Ten (10) Hydronic Rules of Thumb

Ten (10) Hydronic Rules of Thumb

Ten (10) Hydronic "Rules of Thumb"

  1.  PSI x 2.31 = feet of head (TDH, Total Dynamic Head) 
  2. GPM x Delta T x 500 = BTU/hour
  3. Pressure Drop for piping system = Linear Feet of Longest Circuit x .06
  4. Proper flow for boiler in GPM = Output BTU/hr divided by 10,000
  5. Static Height in feet / 2.31 + 4 PSI = Proper fill pressure
  6. Maximum Capacity:
    1. 1/2" Pipe = 1.3 GPM = 13,000 BTU/hr
    2. 3/4" Pipe = 3.5 GPM = 35,000 BTU/hr
    3. 1" Pipe = 7.5 GPM = 75,000 BTU/hr
    4. 1 1/4" Pipe = 12 GPM = 120,000 BTU/hr
    5. 1 1/2" Pipe = 20 GPM = 200,000 BTU/hr
    6. 2" Pipe = 45 GPM = 450,000 BTU/hr
  7. Maximum output radiant floor = 35 BTU / square foot
  8. Typical output snowmelt system = 125 BTU / square foot
  9. "ESTIMATE" for heat loss of "new building" = 35 BTU / square foot
  10. "ESTIMATE" for heat loss of "old building" = 50 BTU / square foot


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