Central Heating System; Domestic Hot Water Mode; Frost Protection Mode; Pump Protection - Dunkirk DCBF-100 Manual

6.8 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.
By-pass (115,125)- Boiler incorporates an automatic
by-pass, However, where all radiators are fitted with
thermostatic radiator valves, an external by-pass must
be fitted.

6.9 Domestic Hot Water Mode

• Priority is given to the domestic hot water supply.
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.
Demand at tap or shower will override any central
heating requirement.
FIGURE 6-5
CH/System
Cold Water
Supply
6 - HYDRONIC PIPING
Pump
• Flow of water, certain minimums are required, will
operate the DHW flow switch which requests the
3 way valve to change position. This will allow the
pump to circulate the primary water through the
DHW plate heat exchanger. (DCCF-115, 150 & 205
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.

6.10 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.

6.11 Pump Protection

Pump will automatically operate for 1 minute in every
24 hours to prevent seizing.
35
240013375 REV A, [07/01/2021]