Power Cables Underground To House?

[enkmd]

Hi All,

I am wanting to check if there are any reason's not to run power cables from the road underground to the house?

We have just got a 5 rai plot and are planning to build in the middle of it, aprox 100m from the power pole. As I can see from around Thailand all of the cables seem to be in the air.

I personaly would prefer to run them underground as they do in NZ.

I would probably dig a trench and cover with a concrete or simillar cover.

Any thoughts or advice on this would be much appreciated.

Many Thanks

[Crossy]

There are no problems running underground provided you size the cables appropriately and follow international standards for the hole.

Your sparks should be able to source a directly-buriable cable (no conduit required) of suitable rating. Put it at least 500mm down with a 'warning electric cable' tape about 100mm above the cable for when Somchai starts digging your garden. No real need for concrete cover. If the directly-buriable cable is not available then you'll need to put a duct in, black PVC with a red tracer is readily available for just this purpose. You'll need to make arrangements to prevent water and the local fauna entering your duct.

Useful information here http://www.tlc-direct.co.uk/Book/7.13.3.htm based on the UK regs.

Let us know the meter type you'll be using (15/45, 30/100) and if you're on single or 3-phase so we can give you an idea what cable you'll need.

EDIT For a start.

100m on a 15/45 meter will need 25mm² cable.

100m on a 30/100 meter will need 50mm² cable.

Both the above assume single phase, 5% Volt drop and copper cable.

Edited February 6, 2009 by Crossy

[enkmd]

Thanks Crossy

I will have to do some home work, no idea about the meter and I would guess it's only single phase but not sure. I will try and track down some armoured cable and warning tape.

The 500mm trench sounds like some hard work, wish i had a tractor or mini digger. Could probably get someone to dig it for a few hundred baht.

regards

[jimmym40]

Conduit may or may not be required. However, for a couple reasons, I would recommend putting the cable in appropriate sized PVC conduit (yellow, used for power cable). It would be double protection in case of digging, and also, in case for some very slim reason, the cable goes bad, you can pull new cable thru the conduit instead of having to dig up the whole length of the cable to find the problem. I know it's very unlikely this would happen, but the cost of the conduit would be relatively inexpensive the give a great peace of mind.

[Rimmer]

Conduit may or may not be required. However, for a couple reasons, I would recommend putting the cable in appropriate sized PVC conduit (yellow, used for power cable). It would be double protection in case of digging, and also, in case for some very slim reason, the cable goes bad, you can pull new cable thru the conduit instead of having to dig up the whole length of the cable to find the problem. I know it's very unlikely this would happen, but the cost of the conduit would be relatively inexpensive the give a great peace of mind.

Yellow conduit as sold here is porus and offers little protection against mechanical damage. NYY cable is suitable for direct burial, if you cant find cable tiles use cinder blocks placed on top of the cable with a warning tape.

As for pulling a 25mm 4 core NYY copper cable through 100 meters of of plastic conduit, don't think so

Global House shops have the proper underground cable pipe, not expensive.

[longball53098]

Rimmer, what is the proper conduit for underground?

Crossy suggests a black PVC with a red tracer?

How about the HDPE rated for electrical underground?

Any and all are available at Global House?

[Rimmer]

Rimmer, what is the proper conduit for underground?

Crossy suggests a black PVC with a red tracer?

How about the HDPE rated for electrical underground?

Any and all are available at Global House?

Yes that's the stuff as Crossy says it's the black PVC type with the red tracer and is standard for underground cable here. Usual size is about four inch but depends on your cable size and number of cores.

Global House has big coils of the stuff stacked up outside their shop in Rayong, I assume it's the same at other shops.

Don't do as I did! Or as my electrician did when I was not looking, He put the NYY cable into yellow conduit. It's OK but not correct and can lead to moisture problems in a number of years. I let it go because I will probably not be around then.

When you get your main switch and temporary meter fitted get some one to take a voltage reading off the switch terminals.

