Frame [14]
The frame is constructed from steel profi le sections. Vibration absorption dampers are supplied
separately and must be fi tted after the unit has been placed in position.
The casing [27]
The casing consists of panels that can be removed easily without the aid of tools.
The electrical section
This includes the control and safety circuits for the unit.
Connection box [25]
The electrical power supply for the boiler, the terminals, the pump connections and the pump
relay are mounted in an easily accessible connection box. The supply cables can easily be fed to
the connection box via the cable duct inside the boiler [21].
2.3 Boiler control
The principle employed for the Boiler Management Unit is as follows: The boiler begins operating
on receipt of a heating demand. This heating demand is generated either:
A. If the measured supply temperature is lower than the desired temperature.
B. As a result of “manual operation” mode having been se lected (W1 or W2 ),
C. in standby mode, when the water temperature falls below the frost protection temperature.
After the unit has started up, the PID controller sends a signal to the frequency converter. This
converter controls the speed of the fan. Depending on the quantity of air moved by the fan, the
proportional pressure regulator ensures that the corresponding quantity of gas is added.
In this way the boiler capacity is continually adjusted and the boiler can accurately follow the
heating demand. If the boiler is operating at minimum capacity and the temperature of the supply
water rises above the desired value, the unit will be shut down. As soon as the temperature of the
supply water falls below the set value, the boiler will be re-started.
2.4 Safety aspects
The unit contains the following safety components:
- Flame protection on pilot and main burner (1x re-start)
- Water fl ow protection
- Maximum water temperature protection
- Gas valve test
- Fan protection
- Boiler pump motor over-heating protection.
If one of these components operates, this results in a lockout fault. Lockout faults can only be
cancelled by resetting the unit.
The unit is fi tted with a safety valve that opens at 3 bar.
