LAARS HP-M2 Series - Installation, Operation and Maintenance Instructions - Manual (Page 27)

H Series Page 27
possible to check for cross contamination in another
way. Loosen the top clamp on the air duct coupling
and remove the gas balance line from the “Tee
fitting”. Lift up the air induction elbow and twist it to
the side so that air from the space around the boiler
can be drawn into the air duct coupling (do not disturb
the air orifice in the coupling). Cover the air induction
elbow with your hand or plug it with a rag and restart
the boiler. If no short cycling occurs there is a leak in
the 3" flue pipe which must be corrected. Do not leave
the boiler operating in this manner. Reassemble the air
duct after removing plug (rag) and connect the balance
line and stack switch tubes. Disassemble flue and fix
leak.
12G. Lock Outs
Integrated Boiler Control Lock Outs
Possible Causes
a. Cross Contamination
b. Moisture in Combustion Chamber
c. Gas Valve Malfunction
d. Poor combustion
e. Boiler control malfunction
f. Control contact failure
1). Stack Switch
2). Operating Control
g. Failure of air source
h. Igniter failure
If cross contamination is suspected see “Cross
Contamination” and check for it. One percent CO2 in
the air duct can cause nuisance lockouts.
Moisture in the combustion chamber will also
cause lock outs by weakening the flame signal to the
boiler control. It should be suspected if the boiler
temperature does not rise above 160°F during long
periods of operation. This condition can be caused by
a defective thermostat in the thermostatic union of
H(P)-M2-series boilers (or the omission of the
thermostatic union at installation) or an improperly
wired system circulator on HW-M2-series boilers. On
sidewall vented units moisture can get into the
combustion chamber from a flue pipe that is pitched
incorrectly (back toward the boiler without a
condensate trap). Quick Vented systems should
always pitch down from the boiler.
A defective gas valve (one that doesn’t always
open properly) can cause a nuisance lockout however
occurrences of this are rare.
A more common cause of nuisance lockouts is
poor combustion. If there is an odor in the flue gases,
this should be suspected. Check CO2 or O2 to
determine if combustion is within limits. Poor
combustion causes a weak flame signal to the burner
control and lock outs may result.
If combustion is within limits and none of the
causes mentioned above seems to be the cause of the
lockout it is possible that the boiler control may be
defective.
SECTION 13.
Sequence of Operation
On a call for heat from the room thermostat on
H(W)-M2 series boilers (or the low limit on the HW-
M2 series), the pump operates and the boiler control is
energized through the operating control, pressure
switch and the safety limit. It checks to ensure that the
stack switch contacts are open and then energizes the
blower. The blower starts and the air pressure
increases until the stack switch contacts close and the
red “PURGE” light lights. The pump and blower
continue to run and for 15 seconds the red “PURGE“
light stays on. Following that the red “PURGE“ light
goes out, the red “igniter” light lights and the igniter
heats for 20 seconds. At the end of the 20 seconds the
red "VALVE\FLAME" light is lit and the gas valve
is energized. For 2 seconds the valve and igniter are
energized and burner will ignite. Following this the
igniter is deenergized and the red “IGNITER” light
goes out and the pump and blower continue to run and
the burner operates under the supervision of the boiler
control. If for any reason the full sequence is
completed and the burner doesn’t ignite, the sequence
will be repeated after a blower “on “ time of 45
seconds (30 seconds post purge and 15 seconds
prepurge for the next cycle). During this part of the
sequence the igniter remains on for 30 seconds and the
balance of the sequence is unchanged. If no ignition
occurs again a third cycle will follow with the same
sequence as the second. After the third “trial for
ignition “ if the burner does not ignite the system will
“lock out” and reset can only be accomplished by
momentarily switching the power off. At the end of a
heating cycle (either space heating or domestic water
heating) after the gas valve is deenergized the blower
will continue to run for a 30 second post purge.
If normal burner operation during a heating cycle
is interrupted by any of the limit controls the unit
pump will continue to run and the blower will
continue to operate for a 30 second post purge.
TROUBLE SHOOTING (DETAILED FLOW
CHARTS ON PAGES 28-34).
If the burner “locks out” for any reason the cause
will be indicated by one of the following lights.
CODE
GREEN "POWER" No light - no power or
Light on - see trouble shooting section.
OUT OF
PRODUCTION