Everyone was telling me about the massive voltage drop I will get between my transformer and the house and how I had to use massive 25mm cable to avoid the problem.

I get 227volts at any socket anywhere in the house with a 4 core 16mm NYY feed.

[Rimmer]

Crossy Help me to understand why you say he will need:

100m on a 15/45 meter will need 25mm2 cable.

100m on a 30/100 meter will need 50mm2 cable.

It will cost a fortune as well as being totally over the top.

The tails from the transformer to the meter are usually only 25mm

[Crossy]

Crossy Help me to understand why you say he will need:

100m on a 15/45 meter will need 25mm2 cable.

100m on a 30/100 meter will need 50mm2 cable.

It will cost a fortune as well as being totally over the top.

The tails from the transformer to the meter are usually only 25mm

No problem, I'm a belt and braces man rather too big than too small. The sizes popped out of a UK cable calculator, although 35mm² is probably more realistic for the bigger meter (reminder to self, check the result is sensible before posting). Without a proper prospective load calculation we must assume maximum the supply can give.

The issue is not cable rating where 16mm² will be fine for the 15/45 fused at 63A and 25mm² for the 30/100 fused at 120A even when derated 0.9 for underground. Incidentally 25mm² is the standard size used now for meter tails in the UK.

BUT he has a 100m run from the pole (and god knows how much more from the tx). 16mm² at 45A will drop about 14V over 100m (6.4%) marginal if you're allowing for a 10% overall drop, next size up is 25mm².

Don't forget if we have a pump and aircon they'll have big start currents (2-3 times rated), too small a cable may put them below a safe starting voltage and reduce the life of the motors. Could be another man like Naam, who like arctic conditions, or one like me who hardly ever bothers putting the aircon on.

I certainly wouldn't use less than 25mm² on that length run, but to do a proper job we need to know how big the house will be and what major equipment will be installed.

Edited February 7, 2009 by Crossy

[Rimmer]

Thanks for that I wondered if you were factoring the voltage drop.

When I calculated mine out all the tables were telling me I would get a hefty drop unless I used 25mm cable or bigger I opted for 16mm and in practice My drop over 100mtrs is nothing and like the tables and like I said I get 227 volts anywhere in the house.

I have my own 50kva transformer with a 16mm TP NYY feed. feeding from a 63a TP main switch. this goes underground for 100mtrs to a TP board. The 16mm conductors are rated around 85amps right? And if the load is balanced correctly that should be more than enough across the TP board right? If I total everything up in the house I can't get more than 56amps total load, then we have the diversity factor. Wot you tink?

100 meters of that NYY 4 core cost me around 30k if I remember correctly at the time. hate to think what 25mm will be.

As you say we need to know what enkmd has on his pole, maybe just a pole, maybe a pole and a transformer, maybe TP or maybe SP.

Edited February 7, 2009 by Rimmer

[Crossy]

Thanks for that I wondered if you were factoring the voltage drop.

When I calculated mine out all the tables were telling me I would get a hefty drop unless I used 25mm cable or bigger I opted for 16mm and in practice My drop over 100mtrs is nothing and like the tables and like I said I get 227 volts anywhere in the house.

I have my own 50kva transformer with a 16mm TP NYY feed. feeding from a 63a TP main switch. this goes underground for 100mtrs to a TP board. The 16mm conductors are rated around 85amps right? And if the load is balanced correctly that should be more than enough across the TP board right? If I total everything up in the house I can't get more than 56amps total load, then we have the diversity factor. Wot you tink?

100 meters of that NYY 4 core cost me around 30k if I remember correctly at the time. hate to think what 25mm will be.

As you say we need to know what enkmd has on his pole, maybe just a pole, maybe a pole and a transformer, maybe TP or maybe SP.

Yup ^^^.

On long runs the volt drop become more of a factor than the actual cable rating. Under ideal conditions 16mm is OK for 80A (it'll get pretty warm though), 3-phase on 16mm is easily good for a total load of more than 150A (50A / phase).

