Honeywell Aquastat L7224U Series Quick Reference Manual page 4

System
Condition
Boiler is Display is ON;
cold, TT-LED is ON
house is B1 LED is ON
cold
Display is ON;
TT-LED is ON
Boiler is Display is ON;
hot, house TT-LED is ON
is cold C1 LED is ON
Display is ON;
TT-LED is ON
C1 LED is OFF;
ZC LED is ON
Display is ON;
TT-LED is ON
ZC 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.
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Golden Valley, MN 55422
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© 2006 Honeywell International Inc.
69-1957—1 Rev. 06-06
Table 3. Troubleshooting Guide
Diagnostic
Condition
b
c
Check
120 Vac at B1-
B2
Refer to err on
display
120 Vac at C1-
C2
Boiler below the
Low Limit
temperature,
wait for boiler to
go above Low
Limit
temperature.
Boiler above
LL? If yes,
check for 120
Vac between ZC
and L2
Honeywell Limited-Honeywell Limitée
35 Dynamic Drive
Toronto, Ontario M1V 4Z9
a
.
Action
• If no, replace control.
• If yes, check burner
and wiring
—
• 120 Vac at C1-C2,
check wiring to pump
• Wiring ok, is pump
running? If not,
replace the pump.
• If pump is running,
check for trapped air
or closed zone
valves.
• If no 120 Vac,
replace control.
• If yes, check zone
relays, circulators
and wiring.