Armoured Cable Size

dark_stranger · 13 Jun 2007

I am currently waiting to connect up a shed/fishroom to the house mains & as per a mates instructions has advised on buying some armoured cable to run from the shed to the house. He has suggested 6mm, but working out the wattage that seems like overkill, but i fix PC's & he's a sparky. Anyway, what cable thinkness would i need... 1.5mm, 2.5mm, 6mm? I also found a calble size calculator on a electrical online store & it suggests only 1.5mm cable for a 1000watt load (roughly)

Heater - 300watts
Fan - ?
MH - 300watts
Pumps - ?
T5/T8 - 100watts
Shed Lights - 100watts
Pond pump - ?
Decking lights - 100watts

so maybe 2kw max load, of which the calculator still suggests 1.5mm cable

Please advise as the price between 1.5 & 6mm is a bit.

luminaire · 13 Jun 2007

You had better ask your electrician why he favoured 6mm?

My guess is to cover any future additions or alterations which then overload the system and necessitate ripping out your original SWA and having to replace with a larger size.

david1805 · 13 Jun 2007

Depends on how far the run is. A 2Kw load over 100m distance would require 6mm to overcome volt drop.

dark_stranger · 13 Jun 2007

the distance would be approx 50meters (well about 40m).

david1805 · 13 Jun 2007

Depends on how future proof you want to be.

2.5mm over 50m is good for 2200w.

4mm might be sensible, this would support up to 3800w over 50m.

dark_stranger · 13 Jun 2007

it might be better to future proof & go for 4mm then again may just go for 6mm as originally advised.

Chri5 · 13 Jun 2007

The cable might be expensive, but building in future proofing is always cheaper than having to re do the work in a few years time.

Only takes a few 500w flood lights, some sockets in a shed drawing 2kw via power tools, the odd jet washer and some garden power tools.

Might seem like over kill, but compared with digging 35m of trench 600mm below surface it's a false economy.

bernardgreen · 13 Jun 2007

Chri5 said:
the odd jet washer and some garden power tools.

Might seem like over kill, but compared with digging 35m of trench 600mm below surface it's a false economy.

Motors often have higher loads at startup and this should be considered when sizing the SWA for voltage drop. If the motor start up load drops the voltage too much ( due to volt drop along the cable ) the motor may be slow coming up to speed and this puts wear on the motor as the current through windings is higher for longer than designed for.

If laying the SWA in a trench future proof with a duct as well.

John M · 16 Sep 2007

300w heater ......... Light a candle ...... Get more heat off that

6 mil would be the way to go really.....

Might as well shove some twisted pairs in wiv ya mains Sheilded O' course

securespark · 16 Sep 2007

What fuse will be on the other end of this SWA?

John M · 16 Sep 2007

A blown one

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Armoured Cable Size

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