When calculating the cable size you should use the maximum expected load. Your 56A total (say 20A / phase) will drop you about 5.6V (2.5%) on 16mm² in practice even less because (assuming good balance) there will only be a small neutral current.

Edited February 7, 2009 by Crossy

[longball53098]

Rimmer, what is the proper conduit for underground?

Crossy suggests a black PVC with a red tracer?

How about the HDPE rated for electrical underground?

Any and all are available at Global House?

Yes that's the stuff as Crossy says it's the black PVC type with the red tracer and is standard for underground cable here. Usual size is about four inch but depends on your cable size and number of cores.

Global House has big coils of the stuff stacked up outside their shop in Rayong, I assume it's the same at other shops.

Don't do as I did! Or as my electrician did when I was not looking, He put the NYY cable into yellow conduit. It's OK but not correct and can lead to moisture problems in a number of years. I let it go because I will probably not be around then.

When you get your main switch and temporary meter fitted get some one to take a voltage reading off the switch terminals.

Everyone was telling me about the massive voltage drop I will get between my transformer and the house and how I had to use massive 25mm cable to avoid the problem.

I get 227volts at any socket anywhere in the house with a 4 core 16mm NYY feed.

I looked at the HDPE in Rayong out front and I think you will find that the stuff there is the lessor rated pipe for water not the Class 1 red stripe. I checked inside about electric HDPE and it is a bit more pricey as it carries a different class rating and they don't stock it. Can be ordered. This web site has some info but not too much. HDPE

[Rimmer]

I looked at the HDPE in Rayong out front and I think you will find that the stuff there is the lessor rated pipe for water not the Class 1 red stripe. I checked inside about electric HDPE and it is a bit more pricey as it carries a different class rating and they don't stock it. Can be ordered. This web site has some info but not too much. HDPE

It was two weeks back since I was there, maybe my poor old eyes saw something I expected to see or maybe it was a special order for someone. Either way it's comforting to know they can get it for you if you order it.

[Rimmer]

Yup ^^^.

On long runs the volt drop become more of a factor than the actual cable rating. Under ideal conditions 16mm is OK for 80A (it'll get pretty warm though), 3-phase on 16mm is easily good for a total load of more than 150A (50A / phase).

When calculating the cable size you should use the maximum expected load. Your 56A total (say 20A / phase) will drop you about 5.6V (2.5%) on 16mm² in practice even less because (assuming good balance) there will only be a small neutral current.

That's very interesting, thanks for that

[enkmd]

It's very comforting to know that there are so many experienced and compitent people from whom I can obtain advice here. I was a little concerned that I would end up doing things the local way and I too am surprised that there are not more people here dying from shocks.

I will be up to the orchard tomorrow and will do my best to sus out the situation, meter type, distance from sub-station etc.

As for the expected loads I quite like the belt and braces aproach, even at extra costs. If I end up living here full time I will definately want to have some machines, like planer/thicknesser, table saw, bandsaw etc

Not too keen on air con but would be best prepared for what ever might be wanted.

On a seperate note, i came across some universal sockets at home pro today and thought it might be worth mentioning, for those who still have foriegn plugs.

[Crossy]

enkmd, is a supply and meter already in position or are you ordering new?

You need to assess your loading. Even a rough idea is useful because big single-phase supplies (over 45A) are rare if not impossible to get if you're out in the sticks so you'll be going to have to look at 3-phase (unheard of in a domestic situation back home).

Just a quick, so many bedrooms, so much aircon, water heating (look hard at solar), water pump etc. should do the trick. How much oomph are you expecting to need for your workshop?

If you do end up with 3-phase, you won't need to use 3-phase appliances but simply need to split your single-phase loads roughly evenly between the phases.

Those 'universal' outlets are handy, but don't use them all over the house, just where foreign plugs are likely to be used. I'm not overly confident about the actual load they can handle (notwithstanding the 16A label).

Edited February 9, 2009 by Crossy

[Naam]

You need to assess your loading. Even a rough idea is useful because big single-phase supplies (over 45A) are rare if not impossible to get if you're out in the sticks so you'll be going to have to look at 3-phase (unheard of in a domestic situation back home).

