Each heater has 2 different types of factory-installed ther-
mal cutouts for overtemperature protection; an automatic
reset thermal cutout for primary protection and a manual
reset thermal cutout to protect against failure of the primary
system. Also provided is an airflow pressure differential switch
to prevent the heater from operating when the fan is not in
operation or airflow is restricted or insufficient. The primary
automatic reset cutout is a bi-metal disk-type cutout. It is
wired into the control circuit which operates the magnetic
disconnecting contactors (the same contactors which also switch
on and off the various steps of the coil). The secondary manual
reset cutout is a bi-metal disk-type cutout. This secondary
thermal cutout is load carrying and is installed in each heater
subcircuit. The primary and secondary overtemperature pro-
tection systems are independent of each other. The second-
ary system is designed to protect against possible failure of
the primary system to deenergize the heater.
Sub-circuits in the heaters are designed in compliance with
paragraph 424-22 of the NEC. The coil is subdivided into
circuits that draw no more than 48 amps each and is fused
for at least 125% of the circuit rating.
Pitot tube is to be positioned so that the airflow switch is
actuated by a minimum negative pressure of 0.07 in. wg.
NOTE: All wiring must be copper and must conform to the NEC (National Electrical Code).
Fig. 59 — Electric Heater Wiring Schematic
67
Summary of Contents for 39T
Page 43: ...Fig 34 Discharge Fabrication Draw Thru Plenum Fans 43 ...
Page 49: ...Fig 41 Coil Connections and Lifting Points Fig 42 Steam Coil PIping 49 ...
Page 78: ...Fig 64 Blow Thru Unit Coil Removal Fig 65 Plan View Typical Coil 78 ...
Page 81: ...Fig 68 Filter Arrangement 2 in and 4 in Flat 81 ...
Page 82: ...Fig 68 Filter Arrangement 2 in and 4 in Flat cont 82 ...
Page 83: ...Fig 69 Filter Arrangement Angle Filters 2 in Only 83 ...
Page 84: ...Fig 69 Filter Arrangement Angle Filters 2 in Only cont 84 ...
Page 85: ...Fig 70 Filter Arrangement BCF1 Bag or Cartridge Draw Thru 85 ...
Page 86: ...Fig 70 Filter Arrangement BCF1 Bag or Cartridge Draw Thru cont 86 ...
Page 87: ...Fig 71 Filter Arrangement BCF3 Bag or Cartridge Blow Thru 87 ...
Page 88: ...Fig 71 Filter Arrangement BCF3 Bag or Cartridge Blow Thru cont 88 ...
Page 92: ...NOTE A frame shown shaded Fig 74 Fan Discharge Positions 92 ...
Page 102: ......
Page 103: ......
