Document K61xXnK0znvyGX270OemJgEbX

American Society of Heating and Ventilating Engineers Guide, 1930 One of the most important considerations is the durability or life of the apparatus. Consideration should be given to the thickness Of the metal in each heater, the provisions made for expansion and contraction, and the protection afforded the firebox at the point of most intense heat. A heater made of thicker metal than others usually will give greater length of service, other things being equal. Proper provisions for expansion and contraction are imperative. With out such provisions a cast-iron heater is likely to crack and a steel heater is likely to warp and buckle. Most furnaces have linings around the periphery of the fuel bed to protect the firebox from the action of the hottest part of the fire, 'fhe linings are removable and are as easily installed as new grates. Table 1. Air Velocities and Register Temperatures for Fan-Furnace Systems Velocities IK Feet per Minute Trra or Buildino Thru Free Area of Heaters Id Horizontal Supply Ducts In Supply Risers Into Room In Vent Outlets In Vent Risen In Rzuxsteb Horizontal TemfebaVent Duets TUBS and Recir culating Duets Schools 800 800 500 300 300 500 600 90" to to to to to to to to 1000 1000 600 400 400 600 800 120" Churches 800 700 400 300 300 400 500 80" to to to to to to to to 1000 900 600 500 500 600 700 120".' Auditoriums 800 800 500 300 300 500 600 80" and to to to to to to to to * Convention Halls 1000 1000 600 500 500 600 800 120" Garages and Industrial Buildings 1000 1000 600 400 400 600 800 80" to to to to to to to to 1400 1400 1000 1000 600 1000 1200 140" Arrangement of Heaters Any number of furnaces may be set in battery; all to be enclosed by an outer casing consisting of either masonry or of some form of insulated, metal. This casing provides space under the heaters for air supply and forms a plenum space above the furnaces from which ducts may lead to the rooms requiring heat. The fan preferably is placed at the rear of the heaters to secure equal air distribution over the heating surfaces. It is considered best practice to blow air around the heaters rather than to draw the air around them by suction, and most fan furnaces are designed for this arrangement. The fan-furnace system can be applied readily to each of the following standard duct systems or to any combination thereof: 1. The straight fan-blast trunk-line system carrying heated air only for a series of rooms on any one run. 154 Chapter 6--Heating with Warm Air Furnaces by Fan Pressure Ii 5Ecnn c -c - - Fig. 2. Fan Furnace with Double D ucts -- Fig. 3. Fan Furnace with Single Duct