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.