Thanks to their space-saving, tankless credentials, unvented hot water systems are continuing to grow in popularity. This is particularly true in the case of medium-sized units, such as our own Velis Evo, Velis Evo Wi-Fi and Pro1 Eco, which offer capacities between 45 and 80 litres.
However, we’re often asked if any particular kits and accessories are required with electric water heaters of this size and there are actually a few additional items to be aware of. The first is the expansion vessel; while this is not required for instantaneous or vented water heaters, unvented models with capacities of 30L or more need to have one. The reason being, as water is heated, it naturally expands – so allowance has to be made for this. An expansion vessel helps to maintain pressure, handling the expansion and contraction of water inside as it heats and cools.
Water regulations also stipulate that you must have a non-return valve to prevent backflow of any hot water into the cold main, therefore preventing any contamination.
Another mandatory accessory is the combination valve, which consists of a pressure reducing valve, a pressure relief valve, a check valve and a filter. The valve will control the mains supply pressure to adjust to maximum inlet pressure.
Finally, a discharge tundish must be fitted. This is needed in the event of the hot water system over pressurising – which, in turn, would cause water to be discharged via the 6-bar pressure relief valve. The tundish not only visually indicates a discharge is occurring but it also provides an air break between two pipes and can be used to ensure that any waste water is taken away from the unit completely. This prevents any water exiting the hot water tank from being sucked back due to high pressure, helping to prevent any cross contamination, particularly if an overflow pipe is connected to a drain or sewage pipe.
These kits are essential – and indeed, mandatory – components for our medium platform electric water heaters. As a result, they are supplied with all units in our Velis Evo and Pro1 Eco ranges, to ensure ease of installation and optimum performance, as well as compliance with UK Building Regulations.