Tails From Electricity Meter To Consumer Unit

[gouda]

I am about to buy some 25mm2 tails for the overhead cable from the electricity meter to the building, the distance is about 35m from the 15/45 Amp meter to the Consumer unit. Therefore will most probably buy a 100M roll as i need 70M as price per roll is cheaper than price per meter

The local electric supply shop has 2 types of the 25mm2 THW cable Copper (Brand Thai Yazaki) at 72B/m or Aluminium (brand Union) at 12B/m. A big price difference of 6000B on a 100M roll

Will the 25mm2 aluminium one be ok?

does it depend on the voltage at the meter? If so, I'll buy a multimeter to check the voltage first as the building is out of town and not sure how close the nearest transformer is. The PEA mentioned there may be power problems as its at the end of supply

Would a larger size Aluminium be better?

ps: was planning to use 16mm2 first but the shop mentioned 25mm2 is standard

many thanks

[Crossy]

Copper is a better conductor than aluminium. To achieve the same current flow as a copper conductor, an aluminium conductor would need to have 1.6 times the cross sectional area. Because of the equivalent aluminium conductor requiring a larger cross sectional area than that of copper the size of the cable is larger. This will result in greater space required to terminate an aluminium conductor than a copper conductor of equivalent current carrying capacity.

If you're going to use aluminium you should go to the next size up cable, so if you're looking at 25mm² copper you'll be looking at 35mm² aluminium.

The termination of an aluminium conductor requires great care to avoid problems due to the formation of aluminium oxide on the metal surface, which will interfere with the conductivity of the termination. Aluminium would be OK but there are often problems with loose connections where it enters the CU as there are supposed to be crimp ferrules installed on the ends, these are invariably omitted.

Do check the voltage at the meter, at various times of day, but that's not going to tell you what extra drop you'll get if you're miles from the Tx.

Personally, for 6 Grand I'd get the 25mm² copper

[gouda]

thanks Crossy, very helpful as always

I think I'll go for the copper as have read some more info about the problems of aluminium wiring

Also noticed you mentioned using 16mm2 copper meter tails for 15/45 Amps in another thread, I now think why the shop mentioned that 25mm was standard is that most Thai developers use 25mm2 aluminium i.e. 1 size up from 16mm2 copper due to the big cost difference and 16mm copper has an adequate current rating

but that's not going to tell you what extra drop you'll get if you're miles from the Tx

by extra drop do you mean voltage drop? current? both? I'm presuming the voltage drop can be read at the meter ??

[Crossy]

Also noticed you mentioned using 16mm2 copper meter tails for 15/45 Amps in another thread, I now think why the shop mentioned that 25mm was standard is that most Thai developers use 25mm2 aluminium i.e. 1 size up from 16mm2 copper due to the big cost difference and 16mm copper has an adequate current rating

but that's not going to tell you what extra drop you'll get if you're miles from the Tx

by extra drop do you mean voltage drop? current? both? I'm presuming the voltage drop can be read at the meter ??

Yeah, 16mm² copper would be standard for a 15/45 meter but watch volt drop, 35m of 16mm² will drop 4.4V at 45A, not a lot (only 2%) but if your supply is already down to 205V you need every volt you can get

Measuring at the meter only gives you half the story as it doesn't give you any real idea what the voltage will do once you add your 45A load (although it will certainly give you a clue). Are there other homes in the immediate vicinity running off the same feed? Big ones? How far are you from the Tx? How big is the Tx? (photos).

I would still go for 25mm² copper if the budget will handle it but I'm a conservative type, in most cases bigger is better (except air conditioners)

[lopburi3]

I fully agree with Crossy and would not touch aluminium when you have a choice. Back about 30 years ago there was severe shortage of copper and we often had no choice - and a lot of buildings burned down because of it. If you use you have to make sure that connections are very tight and regularly check/tighten them (unless they have improved the connectors - have not kept up). They did tend to get loose and allow sparking with all too often results in fire.

[Lancelot]

I fully agree with Crossy and would not touch aluminium when you have a choice. Back about 30 years ago there was severe shortage of copper and we often had no choice - and a lot of buildings burned down because of it. If you use you have to make sure that connections are very tight and regularly check/tighten them (unless they have improved the connectors - have not kept up). They did tend to get loose and allow sparking with all too often results in fire.

Agree, go with copper if you can. Aluminum expands and contracts more than copper and that causes bolted (mechanical) connections to loosen. If you do use Aluminum, I agree with lop, go back and retighten connections and check for aluminum oxide.

[technocracy]

I do not understand when threads like this come up about aluminium cable - everyone instantly says 'don't use it' etc etc. However the plain fact is that basically about 95% of all overhead cables around the world is aluminium including ACSR (Aluminium Conductor Steel Reinforced) used for the high power lines.

So why do people make out it isn't good enough for tails from a meter?

[Crossy]

So why do people make out it isn't good enough for tails from a meter?

It's plenty good enough IF correctly installed with the correct compression connectors (correctly crimped with the correct tool) or using copper pigtails.

Yes, I know I used the word 'correct' a lot there, how many times does this word come up when referring to domestic electrics in Thailand?

The fact is, if you simply bung Al cable into the regular screw connectors found on the breaker it WILL loosen over time and cause a high-resistance joint and potential fire (or at the least damage to your CU)!!

Safest is to avoid unless you know your man is going to do the job properly.

Paragraph 5 refers RecommendationsforConnectors.pdf