LAARS Mighty Therm2 MT2P (Sizes 500–2000 MBTU/h) - Install and Operating Manual - Manual (Page 22)

LAARS Heating Systems Page 22
surface ignitor(s) and prove that the flame signal is
appropriate for powering the gas valves. It also controls
the blower’s pre-purge and post-purge. MT2P sizes 500
and 750 have one ignition control. Sizes 1000, 1250,
1500, 1750 and 2000 have two ignition controls. On
these models, one ignition control provides for part-
load start-up and the second control brings the heater to
full rate, after the first control has started the part-load
burners.
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.
7.2.8 Ignitors
The ignitors used are 120v “Hot Surface” type.
They are energized whenever there is a call for heat and
switched off when ignition is established and the flame
has been sensed. MT2P sizess 500 and 750 have one
ignitor. Sizes 1000, 1250, 1500, 1750 and 2000 have
two ignitors. To replace the ignitor, 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 flange, and pull the
ignitor out. Install in reverse order, always using a new
ignitor gasket with the replacement ignitor.
Caution
Ignitor gets hot.
7.2.9 Ignition Sensors
The ignition sensors ensure that the main flame
is ignited, so that raw gas is not allowed to fill the
combustion chamber. The ignitors are the ignition
sensors on MT2P appliances. There are no separate
ignition sensors.
7.2.10 Transformer
The MT2P’s transformer is not capable of
supplying control voltage for external devices. Should
a transformer need replacing, shut off the 120-volt
power. Unplug the transformer wires, remove the
mounting screws and remove the transformer. Replace
transformer in the reverse order.
7.2.11 Blowers
The combustion air blowers bring the combustion
air for the MT2P from the upper chamber to the lower
chamber. Mixing of the gas and air occurs in the burners.
If a blower change is required, turn off the 120-volt
power and gas supply to the unit. Remove the front
panel. Disconnect the blower’s wire harness. Remove
the screws at the blower flange, and pull the blower out.
Replace blower in reverse order, ensuring that all joints
are made correctly. After replacement, ensure that the
Figure 13. Typical Gas Train Configuration.
7.2.4 Pool Loop High Limit Control
The high limit switch is an automatic reset switch
with an adjustable set point, up to 135°F (57°C). 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 capillary and
bulb from the thermal well located in the pool loop
adjacent to the heater outlet. Replace in reverse order.
7.2.5 Automatic Reset High Limit Control
An automatic reset high limit is used to limit
heater water from exceeding 210°F (99°C) (CSD-1
models will be equipped with a manual reset high limit
rather than the automatic reset version). The high limit
switch has an adjustable set point, up to 200°F (93°C).
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 capillary
and bulb from the thermal well located in the header.
Replace in reverse order.
7.2.6 Temperature Control
The temperature control is a single stage
electronic device. To replace control, shut-off the 120-
volt power to the appliance. Remove the cover, then
the low voltage wires and sensor wires (assuming the
sensor is functional). Remove the mounting screws
and pull the switch off of the control panel. Replace in
reverse order.
7.2.7 Ignition Controls
The ignition controls ensure the proved
interrupted-type ignition system. They control the hot