Burying Electric Main Line to House

[Silencer]

I have a new home construction starting soon and want to have the main power line connected to the house underground (about 15m from pole on street) and come up into an enclosed (ventilated) 3mx5m concrete floored room that will serve as the main electrical room, pool pump room, and for general storage. I will ofcourse discuss this with my contractor and everything may go smoothly. However, I would like to have some knowledge in understanding the correct way to bring, bury, protect, and insulate this main up into the room myself. The government electric pole is 1m from my perimeter wall and I assume the first step would be to bring the main over the wall to "my" electric pole, then down to the earth, where it can be buried, run to the new room, come up from the floor and into the main box. I am looking for what the proper materials (wiring type, conduit) should be used and what depth the main should be buried at as standard or best practice. Also any potential problems/issues with this type of arrangement. Again, maybe this is done routinely, so should be no worries, but I see so many installations where the wires are run above ground along several poles to the house connection. P.S. The land is not prone to flooding/sloped. 

[KhunLA]

The obvious, we put ours in PVC pipe, and ran from meter, to a cut off on inside of perimeter wall, then underground to house wall.  New construction, so wired up & over the ceiling to breaker box.

 

Don't think there is any standard, since most don't do here.  Just using the proper wire and place in conduit is enough.  Don't know the specs used, as wife and contractor/electrician oversaw it.

 

[Rimmer]

We used 20mm NYY four core underground cable straight off the transformer inside plastic conduit which was buried in a trench and filled in then covered with stone slabs to prevent mechanical damage.

 

Now you can buy HDPE plastic pipe conduit to run the cable in, most building supplies have it.  

[Dante99]

Good Under ground conduit is not just normal electrical conduit.  It is not just yellow pvc pipe.   Best use the black tubing, one piece from pole into house, can buy by length in a coil.

 

Phone and internet go into separate conduit to avoid interference.  Can go into same trench.  Does not have to be deep, about 30 cm is common.

[MJCM]

15 minutes ago, Dante99 said:

Good Under ground conduit is not just normal electrical conduit.  It is not just yellow pvc pipe.   Best use the black tubing, one piece from pole into house, can buy by length in a coil.

 

Phone and internet go into separate conduit to avoid interference.  Can go into same trench.  Does not have to be deep, about 30 cm is common.

It’s AFAIK called HDPE pipe.

 

You have have I believe 2 kinds, 1 for water, which has a blue stripe and 1 for electric, which has a red stripe.

 

The one for water is more expensive

 

You have them in many sizes as small as 32mm to as big as 1-2m. 
 

https://www.tpp-pipe.com

edit: these are readily available for example at DoHome 

 

Edited February 18, 2023 by MJCM

[Crossy]

Task A - Determine what size supply you will need, single or 3-phase?

We can help with this if we know what your major loads will be (Aircon, water heaters, cooking appliances, Man Cave).

 

This will determine the size of NYY cable you need (verify with PEA and your contractor).

https://www.bangkokcable.com/system/product/file_upload/211102_450!750V 70C NYY_1-4core_Rev04.pdf

This will then determine the size of HDPE pipe to run.

 

Put a separate length of HDPE for your phone / fibre connection. Make this at least 150mm from the electrical one.

 

Maybe run your water supply in the trench too.

 

 

 

 

 

[brianthainess]

 it is no longer legal to use 'normal' aluminum power cable underground , it must be 'special' underground cable, it is double  insulated and in yellow pvc. 5yrs ago when my house was built, PEA came to check and my electrician had to change it.

  

[Crossy]

13 minutes ago, brianthainess said:

it is no longer legal to use 'normal' aluminum power cable underground

 

Aluminium underground for domestic installations hasn't been permitted for many years here.

 

Copper NYY is the stuff you need. It CAN be direct buried but is far better in black HDPE with a red tracer (for electricity).

[NanLaew]

1 hour ago, brianthainess said:

 it is no longer legal to use 'normal' aluminum power cable underground , it must be 'special' underground cable, it is double  insulated and in yellow pvc. 5yrs ago when my house was built, PEA came to check and my electrician had to change it.

  

I hate it when they supply and charge you ~800 baht for a weatherproof box with punch-outs for 5 baht sealing glands... and then just drill holes and wrestle the conductors through.

 

It's called a gecko house.

[Silencer]

2 hours ago, Crossy said:

Task A - Determine what size supply you will need, single or 3-phase?

We can help with this if we know what your major loads will be (Aircon, water heaters, cooking appliances, Man Cave).

 

This will determine the size of NYY cable you need (verify with PEA and your contractor).

https://www.bangkokcable.com/system/product/file_upload/211102_450!750V 70C NYY_1-4core_Rev04.pdf

This will then determine the size of HDPE pipe to run.

