PEA and the 290k transformer :(

[Alantct]

Hi guys
 
My mate is building a house and was basically told that because there is not enough power near his plot that he needs to buy a transformer.
This is his predicament and some questions.
Would any of you electric gurus have some advice for him?
My expertise doesn't rise to 3 phase and transformer capacity.

Thanks in advance.

This is his email to me.
 
Hey mate,
 
Here we go …………..
 
The PEA has now come back and said THB 230K for a 50 Amp transformer and THB 290K for a 100 Amp transformer. This is installed apparently. I have no clue who owns it when they are done either – I mean, who buys a new one when it fries in an electrical storm – but I’ll find that out.
 
There’s a couple of things I don’t know and I think it would be good if you can ask for some advice from any electrical farangs you know.
 
I don’t know if when they say 50amp or 100amp, whether they mean Kva or A
 
For example 22Kva would be all that is needed for a 100A supply:
 
100 amps x 220vac = 22,000 va = 22kva
 
So, in this case, a 50Kva transformer will give me more than 200 Amps which is plenty.
 
How many amps am I going to need for this house? What I have quickly figured is:
 
2 x 18,000 BTU AC 8A ea
3 x 9,000 BTU AC 3.5A ea
 
AC’s on 1 x 32A circuit 32A
 
Water Heater, hob, water pump etc. 1 x 20A circuit 20A
 
Probably 2 x 10A lighting circuits although 1 may do? 20A
 
Probably 2 x 16A power circuits although one may do? 32A
 
So, that’s a little over 100A for the house and, even if I provided 150A for the house, a 50Kva transformer would do.
 
If I ended up building some more small resort houses – say 4 – I doubt they would need more than about 20A each. It would only be a few lights, 1 aircon and a water heater in each.
 
Have you got someone you could ask?
 

[bankruatsteve]

Wait for Crossy.  That doesn't "sound" right to me.  Meters go for 50amp/100amp (and nowhere near that price) but transformers do not.  Suggest your mate goes back to PEA for better explanation.

[KhunBENQ]

Quite certain they meant 50 kVA or 100 kVA.

Both numbers are quite high for a normal private house.

Did he explicitly ask for a three phase installation?

For one phase installation PEA has smaller transformers (at least I seem them here in the area).

 

[Alantct]

Quite certain they meant 50 kVA or 100 kVA.
Both numbers are quite high for a normal private house.
Did he explicitly ask for a three phase installation?
For one phase installation PEA has smaller transformers (at least I seem them here in the area).
 

3 phase is the the only option they are giving him. They say that's what's in the area.


Sent from my iPhone using Tapatalk

[Crossy]

Something is definitely being lost in translation.

 

Thailand is 3-phase, 4-wire (3 phases and neutral), a single phase supply is simply 1/3 of a 3-phase (supply between 1 phase and neutral) and single-phase transformers are definitely available. I suspect PEA want him to buy them a nice 3-phase beastie (it will belong to them even if he pays for it) which they can then load up to the limit anyway.

 

From the description of the requirements (seems a fairly average 'farang' home) he would most likely be fine on a single-phase 50A supply (a 15/45 meter) unless he intends running all the A/C and water heating together.

 

He does need to look at those loadings, "Water Heater, hob, water pump etc" on one 20A circuit??? But at this stage that's not the issue, we need to determine his prospective load. I'll do some sums and get back on that one.

 

Transformers are indeed sized in kVA, a 30kVA (about 50A per phase) is a pretty small one.

 

He needs to talk to PEA and find out exactly what they are offering for his 300 odd k Baht. Will they have to run poles to the property (who will be paying for those)?

 

Is there already 220V at the street? What is the biggest supply they could offer without a transformer?

[Crossy]

A quick-and-dirty prospective load calculation:-

The major loads are:-

2 x 18,000 BTU – about 1.7kW each when running – applying 30% diversity = 1.1kW total

3 x 9,000 BTU – 800W each when running – applying 30% diversity = 0.8kW total

Water heater (let’s say 6kW) – no diversity (assuming there’s just one, if there are multiple smaller heaters we need to think again) = 6kW

Hob (if electric) about 5kW – we can probably reckon on 3kW after diversity

Other stuff is going to be low power, let’s say another 2kW or so.

