Electric Cable Prices...

[kloghead]

I've been looking at meter-to-home cable and found a wide difference in prices. I need: single-phase, 25 mm2, aluminum core, 750 Volt, insulated and sheathed. It won't be buried so I don't need the NYY brand. What have some of you fellas found to be the cost per meter sold at builders supply/electric shops? Cheap-Charlie to top-of the-line quality...I'll welcome any and all answers.

I've searched on this forum (and others) all this morning and either missed the info I seek or it's just not here. Thanks

edit: I meant to type "elecTric" in the subject title

Edited November 21, 2010 by kloghead

[Crossy]

Can't help with prices, but I've fixed the topic header.

Please be careful using Aluminium cable, you need at least one size bigger than copper to maintain your required volt drop and it is very important to use the correct termination process (you can't just bung it in the regular screw terminals).

[kloghead]

Can't help with prices, but I've fixed the topic header.

Please be careful using Aluminium cable, you need at least one size bigger than copper to maintain your required volt drop and it is very important to use the correct termination process (you can't just bung it in the regular screw terminals).

Thanks Crossy. Your advice is appreciated. I have a 235 meter run from the utility pole (twin transformers) to my house. My neighbor installed 25mm2 aluminium cables and hasn't experienced any problems even with a load which is probably double what mine will be. Can you give me a link or a rough idea what the voltage drop would be in my case?

I've been quoted from 18 to 48 baht per meter for the same spec cable and don't understand why the big difference in prices. Thanks again.

[electau]

What is your max demand in amps? The reference to twin transformers, do you mean two individual single phase transformers? Do you know their size in kVA each ?

One needs to know the max demand so as to calculate the size of cable and voltage drop from the point of supply.

Edited November 21, 2010 by electau

[kloghead]

Hi electau--the max amperage demand will never be more than 45--the average will be closer to 15-20. The two transformers are both single phase (don't know their KVA, sorry, but they seem to be the standard size for my area).

I found some online voltage drop conversion modules last night and reckon an aluminium core 25 mm2 cable is close to AWG 3 size. The conversion works out to a ~4.3 V drop over 235 meters @ 20 amps...

AWG 3 = 53 kcmil = 26.7 mm2...does this make sense to you? I couldn't find any conversion that worked using square mm cable size--only AWG.

Do you think an aluminium 25 mm2 cable is sufficient or should I go up or down one size?

PS The reasons I need to use aluminium are cost and the fact that several thefts of copper cable have occurred nearby my building site.

Thanks mate, I really appreciate your help.

Edited November 22, 2010 by kloghead

[Pib]

I've been quoted from 18 to 48 baht per meter for the same spec cable and don't understand why the big difference in prices. Thanks again.

Preaching to the choir I know but it's like when you find the exact same item in say a Big C store and a Central store, and there is a HUGE price difference. The answer is one store is just marking up their retail price much higher due to the price they paid the wholesaler/factory or just to make a much larger profit. And since I expect big box stores probably get about the same price from the wholesaler/factory, the store's different profit/retail pricing policy (sometimes influenced by the income status of most its customers) is probably the answer. Stores all over the world play this max profit game. I see fairly significant electrical cable prices (on the exact same cable/made by the same manufacturer) between HomePro, HomeWorks, and Global hardware stores here in the Bangkok immediate area. In my experience based on the items I buy usually Global is the cheapest, followed by HomePro, and then comes HomeWorks. Definitely pays to shop around as you are doing.

[kloghead]

Thanks Pib--I've just called a few cable vendors I found on the Yellow Pages to try to get some idea of what the cost per meter should be. No luck so far so I guess my next calls will be to the usual suspects you mentioned. Gracias amigo.

[Crossy]

KH.

Did you factor in the length of BOTH legs (L&N) into your calculation? I calculate that 235m of 25mm2 copper (my calculator doesn't do Al) will drop 8.93V @ 20A (out and back). Al will drop about 1.7x the copper drop so something like 15V (6.8% @ 220V).

You really either need to do a proper max demand calculation or at least assume that the max demand will be whatever your supply is rated at (45A for a 15/45 meter).

[kloghead]

Crossy--yep I sure have but it's a bit inaccurate because all the calculators I've found have inputs in feet, 240 V (not 220), AWG and kcmil. Like this one:

http://www.csgnetwork.com/voltagedropcalc.html

If I could just convert 25 mm2 into AWG or kcmil size I'd be able to nail it. Or work backwards to get the correct size cable. Any suggestions? Thanks

PS Found a distributor in Bangkok that sells a Euro-brand cable (25 mm2 aluminium) for 12.75 per meter...

[Crossy]

Doncaster cables have a simple calculator that does mm2 at 230V (near as makes no odds) http://www.doncastercables.com/cableCalculator.asp it only works in copper, but multiply by 1.7 to get the drop for Al.

Like all these things we have to work around with the tools we have

BTW, I found that one (and others) by Googling 'cable calculator uk'

It's a simple Java script, if I get a minute I'll modify it for other voltages, volt drop choices and maybe include Aluminium cables too

[kloghead]

Crossy--you the man! I also retrieved a dozen or so calculators from Google but obviously couldn't find any that did metric (as yours does). My sparky here on Koh Chang today said a 35 mm core would be about a 9% drop

The guy next to me is drawing a helluva load because he's building two villas simultaneously and using heaps of power tools. He's on a single-phase 25 mm2 temporary line and said so far no probs. The PEA office here was closed today but I'll swing by there tomorrow and get their opinion. I def want to do this correctly the 1st time!

Here's what I got using the Doncaster calculator:

Phase: Single Phase

Power:10.35 kilowatts / 45 amps

Length: 235m

Core Size: 50 mm²

Voltage Drop: 10.58 volts {X 1.7 = 18 V}

Is this correct or did I muck it up

Thanks a bunch and I'll let you know what the outcome finally is. Also thanks to Pib and electau.

[electau]

Based on 5% voltage drop and AS3000.

Single phase. minimum sizes in sqmm.

45A would require 50sqmm copper conductor.

20A would require 25sqmm copper conductor.

16A would require 16sqmm copper conductor.

For Aluminium multiply these sizes by 1.7.

[Crossy]

My sparky here on Koh Chang today said a 35 mm core would be about a 9% drop

The guy next to me is drawing a helluva load because he's building two villas simultaneously and using heaps of power tools. He's on a single-phase 25 mm2 temporary line and said so far no probs. The PEA office here was closed today but I'll swing by there tomorrow and get their opinion.

Your local sparks is certainly in the right ball park, but 9% before you take into account drops in the building wiring is too much. Unless you're on a really tight budget I'd use at least 50mm Al which will keep you around 5% drop at 30A ish. As with many things, bigger is better.

The power tools are an intermittent load and will rarely all be drawing power at the same time, also the universal motors most of them use are pretty good at handling voltage variations so unless he's really pushing his supply your neighbour is unlikely to see any problems.

The real killers are water heaters and aircons, these are the most significant load that most of us will we using, so at the minimum add up all the water heaters and aircons you intend installing and use that as your max demand figure.

[kloghead]

I hear ya Crossy. Today I went over to his place, checked out what appliances were on (constantly) and came up with 25A and ~7000 W. He still has no probs with an aluminium 25mm2 cable. Go figure...

Anyway, the PEA turned on my juice this afternoon so we'll see what happens in the coming weeks when the changs do their thing. Thanks for the replies--I DO appreciate it.

Edited November 25, 2010 by kloghead