LAARS EBP 175 MBTU/h - Installation, Operation and Maintenance Instructions - Manual (Page 30)

Page 30 LAARS Heating Systems
If the ignitor fails and the assembly must be
replaced, always install a new ignitor gasket with the
replacement assembly.
For sequence of operation, see Section 9.1 ,
Servicing.
Caution
Ignitor gets hot.
8.7 Transformer
The control transformer accepts 120 VAC line
voltage and provides 100 VA of 24 VAC control
voltage for the boiler control ONLY. It is NOT capable
of supplying control voltage for external devices such
as zone valves, which MUST have their own separate
power supply.
Should the transformer require replacing, shut off
the 120 volt power. Unplug the transformer wires from
the transformer, unscrew the two fixing screws and
remove the transformer.
Fit the replacement transformer in reverse order.
8.8 PWM Board
The PWM board converts the 0-10V modulating
signal that comes from the boiler control to the PWM
(pulse width modulating) signal that is sent to the
blower to control the blower speed, and hence, the
modulating point of the Endurance.
This board also converts 24V AC to 24V DC,
which is used to power the boiler.
To replace the PWM board, shut off the 120 volt
power. Unplug the two electrical connectors to the
PWM board. Depress the barbs on the four standoffs to
free the board, and pull it out. Replace in reverse order.
8.9 Blower
The combustion air blower is a high pressure
centrifugal blower. It is powered by a 24VDC motor
which is controlled by the boiler control with voltage
that has been converted by the PWM board. Its speed
will be varied according to the temperature of the
boiler flow.
If a blower change is required, turn off the 120
volt power and unplug the wires from the blower
motor. Remove the four nuts from the blower
discharge flange and the four screws that secure the
gas manifold to the gas valve. Remove the complete
assembly. Unscrew the combustion air inlet assembly
and register plate from the fan.
Fit the replacement fan in reverse order, ensuring
that all joints are made correctly and sealed.
After replacement the combustion should be
checked for correct air fuel ratio ( see Section 10 ).
8.10 Transfer Tank
The transfer tank contains approximately 20
gallons of boiler water. It functions as an energy
storage vessel to reduce boiler cycling on small output
heating zones and to provide additional heat for
domestic hot water through the domestic hot water
(DHW) plate heat exchanger.
If a tank change is necessary, access to the tank
is possible by removing the jacket’s front door. This
is done by removing the screws that hold the panel at
the top and lifting the panel away. Isolate the appliance
and drain down using the drain cock at the base of
the tank. Remove the tank sensor. Undo the union
and the pump flange bolts that connect the tank to the
boiler, unscrew the panel between the upper and lower
compartments, support the upper components and
remove the tank. Installation of the new tank is done in
the reverse order. After installation purge all air from
the boiler before restarting.
8.11 Cleaning the Boiler Coil
The Endurance is equipped with a premixed
combustion system. This type of combustion system
does not create free carbon (soot) except in very
rare instances and therefor the combustion chamber
coil will probably never need cleaning. If cleaning
is required, proceed as follows: valve off the boiler,
switch off the electrical power at the disconnect
switch, drain 1-2 gallons (4-8L) of water from the
boiler drain, remove the flue assembly from the top
of the boiler, remove the pump flange bolts from the
top pump flange, disconnect the sensor wires from the
sensors (boiler flow, return and safety limit), undo the
union nut from the boiler flow manifold, and remove
the four (4) screws from the bottom gas valve flange.
Unplug the blower and the ignitor. Remove the bolts
from the blower and pull the blower out. The boiler
assembly may now be removed from the jacket.
After removal of the boiler assembly from the jacket,
remove the ignitor and the burner from the combustion
chamber. Then, remove the four (4) long screws that
secure the top and bottom pans. Remove the air vent
and the top pan. Remove the insulation retainer and
the coil cover insulation. Clean the boiler coil with a
wire brush and vacuum debris from the combustion
chamber (avoid hitting the ignitor or the flame sensor
with the brush or vacuum hose because they are
fragile).
After cleaning, assemble the parts in the reverse
order, open isolation valves and bleed air from the
boiler and the system. Follow the lighting instructions
and start the boiler. Check operation.