Tankless Water Heater 660 EF

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Tankless Water Heater 660 EF

Tankless Water Heater 660 EF

The Therm 660 EF is compact enough to install virtually anywhere. But don’t let the size fool you. This model is loaded with features including freeze protection and built-in high temperature capability (160°F).

Therm 660 EF Specifications:

  • Non-Condensing
  • Residential or Commercial Application
  • Max Input (BTU) 140,000
  • Min Input (BTU) 20,000
  • Capacity at 35°F Rise (gpm) 6.6
  • Capacity at 55°F Rise (gpm) 4.2
  • Min Flow Rate 0.5 gpm
  • Temp Range (°F) 100 - 160
  • Temp Stability (°F) +/- 2
  • Default Temp (°F) 120
  • Energy Factor .82
  • Thermal Efficiency 83%+
  • Installation - Indoor
  • Dimensions (w x h x d) 14" x 20½" x 7"
  • Weight (lbs.) 36
  • Inlet Connection ¾" NPT
  • Outlet Connection ¾" NPT
  • Gas Connection ¾" NPT
  • Max Water Pressure 150 psi
  • Min Water Pressure 30 psi
  • Min NG Presure 4" WC
  • Venting - Stainless Steel
  • Vent Maximun Run 35'
  • Energy Star Rated

Features and Benefits:

  • Super compact 14" x 20½" x 7" size
  • 83%+ thermal efficiency
  • 140,000 BTU maximum input
  • 6.6 gallons per minute capacity at 35F degree rise
  • Minimum activation flow rate of 0.5 gallons per minute
  • Electronic ignition
  • Built in freeze protection
  • Vents vertically or horizontally with 3” or 4” stainless steel
  • Can be used in recirculation and space heating applications
  • Backed with 15-year warranty
  • Also available as an outdoor model, 660 EFO


  • 15 year limited warranty on heat exchanger; 3 year warranty if used in direct recirculating applications
  • 15 year warranty on heat exchanger if used if recirculated through a storage tank, 5 year warranty on all other parts


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