MFC Series Boiler Vent and Combustion Air Guide
TAG-0080_OG
•
GF-148-V
•
3/29/2023
Technical Support
•
(800) 526-0288
•
Mon-Fri, 8 am - 5 pm EST Page 16 of
33
horizontal run, 20 feet of vertical run
2) A rain cap termination
3) A 10-inch diameter ducted combustion air duct with two 90° elbows and 50 feet of run
MFC Series Pressure Drop Calculation
10-INCH DIAMETER EXHAUST VENT PRESSURE
Two 90
°
elbows: 2 x 2.68 = 5.36 ft.
One 45
°
elbow: 1 x 2.05 = 2.05
ft.
95 feet total run (75 hori 20 vertical):
95 x 0.4 = 38.00 ft.
Rain cap exit loss: 1 x 8.81 = 8.81 ft.
Vent drop subtotal:
= 54.22 ft.
Altitude correction: 54.22
= 55.21 ft.
0.982 (CF)
Natural draft for 20 feet @ 20°F outside temperature:
= 12.6 ft.
Altitude correction: - 12.6 x 0.982 CF= - 12.37 ft.
TOTAL VENT DROP:
=
42.84 ft.
10-INCH DIAMETER COMBUSTION AIR DUCT PRESSURE
Two 90
elbows: 2 x 1.88 = 3.76 ft.
50 feet total run: 50 x 0.3 = 15.00 ft.
Entrance loss: 1 x 4.46
= 4.46 ft.
Combustion air drop subtotal:
= 23.22 ft.
Altitude correction:
= 32.22
= 23.65 ft.
0.982 CF
COMBUSTION AIR DROP TOTAL: =
23.65 ft
.
SYSTEM TOTAL PRESSURE DROP
Vent drop + combustion air duct pressure drop:
= 42.84 + 23.65
FINAL PRESSURE DROP TOTAL: =
66.49 ft.
CONCLUSION:
Pressure drop is less than 140 equivalent feet =
SYSTEM OK
.
