Certain items must be integrated correctly into a boiler system at the design stage for it to operate as intended. Without proper design, followup, commissioning and maintenance, the system will not function as planned nor will it be energy efficient. 

Certain items must be integrated correctly into a boiler system at the design stage for it to operate as intended. Without proper design, followup, commissioning and maintenance, the system will not function as planned nor will it be energy efficient.

Parker Boiler Co., a Commerce, Calif.-based designer and manufacturer of all types of hot water and thermal fluid systems, suggests that system designers consider the boiler selection criteria below as they approach their next hot water system.
  • Safety.
  • Application.
  • Operational temperatures.
  • Efficiency.
  • Price.
  • Simplicity.
  • Durability.
  • Ease of maintenance.
  • Size constraints.
  • Operating hours.
  • Pressure and temperature requirements.
  • Venting requirement.
Parker Boiler also notes several important items that have to be addressed regarding the type of system being built.
  • Number of boilers vs. load size ― for example, one boiler at 100 percent of load or two boilers at 50 or 75 percent of load.
  • Design temperature and temperature rise through the boiler.
  • Coil DT and type.
  • Number and GPM of pumps.
  • Number of pumps to normally run.
  • VFD pump operation.
  • Methods of resetting the hot water system temperature, if desired, on the boiler, by primary or secondary pumping, three-way valve or by BAS.
  • Limit of HWS and HWR temperatures.
  • Ways to maintain boiler flow, such as three-way valves at terminal units, end of main(s) bypass per floor, end of main circuit setter, bypass valve (pressure actuated), primary or secondary pumping and runaround pump on boiler.
  • Flow-control valves on multiple boiler jobs.
  • Method and control strategy for starting and stopping system.
When determining the DDC interface and controls, here’s what needs to be included for a complete system, according to Parker Boiler:
  • Start and stop.
  • Alarm DC for any failure.
  • Burner “on” status indication.
  • Operating control function.
  • Control of modulating via 2 to 10 VDC or 4 to 20 mA signal.
  • Flow switch.
  • Reset of HWS temperature from BAS.
  • Lead lag system for boilers (normal or parallel lead lag control).
By addressing all the above, system users can expect an efficient and effective system, although Parker notes that in many instances, a designer will be dealing with an existing building, which may force their hand in the areas of system type, and venting and piping arrangements.

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