= abso-<deleted>-lutely normal since many years in my "back home" Crossy.

Edited February 9, 2009 by Naam

[Crossy]

You need to assess your loading. Even a rough idea is useful because big single-phase supplies (over 45A) are rare if not impossible to get if you're out in the sticks so you'll be going to have to look at 3-phase (unheard of in a domestic situation back home).

= abso-<deleted>-lutely normal since many years in my "back home" Crossy.

OK, OK, blinkered British Earthling outlook, I'll rephrase (unknown in a domestic situation in much of the galaxy). I suppose the personal Transporter and gamma-ray stove are a bit power hungry.

Besides, I would have thought that Qo'noS (Kronos) would have had some form of wireless energy transfer system, nothing so primitive as copper (or aluminum) wires

Edited February 9, 2009 by Crossy

[enkmd]

Pics attached show the meter, the cable, the power pole and the shack where the power is currently connected.

From pole to shack is about 10m I guess. The meter is single phase. We have the last power pole on the soi, under 1 K from main road of village, not far out in the wops at all, still in hearing distance of the horrible early morning announcements.

House will start small and probably grow to be an average 2 storey 3 bed, office, livingroom, falang kitchen and bathroom etc. I am keen on mod cons and gadgets but most of which tend to be easy going on power.

The possible workshop will only have single phase machines, being used one at a time, so probably not too much to worry about there, I guess again.

I would be happy enough with fluro and LED lighting.

Am keen on photo voltaic and solar water heating etc so hopefully no electric showers.

Havent found the solar electric to be cheap enough to compete with the reasonably cheap electric from mains so not sure if will get onto that or not.

Have got a few of those solar garden lights, bug zappers and a neat little solar sensor light though.

All of this is a bit further down the line. I will be back in 2 months to dig the trench and lay whatever cable needed and hopefully start on some concrete frame and roofing.

[Rimmer]

I looked at the HDPE in Rayong out front and I think you will find that the stuff there is the lessor rated pipe for water not the Class 1 red stripe. I checked inside about electric HDPE and it is a bit more pricey as it carries a different class rating and they don't stock it. Can be ordered. This web site has some info but not too much. HDPE

Checked the stock outside the door at Global House today. Black with red tracer, thought my eyes were not deceiving me but on closer inspection you are right it is all LDPE.

I would however have no problem using that underground though with the appropriate cable markers on top of it if nothing else were available.

Prices for LDPE black with red tracer are:

32 mm 200 mtrs 1380

40mm 100 mtrs 1140

50mm 100 mtrs 1650

[Rimmer]

Pics attached show the meter, the cable, the power pole and the shack where the power is currently connected.

From pole to shack is about 10m I guess. The meter is single phase. We have the last power pole on the soi, under 1 K from main road of village, not far out in the wops at all, still in hearing distance of the horrible early morning announcements.

Looks like a 15amp SP meter to me, just right to boil a kettle, have you considered wet string at all

[enkmd]

Hi Rimmer

5(15) amp, just right to boil a kettle, Is this as bad as it sounds? what is normal in the UK or NZ?

what does this all mean?

Will we be poping fuses and heating up the wires with this set up?

[Crossy]

Ahhhh. Good useful photos

You are looking at an upgrade here.

That 5/15 will as Rimmer notes, JUST boil a kettle, and it's on 2x6mm² good for 35A or so flat out. You need to ask the supply company for a minimum of a 15/45 meter for any farang house.

The local PEA office should be your next stop to see what they can provide.

How far away is the transformer? The nearest 3-phase overheads?

EDIT A normal UK domestic supply will be fused at at least 60A (equivalent to a Thai 15/45) more likely nowadays 100A (equivalent to a Thai 30/100).

Edited February 9, 2009 by Crossy

[Rimmer]

Hi Rimmer

5(15) amp, just right to boil a kettle, Is this as bad as it sounds? what is normal in the UK or NZ?

what does this all mean?

