RBI LCD Series Installation & Operation Manual page 24

Page 24
Open the make-up water valve and adjust the system
pressure if necessary. The system should be checked
and bled after three days of operation.
BOILER WATER HEATER
OPERATION
Staging Operation
The LCD boiler/water heater series is separated into on/
off and 2-stage units depending on the model selected.
The 225 and 300 models have on/off staging, while the
400 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. Table 12 identifies the stages and firing modes
associated with the standard single stage units. Table
13 identifies the stages and firing modes associated with
the two stage option.
Table 12 - Firing Modes (L225-L2300)
Stage Firing Mode
Off
1
Table 13 - Firing Modes (L400-L2300)
Stage Firing Mode
Off
1
2
The outlet water temperature is automatically controlled
by the aquastat. The optional staging function is
controlled by a return water aquastat. The 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
Differential pressure switches are provided in the LCD
to shut down gas flow under a blocked flue or inlet
condition. A single pressure switch is used on the
standard models. One low fire and one high fire
pressure switch is used when the two-stage option is
employed. The low fire pressure switch serves to shut
down gas flow if there is a blocked flue or inlet condition
during low fire operation. Similarly, the high fire switches
will shut down gas flow if there is a blocked flue or inlet
condition during high fire operation. The differential
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 differential pressure readings, Figure 17.
Table 14 lists the differential pressure settings for all of
the models.
LCD INSTALLATION AND OPERATION INSTRUCTIONS
Off
On
Off
Low Fire
High Fire
Figure 17 - Pressure Switch Tap(s)
Table 14 - Differential Pressure Settings (All Units)
Firing Mode
Optional Low Fire
High Fire
On all units, the pressure switch(es) will interrupt power
to the control module under a blocked flue or inlet
condition. This will cause the pilot and main gas valves
to close. Tables 15 and 16 identify how pressure switch
control changes during boiler/water heater staging.
Tables 17 and 18 identify the control actions if a low air
condition occurs at any stage.
Table 15 - Pressure Switch Control,
L225-L300
Stage Pressure Switch Mode
Off
1
Table 16 - Pressure Switch Control,
L400-L2300
Stage Pressure Switch Mode
Off
1
2
Table 17 - Low Air Condition Action,
L225-L2300
Stage
1 No Power to Flame Sense Module
Table 18 - Low Air Condition Action,
L400-L2300
Stage
1 No Power to Flame Sense Module
2 No Power to Flame Sense Module
Differential Pressure
Inches W.C. mm W.C.
0.7 ± 0.1 16.8 ± 2.5
24.9 ± 5.1
1.0 ± 0.2
Off
High Fire
Off
Low Fire
High Fire
Control Action
Control Action