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Cable Size From Meter To Property 50M


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So, I know this topic has probably been regurgitated many times but it seems my situation is a bit different...

A family member has some property about 50m away from the meter. To make the story short, she is building a shack about 50m more into the property but her son will maybe build a better house later.

Anyway... they went to the PEA to get the recommendation for poles and cable size. They said should plan for future and use 25mm2. That's given the meter will probably never need bigger than 5/15 and max demand never more than 20a. So, that seems a bit excessive to me and probably not in her budget.

I was thinking 6mm2 Cu or in that range. But, checking Global I don't see any single core that size and wondering what is available and what is "best"? Most of the houses on 5/15 have blue wires but I have no idea what that is - anybody know that?

So what I hope somebody can help is - not what wire size would be OK for 20a and the distance - but what wire size is available and best for this situation. BTW: The PEA also says they do not want using 2core cable above ground - which will be the case.

Cheers

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You should stick to the PEA recommendations for minimum cable sizes or they may not connect a permanent supply, these are:-

5/15 meter - 10mm2 (anything smaller may have difficulty supporting its own weight when strung from poles)

15/45 meter - 16mm2

30/100 meter - 35mm2 (yes I thought that was excessive too but they only allow 25mm2 to 95A)

Source http://www.pea.co.th.../groundwire.pdf (table on page 11, confirmed by our local office).

50m of 10mm2 will provide a volt drop of 4.4V (2%) at 20A.

Single core (Bangkok Cables type THW which is usually used for this application) is available from 0.5 to 500mm2 http://www.bangkokcable.com/catalog/BCC_CATALOG/THWEN.HTML.

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10 sqmm copper conductor with 20A will give a voltage drop of 3% over 50metres. At 50A you will require 16sqmm. At 63A you will require 25sqmm. At 100A you will require 35sqmm. This is from the point of supply to the main switch board. (The max demand may be the setting of the main circuit breaker (switch) on the switchboard).

If you use 5% voltage drop the sizes of conductor will be: 20A / 4sqmm, 50A / 10sqmm, 63A / 16sqmm and 100A / 25sqmm.

The PEA appear to require a minimum size of not less than 10sqmm depending on the max demand.The cable required is single core copper conductor PVC insulated PVC sheathed 700VAC 70C temp rise.

There is a 3 letter code based on the NEC for this type of cable. Refer to the Thai cable manufacturer.

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You should stick to the PEA recommendations for minimum cable sizes or they may not connect a permanent supply, these are:-

5/15 meter - 10mm2 (anything smaller may have difficulty supporting its own weight when strung from poles)

15/45 meter - 16mm2

30/100 meter - 35mm2 (yes I thought that was excessive too but they only allow 25mm2 to 95A)

Source http://www.pea.co.th.../groundwire.pdf (table on page 11, confirmed by our local office).

50m of 10mm2 will provide a volt drop of 4.4V (2%) at 20A.

Single core (Bangkok Cables type THW which is usually used for this application) is available from 0.5 to 500mm2http://www.bangkokca...LOG/THWEN.HTML.

The minimum sizes are most probably based on the fact than there is no protective device ( service fuse) to protect the consumers mains and in the event of a short circuit, ie, at the line side of the main circuit breaker, the cable temperature rise will not exceed the rating for the cable. Fault currents should be cleared in less than 5 secs. Perhaps a HV fuse on the transformer will rupture in the event of a S/C fault or it will just blow itself clear ( and the cable still be alive, a potentially hazardous situation.)

Here are some common HRC service fuse sizes. They do not form part of the electrical installation and are installed by the electricity supplier.

80 amp for 10 and 16sqmm, 125 for 25sqmm. An HRC fuse will carry 1.6 rated current for the conventional time of 1 hour, It will rupture faster than a MCB and carry a higher fault current in kA. They are used to disconnect the installation and provide fault current limiting.

They are not for overload protection.

Edited by electau
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  • 7 years later...

Hi new here and sorry about jumping in, I am next to finished with a house in Esaan. I have ran the poles every 40 meters  now I will be needing 375 meters distance from main road to house, what is recomended for that 15/45 meter - 16mm2  Copper as well or ? I heard I will need to buy 2 500 meters spools. any idea of the cost  Thanks in advance  

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5 hours ago, Billy K said:

Hi new here and sorry about jumping in, I am next to finished with a house in Esaan. I have ran the poles every 40 meters  now I will be needing 375 meters distance from main road to house, what is recomended for that 15/45 meter - 16mm2  Copper as well or ? I heard I will need to buy 2 500 meters spools. any idea of the cost  Thanks in advance  

 

375m is a pretty long run. The Doncaster Cables calculator http://www.doncastercables.com/technical-help/ gives 70mm2 @ 40A which is probably going to be fine.

 

In order to keep the cost down (and reduce the possibility of it wandering off in the night) I'd go with 95mm2 (or even 120mm2) aluminium cable (THW-A) rather than the 70mm2 copper (THW).

 

For that size and quantity you need to go to a specialist supplier SK Universal are well regarded https://www.sk-wires.com/ and their contact person k. Bell speaks passable English.

 

You will also find that size of wire won't fit in your meter or breaker so you will have to splice a length of 25mm2 copper on to each end, put the joint outside the house but sheltered from the elements.

 

40m pole spacing seems large, where did you get that recommendation? What are your poles made of and how high (sag between poles could become an issue at that spacing)?

 

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  • 4 weeks later...

I would go further than Crossy and suggest you skip the Aluminium and use the same heavy gauge steel cables the PEA use on the long 3-phase runs from the low voltage side of transformers, and then at your end use bi-metallic clamps to connect some 16 mm copper drop wires into your building. You could probably get away with 10 mm drop wires even. Your poles are a long way apart and you're going to have them falling over with this kind of weight if they weren't buried well. It's going to be costly in any case. This should have been done properly from the outset.

 

 

 

Edited by NilSS
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On 1/27/2021 at 5:22 AM, Crossy said:

40m pole spacing seems large, where did you get that recommendation? What are your poles made of and how high (sag between poles could become an issue at that spacing)?

A simpler, and probably better, answer would be to add 1 or 2 poles between the current ones bringing it down to 20 or 13.3 metres between poles

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