How Your Water Heater Works - Raypak B0200 Owner's Manual

Hide thumbs

Table Of Contents

Table of Contents

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 open 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 10ºC above the set temperature. Refer to

Features of Electronic

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

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.