Total maximum prospective load = 11.9 kW (about 13 kVA) in the order of 60A (we could shave some off if the shower and hob are assumed not working together and get below 50A).

So a 100A single-phase (30/100 meter) or 45A 3-phase (15/45 3-phase meter).

Either would be looking at a 20kVA (tiny) transformer.

The hob and water heater are the killers, consider a gas hob and possibly a gas water heater or electric tank type heater (only about 3kW).

If PEA are offering a 50A 3-phase transformer then that's the one to go for unless they can offer 3-phase 15/45 from the existing supply.

 

[Alantct]

A quick-and-dirty prospective load calculation:-

The major loads are:-

2 x 18,000 BTU – about 1.7kW each when running – applying 30% diversity = 1.1kW total

3 x 9,000 BTU – 800W each when running – applying 30% diversity = 0.8kW total

Water heater (let’s say 6kW) – no diversity (assuming there’s just one, if there are multiple smaller heaters we need to think again) = 6kW

Hob (if electric) about 5kW – we can probably reckon on 3kW after diversity

Other stuff is going to be low power, let’s say another 2kW or so.

Total maximum prospective load = 11.9 kW (about 13 kVA) in the order of 60A (we could shave some off if the shower and hob are assumed not working together and get below 50A).

So a 100A single-phase (30/100 meter) or 45A 3-phase (15/45 3-phase meter).

Either would be looking at a 20kVA (tiny) transformer.

The hob and water heater are the killers, consider a gas hob and possibly a gas water heater or electric tank type heater (only about 3kW).

If PEA are offering a 50A 3-phase transformer then that's the one to go for unless they can offer 3-phase 15/45 from the existing supply.

 

Thanks for the input Crossy, as always very informative. I will give him the info and see what happens.
Much appreciated.


Sent from my iPhone using Tapatalk

[williamgeorgeallen]

i would go solar. some great stand alone products now. try the goal zero or kodiac solar systems.  a really good one goes for about 60 000thb. just need a gas bottle for cooking.

[Crossy]

You reckon he's going to run all that aircon off a USD 2k solar?

 

[ellathai]

3 hours ago, Crossy said:

A quick-and-dirty prospective load calculation:-

The major loads are:-

2 x 18,000 BTU – about 1.7kW each when running – applying 30% diversity = 1.1kW total

3 x 9,000 BTU – 800W each when running – applying 30% diversity = 0.8kW total

Water heater (let’s say 6kW) – no diversity (assuming there’s just one, if there are multiple smaller heaters we need to think again) = 6kW

Hob (if electric) about 5kW – we can probably reckon on 3kW after diversity

Other stuff is going to be low power, let’s say another 2kW or so.

Total maximum prospective load = 11.9 kW (about 13 kVA) in the order of 60A (we could shave some off if the shower and hob are assumed not working together and get below 50A).

So a 100A single-phase (30/100 meter) or 45A 3-phase (15/45 3-phase meter).

Either would be looking at a 20kVA (tiny) transformer.

The hob and water heater are the killers, consider a gas hob and possibly a gas water heater or electric tank type heater (only about 3kW).

If PEA are offering a 50A 3-phase transformer then that's the one to go for unless they can offer 3-phase 15/45 from the existing supply.

 

Great write up Crossy, i'm building a house in Yang Talat, and was wondering about all this stuff. Has helped me heaps

[Alantct]

Hi Crossy
Please see mates replies to your reply [emoji4]

as far as I know, PEA is offering a three phase transformer which I can then take single phase from. The transformer will be on my land and I expect will still belong to PEA. This still begs the question of who pays for it when it stops working?

I don't think they can load it up as it’s on my land? There are no other domestic residence within a half a mile so they will not be taking any additional single phase off it other than for my house/s. So, the PEA could just run a single phase and neutral right to the house but what would the voltage be? What is the PEA three phase voltage?


