transformer will be 3-phase, hopefully it will be big enough to support his new supply.

A 5/15 will probably be fed by a pair of 10mm² cables, the upgrade to 15/45 3-phase will need 4 x 16mm² cables (depends upon run length from the meter), a 30/100 single-phase will need a pair of 35mm² cables.

These wires belong to the householder, so it's your responsibility to upgrade them, PEA won't connect the bigger meter until that work is completed. You can get PEA to do that work, they have the kit to climb the poles etc.

Getting the meter upgrade, is easy as noted above.

[johnbc]

Thank you all for your help. I will update after getting the new supply from the PEA.