MHS Boilers Ultramax WM 100, Operating & Maintenance Manual, Page: 11 / 50

MHS Boilers Ltd ©
191007
11
Casing [6]
The casing can be removed easily in 3 units. To do this, refer to the section 2.2.1.
Electrical equipment
This comprises of the control system and safety devices of the boiler. The connection terminals are
installed in a fully sealed enclosure behind the control panel [21]. This panel can be tilted through
90
°
after removing the control panel bolt. This provides access to all the electrical connections,
without the need to remove the casing. Slide the front case up to reveal the boiler control panel.
2.3 Boiler control
If heat is required, the boiler will start, if all necessary conditions have been fulfilled and no
safety devices have been triggered. This heat requirement will arise if:
- The flow temperature of the boiler is less than the required flow temperature
- The manual option has been selected using selector switch set to:
- The frost protection has been triggered independently of the operating conditions (
, , ,
The integrated temperature controller adjusts the heat input inside the boiler by changing the fan
speed so that the desired temperature is reached and kept at a constant level. Depending on the
quantity of air displaced by the fan, a specific quantity of gas will be added. As a result, the boiler
capacity can be modulated seamlessly and the heat requirement can be accurately monitored. If
the flow temperature rises above the desired level together with any hysteresis, the boiler will
switch off. The boiler will start again as soon as the flow temperature falls below the desired level.
2.4 Safety aspects
The following safety devices are installed on the boiler:
- Temperature monitoring system
- High limit temperature monitoring system (STW)
- Limit temperature monitoring system (STB) (both are adjustable)
- Frost protection system. Using an external sensor, if the external temperature falls below 0
°
C. Based
on the flow temperature, if this is below 5
°
C and/or the domestic hot water temperature is below 10
°
C
- Flame monitoring by means of ionisation measurement
- Fan speed monitoring
- Flue gas temperature monitoring
- Flow monitoring using a combination of flow water temperature and flue gas sensor readings
If one of these safety systems is activated, the boiler will go to an interlocking or lockout fault and
will be switched off. Lockout faults can only be reset by pressing the reset button, after rectifying
the fault.