Midco HMA-2 & HMA-2A Series - Manual (Page 6)

6
Midco International Inc.
8471 34
1. Required BTU:
BTU/hr = Blower SCFM x Desired Temp. Rise x 1.08 / .92
2. Required Burner Length:
Feet of burner = [Required BTU/hr]÷[Burner Firing Rate (BTU/hr/ft)]
The Burner Firing Rate should correspond to the pressure drop across the burner
shown in Chart 2.
3. Required Profi le Area:
Total Burner Area = Number of burner sections x burner area
(Burner Section) Burner Area
2 inch 0.11 sq. ft.
6 inch 0.32 sq. ft.
12 inch 0.65 sq. ft.
T Section 0.77 sq. ft.
Ell Section 0.65 sq. ft.
Net Profi le Area = Rated Fan (SCFM) ÷ Profi le Velocity (SFPM)
The Profi le Velocity can be determined from the following:
∆P is the pressure drop across the burner
Profi le Area = Net Profi le Area + Total Burner Area
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Sizing the burner and the corresponding profi le for a 5,000 SCFM and a 115 degrees
temperature rise.
1. Required BTU:
BTU/hr = Blower SCFM x Desired Temp. Rise x 1.08 / .92
BTU/hr =5,000 (SCFM) x 115 (∆T) x1.08 / .92 = 675,000 BTU/hr
2. Required Burner Length:
Feet of burner = [Required BTU/hr]÷[Burner Firing Rate (BTU/hr/ft)]
To determine the optimum burner length we can choose from a combination of 12
inch or 6 inch burner sections referring to Table 1. We can either fi re the burner
at a rate of 675,000 BTU/hr per ft, or we can fi re the burner at 450,000 BTU/hr per ft
(1.5 feet of burner). Refer to Chart 3 for the fuel pressures requirements at different
fi ring rates.
3. Required Profi le Area:
Total Burner Area = Number of burner sections x burner area
(Burner Section) Burner Area
2 inch 0.11 sq. ft.
6 inch 0.32 sq. ft.
12 inch 0.65 sq. ft.
T Section 0.77 sq. ft.
Ell Section 0.65 sq. ft.
Total Burner Area = 1.0 (ft) x 0.65 = 0.650 ft 2
Or
Total Burner Area = 1.5 (ft) x 0.65 = 0.975 ft 2
Profi le Setup
Profile Velocity
075 0
945
P Δ
=
.
Profi le Setup Example
Installation