Bosch SSB255 - Technical Data and Efficiency Curves

6720818454 (2016/02) US SSB
10 | Product description
2.7 Technical data
Unit SSB255 SSB399 SSB512
Boiler Category ASME Sect.IV ASME Sect.IV ASME Sect.IV
Type of Gas Natural Gas, Propane * Natural Gas, Propane * Natural Gas, Propane *
Max input rate BTU/hr (kW) 255,900 (75) 399,000 (117) 512,000 (150)
Min input rate BTU/hr (kW) 51,180 (15) 79,800 (23.4) 102,400 (30)
Turndown Rate (%) 5:1 (20 %) 5:1 (20 %) 5:1 (20 %)
Gas Connections (NPT) Ø Inch 1” 1’’ 1’’
Max. NG Pressure Inch W.C. (mbar) 10.5 (26.15) 10.5 (26.15) 10.5 (26.15)
Min. NG Pressure Inch W.C. (mbar) 3.5 (8.72) 3.5 (8.72) 3.5 (8.72)
Max. LPG Pressure Inch W.C. (mbar) 13 (32.3) 13 (32.3) 13 (32.3)
Min. LPG Pressure Inch W.C. (mbar) 8 (19.9) 8 (19.9) 8 (19.9)
Water Connections Ø Inch 1 ½ “ 1 ½” 2’’
Max. Allowable Working Pressure
(MAWP)
PSI (bar) 80 (5.5) 80 (5.5) 80 (5.5)
Recommended water ow @ max
power (∆T 36 °F / 20 °C)
GPM (m
3
/h) 14.2 (3.2) 22.2 (5.0) 28.4 (6.5)
Max water ow @ max power
(∆T 27 °F / 15 °C)
GPM (m
3
/h) 18.9 (4.3) 29.5 (6.7) 37.9 (8.6)
Min water ow @ max power
(∆T 54 °F / 30 °C)
GPM (m
3
/h) 9.5 (2.2) 14.8 (3.4) 18.9 (4.3)
Min water ow @ min power
(∆T 27 °F / 15 °C)
GPM (m
3
/h) 3.8 (0.9) 5.9 (1.3) 7.6 (1.7)
Water Pressure Drop @
recommended water ow
Feet Head (mbar) 3.8 (114) 8.3 (250) 21.7 (650)
Water Pressure Drop @ max water
ow
Feet Head (mbar) 6.4 (190) 13.8 (410) 37.73 (1120)
Water Volume Gallon (liter) 4.0 (15.2) 4.5 (17.0) 6.0 (23.0)
Vent/Air Intake Connections Ø Inch (Ø mm) 3 (80) 4 (100) 4 (100)
Vent Materials
CPVC, PVC, PP, PP Flex,
Stainless Steel AL29-4C
IPEX type IIA & IIB
CPVC, PVC, PP, PP Flex,
Stainless Steel AL29-4C
IPEX type IIA & IIB
CPVC, PVC, PP, PP Flex,
Stainless Steel AL29-4C
IPEX type IIA & IIB
Max operating temperature °F (°C) 194 (90) 194 (90) 194 (90)
Max HE allowable temperature °F (°C) 210 (98.9) 210 (98.9) 210 (98.9)
Ambient storage temperature dry °F (°C) 5 to 150 (-15 to 65) 5 to 150 (-15 to 65) 5 to 150 (-15 to 65)
Ambient functioning temperature °F (°C) 32 to 120 (0 to 49) 32 to 120 (0 to 49) 32 to 120 (0 to 49)
Ambient Relative Humidity [RH] % RH Minimum 30%, Maximum 90% Minimum 30%, Maximum 90% Minimum 30%, Maximum 90%
Surface area heat exchanger SQFT (m
2
) 22.0 (2.0) 27.2 (2.5) 43.0 (4.0)
Standard Listings & Approvals CSA, ASME, AHRI CSA, ASME, AHRI CSA, ASME, AHRI
Electrical Req. 120VAC/1PH/60Hz 2 FLA** 2.5 FLA** 2.5 FLA**
Noise rating dB 46 47 48
Weight (dry) lbs (kg) 198 (90) 220 (100) 242 (110)
Min. clearance to combustibles *** Inch (mm) 2” (50.8) 2” (50.8) 2” (50.8)
Dimension WxHxD
Inch
(mm)
23 31/32” x 61 9/16” x 21 21/32”
(609x1564x550)
23 31/32” x 61 9/16” x 21 21/32”
(609x1564x550)
23 31/32” x 61 9/16” x 21 21/32”
(609x1564x550)
AHRI certied ratings
Unit SSB255 SSB399 SSB512
Input MBH 255 399 511.8
Heating Capacity MBH 237.0 n/a n/a
Gross Output MBH n/a 386.0 495.0
AFUE % 96 n/a n/a
Combustion Efciency % n/a 97.6 95.4
Thermal efciency % n/a 96.9 96.8
Net rating MBH 206.0 336.0 430.0
CO
2 % 10.2 10.1 9.5
(*) With conversion.
(**) FLA (Full Load Amperage) - maximum current drawn by the boiler without pumps.
(***) The 2” minimum clearance is required for all sides of the boiler. The boiler may be installed on combustible (wood) oors excluding carpets.
See Fig. 9 for minimum clearance recommendation for serviceability.