LAARS Mighty Stack MS-080 (Sizes 199, 300, 399) - Install and Operating Manual - Manual (Page 24)

Laars Heating Systems Page 24
7.2.4 Manual Reset High Limit Control
The high limit switch is a manual reset, non-
adjustable switch with a remote bulb-type sensor.
Switches are set at 200°F (93°C).The control is located
behind the front door, on a panel in front of the blower.
The probe is in the outlet side of the header.
To reset the switch, unscrew the black cover that
is over the reset button, and push the button. Replace
the cover after the switch is reset.
To replace, shut off power to the appliance.
Remove the cover that is over the button, and remove
the nut that is around the button. Pull the control
through the panel, and remove the spade terminals.
Replace in reverse order.
7.2.5 Ignition Control
The ignition control controls the hot surface
ignitor and proves that the flame signal is appropriate
for powering the gas valves. It also controls the
blower’s pre-purge and post-purge.
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.
7.2.6 Ignitor
The ignitor used is a 120v “Hot Surface” type.
It is energized whenever there is a call for heat and
switched off when ignition is established and the flame
has been sensed. To replace the ignitor, shut off the
120-volt power to the appliance, remove the ignitor/
burner 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. To avoid injury, handle the ignitor
with caution.
Attention
Le dispositif d’allumage devient très chaud.
Manipulez le dispositif d’allumage avec précaution.
7.2.7 Transformer
The Mighty Stack’s transformer is not capable of
supplying control voltage for external devices, which
must have their own separate power supply. 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.
7.2.8 Flow Switch
The Mighty Stack uses a paddle-type flow switch
to ensure that the unit has water flow before ignition is
allowed. To replace the flow switch, turn off the 120-
volt power to the appliance. Isolate the water heater or
water heater from the system by closing the isolation
valves.
Caution
Water may be hot enough to scald. Allow water to
cool before proceeding.
Attention
L’eau peut être chaude au point de vous brûler.
Laissez refroidir l’eau avant d’intervenir.
Release pressure in the system by actuating the
pressure relief valves or field supplied water heater
drain valve. Remove cover from the flow switch
and disconnect the wires. Unthread the flow switch
from piping. Ensure the new flow switch paddles
are trimmed to the same size as the original paddles,
and reinstall in the reverse order. For water heater
and other static pressure systems, restore the system
pressure to the original setting, (or 10 psi minimum).
7.2.9 Heat Exchanger Coil
WARNING
Black carbon soot buildup on a dirty heat exchanger
can be ignited by a random spark or flame thereby
creating a risk of fire or explosion. To prevent this
from happening, dampen the soot deposits with a
wet brush or fine water spray before servicing the
heat exchanger.
AVERTISSEMENT
L’accumulation de suie sur un échangeur thermique
sale peut s’enflammer au contact d’une étincelle ou
d’une flamme et présenter un risque d’incendie ou
d’explosion. Afin d’empêcher que cela se produise,
humidifier les dépôts de suie à l’aide d’une brosse
mouillée ou par une pulvérisation fine d’eau avant
d’effectuer l’entretien de l’échangeur thermique.
The Mighty Stack has a premixed burner system.
These systems provide the burners with sufficient air
for complete combustion, and black carbon sooting is
seldom experienced. If sooting is suspected, view ports
for inspection of the heat exchanger are provided on
the side of the water heater. In the unlikely event that
there is a buildup of black carbon soot or other debris
on the heat exchanger, clean per the following:
1. Disconnect the electrical supply to the unit.
2. Turn off the gas supply by closing the manual gas
valve on the heater.
3. Disconnect and remove the wires, conduit and