andrews L32/143 Installation Manual, Operation And Service Manual page 38

OPERATION
When properly installed and adjusted, the heater will require minimal attention. Should it
become necessary to completely drain the heater, close the cold water inlet valve and
open a hot water tap to allow air to enter the system. Fit a suitable hose to the drain cock
and open.
Whenever the heater is filled with cold water, condensation will form on the storage
vessel surfaces when the burner is lit. This is normal and will disappear when the heater
warms up.
The gas control fitted to the heater has a built-in limit thermostat (ECO). In the event of
high water temperature, the gas supply will be shut off automatically. The high
temperature condition must be identified and rectified before the heater can be relit. A
replacement gas control valve must be an identical model with the same code number
Robertshaw R110RTS.
Auto-Ignition Unit, Operating Sequence. Standard Range
1. When the control thermostat senses too-cool water, a signal is sent to the control
sequence unit.
2. Gas is allowed to pass to the pilot and simultaneous ignition begins.
3. When the pilot flame is established, the main gas solenoid is allowed to slowly open and
the main burners or burner is lit.
4. When the control thermostat is satisfied, both pilot and main gas solenoids are closed.
Operating Sequence
1. With the pilot lit, the solenoid coil holds the inlet gas port on the gas valve open.
2. The knob on the gas valve is set to the ON position.
3. The control thermostat is set to the desired water temperature, 49ºC to 82ºC (1200ºF
to 180ºF). To set the thermostat, remove the outer cover and turn the adjustment dial
to the required temperature.
4. The thermostat should now be in a closed position allowing the current generated by
the pilot-energised thermopile to open the main burner valve.
5. The gas valve has a slow burning feature. Burners will light several seconds after
setting the thermostat.
6. Burners will continue to heat water until the preset temperature is reached. As the
thermostat opens, the thermopile current is interrupted and the main gas valve will
close.
ECO (Energy Cut-Off)
The heater is equipped with an ECO (Energy Cut-Off) device, fitted to the control
thermostat. This is a temperature sensitive switch which opens at high temperature,
shutting off gas to the burners, including the pilot in an overheat condition. If the pilot
goes out and is associated with high water temperature, the ECO is probably operational
and the cause of overheating should be investigated.
Temperature Stratification (Stacking)
When small amounts of hot water are drawn repeatedly, the thermostat responds to each
feed of cold water and activates the main burners. Each time this occurs, more heat may
be put back in the tank than was drawn off. As this continues, water in the upper level of
the tank gets hotter than the thermostat setting. This hotter water does not mix
completely with the cold inlet water but rises in a 'chimney effect' to the top of the tank.
Many repetitions of this over a short time period result in accumulation of excessively hot
water in the upper part of the tank, even when the thermostat control is within limits.
This is known as stacking.
To counter this condition, an upper thermostat phial is fitted (not on Model L32/143)
which senses abnormally hot water and shuts down the main burner until the water cools.
Most modern commercial pipe installations include a circulating pump which keeps hot
water moving continuously throughout the heater. This stabilises temperatures in the
water heater tank and throughout the pipe system.
SECTION 5
STANDARD
RANGE
FOR AUTO
IGNITION SEE
BELOW
HI-FLO RANGE
33