Crown Boiler 24-07 用户手册

48

of installation.

5.  ON WATER BOILERS WITH TANKLESS 

HEATERS, set low limit operating control dial at 

190°F and high limit dial 210°F.  Operating control 

must be a minimum of 20° below high limit setting.  

Set differential at 25°.

  ADJUST BURNER according to the Burner Manual.

1.  FLAME FAILURE
  The Series 24 boiler controls operate the burner 

automatically.  If for unknown reasons the burner 

ceases to fire and the reset button on the primary 

control is tripped, the burner has experienced 

ignition failure.  Before pressing the reset button, 

call your serviceman immediately.

Set-Up and Operation – The return temperature 

control (RTC) is an important part of the overall boiler 

system.  The primary function of the RTC is to protect 

the boiler from thermal shock and sustained flue gas 

condensation.  The RTC monitors the temperature of 

the water returning into the boiler through a return 

sensor.  The RTC controls the 3-way diverting valve 

mounted on the supply of the boiler to prevent return 

water less than 135º F from entering the boiler.  The 

boiler circulator provides constant and minimum flow 

through the boiler during every heat demand.  Prior 

to the start of any boiler cycle, the diverting valve is 

closed to a full by-pass condition, forcing 100% boiler 

water re-circulation.  The diverting valve opens and 

will continue to open provided the return sensor is 

satisfied.  Conversely, large temperature drops will 

close the diverting valve to a position as to prevent 

low temperature return water.  The RTC along with 

the ancillary components must be properly installed 

as identified in Section III, if there is any possibility 

of system return water temperature less than 135°F.  A 

detailed description of the controller and it’s features 

can be found in the RTC Installation and Maintenance 

Manual.
1.  Initial Start-up - Upon initial start-up, the control 

will be energized, identifying the control name and 

revision on the LED display.  If wired properly, the 

control should be energized at all times.  The RTC 

circuit should be supplied from a different source 

than the burner or boiler circuit.  The RTC control 

should be energized at all times.

2.  Testing – The RTC should be tested on initial start-

up, as well as during any troubleshooting exercise.  

Depressing the test button will activate a test 

sequence and energize the red test light on the front 

of the control.  Each of the controllers outputs and 

relays will be energized and tested.  One may pause 

the test sequence at any time by depressing the test 

button.  See the RTC Installation & Maintenance 

Manual for a detailed description of the sequence 

and the potential error messages.  
a.  Return Sensor - The return sensor must be 

properly connected or an error message will be 

displayed.  Both a short and an open circuit in 

the sensor circuit will cause an error message to 

be displayed and the valve will be moved to a 

partially open position until the error is resolved.

b.  Valve Actuator – During the valve actuator test 

sequence, confirm that the valve travels through 

90 degrees of rotation from a full closed position 

to a full open position.  The pointer on the shaft 

must rotate from “10” to “0” respectively.

3.  Adjust Setpoints – The RTC must have a number of 

setpoints adjusted for proper operation.  Below is 

a summary, however see the RTC Installation and 

Maintenance Manual for more details.  To activate 

the ADJUST menu, simultaneously depress and 

hold the Item,  and  buttons.  ADJUST will 

appear in the upper right hand corner of the LED 

display.
a.  ROOM - Set desired room temperature.  This 

will provide parallel shift to heating curve.  

OUTDR DESIGN OFF

b.  MIX TARGET – This represents a fixed target 

supply temperature when the outdoor reset 

feature in NOT selected. (OUTDR DESIGN = 

OFF)  Set the MIX TARGET temperature to the 

designed boiler supply temperature.  Example:  

If the boiler loop is designed to supply hot water 

to the system at 180ºF, set the MIX TARGET 

to 180ºF.  This is also the same as the operating 

aquastat set point.  The mix target is adjustable 

from 60°F to 200ºF.  The default setting is 180°F.  

NOTE:  This function is only for applications 

where the mix sensor is installed.

c.  MIX DSGN – Mix design temperature represents 

the design heating system supply temperature 

when the outdoor reset feature is selected. 

(OUTDR DESIGN = ON)  This represents the 

design of the system loop.  If unsure of the 

original design temperature, set the MIX DSGN 

to the same temperature as the boiler operating 

aquastat, typically 180ºF.  The MIX DSGN is 

adjustable from 70°F to 210ºF.  The default 

setting is 180°F.

d.  OUTDR DSGN – The outdoor design 

temperature represents the value used in the 

heat loss calculations, when the outdoor reset 

feature is selected. (OUTDR DESIGN = ON)  If 

this value is unknown, use the value found in