Two Wiring Methods for ODES Temperature-Humidity Controller Loads

Environmental control inside switchgear and automation panels depends on precise temperature-humidity regulation. Learn more about ODES’s TH-E Series controllers and complete environmental solutions at www.odes-electric.com

Why Two Wiring Methods Exist

In practical applications, temperature-humidity controllers must not only switch heaters and fans locally but also satisfy requirements for electrical safety, isolation, and EMC compliance.

To meet these demands, the ODES TH-E Series supports two independent load-control methods:

1. Passive (isolated dry-contact) control — for loads powered by an external source.

2. Active (direct-power) control — for loads using the same power supply as the controller.

Understanding when to use each approach is essential during design review, panel assembly, and commissioning.

Method 1 – Passive Control (Different Power Source for Controller and Load)

Concept: In this mode, the controller’s relay acts purely as a dry contact, serving as a switching signal to drive an intermediate relay, contactor, or solenoid that energizes the load from an independent external power circuit.

Typical applications:

• Loads with higher power or inductive characteristics (heaters, fans, solenoid valves).

• Systems requiring electrical isolation, multi-stage protection, or local/remote control interlocking.

Advantages:

• The internal relay handles only low coil current, improving service life and reliability.

• Easy to expand for multiple loads, multi-stage control, or local/remote switching.

Example: In models such as TH-E-10/11-LED, terminals 3–4 (heater) and 5–6 (fan) operate as voltage-free contacts. The controller provides switching only—external power must supply the load.

Method 2 – Active Control (Controller and Load Share the Same Power Source)

Concept: Here, the controller’s internal relay connects its common (COM) and normally open (NO) contacts directly in the same line as the power supply (L or positive terminal). The relay therefore closes or opens the load circuit directly.

Typical applications:

• Small heaters or fans within the rated current of the controller’s relay contacts.

• Panels where space and wiring simplicity take priority.

Advantages:

• Simplified wiring and lower component cost.

• Fast troubleshooting — load and relay status can be verified directly on site.

Example: In models such as TH-E-10/11-A/LED, terminals 3–4 can directly output voltage to the heater. No external power supply is required for load operation.

Engineering Perspective

Selecting between passive and active control depends on load rating, cabinet design, and safety requirements.

• Use passive control when you need isolation or to handle inductive or higher-power devices.

• Choose active control when the load is small, wiring must be minimal, and simplicity is critical.

Both configurations maintain full compatibility with ODES environmental-control accessories and comply with applicable IEC/IEEE design standards for relay isolation and EMC performance.

The TH-E Series temperature-humidity controllers provide flexibility for both complex multi-circuit panels and compact single-cabinet installations. Whether you require isolated dry-contact switching or direct power control, the system architecture can be tailored to your exact safety, reliability, and maintenance needs.

By understanding these two wiring methods, engineers can design cleaner, safer, and more maintainable environmental-control circuits.

Design smarter, safer temperature-humidity control into your next cabinet.

• Request detailed wiring diagrams and current ratings for TH-E Series controllers.

• Consult our engineering team on isolation design, interlock integration, and load sizing.

• Build panels that are safe, efficient, and compliant with international standards.

Contact: 📩 tonyzhang@odes-electric.com

Or visit: www.odes-electric.com

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