L7124U UNIVERSAL OIL ELECTRONIC AQUASTAT® CONTROLLER
5
69-1232—2
OPERATION
High Limit Controller
The high limit opens and turns off the burner when the
water temperature reaches the setpoint. The high limit
automatically resets after the water temperature drops
past the setpoint and through the 15°F (8°C) differential.
Low Limit and Circulator Controller
On a temperature rise, with the adjustable differential at
the minimum setting of 10°F (6°C), the burner circuit
breaks and the circulator circuit makes at the low limit
setpoint. On a temperature drop of 10°F (6°C) below the
low limit setpoint, the burner circuit makes and the
circulator circuit breaks. See Fig. 5.
CAUTION
Equipment Damage Hazard.
Can cause improper operation
1. Setting the Low Limit above the High Limit
disables the device.
2. Setting the Low Limit less than 15°F (8°C)
below the High Limit results in improper
circulator function.
Fig. 5. Setpoints and differentials.
The L7124U can be in any of four operational states:
Normal, High-Limit, Low-Limit and Error. The controller
moves back and forth from High-Limit to Normal to
Low-Limit state as part of normal operation. However, the
controller enters only the Error state when there is an
abnormal condition such as an internal error or a bad
sensor. The operating states are:
1.
Normal: Boiler temperature has gone below the
high limit setting (minus the fixed differential) and
has not exceeded the high limit setting; or, the
boiler temperature has gone above the low limit
setting and has not gone below the low limit setting
(minus the fixed differential).
2.
High-Limit: Boiler temperature has gone above the
high limit setting and has not dropped below the
high limit setting (minus the fixed differential).
3.
Low-Limit: Boiler temperature has gone below the
low limit setting (minus the low limit differential) and
has not gone above the low limit setting.
4.
Error: The controller has detected an error
condition (e.g., open sensor) and has shut down
the burner output. The circulator and ZC output are
energized. The controller continues to function
and automatically restarts if the error condition
clears.
The operating sequence for the L7124U is shown in
Table 2.
CHECKOUT
Put the system into operation and observe operation
through at least one complete cycle to make sure that the
controller operates properly.
Table 2. L7124U Controller Operating Sequence.
LOW LIMIT
SETTING
HIGH LIMIT
SETTING
SWITCH BREAKS ON
TEMPERATURE RISE.
BURNER TURNS OFF.
CIRCULATOR OPERATES
ON A CALL FOR HEAT.
SWITCH MAKES ON
TEMPERATURE FALL.
BURNER OPERATES ON A
CALL FOR HEAT.
WITH NO HEATING
DEMAND, SWITCH BREAKS
ON TEMPERATURE RISE.
SWITCH MAKES ON
TEMPERATURE FALL,
BURNER IS ON TO
MAINTAIN MINIMUM
WATER TEMPERATURE.
CIRCULATOR IS OFF.
M21059
WHEN WATER REACHES LOW LIMIT SETTING, THE BURNER SHUTS
OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING FOR HEAT).
1
1
Action
System Response
Thermostat
calls for
heat.
Circulator starts when water temperature is
above low limit setting (if applicable).
Boiler temperature is checked.
Burner starts when water temperature is
below high limit setting and above low limit
setting.
Boiler
exceeds the
high limit.
Burner is turned off. Burner restarts when
the water temperature drops below the
high limit setting minus the differential.
Thermostat
is satisfied.
Circulator and burner turn off.
Error
condition.
When an error condition is detected, all
outputs except C and ZC are shut down.
Burner is off. Control continues to function
and restarts when error is corrected.
During the error check sequence, the
system checks for drift in the sensor and
corrosion in the connections.
Summary of Contents for L7124U
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