OWB - Oil-Fired Water Boiler Series 3

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OWB - Oil-Fired Water Boiler Series 3

  • Efficiencies 86% - 87% AFUE
  • Enhanced control
    • Temperature limit control
    • LWCO Function
    • Thermal pre-purge function
  • Rear flue outlet
    • Top flue available with optional kit
  • Easy service
    • Swing-away burner door
    • Top access cleanout cover
    • Plug-in wiring harness
  • High efficiency oil burner
    • Solenoid valve
    • PSC motor
    • Solid state ignitor
  • Cast iron sections with built-in air separator
  • Insulated heavy-gauge steel jacket

Additional Information

Efficiency Rating Chart: 
Boiler Model Burner Input AHRI Certified Ratings Minimum Chimney Size
(x 15' High)

Heating Capacity MBH  

 Net Rating (water) MBH Seasonal Efficiency AFUE%
GPH MBH
Rectangle Round
OWB-3 0.70 98 86 75 86.4 8" x 8" 6"
OWB-3* 0.95 133 115 100 86.0 8" x 8" 6"
OWB-4 1.00 140 122 106 86.2 8" x 8" 6"
OWB-4* 1.20 168 146 127 86.0 8" x 8" 6"
OWB-5 1.20 168 147 128 86.1 8" x 8" 7"
OWB-5* 1.45 203 176 153 86.0 8" x 8" 7"
OWB-6 1.40 196 171 149 86.1 8" x 8" 7"
OWB-6* 1.75 245 213 185 86.0 8" x 8" 7"

* The specific higher input rates are compliant when installed with required High Input Damper kit, Part #381-800-515WT
(sold separately)

Williamson has determined the boilers listed below are compliant with ENERGY STAR® Program 3.0 when installed with (optional) OVD kit.
OWB-3-T-S3-D 0.70 98 86 75 87 8" x 8" 6"
OWB-4-T-S3-D 1.00 140 123 107 87 8" x 8" 6"
OWB-5-T-S3-D 1.20 168 148 129 87 8" x 8" 7"
OWB-6-T-S3-D 1.40 196 173 150 87 8" x 8" 7"