Dual Fuel Supplemental Manual
Ratings
Crest
AHRI Rating
Model Number
Note: Change “N” to
“L” for L.P. gas models.
Input
MBH
(Notes 4 - 8)
Min Max
Gross
Output
MBH
(Note 1)
Net
AHRI
Ratings
Water,
MBH
(Note 2)
FB(N,L,D)2500 125 2500 2300 2000
FB(N,L,D)3000 150 3000 2760 2400
FB(N,L,D)3500 200 / 290 3500 3220 2800
FB(N,L,D)4000 335 / 435 4000 3720 4043
FB(N,L,D)5000 500 / 833 5000 4650 3235
FB(N,L,D)6000* 600 / 950 6000 5520 4800
UNIT EQUIPPED FOR
HIGH ALTITUDE
3,000 FT. TO 12,000 FT.
Figure A High Altitude Label Location
5
Other Specifications
Appliance
Water
Content
Gallons
Pipe
Size
Outlet
Pipe
Size
Inlet
Gas Inlet
Size
Air
Size
Vent
Size
(Note 3)
Weight
w/Water
(lbs.)
161 4" 4" 2" 8" 9" 3650
181 4" 4" 2" 10" 10" 4125
215 4" 4" 2" 10" 10" 4750
291 4" 4" 2 1/2" 12" 12" 6500
380 4" 4" 2 1/2" 14" 14" 8000
380 6" 6" 2 1/2" 14" 14" 8000
Maximum allowed working pressure is located on the rating plate.
NOTICE
Notes:
1. The ratings are based on standard test procedures
prescribed by the United States Department of Energy.
2. Net AHRI ratings are based on net installed radiation of
sufficient quantity for the requirements of the building
and nothing need be added for normal piping and pickup.
Ratings are based on a piping and pickup allowance of
1.15.
3. Crest boilers require special gas venting. Use only
the vent materials and methods specified in the Crest
Installation and Operation Manual.
4. Standard Crest boilers are equipped to operate from sea
level to 4,500 feet only. The boiler will de-rate by 2.2%
for each 1,000 feet above sea level up to 4,500 feet.
5. High altitude Crest Models 2.5, 3.0 and 3.5 are equipped
to operate from 3,000 to 12,000 feet only. e boiler will
de-rate by 1.4% for each 1,000 feet above sea level up to
5,500 feet and 1.8% for each 1,000 feet above 5,500 feet.
e operation given in this manual remains the same as
the standard boilers. A high altitude label (as shown in
FIG A.) is also a xed to the unit.
De-rate values are based on proper combustion
calibration and
CO
2
’s adjusted to the recommended
levels.
*For high altitude models the minimum input is 700 MBH (natural) and 1000 MBH (LP).
6. High altitude Crest Models 4.0 and 5.0 will not de-rate up to
5,500 feet.
7. e high altitude Crest 6.0 model will de-rate by 2.0% for
each 1000 feet above sea level up to 5,500 feet.
8. For Crest Models 4.0, 5.0 and 6.0, installations above 5,500
feet contact the factory.
9. Ratings have been con rmed by the Hydronics Section of
AHRI.
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