Correct cable size for length of run

[calvert]

I need to run approx. 50 metres of armoured cable to a domestic sewage treatment plant using 100 watts. I also want a 13 amp socket by the plant. Is 2.5 twin and earth big enough for the job please? Thanks in advance.

 

[Taylortwocities]

13A socket, for what? 100watts is not significant. 3000watts may be.

If you are doing this (notifiable) work then surely you know the principles of cable calculations and should not need to ask an a DIY forum?

 

[calvert]

I'm not doing it myself, I'm ringing my sparky today. I just wanted to get a bit of knowledge

 

[bernardgreen]

Are you sure the power requirement is 100 watts ? That seems low for a sewage treatment system.

Are there are any motors involved ?

With a motor you will need to allow for the starting current of the motor. This will require a cable size such that the voltage drop along the cable while carrying the start up current does not reduce the supply voltage at the motor below the minimum for the motor.

 

[ericmark]

At 13A the volt drop is around 18 volts so for your 100W not a problem for the socket depends what is being used.

 

[ricicle]

If it is just control/monitoring they it may well be only 100w. If there is any form of aeration motor then this will more than likely be larger than 100w.
Start up current will need to be taken into account as well as your additional socket load.
Electrician design and responsibility needed.

 

[calvert]

Thanks for your answers. The 100 watt is the blower that keeps the little plastic balls moving, for the bacteria to grow on. I just thought a 13 amp socket might be a handy thing to have nearby, maybe for some tool during maintenance, a lead lamp?

 

[Taylortwocities]

I'm not doing it myself, I'm ringing my sparky today. I just wanted to get a bit of knowledge

Fair enough, but there are a lot of variables, your electrician will know about these when he does the design for the circuit. He is the obe who will say the cable size required.

With cables run over a reasonable distance then there is no "one size fits all" answer.