It is estimated that 90% of H&V control systems in buildings are inadequate. This costs industry and commerce £500m p.a. in additional costs (Dept. of Environment) As HVAC design engineer I normally concentrate on the hardware of the heating system and allow design specialists to take care of detail design of controls. How does Marshall/Milton controllers allow designers to have greater command of control requirements and embrace control of not just boilers but also other control periphals such as averaging room temp sensors, outside air temp sensors, motorised valves etc. ?
The Hamworthy range of boiler sequencer controls (Marshall / Milton) are a means of controlling the primary circuit within a commercial heating system. Accordingly the functionality of the control is limited to the primary loop circuit which, in a simple system, could prove adequate. Hence the functionality in these controllers includes time control, primary circulating pump control, optimised or compensated performance based on internal/external sensors and remote overides.The compensation action is directly on the boilers, it will not drive an external mixing valve.

Invariably most boilers rely on constant flow to obtain optimum performance, those which can cater for variable flow, do so under their own controls which cannot be overidden by external influences.

The use of modular boilers to satisfy heating loads brings with it the dilemma of how to control the modular boilers. The Hamworthy range of boiler sequence controls gives the flexibility of control philosophy to the system designer by, depending on the equipment (simple on/off, two-stage high/low or fully modulating), allowing the boilers to operate at their most efficient.

On more sophisticated systems, with a BMS controlling the building, there is still a role for the sequencer to provide the optimum sequencing mode in response to a demand from the BMS, hence achieving better system performance. Otherwise the BMS software engineer would have to program/ configure the system to sequence the boilers specific to the application.

They are not boiler experts and we are not building control experts, however, working together in this way, the client would benefit from improved heating controls.

Source

Building Sustainable Design