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Home TechTime May 2017 Electric Heaters
TechTime is a Neptronic publication aiming to inform you on the best ways to deal with common issues highlighted by our technical support team. Each edition features three new topics and will be posted on neptronic.com.

Know Your Signals
Control Signals to Heat

The following signal types can control Neptronic heaters: electric ON-OFF, electric modulating, pneumatic ON-OFF and pneumatic modulating. Here is a simple explanation of how each of them operates and what’s inside the control panel for each control signal type.


ELECTRIC CONTROL

ON-OFF Control


With this control system, the heater is either 100% ON at full capacity or 100% OFF. A thermostat dry contact activates the electric heater. The control panel of an ON-OFF electric heater includes the following components:

  • Transformer and control fuse
  • Automatic thermal cutout
  • Manual reset thermal cutout (when required by code, otherwise optional)
  • Airflow switch
  • Contactor(s)
  • Fuses (when required by code, otherwise optional)
  • Disconnect switch (when required by code, otherwise optional)

Proportional Control (Modulating)

A perfect example of this type of control system is a lamp with a dimmer or a regulator switch that controls the brightness by changing the applied voltage waveform. On a modulating heater, an electric signal from a proportional thermostat is transmitted to the HEC controller. The HEC activates the proportional stage of the electric heater. Modulating heaters can also have a vernier control with stages ( see TechTime article on Vernier Control). The control panel of a modulating heater includes the following components:

  • Transformer and control fuse
  • Automatic thermal cutout
  • Manual reset thermal cutout (when required by code, otherwise optional)
  • Neptronic HEC controller
  • Solid-State Relay(s)
  • Airflow switch or electronic airflow sensors
  • Contactor(s)
  • Fuses (when required by code, otherwise optional)
  • Disconnect switch (when required by code, otherwise optional)

PNEUMATIC CONTROL

ON-OFF Control


In pneumatic control systems, the heater is controlled with the use of pressurized air. A pneumatic signal from a pneumatic thermostat activates the electric heater. The operation is similar to electric ON-OFF control but uses a pneumatic signal instead of an electrical signal. The control panel of an ON-OFF heater with a pneumatic input includes the following components:

  • Transformer and control fuse
  • Automatic thermal cutout
  • Manual reset thermal cutout (when required by code, otherwise optional)
  • Airflow switch
  • Pneumatic Electric Switch/Proportional
  • Contactor(s)
  • Fuses (when required by code, otherwise optional)
  • Disconnect switch (when required by code, otherwise optional)

Proportional Control (Modulating)

This control system is similar to electric modulating control, but with a pneumatic signal. A proportional signal from a pneumatic thermostat is transmitted to the HEC controller. The HEC controller activates the proportional heater. The control panel of a pneumatic modulating heater includes the following components;

  • Transformer and load fuse
  • Automatic thermal cutout
  • Manual reset thermal cutout (when required by code, otherwise optional)
  • Neptronic HEC controller
  • Pneumatic Electric Controller
  • Contactor(s)
  • Solid State Relay(s)
  • Fuses (when required by code, otherwise optional)
  • Disconnect switch (when required by code, otherwise optional)

Besides wiring of the power supply, you must connect the appropriate wires to the thermostat for electric heaters and a 1/4” diameter pneumatic signal tube for pneumatic control heaters.