| 摘要 |
A water heating apparatus (10) uses a low range blower assembly (52) and a high range blower assembly (54), each providing a variable flow of premixed fuel and air to a burner assembly (42). Appropriate choice of the operating ranges of the blower assemblies can provide a high turndown ratio approximately equal to the product of the turndown ratios of each of the individual blower assemblies. Turndown ratios as high as 25:1 are achievable. |
