User Manual

1-150.16
8
DESIGN BENEFITS
Power Code Descriptions & Control Sequence
Control Sequence
The following control sequence descriptions are typical for steam/hot water unit heaters:
Intermittent Fan Operation - Hot Coil
When a room thermostat calls for heat, the motor is energized. Hot water or steam is continuously supplied to the unit heater, even
when the motor is not running. When the thermostat is satisfied, the motor is de-energized.
Continuous Fan Operation - Intermittent Hot/Cold Coil
When a room thermostat calls for heat, a valve is opened, allowing steam or hot water to enter the unit heater. When the
thermostat is satisfied, the valve is closed. The fan runs continuously.
Intermittent Fan Operation - Intermittent Hot/Cold Coil
When a room thermostat calls for heat, the motor is energized. At the same time, a valve is opened allowing steam or hot water to
enter the unit heater. An aquastat may be attached to the supply or return piping to prevent fan operation until the coil is adequately
heated to avoid cold air delivery. When the thermostat is satisfied, the valve closes and the motor is de-energized.
Supply Voltage
Motor Enclosure
Motor Type
Motor Starter
Table 8.1
Power Code Descriptions
Power Thermal Overload
Code Protection
01 115/60/1 Totally Enclosed M Yes N/A
02 230/60/1 Totally Enclosed M Yes N/A
04 200-208/60/3 Totally Enclosed Polyphase Induction No Field Supplied/Installed
05 230/460/60/3 Totally Enclosed Polyphase Induction No Field Supplied/Installed
06 115/60/1 Explosion-proof N Split Phase Yes N/A
09 230/460/60/3 Explosion-proof N
Polyphase Induction Yes Field Supplied/Installed
10 575/60/3 Totally Enclosed Polyphase Induction No Field Supplied/Installed
M Motors are shaded pole for models HSB/HC 18-33 and V/VN 42-95. Models HSB/HC 47-340 and V/VN 139-333 are permanent split capacitor.
N Explosion-proof motors are suitable for Class I, Group D, Class II, Groups F and G, and Class III, Division 1 and 2 environments. Canadian Standard Association
(CSA) requirements state that the explosion-proof units may not be used with a fluid temperature in excess of 329°F or pressures greater than 87 psig and still
maintain their T3B temperature rating.
Class I, Group D motors are for operations in areas containing gasoline, petroleum, naphtha, benzene, butane, propane, alcohol, acetone, lacquer solvent or
natural gas.
Class II, Group F motors are for operations in areas containing carbon black, coal or coke dust.
Class II, Group G motors are for operations in areas containing flour, starch or grain dust.
Class III motors are for operations in areas containing easily ignitable fibers and flyings.