Turn Down Ratios for Bosch Greenstar Straight & Combi Boilers

The turn down ratio can be calculated by dividing the input rating by the minimum input. See below for the appropriate turn down ratio for each boiler in the Greenstar series. The figures outlined in this bulletin are calculated using NG inputs and rounded to 2 decimal places.

Turn down ratios for Greenstar Condensing Combination (Combi) Boilers:

Bosch Greenstar Wall-Hung Combi 100 - ZWB28-3A23S3123

•    Part number: 7738 100 002
•    Input Rating: 100,800 BTU
•   Minimum Input: 24,600 BTU
•    Turndown Ratio: 4.1 : 1

Bosch Greenstar Floor-Standing (FS) Combi 100 - KWB28-3A23S3123

•  Part number: 7-733-600-082
•  Input Rating: 100,800 BTU
•  Minimum Input: 24,600 BTU
•  Turndown Ratio: 4.1 : 1

Bosch Greenstar Wall-Hung Combi 131 - ZWB35-3A23S3123

• Part number: 7738 100 256
• Input Rating: 131,900 BTU
•  Minimum Input: 36,000 BTU
•  Turndown Ratio: 3.7 : 1

Bosch Greenstar Floor-Standing (FS) Combi 131 - KWB35-3A23S3123

•  Part number: 7-733-600-083
•  Input Rating: 131,900 BTU
•  Minimum Input: 36,000 BTU
•  Turndown Ratio: 3.7 : 1

Bosch Greenstar Wall-Hung Combi 151 - ZWB42-3A23S3123

•  Part number: 7713 331 041
•  Input Rating: 151,600 BTU
•  Minimum Input: 36,000 BTU
•  Turndown Ratio: 4.2 : 1

Bosch Greenstar Floor-Standing (FS) Combi 151 - KWB42-3A23S3123

•  Part number: 7-733-600-084
•  Input Rating: 151,600 BTU
•  Minimum Input: 36,000 BTU
•  Turndown Ratio: 4.2 : 1

Turn down ratios for Greenstar Condensing Straight Boilers:

Bosch Greenstar Wall-Hung 57 - ZBR16-3A23S3123

•  Part number 7712 231 416
•  Input Rating: 57,200 BTU
•  Minimum Input: 12,900 BTU
•  Turndown Ratio: 4.4 : 1

Bosch Greenstar Floor-Standing (FS) 57 - KBR16-3A23S3123

•  Part number 7-733-600-077
•  Input Rating: 57,200 BTU
•  Minimum Input: 12,900 BTU
•  Turndown Ratio: 4.4 : 1

Bosch Greenstar Wall-Hung 79 - ZBR21-3A23S3123

•  Part number: 7738 100 322
•  Input Rating: 79,200 BTU
•  Minimum Input: 24,600 BTU
•  Turndown Ratio: 3.2 : 1

Bosch Greenstar Floor-Standing (FS) 79 - KBR21-3A23S3123

•  Part number: 7-733-600-078
•  Input Rating: 79,200 BTU
•  Minimum Input: 24,600 BTU
•  Turndown Ratio: 3.2 : 1

Bosch Greenstar Wall-Hung 100 - ZBR28-3A23S3123

•  Part number: 7712 231 415
•  Input Rating: 100,800 BTU
•  Minimum Input: 24,600 BTU
•  Turndown Ratio: 4.1 : 1

Bosch Greenstar Floor-Standing (FS) 100 - KBR28-3A23S3123

•  Part number: 7-733-600-079
•  Input Rating: 100,800 BTU
•  Minimum Input: 24,600 BTU
•  Turndown Ratio: 4.1 : 1

Bosch Greenstar Wall-Hung 131 - ZBR35-3A23S3123

•  Part number: 7712 231 414
•  Input Rating: 131,900 BTU
•  Minimum Input: 36,000 BTU
•  Turndown Ratio: 3.7 : 1

Bosch Greenstar Floor-Standing (FS) 131 - KBR35-3A23S3123

•  Part number: 7-733-600-080
•  Input Rating: 131,900 BTU
•  Minimum Input: 36,000 BTU
•  Turndown Ratio: 3.7 : 1

Bosch Greenstar Wall-Hung 151 - ZBR42-3A23S3123

•  Part number: 7712 231 413
•  Input Rating: 151,600 BTU
•  Minimum Input: 36,000 BTU
•  Turndown Ratio: 4.2 : 1

Bosch Greenstar Floor-Standing (FS) 151 - KBR42-3A23S3123

•  Part number: 7-733-600-081
•  Input Rating: 151,600 BTU
•  Minimum Input: 36,000 BTU
•  Turndown Ratio: 4.2 : 1