Electric Supply

[petertucker48]

Could someone advice ,I need to run electric mains cable from the road side (from the supply meter) 40 metres to my house fuse box.

Total current required around 32 amps.Will be using yellow piping

Just wondering what would be the best diameter 6mm/8mm or 10mm.

No aircon, swimming pool just electric oven (can use on 2.5 mm cable) two 6kw water heaters (kitchen and main bathroom) micro wave ,cold water washing machine, usual TV/amp/dvd player and ceiling fans (4 ??),low energy (11watt) lighting through out.

How bad would using aluminium instead of copper be just from supply meter to fuse box (Copper฿9000 !!! aluminium ฿1000) once inside house all wiring will be copper.

Any advice appreciated .

[longball53098]

I'm sure Elk and Crossy will lead you to the most correct answer on cable size. You need to make some calculations based on current draw and distance.

This link may help you: Cable size

[Crossy]

OK, if you have a load of 32A you'll likely have a 15/45 meter installed (please confirm).

This will likely have an MEA / PEA supply fuse of 63A.

You should size your meter tails with this supply in mind.

16mm² would be appropriate in this instance.

Be VERY careful if you want to use aluminium cable, you cannot just use the regular screw terminals found on the incomer and meter, these will work loose over time and could cause arcing along with the potential fire risk. Your installer should use the proper Al crimps and copper pigtails to protect the cable before terminating. Also you need to use one size bigger than copper.

Ensure the tubing you lay (assuming underground) is big enough to easily pass the cable and that the ends are sealed to prevent entry of water and any critters that may want to call it home. You should also protect your cable run from damage during gardening or other earthworks, bury it at least 450mm deep and include a warning tape about half way to the surface, of course a Thai installer would just forget to do the latter.

[petertucker48]

Many thanks for the address .

I spent 2 hours trying to Google this info yesterday without any simple answer.

Cheers

This link may help you: Cable size

[petertucker48]

OK, if you have a load of 32A you'll likely have a 15/45 meter installed (please confirm).

This will likely have an MEA / PEA supply fuse of 63A.

You should size your meter tails with this supply in mind.

16mm² would be appropriate in this instance.

Be VERY careful if you want to use aluminium cable, you cannot just use the regular screw terminals found on the incomer and meter, these will work loose over time and could cause arcing along with the potential fire risk. Your installer should use the proper Al crimps and copper pigtails to protect the cable before terminating. Also you need to use one size bigger than copper.

Ensure the tubing you lay (assuming underground) is big enough to easily pass the cable and that the ends are sealed to prevent entry of water and any critters that may want to call it home. You should also protect your cable run from damage during gardening or other earthworks, bury it at least 450mm deep and include a warning tape about half way to the surface, of course a Thai installer would just forget to do the latter.

Many Thanks Crossy information very much appreciated

[stgrhe]

This is a formula which can be used to calculate the core area of the cable.

Known Parameters:

Mains supply per phase [V]: 220

Dist. between transformer and distrb. Board [L] (m): L (add the distance in metres from the meter to your distribution board)

Material (Cu) - Cable resistance/m/mm² at 20^°C [R₁]: 0.018 Nominal temperature [T₁] (°C): 20

Temperature coofficient [ρ] (rho): 0.004

Estimated ground temperature [T] (°C):  25 (estimated temp. if cable is run half a metre underground)  

Max phase load (A): 32 (your estimated max current)

Maximum allowed voltage drop [V_d] (%): 3 (should preferably not exceed 5%, but a 3% max drop is better)

Sought: Cable Size (mm²⁾ : X

Total Resistance [R] (Ω) per mm² 

R' = 2L [R₁ + ρ(T - T₁)]

R' = 2*L*(0.018+0.004*(25-20))

R = R' Ω

Sought Cable Size [X] (mm²)

X = I x R x L / V_d x V

[BlackGrape]

Google is a great thing...

[T_Dog]

I tried those equations on a prior post, but there seems to be a missing paren somewhere in my head! Here's a nice website calculator that is pretty handy. Look at the bottom of the page and you can find the calculator. Note that the distances are in feet.

http://www.powerstream.com/Wire_Size.htm

Would be curious to know what nominal currents people are using. Like on poster said, it is very unlikely to have every appliance, air con and light on at the same time. Anybody using a clamp-on amp meter that has some empirical data?

[electau]

Max demand 32A supply single phase 2 wire.

You could use 2core 10sqmm pvc/pvc (sheathed) cable 75C. 16sqmm is recomended. Service fuses are not always used in Thailand, and they are there for short circuit protection and a point from which to disconnect the electrical installation.

Conduit should be 32mm heavy duty buried to a minimum of 500mm in trafficable areas. It would be recommended that a printed warning tape is buried at a depth of about 300mm from the surface.

Copper conductors should be used.

3% voltage drop has been use in this calculation.

　

Edited August 22, 2010 by electau