Troubleshooting - Honeywell AQUASTATIC L7224 Series Technicianís Quick Reference Manual

Table 2. L7224 Controller Operating Sequence
Action
Thermostat
calls for heat.
Boiler exceeds
the High Limit.
Thermostat is
satisfied.
Error conditions
1-5.
Error conditions
6-7.
Error condition
8.

Troubleshooting

When attempting to diagnose system performance, reference the
LED display to help identify specific areas not working properly.
The LED display will scroll "err", followed by a digit (1-8). See
Table 1 for a description of the error and suggested actions. See
below for a troubleshooting guide.
System
Condition
Boiler is Display is OFF 120 Vac system
cold,
house is
Display is ON;
cold
TT-LED is OFF
Display is ON;
TT-LED is OFF
a
. Refer to Fig. 5 for Display and LED locations.
b
. ZC LED ON indicates ZC terminal power is OFF.
c
. ZC LED OFF indicates ZC terminal power is ON.
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.
Burner is turned off. Burner restarts when the
water temperature drops below the High Limit
setting minus the differential.
Circulator and burner turn off.
If an error condition is detected, all outputs
except 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.
If error condition 6 or 7 occurs, the control has
reset the High Limit, Low Limit and Differential
Setting to a default setting and will continue to
run at those settings. Performance of the system
will be degraded.
If the error condition is detected, all outputs
except ZC are shut down. Burner is off. Control
continues to function and restarts when all three
user keys have been pressed longer than 60
seconds.
Table 3. Troubleshooting Guide
Diagnostic
Condition
System Response
Check
power.
24 Vac T-T
24V present;
disconnect
thermostat,
short T-T
3
L7224 SERIES
a
.
Action
Turn system power on.
No 24V; replace
control
Boiler starts, check
wiring and thermostat
69-1957—1