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6.7 Central Heating System
Boiler is designed for use in a sealed central heating system.
Design the system to operate with flow temperatures of up to
176°F (80° C), take pump head, expansion tank size, mean
radiator temperature, etc. into account.
Boiler is supplied with the following components: Pressure
relief valve - 30.0 psi (2.1 bar). Boiler internal pressure switch
will shut boiler off below 7.5 psi / 0.5 bar and above 43.5 psi
/3.0 bar.
Pressure gauge - to indicate the system pressure to be
maintained.
6.8 Domestic Hot Water Mode
Dunkirk Boiler DCCF-150 and DCBF-125 with indirect
WARNING
!
Burn, Scald Hazard! Water temperature over 125°F
(51°C) can cause severe burns and scalding. See
User's Manual before setting water temperature.
Failure to follow these instructions could result in death
or serious injury.
tank
• Priority is given to the domestic hot water supply.
Demand at tap or shower will override any central heating
requirement.
• Flow of water will operate the DHW flow switch which
requests the 3 way valve to change position. This will allow
FIGURE 6-6
CH/System
Pump
Cold Water
Supply
6 - HYDRONIC PIPING
the pump to circulate the primary water through the DHW
plate heat exchanger. (DCCF 150 only)
• Combustion fan will then come on and begin to run at
ignition speed.
• Once the fan reaches ignition speed the control board will
allow power to flow to the spark generator and gas valve
creating ignition in the combustion chamber. The flame
sensor will acknowledge the presence of the flame in the
combustion chamber and send a signal to the control
board.
• Temperature sensors will send a signal to the control board
allowing the control board to increase/ decrease the speed
of the fan. The combustion fan will in turn modulate the
gas rate accordingly.
• When the domestic hot water demand ceases the burner
will extinguish, unless there is a demand for central
heating.
6.9 Frost Protection Mode
Frost protection mode is integrated into the appliance when
electricity is connected to the boiler, regardless if power is "on"
or "off".
If temperature falls below 41°F / 5° C boiler will fire on its
minimum setting until flow temperature of 86°F / 30° C is
reached.
6.10 Pump Protection
Pump will automatically operate for 1 minute in every 24 hours
to prevent seizing.
29
240012564 REV A, [05/15/2019]
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