U.S. Boiler Company SERIES 3, Installation, Operating And Service Instructions

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Series 3
Boiler Model Input (MBH) DOE Heating Capacity (MBH) Net AHRI Rating (MBH) AFUE (%)
303B 70 59 51 84
304B 105 88 77 84
305B 140 117 102 84
306B 175 146 127 84
307B 210 176 153 84
308B 245 205 178 84
309B 280 234 203 84
Ratings
SPECIFICATIONS
Boiler
Model
Depth Width Height
Supply NPT
(inch)
Return NPT
(inch)
Vent
(inch)
Gas NPT
(inch)
Relief Valve
NPT (inch)
Drain
NPT (inch)
303B 33 12¾ 41 1¼ 1¼ 4 ½ ¾ ¾
304B 33 15½ 41 1¼ 1¼ 5 ½ ¾ ¾
305B 33 18½ 41 1¼ 1¼ 6 ½ ¾ ¾
306B 33 21½ 41 1¼ 1¼ 6 ½ ¾ ¾
307B 33 24¾ 41 1¼ 1¼ 7 ¾ ¾ ¾
308B 33 27¾ 41 1¼ 1¼ 7 ¾ ¾ ¾
309B 33 30¾ 41 1¼ 1¼ 8 ¾ ¾ ¾
Dimensions and Connections
Electrical Requirements: 120VAC, 60 hz, 1-ph, 15A
Maximum Allowable Working Pressure - 50 psi. Boiler shipped from factory with a 30 psi relief valved.
Boiler Model
Allowable Supply
Water Temperature
(°F)
Minimum Return
Water Temperature
(°F)
Minimum Flow
(GPM)
Waterside Pressure Drop
at 20°F
D
T
(Ft. of Head)
303B 130-220 110 None <1
304B 130-220 110 None <1
305B 130-220 110 None <1
306B 130-220 110 None <1
307B 130-220 110 None <1
308B 130-220 110 None <1
309B 130-220 110 None <1
Water Temperatures and Flows
Boiler
Model
Shipping Weight
(lbs)
Empty Weight
(lbs)
Water Content
(gal)
303B 254 180 2
304B 304 231 3
305B 357 284 4
306B 405 332 5
307B 462 382 5
308B 518 438 6
309B 564 484 7
Weights and Volume