Bosch 940 ES Installation Manual page 20

Installation instructions
3.3.8 Fan speed adjustment
IMPORTANT! Installation adjustment:
After installing the water heater, the fan speed values for minimum power (P2) and maximum power (P1) may need
adjustment due to variations in altitude and vent pipe length.
Failure to make necessary adjustments to fan speed values may result in improper operation of the appliance.
First calculate the total equivalent vent length. This is the straight pipe length of both exhaust and combustion air plus
the number of elbows used. To determine the length equivalency of each elbow refer to table 6.
Use the equivalent vent length value to determine the appropriate fan speed values found in Table 20 and 21. Refer
to page 21 on how to adjust the fan speeds if an adjustment is necessary. After changing fan speed values, proceed
to section 6.4 to confirm CO2 values are within specified ranges.
Fan speed adjustment
Altitude Total
(above sea equivalent
level) vent length
3.5 - 32 ft
0 - 2000 ft
(0 - 610 m)
33 - 57 ft
3.5 - 32 ft
2000 - 4500 ft
(610 - 1372 m)
33 - 57 ft
3.5 - 32 ft
4500 - 8000 ft
(1372 - 2439 m)
33 - 57 ft
* Above 2000 ft, CO levels must be checked with a combustion gas analyzer, see section
2
Table 20 Fan speed adjustment for 3" piping
1) Full equivalent length (inlet + outlet piping + fittings)
Altitude Total
(above sea equivalent
level) vent length
2.25 - 59 ft
0 - 2000 ft
(0 - 610 m)
60 - 122.5 ft
2.25 - 59 ft
2000 - 4500 ft
(610 - 1372 m)
60 - 122.5 ft
2.25 - 59 ft
4500 - 8000 ft
(1372 - 2439 m)
60 - 122.5 ft
* Above 2000 ft, CO levels must be checked with a combustion gas analyzer, see section
2
Table 21 Fan speed adjustment for 4" piping
1) Full equivalent length (inlet + outlet piping + fittings)
20
Natural Gas
Minimum Maximum
power fan power fan speed
1)
speed (P2)
7
modification required
8
8*
8*
9*
9*
Natural Gas
Minimum Maximum
power fan power fan speed
1)
speed (P2)
7
modification required
8
8*
8*
9*
9*
Liquid propane
Maximum
power fan speed
(P1) (P1)
No No
modification required
54* 47*
55* 48*
55* 48*
55* 49*
6.4
Liquid propane
Maximum
power fan speed
(P1) (P1)
No No
modification required
54* 47*
55* 48*
55* 48*
55* 49*
6.4
For operation at elevations
above 2,000 ft (610 m) the
equipment ratings shall be
reduced at the rate of 4% for
each 1,000 ft (305 m) above sea
level
for instructions.
For operation at elevations
above 2,000 ft (610 m) the
equipment ratings shall be
reduced at the rate of 4% for
each 1,000 ft (305 m) above sea
level
for instructions.
6 720 644 930