LCD Series Finned Copper Tube Gas Boilers & Water Heaters – Boiler Manual
33
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 efficient trouble-free operation of the boiler.
Mount the thermostat to an inside wall at a height approximately
five feet above the floor.
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 drafty 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 setting may be necessary if the unit
cycles frequently. If the room temperature over-shoots the thermostat
setting, reduce the anticipator setting.
Operating Control
The preferred control setting for potable hot water is
130°F
,
54°C
.
The operating control should be set to the lowest setting that will
satisfy the consumer’s needs.
Setting the thermostat or operation control too high
can result in scalding resulting in severe personal injury!
High Limit (Aquastat)
The 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. The high limit can be reset by depressing the
reset button on the left jacket panel.
The 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 flow switch is provided in the water outlet piping to prevent the
boiler/water heater from firing without adequate water flow through
the heat exchanger.
Low Water Cutoff
If the boiler is to be installed above radiation or if required by other
codes or regulations, install a low water cutoff 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 cutoff device(s) will
function properly.
Flame Sense Module
The flame sense module is located in the control box. It is an
intermittent pilot control device that controls the pilot gas flow,
spark energy to ignite the pilot gas and the main valve(s) once pilot
ignition has been proven.
Two flame failure alarm terminals are provided on the flame sense
module. For CSD-1 these terminals are utilized to shut the unit
down in case of flame failure. The two terminals are connected to
a lockout control module located in the control box. This lockout
control module contains a magnetic latch relay that requires manual
reset when de-energized. To reset after flame failure, push and release
the momentary contact switch located on the left jacket panel.
Relay Board
The 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 fire to high fire. The delay enables the blower to
come up to speed before the high pressure side of the pressure
switch confirms proper air flow.
These 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.
