Temporary supplies for construction sites present some unique challenges for electricity suppliers, meter operators, electrical contractors and building contractors.
Provision has to be made for temporary supply cables to be terminated in a secure and robust manner, in strict accordance with the requirements of different electricity suppliers.
Most electricity suppliers will not guarantee the integrity of the supply earth and will only provide construction sites with a TT supply, necessitating the addition of an RCD to protect the overall installation and for all enclosures upstream of the RCD to be all-insulated.
Meter operators require a secure housing for their meter and a sealable compartment to house their current transformers.
Blakley Electrics introduced combined CT Chambers and RCDs a number of years ago. Initially these were rated at 200A / 400A but the range has now been expanded to include versions rated at 800A and 1600A. These assemblies can either be supplied in wall mounting format (requiring a suitable wall / room to be found on site) or, more commonly, they can be supplied fitted into a robust, GRP housing, which can be positioned anywhere on the site without any further protection required. The requirements of the different electricity providers differs from company to company but we have experience or producing combined assemblies to suit the requirements of many of the leading electricity suppliers.
The image above shows an 800A Site Intake Assembly supplied for a Temporary Builders Supply in Kent. The assembly is fitted with incoming terminals which are punched for 4 hole fixing lugs. These terminals are designed to accept 740mm2 single core, aluminium cables, either one or two per phase. A wooden clamp is incorporated at ground level to secure the cables.
The CT chamber (main compartment on the right hand side) is sealable and incorporates removable links and shelves for the CTs. The electricity meter can be mounted on to the door of the CT chamber (there is a minimum distance of 150mm from the door of the CT chamber to the back of the door of the outer cabinet). The meter and CTs are provided and fitted by others.
The outgoing cables feeding the site terminate in the CT chamber. A steel extension box is fitted to the underside of the CT chamber allowing the glanding and termination of large, 4 core, steel wire armoured cables.
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SP5___SIA_for_South_Eastern.pdf (319.79 KB)
TDS11_What_is_a_CT_chamber.pdf (435.88 KB)