
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
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
Literature
1000
Submittal
- FlexCore Firetube 1000 Plan View Drawing.dwg
- FlexCore Firetube 1000 Plan View Drawing.pdf
- Futera Fusion 1000 Plan View Drawing_2.dwg
- Futera Fusion 1000 Plan View Drawing_2.pdf
- Futera II 1000 Plan View Drawing.dwg
- Futera II 1000 Plan View Drawing.pdf
- Futera III 1000 Plan View Drawing_1.dwg
- Futera III 1000 Plan View Drawing_1.pdf
- IE2 1000 Plan View Drawing.dwg
- IE2 1000 Plan View Drawing.pdf
1500
Submittal
- Dominator 1500 Plan View Drawing (RSUB-34.G).dwg
- Dominator 1500 Plan View Drawing (RSUB-34.G).pdf
- FlexCore Firetube 1500 Plan View Drawing.dwg
- FlexCore Firetube 1500 Plan View Drawing.pdf
- Futera Fusion 1500 Plan View Drawing_2.dwg
- Futera Fusion 1500 Plan View Drawing_2.pdf
- Futera II 1500 Plan View Drawing.dwg
- Futera II 1500 Plan View Drawing.pdf
- Futera III 1500 Plan View Drawing_1.dwg
- Futera III 1500 Plan View Drawing_1.pdf
- Torus 1500 Dual Fuel Plan View Drawing (RSUB-312.B).dwg
- Torus 1500 Dual Fuel Plan View Drawing (RSUB-312.B).pdf
- Torus 1500 Plan View Drawing (RSUB-302.B).dwg
- Torus 1500 Plan View Drawing (RSUB-302.B).pdf
- Torus 1500 Vertical Plan View Drawing (RSUB-307.B).dwg
- Torus 1500 Vertical Plan View Drawing (RSUB-307.B).pdf
2000
Submittal
- FlexCore Firetube 2000 Plan View Drawing.dwg
- FlexCore Firetube 2000 Plan View Drawing.pdf
- Futera Fusion 2000 Plan View Drawing.dwg
- Futera Fusion 2000 Plan View Drawing.pdf
- Futera III 2000 Plan View Drawing_1.dwg
- Futera III 2000 Plan View Drawing_1.pdf
- Torus 2000 Dual Fuel Plan View Drawing (RSUB-313.B).dwg
- Torus 2000 Dual Fuel Plan View Drawing (RSUB-313.B).pdf
- Torus 2000 Plan View Drawing (RSUB-303.B).dwg
- Torus 2000 Plan View Drawing (RSUB-303.B).pdf
- Torus 2000 Vertical Plan View Drawing (RSUB-308.B).dwg
- Torus 2000 Vertical Plan View Drawing (RSUB-308.B).pdf
3000
Submittal
- FlexCore Firetube 3000 Plan View Drawing.dwg
- FlexCore Firetube 3000 Plan View Drawing.pdf
- Futera Fusion XLF 3000 Plan View Drawing_2.dwg
- Futera Fusion XLF 3000 Plan View Drawing_2.pdf
- Futera XLF 3000 Plan View Drawing_1.dwg
- Futera XLF 3000 Plan View Drawing_1.pdf
- Torus 3000 Dual Fuel Plan View Drawing (RSUB-314.A).dwg
- Torus 3000 Plan View Drawing (RSUB-304.A).dwg
- Torus 3000 Plan View Drawing (RSUB-304.A).pdf
- Torus 3000 Vertical Plan View Drawing (RSUB-309.A).dwg
- Torus 3000 Vertical Plan View Drawing (RSUB-309.A).pdf
4000
Submittal
- FlexCore Firetube 4000 Plan View Drawing_1.dwg
- FlexCore Firetube 4000 Plan View Drawing_1.pdf
- Futera Fusion XLF 4000 Plan View Drawing_2.dwg
- Futera Fusion XLF 4000 Plan View Drawing_2.pdf
- Futera XLF 4000 Plan View Drawing_1.dwg
- Futera XLF 4000 Plan View Drawing_1.pdf
- Torus 3000 Dual Fuel Plan View Drawing (RSUB-314.A).pdf
- Torus 4000 Dual Fuel Plan View Drawing (RSUB-315.A).dwg
- Torus 4000 Dual Fuel Plan View Drawing (RSUB-315.A).pdf
- Torus 4000 Plan View Drawing (RSUB-305.A).dwg
- Torus 4000 Plan View Drawing (RSUB-305.A).pdf
- Torus 4000 Vertical Plan View Drawing (RSUB-310.A).dwg
- Torus 4000 Vertical Plan View Drawing (RSUB-310.A).pdf