Raypak B0200, Owner'S Manual

Page: 7 / 40

7
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 14 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 14.
ELECTRONIC THERMOSTAT (ON/OFF MODELS)
On/Off models are fitted with an electronic thermostat that operates the gas control by switching its power on and
off, so a constant temperature is maintained. The thermostat is mounted on the control panel of the water heater
and the protective over temperature cut out is mounted inside the lower front cover of the water heater.
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 ope
n when the burner requires gas for heating. The thermostat may flash “AH” (alarm
high) and the current water temperature, or “AL” (alarm low) and the current water temperature. This is not a cause
for concern unless the temperature displayed is more than 1
0ºC above the set temperature. Refer to “
Diagnostic
Features of Electronic Thermostat
” on page 8. To adjust the thermostat settings refer to “
Temperature Control
” on
page 30.
MECHANICAL CONTROL (MODULATING MODELS)
Modulating models are fitted with a mechanical modulating gas control that varies the gas flow to the burner in
order to maintain a constant temperature. The temperature adjustment is on the body of the modulating control,
mounted inside the lower front cover of the water heater. The protective over temperature cut out is also mounted
inside the lower front cover of the water heater.
To adjust the thermostat setting refer to “
Temperature Control
” on page 33.
BURNER IGNITION
The water heater incorporates an automatic burner ignition system, incorporating an automatic pilot burner, which
lights the main burner gas when the thermostat registers a need for heating.
On/Off models have a hot surface igniter (HSI) that heats up when there is a call for heating. When the HSI probe
is up to temperature, a valve opens allowing gas to the pilot burner and this is ignited by the HSI probe. When
successful ignition of the pilot flame is detected, the valves open to supply gas to the main burner. If the pilot fails
to ignite after two attempts, the ignition system will lock out.
Modulating models have a spark generator that begins operating when power is applied and any external controls
call for the water heater to operate. At the same time a valve opens to supply gas to the pilot burner. After
successful ignition of the pilot flame has been detected, the valves open to supply gas to the main burner, when
there is a call for heating. If the pilot fails to ignite within 15 seconds, the ignition system will lock out.