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81Part number 550-141-850/0699
• Installation • Start-Up • Parts • Maintenance
CHART 8
— Insufficient heat or no heat to system (
POWER
light on steady)
Electrical shock hazard — Wherever you see
▲
TURN OFF POWER
▲
, follow the instructions. Failure to follow
instructions could result in severe personl injury, death or substantial property damage.
• Excessive block temperature has been reduced to safe
operating level. Check for low water level or mineral
deposits in sections. Correct before proceeding.
• Restart boiler and check normal sequence of operation.
(See normal sequence of operation, Figure 22.)
• Boiler is in standby.
• Set thermostat to call for heat
and recheck operation.
• Verify Sequence of operation,
Figure 22.
Replace control module.
Retest.
• Boiler water temperature exceeded setting on limit switch
with thermostat calling for heat. Boiler is OK. (See normal
sequence of operation, Figure 22.)
• Also check operation of setting on limit switch (should be
above 140˚F.).
• Has it been at least 5 minutes since setting thermostat to
call for heat? If not, wait 5 minutes. Is system heating?
• Is thermostat set to call for heat? Remove thermostat
wires at boiler and check continuity across the two wires.
If circuit isn't closed, check external thermostat (zone
valve, relay, etc.) wiring. Correct problems and retry.
• Reconnect external thermostat wiring at boiler.
Is thermostat circuit closed (continuity across wires)?
• If you have sufficient heat — boiler should be in normal
operating sequence. (See normal sequence of operation,
Figure 22.)
• If you have less than sufficient heat —
Is vent or combustion air piping free of blockage?
No Yes
• Correct conditions and
recheck operation.
• See Figure 22 for
normal sequence of
operation.
Contact your Weil-McLain
sales representative.
• Replace control
module.
• Retest.
• Repair/replace
circulator. Retest.
• Repair/replace
wiring. Retest.
• Remove CIRCULATORS harness plug from
CIRCULATORS plug receptacle (
Figure 34, Item
4
). Check with voltmeter across left-side 120 VAC
N and 120 VAC H pins of receptacle.
Does voltmeter show 120 VAC across pins?
No Yes
Is boiler System circulator operating?
• Wait 5 minutes.
Is
FLAME
light on?
No Yes
• Wait for boiler water to cool to temperature 20 to 30 ˚F
lower than temperature set on limit switch.
Are limit switch contacts closed?
• Check block switch on top of boiler with continuity
checker.
Are block switch contacts closed?
No Yes
Are all red lights off?
No Yes
Wait 30 seconds.
Are all red lights off?
No Yes
Replace block
switch. Retest.
Replace control
module. Retest.
• Check limit switch
contacts with continuity
checker.
Are limit switch
contacts closed?
NoYes
• Wait for cast iron block to
cool to room temperature.
Are block switch
contacts closed?
No
Yes
No Yes
No Yes
Replace limit
switch. Retest.
No Yes