Dunkirk Q95M-200 Modulating Condensing Boiler - Manual (Page 21)

Refer to Repair Parts Manual for illustrations, and Control
Manual and Troubleshooting Guide for detailed sequence of
operation and troubleshooting guide.
11.1 Aluminum Heat Exchanger
• Monoblock design cast aluminum heat exchanger
eliminates need for mating sections eliminates leaks
between sections.
• Cast aluminum has better heat transfer properties
which leads to higher efficiency and cooler exhaust
temperatures.
• Cooler exhaust temperatures create condensation of
flue gas, which would cause corrosion in traditional cast
iron heat exchangers.
11.2 Main Power Switch
Main power switch is located on the display panel. Main power
switch is illuminated when receiving power and in ON position.
11.3 Modulating Boiler Control
Integrated modulating control senses load necessary
to heat structure and therefore uses less fuel than
conventional fixed firing rate boiler when there is lower
than peak demand for heat.
Control senses supply water, return water, and outside
air temperatures. If outside air sensor is connected and
calculates load on system it adjusts firing rate to deliver
amount of heat needed at that particular time.
11.4 NTC Sensors
NTC sensors measure supply water, return water, and
outside air temperature. Configured to operate with
modulating boiler control.
11.5 Modulating Blower
• Modulating blower provides introduction of gas/air
mixture through burner and into combustion chamber
then out exhaust vent where combustion products are
discharged to outdoors.
• Blower is designed to communicate with modulating
control to run at variable speeds dependent on heating
system heat load.
• Variable speeds create pressures felt by gas valve and
gas/air mixer that dictate how much fuel is introduced
to combustion process.
11.6 Gas Control Valve
• Boiler gas controls have been developed for domestic
heating appliances with premix burners and automatic
direct burner ignition and are suitable for natural and
LP gas.
• Gas controls perform all functions required to safely
regulate gas flow to main burner of boiler.
• Gas valve is directly connected to gas/air mixer.
11.7 Gas/Air Mixer
Venturi design of gas/air ensures correct mixture of air and
gas.
11.8 Modulating Burner
Burner is designed to operate over full range of input.
Burner can operate under normal (blue flame) and infrared
conditions.
11.9 Direct Spark Igniter (DSI)
Boiler uses DSI to ignite fuel/air mixture in combustion
chamber and sense flame during operation. DSI is durable,
reliable, and resists breakage.
11.10 Manual Reset Low Water Cut Off
• Installed integral low water cut off (LWCO) must be
manually reset if there is a low water condition.
• LWCO senses water through probe at boiler top that
sends signal through water to ground. If the signal is
not sensed LWCO enters lockout mode that disables
boiler.
• LWCO in normal mode illuminates red indicator light on
LWCO panel in boiler.
• During low water condition, red light goes out and
LWCO and control reset buttons on display panel must
be pressed to reset LWCO.
11.11 Normally Closed LWCO Switch
• Round button switch located next to digital display is
normally closed and spring loaded, when depressed will
open, when pressure is removed closes.
• Switch is used as manual reset for LWCO. LWCO will
remain in lockout when tripped until water level reaches
probe and switch is pressed to open state and then
released to closed state, which sends signal to LWCO to
resume normal operation.
• Boiler control reset button must then be pressed to
reset from low water condition. LWCO switch and
control reset button are located on boiler panel display.
11.12 High Limit Control
• High limit control is safety limit control provides
protection for boiler and heating system from unsafe
operating conditions which could damage the boiler.
11 - CONTROLS AND ACCESSORIES
21