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All Categories > Commercial Water Heaters > NON NOx Commercial Water Heaters > A.O. Smith® NON NOx Commercial Water Heaters > Master-Fit® Standard Draft Commercial Gas Water Heaters > Item # BTR-251 (A)  

Item # BTR-251 (A), Master-Fit® Standard Draft Commercial Gas Water Heaters

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Unit of Measure: Imperial Metric Both

Specifications  · Maximum Recovery (ºF)  · Maximum Recovery (ºC)  · Dimensions  · Features  · Testing and Certifications  · Other Master-Fit® Features  · Warranty  · Note



A. O. Smith®

Input Power

251000 BTU/hr

Tank Capacity

65 U.S. gal

Standard Shipping Weight

750 lb

ASME Shipping Weight

862 lb


Liquid Propane Gas
Natural Gas

Maximum Hydrostatic Working Pressure

160 psi

Thermal Efficiency

80 %

Maximum Gas Supply Pressure

14 inWc

Minimum Gas Supply Pressure

For Natural Gas: 4.5 inWc
For Liquid Propane Gas: 11

Manifold Pressure

For Natural Gas: 3.5 inWc
For Liquid Propane Gas: 10

Industry Standards

ANSI Z-21.10.3 - CSA 4.3

ASME Certified

CSA® Certified


UL® Listed

Maximum Recovery (ºF)

Recovery at 40 ºF Temperature Rise

608 gal/h

Recovery at 100 ºF Temperature Rise

243 gal/h

Recovery at 140 ºF Temperature Rise

174 gal/h

Maximum Recovery (ºC)

Recovery at 22 ºC Temperature Rise

2303 L/h

Recovery at 56 ºC Temperature Rise

921 L/h

Recovery at 78 ºC Temperature Rise

658 L/h



Dimension A

75 in

Dimension B

4-1/2 in

Dimension C

65-3/4 in

Dimension D

57-1/4 in

Dimension E

20 in

Dimension G

1/2 in

Dimension H

58-3/4 in

Dimension I

8 in

Dimension J

27-3/4 in

The Master-Fit® BTR series provides outstanding performance and maximum installation flexibility for both new construction and replacement applications. Multiple options for placement of water connections and low installation clearances are additional installer-friendly features.

The Eliminator™ Self-Cleaning System
  • Designed to significantly reduce or eliminate sediment build-up inside the tank.
  • Reduced sediment build-up maintains rated thermal efficiency and reduces water heating costs.
  • Self-cleaning system maximizes tank life.
Factory-Installed Draft Diverter and Automatic Flue Damper (BTR-120-400 Models)
  • Low-profile draft diverter helps for installation in tight spaces.
  • Automatic motorized flue damper helps minimize standby heat loss.
  • BTR-500 Model features induced draft design and no damper.
Three Water Connection Options for Added Flexibility
  • Hot and cold water connections can be made through front, top or rear of unit.
  • Eliminator™ system operates when cold water is connected through front.
Permaglas® Ultra Coat™ Glass Lining
  • Exclusive process provides superior protection against corrosion.
  • CoreGard™ anode rods with stainless steel core provide additional corrosion protection.
Intermittent Electronic Ignition
  • Eliminates standing pilot, saves energy.
  • Includes power ON/OFF switch.
  • Provides flame failure response in less than one second.

Testing and Certifications
Factory-Installed, CSA® Certified and ASME Rated T&P Relief Value
  • Design-certified by UL (Underwriters Laboratories), according to ANSI Z.21.10.3 - CSA® 4.3 standards governing storage-type water heaters
  • Meets the thermal efficiency and standby loss requirements of the U.S. Department of Energy and current edition of ASHRAE/IESNA 90.1
  • Design-certified by Underwriters Laboratories Sanitation to NSF Standard 5 for 180 ºF (82 ºC) water
  • Optional ASME tank construction available

Other Master-Fit® Features
Fully Automatic Control System
  • Manual-reset gas shut-off device prevents excessive water temperature
  • Adjustable thermostat with 120 to 180 ºF range
  • Gas pressure regulator and pilot filter
Handhole Cleanout
  • Allows easy access to tank interior for cleaning
Plug Kits
  • Pipe nipples and caps included to plug unused water connections MASTER-FIT® OPTIONS:
Manifold Kits for Multiple Heater Installations
  • 2-unit kit, Part Number 9003426205
  • 3-unit kit, Part Number 9003427205
  • 4-unit kit, Part Number 9003428205
Optional Leg Kit to Meet NSF Standard 5
  • For all BTR models, Part Number 9003425205
Mechanical Venting Kits
  • For BTR-120 through BTR-200, Part Number 9006015005
  • For BTR-250 through BTR-400, Part Number 9006016005
  • For installation of approved power venter to operate in conjunction with water heater thermostat
  • Field wiring should conform to latest version of the National Electric Code ANSI/NFPA No.70

  • 3-Year Limited Tank Warranty.

Electrical requirements: 120 VAC, 0.7 Amp, Electrical requirements with Power Venter: 120 VAC,3.0 FLAAmps.

Model Shipped with 8" to 6" vent reducer. Certified for both 6" to 8" vent.


·  The Eliminator™ for Master-Fit® Standard Draft Commercial Gas Water Heaters

·  Standards for Master-Fit® Standard Draft Commercial Gas Water Heaters

·  Water Connections Chart for Master-Fit® Standard Draft Commercial Gas Water Heaters


Brochure for Master-Fit® Standard Draft Commercial Gas Water Heaters
(PDF, 665KB)