Miscellaneous

Sheet Metal Weights

Hot Rolled Steel
US ga. Thickness, in. Wt., lb/ft2
26 0.0179 0.750
24 0.0239 1.000
22 0.0299 1.250
20 0.0359 1.500
18 0.0478 2.000
16 0.0596 2.500
14 0.0747 3.125
Galvanized Steel
US Ga. Thickness, in. Wt., LB/ft2
26 0.022 0.906
24 0.028 1.156
22 0.034 1.406
20 0.040 1.658
18 0.052 2.156
16 0.064 2.656
14 0.080 3.281
Aluminum (35)
B&S Ga. Thickness, in. Wt., LB/ft2
- - - - - - - - -
- - - - - - - - -
24 0.020 0.288
22 0.025 0.355
20 0.032 0.456
18 0.040 0.575
16 0.051 0.724
14 0.064 0.914
Stainless Steel
US Ga. Thickness, in. Wt., LB/ft2
28 0.016 0.66
26 0.019 0.79
24 0.025 1.05
22 0.031 1.31
20 0.038 1.58
18 0.050 2.10
16 0.063 2.63
14 0.078 3.28

Recommended Metal Gauges for Ducts

Rectangular Duct
Greatest
dimension 		U.S. Ga. B&S Ga.
to 30 in. 24 22
31-61 22 20
61-90 20 18
91-up 18 16
Round Duct
Diameter Galv. Steel
US Ga.		 Aluminum
B&S Ga.
to 8 in. 24 22
9-24 22 20
25-48 20 18
49-72 18 16

Conventional duct fabrication includes "S" clips on small sizes; bar slips or standing seams on larger sizes. All panels over 18 in. (1 dim) are to be cross broken.

Adapted from "Numbers", Bill Holladay and Cy Otterhelm, 1985.

Fuel Comparisons**

This provides equivalent BTU Data for Various Fuels

Natural Gas 1,000,000 BTU = 10 Therms or
1,000,000 BTU = (1000 Cu. Ft.)
Propane Gas 1,000,000 BTU = 46 Lb. or
1,000,000 BTU = 10.88 Gallon
No. 2 Fuel Oil 1,000,000 BTU = 7.14 Gallon
Electrical Resistance 1,000,000 BTU = 293 KW (kilowatts)
Municipal Steam 1,000,000 BTU = 1000 Lbs. Condensate
Sewage Gas 1,000,000 BTU = 1538 Cu. Ft. to 2380 Cu. Ft.
LP/Air Gas 1,000,000 BTU = 46 Lb. Propane or
1,000,000 BTU = 10.88 Gallon Propane or
1,000,000 BTU = 690 Cu. Ft. Gas/Air Mix

Fuel Gas Characteristics

Natural Gas 925 to 1125 BTU/Cu. Ft. .6 to .66 Specific Gravity
Propane Gas 2550 BTU/Cu. Ft. 1.522 Specific Gravity
*Sewage Gas 420 to 650 BTU/Cu. Ft. .55 to .85 Specific Gravity
*Coal Gas 400 to 500 BTU/Cu. Ft. .5 to .6 Specific Gravity
*LP/Air Mix 1425 BTU/Cu. Ft. 1.29 Specific Gravity

Heat Loss Estimates

The following will give quick estimates of heat requirements in a building knowing the cu. ft. volume of the building and design conditions.

Indoor Temp (F) - BTU/Cubic Foot
Masonry Wall Insulated Steel Wall
Type of Structure   60 65 70 60 65 70
Single Story
4 Walls Exposed		 3.4 3.7 4.0 2.2 2.4 2.6
Single Story
One Heated Wall		 2.9 3.1 3.4 1.9 2.0 2.2
Single Floor
One Heated Wall
Heated Space Above		 1.9 2.0 2.2 1.3 1.4 1.5
Single Floor
Two Heated Walls
Heated Space Above		 1.4 1.5 1.6 0.9 1.0 1.1
Single Floor
Two Heated Walls		 2.4 2.6 2.8 1.6 1.7 1.8
Multistory 2 Story 2.9 3.1 3.4 1.9 2.1 2.2
3 Story 2.8 3.0 3.2 1.8 2.0 2.1
4 Story 2.7 2.9 3.1 - - - - - - - - -
5 Story 2.6 2.8 3.0 - - - - - - - - -

*Before attempting to operate units on these fuels, contact mfr.
**Chemical Rubber Publishing Co., Handbook of Chemistry and Physics

Estimated Seasonal Efficiencies of Heating Systems

Systems Seasonal Efficiency
Gas Fired Gravity Vent Unit Heater 62%
Energy Efficient Unit Heater 80%
Electric Resistance Heating 100%
Steam Boiler with Steam Unit Heaters 65%-80%
Hot Water Boiler with HYD Unit Heaters 65%-80%
Oil Fired Unit Heaters 78%
Municipal Steam System 66%
INFRA Red (High Intensity) 85%
INFRA Red (Low Intensity) 87%
Direct Fired Gas Make Up Air 94%
Improvement with Power Venter Added to Gas Fired Gravity Vent Unit Heater 4%
Improvement with Spark Pilot Added to Gas Fired Gravity Vent Unit Heater 1/2%-3%
Improvement with Automatic Flue Damper and Spark Pilot Added to Gravity Vent Unit Heater 8%

Annual Fuel Use

Annual fuel use may be determined for a building by using one of the following formulas:

Electric Hesitance Heating H / (T x 3413 x E) x D x 24 x .79 = KWH/YEAR
Natural Gas Heating H / (T x 100,000 x E) x D x 24 x .6 = THERMS/YEAR
Propane Gas Heating H / (T x 21739 x E) x D x 24 x .6 = POUNDS/YEAR
H / (T x 91911 x E) x D x 24 x .6 = GALLONS/YEAR
Oil Heating H / (T x 140,000 x E) x D x 24 x .6 = GALLONS/YEAR

Where:
T = Indoor Design Minus Outdoor Design
H = Building Heat Loss
D = Annual Degree Days
E = Seasonal Efficiency (See above)