I think the highest load would be most likely be 4 AC’s running at the same time during the night. Apart from the home, which is fairly typical, we also have a small bungalow which I will run off the same supply. We may, in the future, build additional bungalows so it may be a good idea to invest in the 100A now and not have to worry about it?

Re. Water heater/water pump loading etc.

Those numbers were just put down and I sort of guessed what would be required on each circuit. I was just trying to work out what I will required. Not knowing what is offered, and what the standards are, makes it difficult for me to understand. I am an Aircraft Avionics Technician by trade so have a reasonable understanding of things but have no clue on what standards are.

Every time I ask,
I keep getting back from PEA that it’s a 50A or 100A transformer but I have no clue what this refers to.


As far as I know this cost includes 2 poles, transformer and installation on my land. I have asked for a written quote and will see what they come back with.


Currently, the street has only three phase poles and wiring. The nearest transformer is about 1km away and the nearest house with single phase is about 500m away. If PEA is using three phase 220vac then I guess there is 220vac at the street but not single phase.

There will be one storage type water heater in the main house and one instantaneous wall type in the small house

we will probably go for gas hob


When they say 50A three phase transformer, is it 50A per phase? Am I able to use up to 150A?
......................................................
He is wondering if he could call you for a chat or email directly rather than me relaying the info?

Thanks again


Sent from my iPhone using Tapatalk

[wayned]

I.m not sure how the transformer will be on your land.  Some years ago I was considering building a large commercial farm equipment repair shop  and I asked PEA about having a three phase transformer installed on my land . It would have required four additional poles on the existing right away street and three poles on my land.  They told us that they could mount the transformer on the pole in the street on the existing right away but if I wanted the transformer on the last pole which would be on my land we would have to sign a document giving PEA the right away.  Once installed PEA would own the transformer and would be responsible for all maintenance costs.  The cost quoted to me then was 197,500 baht for the seven poles and transformer but I never went ahead with the project.

 

I had to do exactly the same thing when I built a house in rural Mississippi in the US to get electric, water and sewer to my house.  I also deeded the road to the county and they maintained it.

[Crossy]

OK PM sent with email addy.

 

I'll put some answers here too as others are reading.

 

If PEA are offering a 3-phase transformer, take three phases. One of my main moans about being on single-phase is we go off and 60% of the village doesn't (one phase out, always ours or so it seems). With 3 phases you can balance your load around so you always have some lights, some aircon and working outlets for the telly. In India we had three outlets on different phases right next to the TV.

 

PEA can do pretty much what they like even if it's "your" transformer, but they will fix it if the drop-fuses open (usually what goes wrong, transformers rarely fail catastrophically).

 

PEA are certainly referring to Amps per phase, so a 50A would be 3 phases at 50A each (about 33kVA so you can verify that you're getting what you think).

 

All domestic is 220V phase-neutral, 3-phase 220V has 4 wires on small insulators fairly low down on the pole. There will also be 3 wires high up on big insulators, that's the 25kV supply that your transformer will tap into, it's always 3-phase, a single-phase transformer would be supplied between two of the HV phases, but you still get 220V.

 

If there is 3-phase 220V then there is single-phase 220V (it just uses one phase).

 

With a gas hob and tank water heater I reckon it would run  just fine on a 15/45 single-phase supply at least to start with, that may be possible with what's available. Can upgrade with a transformer later when more load goes on.

 

EDIT We have a similar sized home. Although we have less aircon (only in the bedrooms), we do have 6HP of irrigation pumps to keep her garden happy and two 6kW water heaters. We also have a pool pump and pump / UV for the koi pond. Our load rarely goes over 30A and our 50A incoming breaker has never opened on overload.

 

 

[perconrad]

 If 3 fase then it is 400 volt between the fases

[wayned]

Actually 380, but it's not the volts that will get you the amps will!

[Crossy]

9 hours ago, perconrad said:

 If 3 fase then it is 400 volt between the fases

 

Indeed, but you don't connect single-phase loads between phases do you?

 

In Thailand single-phase loads go between phase and neutral where it's 220V, if you have a 3-phase supply simply treat it as three single-phase installations.

