15
Model MSCF Modular Small Cabinet Fan
®
Sequence of Operation - Electric
Heater
1. Electric heaters are divided in to equally sized
steps. For example, a 60 kW heater with 3 steps
will have 20 kW per step. The thermostat and
step controller will control these steps.
2. 120 Volt power from the control center (when
supplied) or by others with out a control center,
is delivered to the electric heater for the step
controller. This power must be interlocked with
the supply fan, so when the fan is off, the heater
control power is off.
3. A step control with the thermostat set to
70ºF the heater will be off with a temperature
sensing above 70ºF. As the temperature varies
the steps turn on and off to hold the setpoint
discharge temperature. The colder the discharge
temperature becomes the more steps the
controller will energize.
4. With a step controller, in addition to the fan
interlock mentioned in Step 2, the heater has an
airflow switch to prove that airflow is established
before energizing the steps. The heater also
has an automatic resetting highlimit switch and
manual resetting highlimit switch set above the
automatic switch to protect from overheating.
5. For more detailed information on your specific
controller, please review the controller spec
sheet supplied with the heater.
