Instruction manual

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BOILER/WATER HEATER OPERATION
Staging Operation
 e LCD boiler/water heater series is separated into on/o and
2-stage units depending on the model selected.  e 225-400 models
have on/o staging, while the 600 through 2300 models have a
two stage option. Input staging is controlled from an aquastat
controller that signals the relays to select the blower and gas valve
modes. Per DOE mandate, the (LB225/300) operator control
incorporates an automatic means (outdoor reset) of adjusting the
boiler water temperature for hot water heating.  e boiler will not
operate without the outdoor sensor installed. Table 13 identi es
the stages and  ring modes associated with the standard single stage
units. Table 14 identi es the stages and  ring modes associated
with the two stage option.
Table 13 Firing modes (L225-L2300)
Stage Firing Mode
O O
1On
Table 14 Firing modes (L600-L2300)
Stage Firing Mode
O O
1Low Fire
2 High Fire
 e outlet water temperature is automatically controlled by the
aquastat.  e optional staging function is controlled by a return
water aquastat.  e return water aquastat utilizes inputs from the
inlet water temperature sensors or optional tank sensors to stage
the boiler/water heater as required.
Pressure Switch Settings
Di erential pressure switches are provided in the LCD to shut down
gas  ow under a blocked  ue or inlet condition. A single pressure
switch is used on the standard models. One low  re and one high
 re pressure switch is used when the two-stage option is employed.
 e low  re pressure switch serves to shut down gas  ow if there
is a blocked  ue or inlet condition during low  re operation. Similarly,
the high  re switches will shut down gas  ow if there is a blocked
 ue or inlet condition during high  re operation.  e di erential
pressure is taken between the air plenum and the pressure
inside one of the main burners.
Pressure taps are provided in the control compartment for taking
the di erential pressure readings, Figure 17. Table 15 lists the
di erential pressure se ings for all of the models.
Figure 17 Pressure switch tap(s)
Table 15 Differential pressure settings (all units)
Model
Di erential Pressure
Requirement at High Fire
(All Units)
Inches WC mm WC
225-300 1.0 ± 1.1 25.4 ± 27.9
400 0.7 ± 0.8 17.8 ± 20.3
600-2300 1.0 ± 1.1 25.4 ± 27.9
On all units, the pressure switch(es) will interrupt power to the
control module under a blocked  ue or inlet condition.  is will
cause the pilot and main gas valves to close. Tables 16 and 17 identify
how pressure switch control changes during boiler/water heater
staging. Tables 18 and 19 identify the control actions if a low air
condition occurs at any stage.
Table 16 Pressure switch control, L225-L400
Stage Pressure Switch Mode
O O
1 High Fire
Table 17 Pressure switch control, L600-L2300
Stage Pressure Switch Mode
O O
1Low Fire
2 High Fire