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Electrical installation safety bulletin from the HWA
Published:  08 March, 2018

Isaac Occhipinti updates installers on the correct electrical installation of water heating products.

A large number of installed water heating products will have electrical connections – usually to the thermal controls (thermostat and thermal cut-out), and, where fitted, to an electrical immersion heater.

Following recent events, such as the Grenfell Tower fire, the Hot Water Association feels it is timely to remind installers of the importance of the correct electrical installation of water heating products and their associated ongoing maintenance.

Incorrectly made electrical connections can result in overheating and create a fire risk. When installing the product, the wiring needs to be adequate to minimise the risk of overheating.

Please ensure you:

  • Use the correct type and cross sectional area cable to meet manufacturer and Wiring Regulation requirements
  • Take care to not damage the strands of the conductor wire when stripping the insulation from the individual conductors, which would reduce the cross-sectional area of the conductor
  • Ensure the conductors are tightly and securely connected to the controls or immersion heater
  • Ensure the bared conductors are correctly inserted into the terminals, to avoid bearing on the insulation sleeving, or only partially clamping the conductors
  • Securely anchor the supply cable using the means provided to avoid exerting any external strain on the cable and the terminals
  • Check to ensure the product is earthed correctly, the live and neutral connections are to the correct terminals, and the residual current device operates correctly
  • Regularly check the electrical connections as part of the maintenance schedule, to ensure the wires remain in good condition and terminations remain secure
  • Ensure any spare parts used during maintenance of the product are an authorised spare part and meet the manufacturers’ requirements.

Most importantly of all, the manufacturers’ wiring instructions must always be followed.

Thermal cut-outs

Any new water heater or immersion heater must be fitted with a thermal cut-out, which will operate should the normal control thermostat fail, to prevent the water heater from possibly continuing to heat and leading to components overheating. In the case of vented products, the thermal cut-out would prevent the unit from boiling.

If the unit is supposed to be manually filled or topped up, a thermal cut-out is particularly crucial to avoid the risk of overheating the exposed immersion heater, in the event of the user forgetting to top up.

Some older types of vented water heater or immersion heater may not have been factory supplied with a thermal cut-out device. Please check all products for the presence of a thermal cut-out device, and, if one is not present, please ensure one is fitted. If it is not possible to add a thermal cut-out device, you may need to update the immersion heater assembly to one that incorporates a thermal cut-out.

If you are unsure whether the product includes a thermal cut-out, please contact the manufacturer of the product in question for further advice.

Water heating products, when installed and maintained correctly, give many years of exceptional performance. However, as with many household and commercial appliances and equipment, many will require electrical connections to enable them to work correctly. Their continued safe operation will rely on the correct connection to the electrical supply, and regular inspection to check the integrity of electrical connections and components.

If in doubt, further advice should be sought from the manufacturer of the water heater or immersion heater. Any electrical work must be carried out in a safe manner by a person qualified to do so.

Isaac Occhipinti is Head of External Affairs at the Hot Water Association.