2007-12-03
Our Voltimum Experts answer your questions on a daily basis in our Technical Expertise area. This Question of the Day, concerning emergency genset installation and connection, is answered by the ECA:
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| A back-up genset. |
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| Use an isolator switch or changeover switch. |
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Question: I have been asked whether it is possible to install a 5kVA backup generator to supply emergency power during power outages.
The supply is single-phase, taken from a three-phase service head in an outbuilding/workshop. The supply then runs under the drive via 25mm two-core SWA to a cellar. The earth is disconnected in the box that the SWA is terminated in, and is not connected to the MET of the house, which has an earth rod and an 100ma Type S RCD. I believe that this is because the Zs reading at the house end of the SWA is over 1.5 ohm.
My thinking was to connect the generator to a break-before-make switch, connect the neutral to an earth rod installed beneath the SW, and feed the SWA via an 30mA RCD and a fused isolator to the house CU.
Can you see any problems with this approach?
Answer: You will also need to provide an isolation switch for the permanent supply, or use a changeover switch. The whole installation should be done in accordance with BS 7671.
To see many more Q & A in Voltimum UK's Experts Area, please click on the link: http://www.voltimum.co.uk/consult.php?universe=consult.index.questions
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Related contacts
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The Electrical Contractors’ Association (ECA)
ECA Head Office, ESCA House,
34 Palace Court, London W2 4HY
Tel: 020 7313 4800
Fax: 020 7221 7344
Email: electricalcontractors@eca.co.uk
Web: www.eca.co.uk |
ECA
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Source: The ECA & James Hunt |
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