TT supply to a static caravan

Darren80 · Dec 19, 2020

Hi I have a property and the mains supply is a TT system I need to put a temporary static caravan in the garden. The caravan will have a water supply to it and the cooker is gas. The caravan has its own CU rated at 40A with a 32A RCD. The distance is about 100m. My question is do I need a earth rod at the van and if so do I need to keep the earth in the SWA separate like you do in a PME system or can they be connected together.
Thanks
Darren

westward10 · Dec 19, 2020

You have a TT system so PME has no relevance.

loz2754 · Dec 19, 2020

This is something that requires a proper design by a competent electrician and is outside the scope of DIY.

Darren80 · Dec 19, 2020

Hi mate what do you think is the best way to do this job. Run a 3core or a 2core cable

suffolkspark · Dec 19, 2020

With a run of 100m that cable will be a fair size due to volt drop, even if you take 40A, it's a circuit that needs proper design by an electrician, from cable sizing to fault protection, and should also legally notified to building control. It is outside the scope of a diyer. You require an electrician to do the job.

pc1966 · Dec 20, 2020

If it is a new circuit in England & Wales that is notifiable work, so getting a professional in is the best answer in many ways. There may be folk on this forum in your area who can do a good job.

You also need to identify the actually demands of the caravan - not just the 40A rating of the caravan CU, as that will have a big impact on the design in terms of cable size and hence cost to keep the voltage drop within the regulations.

As for earth rods on TT there is no harm in having another rod at the caravan as lower impedance is generally safer, though as the main property is TT you should not need it as the cable's armour will generally be adequate and should be reliable if properly glanded at both ends. Whoever does the job ought to check the supply characteristics first in any case.

Also note that caravans must have double-pole 30mA RCD protection, and obviously waterproof connectors. Normally you get outdoor rate socket/RCD outlets to allow them to be plugged in using something like a 16A or 32A commando style plug (assuming your max load is 16A or 32A of course). So your circuit would be SWA to the socket outlet next to the caravan (as you specify it as 'temporary' and so not hard-wired).