LAARS Mighty Therm2 MT2V (Sizes 500–2000 MBTU/h) - Install and Operating Manual - Manual (Page 30)

LAARS Heating Systems Page 30
Only genuine Laars replacement parts should be used.
Caution
Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and
dan-gerous operation. Verify proper operation after
servicing.
See Figure 5 for location of gas train components.
The gas and electric controls on the appliance are
engineered for long life and dependable operation, but
the safety of the equipment depends on their proper
functioning. It is strongly recommended that a qualified
service technician inspect the basic items listed below
every year.
a. Ignition controls
b. Ignitors
c. Water temperature control
d. Automatic gas valve
e. Pressure switches
f. Blowers
7.2.1 Burners
Close main manual gas valve before proceeding.
Checking the burners for debris - Remove the ignitor
inspection panels(s) and ignitor(s) and inspect the burners
through the ignitor hole(s) using a flashlight to illuminate.
If there is any indication of debris on the burners that
are visible, all the burners will need to be inspected
more thoroughly. Remove the screws from around the
front of the air box (large panel from which the ignitor
inspection panel(s) were removed), and remove the
large panel. Remove the gas manifold assemblies and
the burner panels. Inspect the burners. Clean burners, if
necessary, by blowing compressed air from the outside
of the burners into the center of the burner. A dirty
burner may be an indication of improper combustion or
dirty combustion air. Determine the cause, and correct.
Replace the burners in the reverse order
7.2.2 Filter
The filter used in the Mighty Therm2 is washable
with an 83% arrestance. Since the filter is washable,
it will only need replacement when unwashable,
deteriorated or damaged. If filter replacement is needed,
it should only be replaced with a factory part. Inspect
the air filter. If there is debris on the air filter, remove
it from the filter box, and wash it with mild soap and
water. Ensure that the filter is completely dry before re-
installing, in reverse order.
7.2.3 Gas Valves
The gas valves are designed to operate with supply
pressures of 4-13 inches w.c. (1.0 to 3.2 kPa).
To remove a valve, shut off 120-volt power and the
manual gas shutoff valve. Remove the top front panel
from the unit. Disconnect the wires to the valve. Disen-
gage the flanged fitting before and after the valve, and
remove the valve. Re-install in reverse order. Ensure
o-rings are properly installed for both inlet and outlet.
Turn on manual gas shutoff valve and 120 volt power
and check appliance operation and tightness of gas valve
connections.
7.2.4 Manual Reset High Limit Control
The high limit switch is manual reset switch with
an adjustable set point, up to 240°F (116°C) on boiler
models and 200°F (93°C) on water heater models
and boilers ordered with low temperature controls. To
replace the switch, shut off the 120-volt power to the
appliance. Remove the cover from the switch to access
the mounting screws. Remove the screws, and pull the
switch off the control panel. Remove the capilliary and
bulb from the thermal well located in the header. Replace
in reverse order.
7.2.5 Temperature Control
The temperature control is a Honeywell L6008. To
replace the control, shut off the 120-volt power to the
appliance. Remove the cover from the control panel, and
remove the mounting screws to remove the controller.
Replace in reverse order.
7.2.6 Ignition Controls
The ignition controls ensure the proved interrupted-
type ignition system. They control the hot surface
ignitors and prove that the flame signal is appropriate
for powering the gas valves. It also controls the blower’s
pre-purge and post-purge. Mighty Therm2 sizes 500 and
750 have one ignition control. Sizes 1000 to 2000 have
two ignition controls. On sizes up to 750, one ignition
control controls stages 1 and 2. On unit sizes 1000–2000,
one ignition control is for stage 1, and the other is for
stage 2.
To replace a control, shut off the 120-volt power to
the appliance. Remove the cover from the control panel.
Remove the electrical connectors from the ignition
control. Take out the controller’s mounting screws, and
pull the controller out. Replace in reverse order.
7.2.7 Ignitors/Sensor
The ignitor/sensor used are 120v "hot surface"
type. They are energized whenever there is a call for heat
and switched off when ignition is established and flame
has been sensed. Mighty Therm2 sizes 500 and 750 have
one ignitor/sensor. Sizes 1000 to 2000 have two ignitor/
sensors. To replace the ignitor/sensor, shut off the 120-
volt power to the appliance, remove the ignitor access
panel, disconnect the Molex connector, remove the two
mounting screws on the ignitor/sensor flange and pull the
ignitor out. ((Hot Surface) Ignitor and the Flame Sensor
are the same items). Install in reverse order, always using
a new ignitor gasket with the replacement ignitor.
Caution
Ignitor gets hot.