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5
Operating Instructions
5.5
ECO (Energy Cut-Off)
5.6
Temperature Stratification (Stacking)
5.7 Thermostat and High Limit
43
The heater is equipped with an ECO (Energy Cut-Off) device,
fitted to the control thermostat. It is a temperature sensitive
switch which opens at high temperature, shutting off gas to the
burner in an overheat condition. When the water has cooled
sufficiently, the manual reset on the ECO needs to be depressed
to allow the heater to be re-lit. If the burner shuts down and is
associated with high water temperature, the ECO is probably
operational, and the cause of overheating should be
investigated.
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. The 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 results 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
which senses abnormally hot water and shuts down the main
burner until the water cools. Most modern commercial pipe
installations include a pumped secondary return system which
keeps hot water moving continuously throughout the heater. This
stabilises temperatures in the water heater tank and throughout
the pipe system.
LIMIT CONTROLS
Honeywell L6189A 2043B aquastat. Temperature adjustment
range: Below 40°C to maximum of 82°C (dial stop to limit
maximum temperature). Differential set to 4°C capillary bulb
inserts into well in top of tank. Thermostat dial adjustable on top
front section of water heater jacket.
Honeywell L6189C 2023 1 High limit control. Set point fixed to
93°C with screw. Mounted to control panel inside control
compartment. Capillary bulb inserts into separate well in top of
tank. Manual reset control button accessible through clearance
hole in control panel.
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