How Your Water Heater Works, Mains Pressure, Hi/Lo Operation

HOW YOUR WATER HEATER WORKS

The water heater consists of a gas burner, a combustion chamber lined with refractory tiles and a heat-exchanger made of finned copper tubes. Hot flue gases from the burner pass between the fins on the heat exchanger tubes and heat is transferred first to the fins and then by conduction into the water. Baffles are placed between the tubes to control the flow of the hot flue gases and ensure efficient operation of the water heater. The refractory tiles insulate the combustion chamber to minimise loss of heat and protect the surroundings from the temperature of the burner flames. The gas supply to the burner is controlled by a thermostat, which senses the temperature of the water.

Automatic safety controls are fitted to the water heater:

•to ensure safe ignition of the gas whenever there is a call for heating;

•to continuously monitor the burner flame; and

•to prevent excessive temperatures or pressures in the water system.

MAINS PRESSURE

In water heating applications, the water heater is designed to operate in conjunction with one or more hot water storage tanks, which would be connected directly to the mains water supply. If the mains supply pressure in your area exceeds the value shown in the table on page 15 or the maximum inlet pressure for the storage tanks, a pressure limiting valve must be fitted.

In mechanical and process heating applications, the system pressure must not exceed the value shown in the table on page 15.

109MODELS

On/Off Operation

109 On/Off models are fitted with a mechanical thermostat, adjustable from 0°C to 95°C that operates the gas control by switching its power on and off, so a constant temperature is maintained. The thermostat and the protective over temperature cut out are mounted on the control panel which is located behind the lower front cover of the water heater (refer to "Location of Controls" on page 29).

There is no need to switch the water heater off when it is not in use. The thermostat is fully

automatic and only allows the gas control to open when the burner requires gas for heating. To adjust the thermostat settings refer to “Temperature Control” on page 35.

Hi/Lo Operation

109 Hi/Lo models are fitted with a mechanical thermostat, adjustable from 45°C - 85°C that operates the gas control by switching its power from high fire to low fire and off, so a constant temperature is maintained. The thermostat and the protective over temperature cut out are mounted on the control panel which is located behind the lower front cover of the water heater (refer to "Location of Controls" on page 29).