Electrical Installation, Testing and Maintenance in the Borders/Lanarkshire area

17th Edition Qualified


Immersion Heaters

These are often installed at the same time as the hot water tank and not maintained well. This heater is probably about 35 yrs old.  The cable has degraded so badly at the heater that the insulation fell off when the cover was removed as part of an inspection.

The wires were twisted around each other and close to contacting the metal tank and through that all the pipes and water taps.  Normally the earth wire in the immersion heater cable would make the situation safer by allowing the mains voltage to escape to earth and usually blow a ‘fuse’.   

In this case the earth wire was broken inside the immersion heater switch, and there was no bonding of the main water pipe coming into the house. This meant that the risk of electrocution was high especially in the bathroom. 

The only safety device operational was a rewireable fuse, which can take too long to respond for complete safety, especially if the fuse wire has been replaced using the wrong type of wire.  Modern fuse boxes do not use fuse wire and have RCDs or RCBOs which can detect faults and react very fast to make this type of situation much less life threatening.

BM Electrical - 1 Mackenzie Gardens - Dolphinton - West Linton - Peeblesshire - EH46 7HS
 Tel: 07766 051 672   Email: bmelectech@talktalk.net