New 3-phase service

[Yellowtail]

I am thinking of buying a new home and would like to upgrade the power to three-phase.

 

Looking at the photo below, does it look like 3-phase is available?

 

 

 

 

 

[terryq]

Yes.

[Yellowtail]

So four wires are three-phases and a neutral, and no ground, correct? 

[terryq]

Yes , neutral is likely grounded every 3rd pole.  

 

The ground will be a separate wire running down the pole to ground or as I have seen in some older installations, joined to the protruding rebar at the top of the pole.  Of course you will still be providing your local earth.

 

 

[SAFETY FIRST]

1 hour ago, Yellowtail said:

I am thinking of buying a new home and would like to upgrade the power to three-phase.

 

Looking at the photo below, does it look like 3-phase is available?

 

 

 

 

 

Yes, it's available. 

 

Send a photo of the electricity meter. 

You may already have 3phase. 

 

 

 

[Jerzy Swirski]

My guess would be......NO

 

I have 3 phase electricity in my house and outside in the road there are 5 lines

 

One for each phase, one ground and one for street lighting.

[UWEB]

1 hour ago, Yellowtail said:

I am thinking of buying a new home and would like to upgrade the power to three-phase.

 

Looking at the photo below, does it look like 3-phase is available?

 

 

 

 

 

Yes looks like 3 phase. from top to bottom is neutral, phase 3,2,1

[Crossy]

Yup, 3-phase supply is available.

 

Ground is not supplied by the MEA/PEA although the neutral is usually grounded every 3rd pole of so for a TNC-S (MEN) system.

 

It is worth talking to the local PEA office to check what they will actually provide.

[carlyai]

@Yellowtail . I've got a 3 phase supply to my house.

I  am only using 3 phase multipoint instant water heaters. 

I treat the 3 phase supply as 3 single phases.

Give us a yell if I can help.

[Yellowtail]

2 hours ago, SAFETY FIRST said:

Yes, it's available. 

 

Send a photo of the electricity meter. 

You may already have 3phase. 

 

 

 

Only two wires going from the pole to the house. 

[Yellowtail]

28 minutes ago, carlyai said:

@Yellowtail . I've got a 3 phase supply to my house.

I  am only using 3 phase multipoint instant water heaters. 

I treat the 3 phase supply as 3 single phases.

Give us a yell if I can help.

Thanks, I want three-phase for air conditioning and a few old machine tools I have. 

 

[Yellowtail]

1 hour ago, Crossy said:

Yup, 3-phase supply is available.

 

Ground is not supplied by the MEA/PEA although the neutral is usually grounded every 3rd pole of so for a TNC-S (MEN) system.

 

It is worth talking to the local PEA office to check what they will actually provide.

I assume t's MEA and I'll get my wife to call. 

[SAFETY FIRST]

6 minutes ago, Yellowtail said:

Only two wires going from the pole to the house. 

OK, that's single phase 👍

[carlyai]

12 hours ago, Yellowtail said:

Thanks, I want three-phase for air conditioning and a few old machine tools I have. 

 

.

 .Don't know how much you know about 3 phase but the most difficult part I found to start with was getting an electrician who actually knew about and had installed 3 phase. 

I studied a little on 3 phase first year engineering college, a million years ago, so didn't remember much.

I ended up finding a guy who installed 3 phase in factories.

If you're out in the sticks, hard to find a 3 phase electrician, but the guy who knows the most is Crossy. 🙂

[Yellowtail]

6 hours ago, carlyai said:

.

 .Don't know how much you know about 3 phase but the most difficult part I found to start with was getting an electrician who actually knew about and had installed 3 phase. 

I studied a little on 3 phase first year engineering college, a million years ago, so didn't remember much.

I ended up finding a guy who installed 3 phase in factories.

If you're out in the sticks, hard to find a 3 phase electrician, but the guy who knows the most is Crossy. 🙂

I have a bit of experience with 3-phase working in manufacturing, but I have no interest in getting up in the crawlspace and whatnot.

 

I have still not made an offer on the property. I would also like to add a good bit of shade, and would likely go with solar panels for that, which (I think) may be problematic with 3-phase. 

 

The issue is that it seems all the big AC units are 380. I'd hate to go with two smaller units. 

[Crossy]

3 minutes ago, Yellowtail said:

The issue is that it seems all the big AC units are 380. I'd hate to go with two smaller units. 

