Question from Boyd Darling, via e-mail:
Do the changes in Part G of the Building Regulations require any changes to cold water storage cistern specifications when the cistern is supplying a vented hot water tank with immersion heaters? This is in the light of the tragic death of the baby who was scalded by boiling water from a ruptured cistern being fed by a faulty immersion heater.
Answer from Martyn Bridges, director of marketing and technical support at Worcester, Bosch Group:
Part G of the regulations addresses the incident in question with the following requirements: firstly the control of heat to the cylinder and secondly the improved requirements of the cold water storage cistern, in the now unlikely event that the cylinder temperature is extreme.
Vented hot water storage systems
In addition to the vent pipe and any thermostat provided to control the temperature of the stored water, vented hot water storage systems should include either:
• For all direct heat sources, a non self resetting energy cut-out to disconnect the supply of heat to the storage vessel in the event of system overheating; or
• For all indirect heat sources, an overheat cut-out to disconnect the supply of heat to the storage vessel in the event of the stored water overheating so that the temperature of the stored water does not exceed 100°C.
Cold water storage cistern
The cold water storage cistern into which the vent pipe discharges should be supported on a flat, level rigid platform which is capable of withstanding the weight of the cistern when filled with water to the rim and fully supporting the bottom of the cistern over the whole of its area. The platform should extend a minimum of 150mm in all directions beyond the edge of the maximum dimensions of the cistern.