You need to add up how many watts you expect to burn in your shed, I guessed:. You probably wouldn't have it all switched on at once but I'd still use 4mm to reduce the voltage drop.
Edit : I see Brian got in first recommending 6mm for a 5V drop. In comparison 4mm would drop 7V with a 5kW load. If money is no object, buy the bigger cable. There are a number of volt drop calculators on the www. Assuming 10 kW load, and 30 metres, assuming volts incoming at the meter position, it recommends 6 mm cable, for a 10Volt drop.
For 6 kW the cable size can be reduced to 4mm. To check your typical load, look at the rating of the motors on your lathe and milling machine, and pick the largest.
My recommendation would be to go for a minimum of 6mm, especially if you are digging a trench to bury it underground. So use that for the calculations. Haven't got 3 ph, because the cost of getting it installed was steeper than I liked and I got an excelent deal on a 23kVA inverter that feeds the entire shop.
Remember, if you get flickering lights, you'll regret it more over time than you'll regret the extra cost of going up a wire size or two. I'm not sure your advice about not using the armour as a protective earth is quite right there. If you use SWA, it would certainly be bad practice not to use the armour as an earth conductor.
It is very much more than sheathing. Indeed it is the very definition of an electrical protective earth. It is virtually impossible to damage a phase conductor without first cutting the protective sheath. The very act of encircling the phase conductors with the earth offers a method of electrical protection and essentially guarantees fast circuit breaker action if the cable is accidentally cut. There is much uncertainty out there on this matter, so lack of awareness can be excused.
One thing is certain, poor implementation will not be excused by mother nature under fault conditions. People have generally noticed that corrosion can set in at glands and where the outer plastic sleeve becomes damaged. This can compromise the earth bond, and provide less than adequate protection.
Some recommend using an additional copper earth conductor inside the armour, others an additional copper earth conductor outside the armour. If the digger bucket scrapes along the length of the conductor then phase can be exposed without shorting to the protective earth.
One is dependent on soil resistance to operate the circuit breaker in this situation, and it is not good. In conclusion; if the armour is not good enough to do the job because of corrosion, then it has not been monitored and maintained properly. In most cases there is no reason why a steel wire armour cannot perform the function of a protective earth.
If the calculations show that the armour can trip the fault circuit in the prescribed time, then my opinion is that it is safer only to use the steel wire armour. Like all engineered installations it is important to periodically check and maintain equipment to ensure safety. So if not wanting to go too mad 4mm will be enough, like you say I will never have everything on at the same time.
I assume the electrician will but 3 core cable, will he not just use the earth wire withing the cable? As you are putting a spur it 1. What amp junction box do I need for lighting?
Rating of Junction boxes The size used should equate to the current rating of the circuit being connected into — you can always use a higher rated box than the circuit but never a lower rated box. For a lighting circuit use a 20amp junction box and for a ring main or radial circuit use a 30 amp junction box. How many amps can a 1mm cable take? Is 1mm cable OK for lighting? How many amps can 4mm cable take?
What is 2. The most common use for this type of cable is for circuits that provide power to sockets. It is made up of two cores and an earth core which must be covered with the identifying green and yellow sleeve when installed. What size cable do I need for an extractor fan? The Minimum cable size for fans like this is 1. It is acceptable to use 1. Cable types required for the timer fan above are 2 core twin and earth.
How do you determine cable size? Divide the voltage running through the cable by your target current. This is your target resistance, measured in ohms. SWA is a power and auxiliary control cable, designed for use in mains supply electricity. It is one of the various protected electrical links — including 11 kV Cable and 33 kV Cable — and is found in underground systems and frameworks, cable networks, control systems, power networks, outdoor and indoor applications, and cable ducting.
Steel Wire Armoured Cable is designed to have mechanical protection, which is why the cable is often used for external use. The armour is used to reduce any risk of the cable getting pinched or damaged; the steel is used to protect the armoured cable. SWA cables are heavy, which makes them extremely difficult to bend; therefore they are most suited to underground cabling or fixed to outdoor walls using cable cleats.
For our fellow Americans: replace Armoured with Armored. This function is technically known as circuit protective conductor or CPC. Usually an additional core within the cable is specified as the CPC for example, a three core cable is used instead of using a two core cable for line and neutral, and the armouring as the CPC or an outside earth wire is run alongside the cable, serving as the CPC.
0コメント