Description
Electric Circular Duct Heaters & Preheaters – EHC Series
Electric Round Duct Heaters for Ventilation and Air Handling Systems
The EHC Series Electric Circular Duct Heaters and Preheaters is designed for efficient heating and preheating of clean air in ventilation systems and air handling units (AHUs).
With compact circular construction, multiple duct diameters, flexible electrical configurations and optional electronic controls, the EHC series provides a practical solution for HVAC ventilation systems requiring reliable electric air heating.
The heaters can be supplied as standard units or configured with temperature control, airflow monitoring, pressure monitoring, contactors and other options according to project requirements.
Key Features
- Electric circular duct heater for ventilation systems
- Suitable for heating and preheating clean air
- Output power from 0.5 kW to 24 kW
- Available for 230 V and 400 V electrical systems
- Circular duct diameters from Ø100 to Ø630 mm
- Aluzinc-coated steel housing
- Stainless steel heating elements
- IP44 protection
- Integrated or external temperature control options
- Optional airflow monitoring
- Optional pressure monitoring
- Optional contactor
- Suitable for AHU and ventilation applications
- Preheater versions available with additional insulation
- Custom configurations available
The manufacturer’s current EHC specification lists power ratings from 500 W to 24,000 W and duct diameters from 100 mm to 630 mm.
Applications
HVAC Ventilation Systems
EHC electric round duct heaters can be installed directly into circular ventilation ductwork to heat supply air to the required temperature.
They are particularly suitable for ventilation systems where a compact inline electric heater is required.
Air Handling Units
The EHC series can be used as a heating or preheating section within air handling units (AHUs).
For fresh-air systems, the preheater configuration can help raise the temperature of incoming outdoor air before it enters the air-handling system.
Fresh Air Heating
When outdoor air must be heated before being supplied to a building, an electric duct heater provides a compact alternative to water-based heating coils.
Industrial Ventilation
EHC heaters can also be used in industrial ventilation systems for controlled heating of clean air.
Typical applications include:
- Industrial buildings
- Commercial buildings
- Warehouses
- HVAC systems
- Fresh-air systems
- Air handling units
- Supply-air systems
- Ventilation systems
- Equipment ventilation
Heating and Preheating
The EHC series can be configured for either heating or preheating applications.
The standard heater temperature setpoint is 0 to +30°C.
For preheating applications, standard temperature ranges include:
- -10 to +20°C
- -30 to 0°C
Other temperature setpoints can be configured according to project requirements.
Preheater versions are additionally insulated to suit their intended operating conditions.
Technical Specifications
| Parameter | EHC Series |
|---|---|
| Product type | Electric Circular Duct Heater / Preheater |
| Application | Ventilation / AHU |
| Heating medium | Clean air |
| Supply voltage | 1~230 V / 2~400 V / 3~400 V |
| Power range | 0.5–24 kW |
| Duct diameter | Ø100–Ø630 mm |
| Protection rating | IP44 |
| Heating elements | Stainless steel |
| Housing | Aluzinc-coated steel |
| Temperature control | Optional |
| Airflow monitoring | Optional |
| Pressure monitoring | Optional |
| Contactor | Optional |
| MODBUS | Available on EHC../MB |
| BMS integration | RS-485 MODBUS |
| Preheater insulation | Available |
| Custom configuration | Available |
Circular Duct Diameter Options
The EHC series is available for a wide range of standard circular duct sizes:
Ø100, Ø125, Ø160, Ø200, Ø250, Ø315, Ø355, Ø400, Ø450, Ø500 and Ø630 mm.
This range allows the heater to be matched to commonly used circular HVAC ductwork.
Electrical Power Options
The EHC range covers applications from small ventilation systems to higher-capacity air-handling applications.
Typical available power ratings include:
- 0.5 kW
- 1.0 kW
- 1.5 kW
- 2.0 kW
- 3.0 kW
- 4.5 kW
- 6.0 kW
- 9.0 kW
- 12.0 kW
- 15.0 kW
- 18.0 kW
- 21.0 kW
- 24.0 kW
The exact available power depends on the selected duct diameter, voltage and phase configuration.
Temperature Control Options
The EHC series can be supplied with different electronic control configurations.
EHC SI – Internal Temperature Setpoint
The SI configuration uses a duct temperature sensor with the temperature setpoint adjusted directly on the heater.
This configuration is suitable for applications where local temperature adjustment is required.
EHC SE – External Temperature Setpoint
The SE configuration uses a duct temperature sensor while allowing the temperature setpoint to be adjusted externally.
This is useful when the temperature control device needs to be located outside the ventilation duct.
EHC CE – 0–10 VDC Control
The CE configuration accepts an external 0–10 VDC control signal from another controller.
This makes it suitable for integration with HVAC control systems.
EHC FC – Flow and Pressure Control
The FC configuration provides airflow and pressure monitoring.
The airflow monitoring function can prevent the heater from operating when sufficient airflow is not detected, helping protect the heating elements against overheating.
EHC SR – Pressure Monitoring
The SR option provides pressure monitoring.
Available pressure switch ranges include:
- 0–200 Pa – SR200
- 0–500 Pa – SR500
Airflow Protection
Proper airflow is essential for electric duct heater operation.
