Hamworthy in control

For Experts Online, Hamworthy has chosen to take a stand on the potentially contentious issue of boiler failure, or as Hamworthy would phrase it, boiler system failure. Increasingly Building Management Systems (BMS) controls are attempting to control both the primary circuit (boilers) and secondary (DHW) circuits, and are often failing to achieve proper control of the boilers. Hamworthy is championing the cause for the boiler manufacturer to sequence the boilers (primary circuit) and the BMS to integrate control of the heating system (secondary circuits) for effective control of the boilers and maximum energy efficiency.

Hamworthy has nominated three 'industry experts' to take questions on the subject; Bob Walsh is Technical Director at Hamworthy Heating and has over 21 years experience in the gas industry with a vast knowledge and appreciation of the industry. Malcolm Gunn is Engineering Quality Manager at Hamworthy Heating and represents UK interests on the European Technical Committee to advise on Technical Standards for commercial boilers. Malcolm supports troubleshooting activity on site and experiences first hand the conflicts which often exist in controlling commercial boiler plant. Adam Clatworthy is one of Hamworthy's Project Engineers. Adam has particular responsibility for designing control solutions for multiple commercial boiler installations.

In the quest for increasing boiler efficiency, boiler controls have advanced considerably since the days of simple on/off operation. The progression from on/off burner control to two stage firing, known as high/low, was the first move towards greater combustion efficiency. Then Hamworthy developed a new sequencing philosophy with the introduction of low/high two stage firing on their Purewell Classic boiler, to maximise boiler efficiency by firing multiple boilers at low fire initially and through application of a primary flue damper, achieving a higher efficiency at part load, contrary to traditional approaches.

Finally, there is fully modulating control, which presents another variant on control of multiple boilers. Modulating boilers can be controlled in unison, where all boilers are sequenced to modulate to meet the load together, or in cascade mode, bringing each boiler through modulation in turn to meet the system demand.

Unfortunately in many cases where the BMS sequence controls are attempting to control boiler operation, in practice the boilers do not actually operate as intended. In fact, Hamworthy frequently finds boilers installed where the control system design is flawed and this often results in excessive switching of boilers on and off, causing undue wear and tear on the boilers and ancillary equipment, plus the failure to satisfy the building heating requirements. To achieve the full potential of system controls with respect to multiple boilers, the boiler manufacturer should sequence the boilers. To find out more or to test the theory, ask our experts.