LAARS EBP 175 MBTU/h - Installation, Operation and Maintenance Instructions - Manual (Page 29)

Endurance Page 29
SECTION 8.
Maintenance and Component
Description
Figure 34 shows the location of the control
panel components. The parts sections show the other
components on the Endurance.
8.1 Unit Pump
The unit pump operates whenever there is a call
for heat or hot water.
It is a wetted-rotor type pump and should always
be filled with water when it is operating so that it will
cool properly.
If a pump change is required for any reason,
valve off the boiler and drain approximately 1 or 2
gallons (approx. 4-8L) of water from it. Turn off the
main disconnect switch and unplug the pump wires,
remove the pump motor. The pump housing need not
be removed. The replacement pump motor should be
installed in the reverse order from which the old pump
motor was removed. After filling the system be sure
the combustion chamber coil vents through the air vent
located on top of the boiler chamber (inlet manifold
extension).
8.2 Gas Valve
The gas valve is a 24VDC solenoid operated,
negative pressure regulated ratio valve. The outlet
pressure may be adjusted as described in the service
section. It is designed to operate with supply pressures
of 4-13 inches w.c. (1.0 to 3.2 kPa). To remove the
gas valve, shut off 120 volt power and the gas shutoff
valve, remove the 4 screws on the upper and lower
flanges and disconnect the wires from the gas valve,
the valve may now be removed. After the valve has
been removed, replace with a new valve in the reverse
order in which the old valve was removed. Turn on
gas shutoff valve and 120 volt power and check boiler
operation and gas tightness of gas valve connections.
8.3 Safety Limit Switch
The Safety Limit Switch is an automatic reset
switch with a fixed set point of 230°F (110°C).
To replace the switch, shut off the 120 volt power.
Disconnect the 2 wires from the quick connects at the
switch and remove the switch. To replace, perform the
same operations in reverse. Turn on disconnect switch
and check boiler.
8.4 Boiler Control
The Endurance uses an FX05 boiler control. The
control takes inputs from a domestic hot water flow
switch, an overheat thermostat (safety high limit),
external space heating switch, and temperature sensors
throughout the Endurance unit. Using these signals,
it works with the ignition control to ensure proper
and safe operation of the Endurance. It controls call
for heat, the modulating point for the blower, the
Endurance pump, and the signals that are sent to the
ignition control.
The control displays the supply temperature, by
default, and the user can access the heat exchanger
inlet temperature, tank temperature, heat exchanger
delta T, outdoor air temperature (if reset is used), and
all of the setpoint and differentials that are set on the
boiler. Seven (7) fault codes can also be displayed, for
diagnostic help.
To replace the boiler control, shut off 120V
power to the Endurance. Remove the two sheet metal
screws from the controller mounting bracket. Pull the
controller, attached to the mounting bracket out, to
access the electrical connectors.
Remove the electrical connectors from the
control. Pull out the tabs on the retaining clip, while
pulling the controller out through the front.
Replace in reverse order.
8.5 Ignition Control
The ignition control controls the hot surface
ignitor and proves that the flame signal is appropriate
for powering the gas valve. It also controls the
blower’s pre-purge and post-purge timing. It works
with the boiler control to ensure proper and safe
operation of the Endurance.
To replace the ignition control, shut off the
120-volt power to the appliance. Remove the cover
to the Endurance 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.
8.6 Ignitor / Flame Sensor Assembly
The ignitor is a hot surface ceramic composite
device. It is energized whenever there is a call for heat
and switched off when ignition is established.
The flame sensor is a remote sensing flame rod
which is connected directly to the ignition control. The
ignitor should read 50 to 100 ohms resistance when at
room temperature.
Figure 34. Control Panel.