Instruction manual
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CONTROL DESCRIPTION 
Boiler Thermostat 
If a thermostat is to be used to control the boiler always follow the 
instructions included with the thermostat. Proper location of the 
thermostat will ensure e  cient trouble-free operation of the boiler. 
Mount the thermostat to an inside wall at a height approximately 
 ve feet above the  oor. 
Avoid placing the thermostat in areas that will not provide an accurate 
measurement of the room temperature. Locating the thermostat 
behind a door, in an alcove, close to a source of thermal radiation 
or in a dra y area will cause poor or sporadic heating.
For a thermostat that employs an adjustable heat anticipator, adjust 
the anticipator to match the current measured in the thermostat 
circuit. An increased anticipator se ing may be necessary if the unit 
cycles frequently. If the room temperature over-shoots the thermostat 
se ing, reduce the anticipator se ing.
Operating Control 
  e preferred control se ing for potable hot water is 130°F, 54°C. 
 e operating control should be set to the lowest se ing that will 
satisfy the consumer’s needs.
 Se ing the thermostat or operation control too high 
can result in scalding resulting in severe personal injury! 
High Limit (Aquastat) 
  e high limit is located in the top control area of the boiler/water 
heater. A remote capillary bulb is run to a well on the outlet side 
of the supply header.   e high limit can be reset by depressing the 
reset bu on on the le jacket panel.
  e water heater high limit should be set a minimum of 20°F,
11°C higher than the operating control. Refer to the HOT WATER 
SUPPLY section for the proper supply water temperature.
Flow Switch 
A  ow switch is provided in the water outlet piping to prevent the 
boiler/water heater from  ring without adequate water  ow through 
the heat exchanger. 
Low Water Cuto 
If the boiler is to be installed above radiation or if required by other 
codes or regulations, install a low water cuto  in appropriate piping. 
Wire the switch and any external controls in series to the “Interlock” 
contacts in the control box, see the wiring diagrams included with 
the unit for details. Ensure that the low water cuto device(s) will 
function properly. 
Flame Sense Module 
  e  ame sense module is located in the control box. It is an 
intermi ent pilot control device that controls the pilot gas  ow, 
spark energy to ignite the pilot gas and the main valve(s) once pilot 
ignition has been proven.
Two  ame failure alarm terminals are provided on the  ame sense 
module. For CSD-1 these terminals are utilized to shut the unit 
down in case of  ame failure.  e two terminals are connected to 
a lockout control module located in the control box.  is lockout 
control module contains a magnetic latch relay that requires manual 
reset when de-energized. To reset a er  ame failure, push and release 
the momentary contact switch located on the le jacket panel.
Relay Board
  e relay board is located in the control panel. It provides sequencing 
of the gas valves and blower(s) based on the staging controller's 
input. It also provides the following time delays for proper unit 
operation:
•  A 10 second prepurge when stage 1 is energized.
•  A 30 second pressure switch sequencing delay when the blowers 
switch from low  re to high  re.   e delay enables the blower to 
come up to speed before the high pressure side of the pressure 
switch con rms proper air  ow.
  ese time delays are set within the separate time delay board 
connected to the relay board. 
Gas Pressure Switch 
Optional low and/or high-pressure gas pressure switches will shut 
down the 24V circuit if excessively high or low gas pressure exists 
in the gas train or supply piping.










