MHS Boilers Ultramax 115, Operating & Maintenance Manual, Page: 11 / 46

MHS Boilers Ltd ©
011204 11
Frame [17]
The frame is constructed from steel profile sections and is fitted with vibration absorbing adjusting
feet [16].
Casing [1]
The casing consists of easy-to-remove panels. Once the cover has been opened (using tools), all
other panels can be removed without using tools.
The electrical section
This includes the control and safety circuits for the unit.
Connecting terminals [23]
The boiler power supply, the connecting terminals, the pump connection and the pump relay are
all fitted in the top of the boiler. The terminal strip is located under the cover, on the right hand side.
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 “service operation” mode having been selected
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 fan, thus controlling the fan
speed. Depending on the quantity of air displaced by the fan, the proportional pressure regulator
will add the corresponding quantity of gas. In this way, the boiler power is continuously modulated,
enabling the boiler to accurately follow the demand for heat. The fan is equipped with a
speed feedback, enabling an even more accurate control behaviour.
Once the supply water temperature exceeds the desired value, the unit will shut down. As soon as
the supply water temperature falls below the set value, the boiler restarts.
2.4 Safety aspects
The boiler contains the following safety components:
- Flame protection (1x re-start)
- Water flow protection
- Maximum water temperature protection
- Gas valve test
- Fan protection
- Overload and underload protection.
If one of these components operates, this results in a lockout fault. Lockout faults can only be
cancelled by resetting the unit.
3 Safety
Installation instructions
Read through these instructions carefully before starting the installation.