Water Heater Regulations Flashcards

What does WRAS stand for and why is it relevant to water heaters?

Answer: Water Regulations Advisory Scheme — it approves fittings as compliant with Water Supply Regulations

WRAS is the Water Regulations Advisory Scheme; products bearing the WRAS mark have been tested and approved as complying with the Water Supply (Water Fittings) Regulations 1999.

What solar thermal system component stores heat collected by solar panels?

Answer: Solar thermal storage cylinder (twin-coil cylinder)

A solar thermal system uses a twin-coil (or dedicated solar) cylinder; the lower coil is connected to the solar collector circuit and the upper coil to the conventional boiler, maximising solar contribution.

What is the 'dead volume' risk in a hot water distribution system?

Answer: Water sitting stagnant in long pipe runs cooling below 50°C, creating Legionella risk

In long pipe runs, water can cool below 50°C in sections distant from the cylinder, creating conditions where Legionella can proliferate — this dead volume or stagnant water is a significant risk in large buildings.

What is the minimum cold water temperature required to prevent Legionella growth?

Answer: Below 20°C throughout the cold water system

Cold water must be kept below 20°C throughout. Temperatures between 20°C and 45°C are the danger zone for Legionella growth; above 60°C the bacteria are killed.

What is an unvented system's 'line strainer' and why is it fitted?

Answer: A filter on the incoming supply that prevents debris from reaching and blocking safety valves and the cylinder inlet

The line strainer filters particulate matter from the incoming mains supply, protecting the expansion valve, check valve and PRV from debris that could prevent them from operating correctly.

What is a combination storage water heater?

Answer: A unit that combines an instantaneous water heater with a small buffer storage vessel to improve flow rate

A combination storage water heater (combi store) uses a small storage vessel to buffer demand; the instantaneous heater pre-heats the stored volume so full hot water flow is immediately available at the tap.