Condensing boilers
are very efficient at part load conditions when high supply water temperatures
are not required; however, as always, there are unique items to consider when
designing around a condensing boiler:

• Condensing boilers require both an outside air intake flue and an exhaust flue; therefore, space for these flues must be considered. This is very important when you have multiple boilers.
• Condensate from each boiler must be treated (neutralized) prior to dumping into floor drains. Many boiler manufacturers now offer neutralizers as a built-in optional device.  If so, spec this option.
• Space must be considered; it is not uncommon to have many boilers side-by-side; thus, spacing of boilers and piping and flues, etc. becomes critical.
• Service clearance areas must always be considered.
• Each boiler’s gas load and gas pressure requirements must be coordinated with the plumbing engineer.  In addition, vents from gas trains must be routed to outdoors.
• Close coordination between boiler manufacturer’s recommended controls and the building’s BMS must occur.
• It is important to coordinate the sequence of operation with flow diagrams.
• Electrical engineer must be made aware of the boiler’s electrical requirements as well as providing emergency burner shut-off controls.
• Pulse with modulation type condensing boilers have special noise and vibration concerns that must be addressed in the design.  Carefully coordinate these types of requirements with the manufacturer’s sales representative.