Trenching & Ducting

When providing trenching for a Naked Solar installation, there are certain standards and regulations to adhere to. We recommend engaging the services of a groundworks company to carry out your trenching needs. Naked Solar kindly requests customers to arrange their own trenching as we are unable to provide this service.

Trenching for Armoured cable

We always use armoured (SWA) or duct-grade cable when putting cable in a trench. For this, there are recommendations for underground cable runs, as per the regulation clauses below.

 

522.8.10 Except where installed in a conduit or duct which provides equivalent protection against mechanical damage, a cable buried in the ground shall incorporate an earthed armour or metal sheath or both, suitable for use as a protective conductor. The location of buried cables shall be marked by cable covers or a suitable marker tape. 

Buried conduits and ducts shall be suitably identified. Buried cables, conduits and ducts shall be at a sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground. 

NOTE: BS EN 61386-24 is the standard for underground conduits. 

 

 

There are further recommendations and guidance regarding these depths from various documentation and codes of practice. We heavily advise 600mm depth from the surface of the soil to the top of the cable, as this is at least the standard height of a shovel head when digging. This also comfortably satisfies the last sentence of the regulation. 

Trenching requirements

electrical-supply-to-an-outbuilding-voltimum-uk

Gentle curve for cabling, recommended

trench-2

Trenching for Ducting

To future-proof against any additional work at another time, and avoid having to trench again, Naked Solar recommend customers lay ducting in the trenches that are being dug.

Ducts/conduits can be made of any plastic (polyurethane, polypropylene, pvc, etc.) material.

Ducts must have pull through cords: many ducts come with this cord already in place, please check with the retailer upon purchase. 

The size of ducting is dependent on how many cables will be laid in each duct, but a minimum of 75mm (3 inch) diameter is typically recommended.  

Please bear in mind the bend radius of a heavy duty, armoured cable. Any sharp bends may prevent us from pulling the cable through and could result in having to dig up the ducting again.  

522.8.3 The radius of every bend in a wiring system shall be such that conductors or cables do not suffer damage and terminations are not stressed. 

The locations of cable ducts and buried SWA will also require to be marked via cable covers or a suitable marker tape as per the images below.

Electrical installations in the garden | Voltimum UK - 1