LAARS EDN Series - Installation, Operation and Maintenance Instructions - Manual (Page 31)

Endurance Page 31
Figure 35. Gas Valve.
8.11 Thermostatic Union (EDP/EDN)
The thermostatic union is a 1¼" NPTF union
which must be mounted at the flow outlet to control
boiler temperature. The union must be installed so that
union nut is on the boiler side of the connection. This
insures that the thermostat is properly positioned with
its spring facing up, toward the system. The element
has small bypass holes that allow some water to flow
into the system at all times. When the boiler first starts
and the element is closed, boiler water is re-circulated
back to the return until the supply water reaches
160°F (71°C). The element then modulates open. If
the temperature does not exceed 150°F (66°C) within
two minutes after firing, the element is not functioning
properly. To replace the element, shut off and drain
the section of the system adjacent to the thermostatic
union. Open the union and replace the element with
a new one. The element should be installed so that its
spring and actuator are facing the system side (up).
Close the union, open the valves, refill and bleed the
system. Ensure that air is venting from the air vent
on top of the boiler chamber and it is left operational.
Restart boiler.
8.12 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.
SECTION 9
Servicing.
9.1 Sequence of Operation
Figures 32 and 33 depict the flow paths and
temperature sensor locations for the space heating,
EDP/EDN, and the combined space heating and
domestic water heating, EBP, appliances.
The model EDP/EDN modulating boilers are
cold start boilers that will start only on a call for heat
from a room thermostat or zone control contact.
During normal operation the boiler control will
display the supply temperature. The Endurance call for
heat may come from any of the following:
1. Heating call for heat (TT) from thermostat, end
switch, etc.
2. Domestic water call for heat from domestic water
flow switch (EBP only).
3. Tank charge call for heat, when transfer tank is
less than 40°F (22°C) below the Off Point (EBP
only).
On a call for heat the following sequence will
occur.
1. For EBP units only, the anti-condensing valve is
put in the proper position.
2. The internal pump starts.
3. Blower pre-purge begins (7-seconds).
4. Boiler control sends the signal to the ignition
control that there is a call for heat.
5. After a self-check and 15 second ignition control
“pre-purge”, the ignition control begins the
ignitor warm-up period.
6. After the ignitor is warmed up, the gas valve
terminal on the ignition control is energized for
the 10-second trial for ignition.