How do I determine what I need?


  • Heat Loss Requirement – You must know reasonably well your building “Heat Loss” (heating requirement), preferably by calculation.  Refer to our “Using a Heat Loss Calculator” Blog for more detail.  If replacing a boiler, don’t assume the same size is required by merely reading off the current unit nameplate! Building efficiency improvements (insulation, doors, windows, etc.) have effectively reduced your boiler size requirement over the years – and it was probably generously sized by practice at prior installation.  If your architect/builder/heating-engineer can’t provide a calculation – go on-line and use the several available!
  • DHW (Domestic Hot Water) Requirements – DELTA-T ECM Hydronic (FHW) Heating Appliance™ system boilers have no internal DHW Coil provisions as you may currently have!  They are “Heat-Only” Boilers to attain their efficiencies.  However they can supply DHW with an Indirect Water Heater at field installation, current or future.  The Indirect Water Heater by design provides the ultimate in DHW generation efficiency.  Sizing is typically determined by number of baths, bedrooms, family size and additional DHW requirements.  (You could also retain your current separate DHW heater — your choice.)
  • Number of Zones – Specify the number of heating zones (thermostats) required both currently and planned (plus one for DHW).  Measure and detail the pipe sizes supplying to and returning from all of your zones.  Residential zones are typically ¾” or 1” supply and return piped.  Indirect Water Heaters typically require 1” piping.
  • Installation Placement – System Dimensional Details must be qualified for installation compatibility.  A lot of flexibility is afforded in our design.  Installation into a lower height clearance site for instance can be accommodated by design modification, utilizing an on-floor expansion tank (option) if necessary.
  • Access Restraints – Refer to our System Dimensional Detail and determine:
    • Can you get it into the building, and safely?  Check widths (26″) and weights in particular!  These systems knock down vertically, so access height is usually not an issue, but weights on stairs can be! The Weil-McLain UO is the HEAVIEST RESIDENTIAL BOILER ON THE MARKET!
    • Door widths and swings must be qualified.
    • Surface quality across yards, etc.
  • The Weil-McLain Boiler Replacement Guide (link) is an excellent planning resource, and we highly recommend it!

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