 

Put a separate length of HDPE for your phone / fibre connection. Make this at least 150mm from the electrical one.

 

Maybe run your water supply in the trench too.

 

 

 

 

 

-Household size: 3 people

-Large (5x11) pool and spa area (water jets), saltwater system.

- Western kitchen (without dishwasher), so fridge, oven, microwave, toaster, hob.

- A/C available in 4 rooms, 3 bedrooms and living room but expect very low usage. (We hardly ever use now)

- Three TV's 

- Many recessed lights (60), outdoor lights (20) but again not used all at same time.

- Indoor/outdoor ceiling fans (5)

- Well/pump

- Simple water heaters in 3 showers.

- Motorized gate

- 190sqm indoor space/320sqm roofed area

No other major electrical usage items I can think of.

[Crossy]

A very quick and dirty max demand calculation.

I've made some assumptions which may not be valid, but should give an idea.

 

Large (5x11) pool and spa area (water jets), saltwater system.
2HP pump = 1.5kW 
Pool load = 7A (daytime)

 

Western kitchen (without dishwasher), so fridge, oven, microwave, toaster, hob.
Oven - 3kW
Hob - 6kW
Cooking load with diversity = 20A

A/C available in 4 rooms, 3 bedrooms and living room but expect very low usage. (We hardly ever use now)
18,000BTU x 3 (bedrooms)     = 5.4kW
24,000BTU (lounge) = 2.4kW (assume not run concurrently with bedrooms)
Night A/C load = 25A = assume running at 30% (inverter units) = 10A
Day A/C load = 11A = = assume running at 30% (inverter unit) = 4A

Simple water heaters in 3 showers.
4.5kW x 3 (assume 2 at once)
Water heater load = 41A

Incidental loads (TVs, lighting, pumps) are negligible assuming LED lighting.

 

=====================================================

 

So, you are really looking at a 30/100 single-phase meter. You will need to verify with your local PEA office if this is available.

If the 30/100 isn't available you're probably going to be looking at a 15/45 3-phase supply.

 

If you switch to a gas hob you should be good to go on a 15/45 single-phase (which is what most of us have).

 

Is there likely to be an EV / plug-in hybrid in the future plans? You will definitely need the larger supplies or a second meter if PEA are still offering one (which could be TOU for cheaper charging).

 

Any thoughts of solar or a genset in future? If so, plan for it now!

 

 

[Silencer]

On 2/18/2023 at 2:30 PM, Crossy said:

A very quick and dirty max demand calculation.

I've made some assumptions which may not be valid, but should give an idea.

 

Large (5x11) pool and spa area (water jets), saltwater system.
2HP pump = 1.5kW 
Pool load = 7A (daytime)

 

Western kitchen (without dishwasher), so fridge, oven, microwave, toaster, hob.
Oven - 3kW
Hob - 6kW
Cooking load with diversity = 20A

A/C available in 4 rooms, 3 bedrooms and living room but expect very low usage. (We hardly ever use now)
18,000BTU x 3 (bedrooms)     = 5.4kW
24,000BTU (lounge) = 2.4kW (assume not run concurrently with bedrooms)
Night A/C load = 25A = assume running at 30% (inverter units) = 10A
Day A/C load = 11A = = assume running at 30% (inverter unit) = 4A

Simple water heaters in 3 showers.
4.5kW x 3 (assume 2 at once)
Water heater load = 41A

Incidental loads (TVs, lighting, pumps) are negligible assuming LED lighting.

 

=====================================================

 

So, you are really looking at a 30/100 single-phase meter. You will need to verify with your local PEA office if this is available.

If the 30/100 isn't available you're probably going to be looking at a 15/45 3-phase supply.

 

If you switch to a gas hob you should be good to go on a 15/45 single-phase (which is what most of us have).

 

Is there likely to be an EV / plug-in hybrid in the future plans? You will definitely need the larger supplies or a second meter if PEA are still offering one (which could be TOU for cheaper charging).

 

Any thoughts of solar or a genset in future? If so, plan for it now!

 

 

Yes, on reflection a gas hob. Thank you very much for your rough calculations and recommendations.  Much appreciated!

Edited February 20, 2023 by Silencer

[Crossy]

Yeah, a gas hob should drop you easily into the single-phase 15/45 box.

 

It might be worth considering tank-type water heaters as these have a much lower peak consumption, or even gas water heaters although many worry about carbon-monoxide issues (proper installation is vital).

 

[Photoguy21]

Bury it deep, say at least 0.5 mtr. and even if you use PVC pipe place tiles over it with a distance between the tiles and the pipe.

Make sure the pipe if used is sealed at both ends to stop vermin (mice, cockroaches etc. getting into the house via the pipe.

Edited February 20, 2023 by Photoguy21