Will we be poping fuses and heating up the wires with this set up?

Sorry about that, couldn't resist it. Just winding you up a bit.

Take note of what Crossy says and check with the PEA for an upgrade. Suggest maybe you should lurk round the corner whilst your mississ talks to the man with forms. Everything is possible here and it is not a big problem.

[enkmd]

Nothing ever seems to be that simple here.

The father in law said this is standard for Thai house, including his. I was wondering how they survive and then I notice as I look around they dont really have alot .

Havent found the nearest transformer yet, will have to find that and then let you know.

PEA will also check that one out, sounds as though this little job is going to get a bit expensive.

Might have to settle for a Thai style house and forget about falang standards and workshops.

Thanks very much for all your input and advice on this issue, I will be intouch no doubt and will let you know how it goes.

Many Thanks

[Beardog]

I am thinking of running a short run underground. Using Hdpe what is the best way to seal off the tubes to stop water from flowing in the lines? I was also thinking for extra digging protection putting the hdpe lines in a pvc housing for extra protection against digging(by hand) . Is this too much or does the HDPE offer enough strength to resist a shovel going through both lines or is it best to spread the wires .40 meters apart to avoid a possible short?

Thanks Guys. I just realized it is time to think about this before the rear retaining wall goes up.

Barry

[trogers]

I am thinking of running a short run underground. Using Hdpe what is the best way to seal off the tubes to stop water from flowing in the lines? I was also thinking for extra digging protection putting the hdpe lines in a pvc housing for extra protection against digging(by hand) . Is this too much or does the HDPE offer enough strength to resist a shovel going through both lines or is it best to spread the wires .40 meters apart to avoid a possible short?

Thanks Guys. I just realized it is time to think about this before the rear retaining wall goes up.

Barry

Dig a trench 60cm deep. Lay 5cm of sand. Lay HDPE duct with both ends turned up above ground. Pass power cables through them and check conductivity. Cover HDPE duct with 10cm of sand and place a layer of 1-inch thick precast concrete slabs and then back fill with planting soil.

A shovel will hit the concrete slab before exposing the duct.

[Crossy]

Dig a trench 60cm deep. Lay 5cm of sand. Lay HDPE duct with both ends turned up above ground. Pass power cables through them and check conductivity. Cover HDPE duct with 10cm of sand and place a layer of 1-inch thick precast concrete slabs and then back fill with planting soil.

A shovel will hit the concrete slab before exposing the duct.

Sounds reasonable although the duct is likely tough enough to resist manual digging anyway (and you don't often dig down 60cm anyway). Those 1" pre-cast slabs are pretty cheap

To seal the ends you could use the expanding PU foam. PEA use a wide self-adhesive tape that seems to provide a good seal, no idea where to get it though If the duct is not huge some heatshrink tube will provide a durable and professional seal.

Don't forget to leave a pull-cord in the duct for when you want to add or replace cables

[Beardog]

Dig a trench 60cm deep. Lay 5cm of sand. Lay HDPE duct with both ends turned up above ground. Pass power cables through them and check conductivity. Cover HDPE duct with 10cm of sand and place a layer of 1-inch thick precast concrete slabs and then back fill with planting soil.

A shovel will hit the concrete slab before exposing the duct.

Sounds reasonable although the duct is likely tough enough to resist manual digging anyway (and you don't often dig down 60cm anyway). Those 1" pre-cast slabs are pretty cheap

To seal the ends you could use the expanding PU foam. PEA use a wide self-adhesive tape that seems to provide a good seal, no idea where to get it though If the duct is not huge some heatshrink tube will provide a durable and professional seal.

Don't forget to leave a pull-cord in the duct for when you want to add or replace cables

Sounds good thanks for the advice!

Edited March 5, 2009 by Beardog

[longball53098]

Beardog if you will please?

What diameter of HDPE and what length do you use? And how much did you pay?

You are using the red stripe Class 1 for electric? Yes?

Thanks

I will be using tis in a few months time.