 

Just how big are the A/C units you're looking at?

 

The problem with 3-phase equipment is that the loss of one phase will take your kit down.

 

And.

 

By far the most common failure mode of power supply here is the loss of one HV phase (it's always the one our single-phase supply is on)! Cue no A/C despite you having at least some lights and outlets.

 

If you have 3-phase machines, get 3-phase for them, but treat the rest of your home as 3 single-phase installations.

 

[Photoguy21]

Probably a silly question but why would you want a 3 phase supply?

[Crossy]

Just now, Photoguy21 said:

Probably a silly question but why would you want a 3 phase supply?

 

If your prospective load is over about 10kW (which would max-out a 15/45 supply) then the supply authority will likely want you to go 3-phase. Some locations will do a 30/100 single-phase supply (20kW or so) but it's by no means a given.

 

And, as our OP notes, he has 3-phase machines.

 

Also, having 3-phase gives you some redundancy. It's common to lose 1 phase, with a 3-phase supply you still have two good phases. You can even get automatic selectors that pick the "best" phase for your essential equipment.

 

[Photoguy21]

1 minute ago, Crossy said:

 

If your prospective load is over about 10kW (which would max-out a 15/45 supply) then the supply authority will likely want you to go 3-phase. Some locations will do a 30/100 single-phase supply (20kW or so) but it's by no means a given.

 

And, as our OP notes, he has 3-phase machines.

 

Also, having 3-phase gives you some redundancy. It's common to lose 1 phase, with a 3-phase supply you still have two good phases. You can even get automatic selectors that pick the "best" phase for your essential equipment.

 

Agreed. If the OP is for a house it is bit over the top. If you have sensitive equipment you will have 3 phase or a heavy load, large motor for example.

[carlyai]

Why have 3 phase?

We had a rice mill in the compound and the 3 phase PEA box was already on a power pole. When the rice mill was decomissioned we just moved the box to a new pole.

As Crossy said it's great to have for redundancy.

Just had an earth fault in the garage on one phase, so power off for to the garage for a couple of days, but the house was still powered up.

Also when a phase goes low, can swap the phases around.

Power, lights, aircons etc are split between the 3 phases, so losing 1 phase doesn't cause a big problem.

Probably didn't need 3 phase multopoint water heaters, but the elecyrician said they were the bees knees.

Has a lot of help from Crossy, including connecting my single phase genset to 3 phase house. Manufacturers said it couldn't be done then Crossy weaved his magic.

 

[Yellowtail]

2 hours ago, Photoguy21 said:

Agreed. If the OP is for a house it is bit over the top. If you have sensitive equipment you will have 3 phase or a heavy load, large motor for example.

I have an old knee-mill, engine lathe and a welder that are three-phase. I've been storing them for years (planning to move) and would like to get them back going. The place we're used to have three-phase, and the panel and wire are still there, but it's been converted to single. 

[Yellowtail]

2 hours ago, Crossy said:

 

Just how big are the A/C units you're looking at?

 

The problem with 3-phase equipment is that the loss of one phase will take your kit down.

 

And.

 

By far the most common failure mode of power supply here is the loss of one HV phase (it's always the one our single-phase supply is on)! Cue no A/C despite you having at least some lights and outlets.

 

If you have 3-phase machines, get 3-phase for them, but treat the rest of your home as 3 single-phase installations.

 

If I go with 380 I'd go with a 60 and four 38s. The 38s are a bit oversized, but I they don't come much smaller. If I go 220 I'd go with six 30s. Two in the big room and one in each of the four bedrooms. 

 

The big room is about 80m^2 and has windows on three sides. I want to go with a cassette and the ceiling's relief is such that there is only one good spot for it. 

 

We're in Bangkok now, and do not seem to have any trouble with the power. The new place is in BKK as well. 

 

How much more difficult/expensive would adding solar be with 3-phase? I want to add about 130m^2 of shade and may want to do it with solar. 

[carlyai]

My Thai friend does solar and I asked him for a price to initially install just one inverter so that I could get the fish tanks, green house and aquaponics setup going again (off at the moment as costs too much running air and water pumps 24/7). So he would install all the panels etc but 1 inverter instead of 3.

Cost was around B90000 and his cost was B20000 labour, which I thought wss OK.

No batteries.

