44
OPERATING THE BOILER - SYSTEM START-UP
To discourage unauthorized changing of Aquastat set-
•
tings, a procedure to enter the adjustment mode is re-
quired. To enter the adjustment mode, press the UP,
DOWN, and I buttons (see
Figure #22
) simultaneously
for three (3) seconds. Press the ‘I’ button until the fea-
ture requiring adjustment is displayed:
High limit
°F -- °C
Then press the UP and/or DOWN buttons to move the
•
set point to the desired value. After 70 seconds without
any button inputs, the control will automatically return
to the READ mode.
II.
display:
in the run mode
,
the Aquastat will flash “bt” (boiler temp.)
followed by the water temperature (i.e., 220), followed by
°F or °C. To read boiler settings, press the “I” key to read
the parameter of interest. For example, press I and HL
(High Limit) is displayed, followed by a three-digit number,
i.e., 220, followed by °F or °C. See
Table 9
for Display
Readout Definitions.
After approximately 60 seconds without any key pressed,
the display will enter a dim display mode. To return to the
bright display mode, simply press any key.
Control operating Characteristics
The L7248A can be in any three (3) operational states:
Normal, High Limit and Error. The controller moves back
and forth from High-Limit to Normal state as part of normal
operation. The controller will enter the Error state when
there is an abnormal condition. The operating states are:
Normal: Boiler temperature has dropped below the
•
high limit setting (minus the differential) and has not
exceeded the high limit setting.
High-Limit: Boiler temperature has risen above the
•
high limit setting and has not dropped below the high
limit setting (minus the differential).
Error: The controller has detected an error condition
•
(e.g., open sensor) and has shut down the burner out-
put. The controller continues to monitor the system
and automatically restarts if the error condition clears.
See
Table 10
.
TABLe 10: eRRoR Codes
Error
Code
Cause / Action
Err1
Sensor fault; check sensor.
Err2
ECOM fault; check EnviraCOM wiring.
Err3
Hardware fault; replace control.
The operating sequence for L7248A is described next
•
and shown in
Table 11
.
TABLe 9: AQuAsTAT disPLAy
TEXT
DESCRIPTION
DISPLAY
bt
Boiler Temperature
bt
HL
High Limit
HL
err
Error Code
Err
f
Degrees Fahrenheit
°F
c
Degrees Celsius
°C
Figure #22
Aquastat layout
