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Automatic Temperature Control (ATC)
• The automatic temperature control (ATC) is a feature
that utilizes a thermistor to regulate the water
fi
ll
temperature.
• The thermistor has a negative temperature
coef
fi
cient (as temperature increases, resistance
decreases).
• The thermistor is located in the outlet of the
fi
ll
funnel and will measure 50K
:
at room temperature
(77°F / 25°C).
• If the thermistor reads outside the expected range
(10K - 120K
:
), the main control will default to the
following pre-programmed
fi
ll temperature settings:
Tap Cold = cold water valve only
Cold = cold water valve only
Cool = hot and cold water valves
Warm = hot and cold water valves
Hot = hot water valve only
• When both valves are energized, the internal ori
fi
ces
in the valves meter the
fl
ow to a 60% cold and 40%
hot ratio.
• With the lid open, ATC is deactivated.
• Extreme water temperatures at low pressure can
cause the ATC to use its maximum number of
activations and revert to a preset
fi
ll routine. The
main control will not allow the water valve to cycle
more than 25 times per
fi
ll.
Resistance can be measured at the wire harness
located on the control board location J12. Make sure to
unplug the connector to isolate the thermistor before
taking resistance readings.
To determine the temperature of the incoming
water, the main control measures the difference
between the voltage sent and the voltage returned
from the thermistor. The main control then makes
temperature adjustments accordingly.
(Continued Next Page)
The main control should
fi
ll the tub with water within
+/- 10 to 15°F of set temperature by opening or
closing the hot and cold water valves.
To remove the ATC thermistor:
Note:
To replace the ATC thermistor; the entire unit
must be removed from its location.
1. Remove the entire unit from its location.
2. Remove the control panel. (See
Control Panel
.)
3. Remove the Phillips-head screw located to the
right of the harness entry.
Note:
The water inlet funnel is attached inside the
unit with 2 Phillips-head screws. The ATC sensor
wiring utilizes 3 wire ties.
Harness Entry
Wire Ties
ATC Temperature Chart
ATC Temperature Chart
Temperature Setting
Water Temperature
Tap Cold
Cold Tap Water
Cold
60°F ( +/- 10°F )
Cool
70°F ( +/- 10°F )
Warm
80°F ( +/- 10°F )
Hot
110°F ( +/- 15°F )
Summary of Contents for Spacemaker GTUP270EMWW
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