[perconrad]

15 hours ago, Crossy said:

 

Indeed, but you don't connect single-phase loads between phases do you?

 

In Thailand single-phase loads go between phase and neutral where it's 220V, if you have a 3-phase supply simply treat it as three single-phase installations.

Where I live in Sisaket we have 230 volt between fase and neutral, so I just thought that Thailand had stepped up to 400 volt between the fases as in Europe at least in Denmark where i come from.

 

And there we write 3 fase supply as 3x 400 volt.

 

Bigger load can be on 2 or 3 fases, but I admit that in Thailand it is legal to have bigger load on 1 fase than where I come from as 16A fuse is the biggest fuse allowed i 1 fase supply.

[janclaes47]

I have a 30Kva single phase transformer which stands on my land. The pole is at the outside of the perimeter, but it is my land.

 

I was always of the thought that I has=d signed it over to the PEA, there are no house near me any way, and I can't read Thai so no idea what I all signed.

 

Recently someone at PEA office looked it up and told me that it was not signed over to them, simply because they would not accept as it was on my land, and that if there was a problem with the transformer i would have to pay myself.

[Crossy]

6 hours ago, perconrad said:

Where I live in Sisaket we have 230 volt between fase and neutral

 

Thailand in nominally 220V phase-neutral but just to confuse the MEA area (Bangkok) is 230V. Some areas may see higher off-peak voltages due to the transformer being wound up to a higher tap to account for heavy loads during the day. Nominal 220V +/- 10% can be anywhere from 198V to 242V.

[wayned]

3 minutes ago, Crossy said:

Nominal 220V +110%

Interesting!  -22vac to +462vac!  Time for another cup of coffee!

[Crossy]

4 minutes ago, wayned said:

Interesting!  -22vac to +462vac!  Time for another cup of coffee!

 

Typo as you well know

 

220V +/- 10%

[wayned]

16 minutes ago, Crossy said:

 

Typo as you well know

 

220V +/- 10%

Couldn't help myself!

[timkeen08]

FYI complete list by country for 3 phase standards.

www.worldstandards.eu/three-phase-electric-power/

Sent from my SAMSUNG-SM-N910A using Tapatalk

[RichCor]

11 hours ago, wayned said:

 

11 hours ago, Crossy said:

Nominal 220V +110%

Interesting!  -22vac to +462vac!  Time for another cup of coffee!

 

-22vac, must be what the neighbors see after @Crossy has engaged the 'boost' and 'overdrive' on his AVR.

[Led Lolly Yellow Lolly]

 

On 7/1/2017 at 6:08 AM, wayned said:

Once installed PEA would own the transformer and would be responsible for all maintenance costs.

That's nearly always the case but not always. Many people are indeed shocked to find they paid for the TX only to find they own nothing. However, we presently have four transformers, all on our land. My sister in law went to great lengths to make sure we truly owned our transformers, considering the vast sums we spent on them. Sometimes the PEA forget we own them though and replace expulsion fuses for free LOL.

 

If you do go down the ownership route though, you have to really up your game and know what you're doing. We had some problems with householders on our land installing ADSL and fibre lines on our power poles without our permission, they just can't seem to get it into their heads that the PEA don't own the poles. I promptly come along and rip them down, I take a zero tolerance approach due to the potential for serious and very costly damage to our systems in the event of a fault (with this in mind, you might opt for the PEA to own). I took the following picture of our biggest TX and send it to the local 3bb office explaining to them if they didn't move their wires and install them MY WAY I would pull them down and they can see me in court. A stiff breeze could blow their drop wires onto my 22,000 Volt side. See attached picture below.

 

I also own a set of hot sticks so I can isolate the transformers as needed. I have exactly the same epoxyglass model certified for use by PEA linesmen. They cost the thick end of 20,000 Baht. This is NOT something you want to be screwing around with if you haven't got big balls and you don't know what you're doing. Even hot sticks rated for 100 KV will kill you dead if they have even a thin film of dust or moisture on them, they require careful maintenance to ensure total non-conductivity. Owning transformers sounds nice, but comes with costs. Just pointing all this out to anyone thinking of taking this route.