FlexCore Symmetrical Firetube boilers bring hydronic heating products to unprecedented levels of operating efficiency.

Unlike other manufacturers; from start to finish the FlexCore was designed, developed and engineered by the experts at RBI.

Engineered for performance and longevity the FlexCore utilizes a perfectly temperature balanced heat exchanger that provides not only the highest efficiencies but also a durability beyond that of any competitive firetube boiler on the market.

features and benefits
  • Up to 99% Maximum Efficiency
  • 850 - 9,000 MBH
  • AHRI Certified Efficiency 97.1%
  • Stainless Steel Firetube Heat Exchanger
  • Variable Volume Flow
  • Full Modulation
  • Patented "Turbo Pilot" Ignition
  • HeatNet 3.0 Integrated Control Platform
  • Touchscreen Programming & Diagnostics
  • Low NOx & CO
  • Modern Jacket Design
  • Superior Durability
  • Easy Installation & Maintenance
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Flexcore
flexcore Dimensions and ratings
  Input   Boiler Output Unit Depth Unit Width Unit Height
Size MBH kW MBH kW In. mm In. mm In. mm
850 850 249 812 238 70 1778 32 812.8 80 2031.9
1000 1000 293 955 280 70 1778 32 812.8 80 2031.9
1500 1500 440 1426 418 70 1778 32 812.8 80 2031.9
2000 1999 586 1901 557 72.4 1838.3 32 812.8 80 2031.9
2500 2500 733 2397 703 72.4 1838.3 32 812.8 80 2031.9
3000 3000 879 2904 851 72.4 1838.3 32 812.8 80 2031.9
3500 3499 1025 3327 975 109.4 2770.7 34 863.8 80 2031.9
4000 3998 1172 3802 1114 109.4 2770.7 34 863.8 80 2031.9
4500 4500 1319 4329 1269 109.4 2770.7 34 863.8 80 2031.9
5000 5000 1465 4795 1405 109.4 2770.7 34 863.8 80 2031.9
6000 6000 1758 5808 1702 109.4 2770.7 34 863.8 80 2031.9
7000 7000 2051 6706 1965 168.125 4273 34 863.6 80 2031.9
8000 8000 2345 7712 2260 168.125 4273 34 863.6 80 2031.9
9000 9000 2638 8712 2553 168.125 4273 34 863.6 80 2031.9
  Cat IV Positive Cat II Air Intake Connections   Shipping Weight
Size UL Listed SS** Negative**   Gas Nat Water Lbs Kg
850 5" 8" 6" 1" 3" 1515 687
1000 5" 8" 6" 1" 3" 1515 687
1500 6" 8" 8" 1-1/2" 3" 1555 705
2000 6" 10" 8" 1-1/2" 3" 1880 853
2500 8" 12" 8" 1-1/2" 3" 1955 887
3000 8" 12" 8" 1-1/2" 3" 2055 932
3500 10" 12" 10" 2-1/2" 4" 3420 1551
4000 10" 12" 10" 2-1/2" 4" 3745 1699
4500 10" 14" 10" 2-1/2" 4" 3600 1633
5000 12" 14" 12" 2-1/2" 4" 3920 1778
6000 12" 14" 12" 2-1/2" 4" 4150 1882
7000 14" 16" 14" 3" 6" 5840 2649
8000 14" 16" 14" 3" 6" 6025 2733
9000 14" 16" 14" 3" 6" 6230 2826

**Diameters may vary based on system design

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