[Yellowtail]

29 minutes ago, carlyai said:

My Thai friend does solar and I asked him for a price to initially install just one inverter so that I could get the fish tanks, green house and aquaponics setup going again (off at the moment as costs too much running air and water pumps 24/7). So he would install all the panels etc but 1 inverter instead of 3.

Cost was around B90000 and his cost was B20000 labour, which I thought wss OK.

No batteries.

How much power does that provide, and how much area/panels? 

[Crossy]

I can see now why you need 3-phase, that is one big home. I'm amazed it was actually on a single-phase supply at all.

 

Do verify whether you are MEA or PEA (look at the meter or the one next-door) as MEA doesn't go that far out of town. We are in Greater Bangkok and on PEA.

 

130m² of panels would be in the order of 21kWP and would generate about 70-80kWh per day (very much dependent upon the weather).

 

I'd initially look at 3 single-phase inverters, one per phase, say 10kW each. Certainly go hybrid even if you start out with no batteries.

[Yellowtail]

2 hours ago, Crossy said:

I can see now why you need 3-phase, that is one big home. I'm amazed it was actually on a single-phase supply at all.

 

Do verify whether you are MEA or PEA (look at the meter or the one next-door) as MEA doesn't go that far out of town. We are in Greater Bangkok and on PEA.

 

130m² of panels would be in the order of 21kWP and would generate about 70-80kWh per day (very much dependent upon the weather).

 

I'd initially look at 3 single-phase inverters, one per phase, say 10kW each. Certainly go hybrid even if you start out with no batteries.

The home is not really that big, it just does not have many rooms, and the living room is huge.

 

It's an old house with great airflow, and currently only has two old AC units (one "ducted" and on floor style) and a few ceiling fans. With all the screens and whatnot, it looks to me like the previous owners did not use AC much, if at all.

 

The phase thing confuses me a bit. I understand that I can get (what I think is) the same single-phase supply using a neutral and any one of the three lines. 

 

But when I have a three-phase motor, I can change the direction of rotation by swapping and two of the three lines. 

 

How is it that they are all the same? 

 

I hope to see the house again Saturday, and I'll try to check the meter. I just assumed that anything in Bangkok province was under the MEA. 

 

 

[Crossy]

1 hour ago, Yellowtail said:

How is it that they are all the same? 

 

They differ in that the three phase voltages are at 120^o to one another. If you are using one phase then phase angle doesn't matter but when you use all three then it does.

 

It's just a fact of life that swapping two phases cause a 3-phase motor to run the other way.

 

There's plenty of on-line tutorial stuff on 3-phase or you can get the text books I used long, long ago 🙂 

 

EDIT This is the exact version we used 🙂 

https://www.amazon.com/Higher-Electrical-Engineering-John-Shepherd/dp/0273400630

That image brings back some (not always good) memories of Bath in the 1970s 

[Yellowtail]

45 minutes ago, Crossy said:

 

They differ in that the three phase voltages are at 120^o to one another. If you are using one phase then phase angle doesn't matter but when you use all three then it does.

 

It's just a fact of life that swapping two phases cause a 3-phase motor to run the other way.

 

There's plenty of on-line tutorial stuff on 3-phase or you can get the text books I used long, long ago 🙂 

 

EDIT This is the exact version we used 🙂 

https://www.amazon.com/Higher-Electrical-Engineering-John-Shepherd/dp/0273400630

That image brings back some (not always good) memories of Bath in the 1970s 

So if I used 3 single-phase inverters, when used as a three-phase supply, they just kind of "automatically" offset the 120 degrees? 

 

The inverters would all be the same, and be set the same, yes? 

 

 

[Crossy]

4 minutes ago, Yellowtail said:

So if I used 3 single-phase inverters, when used as a three-phase supply, they just kind of "automatically" offset the 120 degrees? 

 

The inverters would all be the same, and be set the same, yes? 

 

If going the recommended hybrid inverter route, you would get inverters that can run in parallel (not all can) and tell them they are configured for 3-phase. They talk to each other over an RS-485 link.

 

 

[Yellowtail]

40 minutes ago, Crossy said:

 

If going the recommended hybrid inverter route, you would get inverters that can run in parallel (not all can) and tell them they are configured for 3-phase. They talk to each other over an RS-485 link.

 

 

Thanks, that makes sense.