The EHC series is designed with airflow monitoring options that can detect insufficient airflow and prevent heating operation when airflow conditions are not suitable.
The manufacturer’s technical information specifies a minimum air velocity of 1.5 m/s through the heater.
This protection can reduce the risk of overheating and can simplify integration with ventilation fans and air-handling equipment.
Overtemperature Protection
EHC heaters incorporate overtemperature protection using two thermostats.
For units with smaller diameters, the automatic-reset thermostat operates at approximately 60°C.
For larger units, the automatic-reset thermostat operates at approximately 70°C.
A 100°C manual-reset thermostat provides an additional overheating cut-off function.
The manual reset button is located on the heater cover.
For three-phase heaters, an external relay may be required for the overtemperature protection circuit depending on the configuration.
Construction
The EHC housing is manufactured from aluzinc-coated sheet metal and incorporates sealing rubber to provide a tight connection with the circular ventilation duct.
The heating elements are manufactured using stainless steel tubes, providing a robust construction for clean-air heating applications.
EHC Electric Heater with RS-485 MODBUS
For projects requiring integration with a Building Management System, the EHC../MB version provides RS-485 MODBUS communication.
The EHC../MB can be integrated into a BMS for centralized monitoring and control of the ventilation heating system.
This option is particularly useful for:
- Building Management Systems
- HVAC automation
- Centralized temperature control
- Remote monitoring
- Industrial automation
- Energy management systems
Example Model
A typical EHC model designation can contain information about the duct diameter, heating capacity, phase configuration and control options.
For example:
EHC 250/3.0/2/SE/FC/MB/K
This can be interpreted as:
- EHC – Electric circular duct heater
- 250 – Ø250 mm duct diameter
- 3.0 – 3.0 kW heating capacity
- 2 – Two-phase electrical configuration
- SE – External temperature setpoint
- FC – Flow and pressure control
- MB – RS-485 MODBUS
- K – Contactor
The manufacturer’s catalogue uses this type of designation for identifying the main configuration of the EHC heater.
EHC vs. EHR Duct Heater
The main difference between the two product families is the duct shape.
| Feature | EHC | EHR |
|---|---|---|
| Duct shape | Circular | Rectangular |
| Typical application | Round HVAC duct | Rectangular duct / AHU |
| Diameter / Size | Ø100–Ø630 mm | Rectangular duct sizes |
| Heating | Electric | Electric |
| Preheating | Yes | Yes |
| Temperature control | Available | Available |
| Airflow monitoring | Available | Available |
| MODBUS | Available | Available |
| BMS integration | Available | Available |
For circular HVAC ductwork, the EHC series provides a direct inline heating solution.
For rectangular ductwork and larger air-handling systems, the EHR series is the corresponding rectangular solution.
Engineering Selection
Selecting the correct EHC electric duct heater requires several operating parameters.
1. Airflow
Airflow should be specified in m³/h or m³/s.
2. Inlet Air Temperature
The incoming air temperature is required to determine the required heating capacity.
3. Required Outlet Temperature
The desired outlet temperature determines the required temperature rise.
4. Duct Diameter
The circular duct diameter should be specified, for example:
Ø160 / Ø200 / Ø250 / Ø315 / Ø400 / Ø500 mm
5. Electrical Supply
Specify the available electrical supply:
- 230 V single phase
- 400 V two phase
- 400 V three phase
6. Heating Capacity
The required heating capacity can be calculated from airflow and temperature rise.
7. Control System
Specify whether the application requires:
- Internal temperature control
- External temperature control
- 0–10 VDC control
- Airflow monitoring
- Pressure monitoring
- MODBUS
- BMS integration
How to Select an EHC Heater
For a correct technical selection, Wili recommends providing the following information:
- Airflow: m³/h
- Inlet temperature: °C
- Required outlet temperature: °C
- Duct diameter: mm
- Power supply: V / phase
- Required heating capacity: kW
- Control signal: 0–10 VDC / thermostat / BMS
- Airflow monitoring: Required / Not required
- Pressure monitoring: Required / Not required
- MODBUS/BMS: Required / Not required
Our engineering team can then recommend a suitable EHC configuration for the application.
Applications
EHC electric circular duct heaters are suitable for:
- HVAC systems
- Ventilation systems
- Fresh-air systems
- Air handling units
- Supply-air heating
- Fresh-air preheating
- Commercial buildings
- Industrial buildings
- Warehouses
- Equipment ventilation
- Industrial HVAC systems
- BMS-controlled ventilation systems
Why Choose EHC Electric Duct Heaters?
The EHC series combines compact circular construction with flexible electrical and control configurations.
Depending on the project, the heater can be supplied with temperature control, airflow and pressure monitoring, contactor control or MODBUS communication.
This allows the EHC series to be adapted to both conventional HVAC installations and automated ventilation systems.
Request a Technical Recommendation
Looking for an electric circular duct heater for your ventilation or AHU system?
Send Wili the following information:
Airflow + inlet temperature + required outlet temperature + duct diameter + voltage.
Our engineering team can calculate the required heating capacity and recommend the appropriate EHC electric duct heater / preheater configuration.
Wili – Heating Solutions for HVAC and Industrial Applications
