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C403.3.4 Boiler Turndown
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Boiler systems with design input of greater than 1,000,000 Btu/h (293 kW) shall comply with the turndown ratio specified in Table C403.3.4.
The system turndown requirement shall be met through the use of multiple single-input boilers, one or more modulating boilers or a combination of single-input and modulating boilers.
BOILER TURNDOWN
| BOILER SYSTEM DESIGN INPUT (Btu/h) | MINIMUM TURNDOWN RATIO |
| ≥ 1,000,000 and less than or equal to 5,000,000 | 3 to 1 |
| > 5,000,000 and less than or equal to 10,000,000 | 4 to 1 |
| > 10,000,000 | 5 to 1 |
For SI: 1 British thermal unit per hour = 0.2931 W.
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