Honeywell TC-IDD321 32-Point Digital Input Module

The Honeywell TC-IDD321 is a 32-channel, 24 VDC digital input module for the Experion LS I/O system. It receives discrete signals from field devices and transfers their ON/OFF status to the control system. The module uses a 16-points-per-common input arrangement, supports IEC Type 1+ input compatibility, and provides channel-to-channel and user-to-system isolation.

Input Configuration and Signal Processing

The TC-IDD321 provides 32 digital input channels, arranged as two groups of 16 points per common. It is designed to monitor 24 VDC field signals from discrete devices such as switches and contact-based sensors.

The input thresholds determine how field signals are recognized:

• ON-state: Minimum input current of 2 mA.
• OFF-state: Maximum input voltage of 5 V.
• OFF-state current: Maximum 1.5 mA.
• Input compatibility: IEC Type 1+.

These limits should be checked against the field device output characteristics to ensure correct state detection and avoid unintended input transitions.

Electrical Characteristics and Isolation

The module has a maximum power dissipation of 6.1 W. Its channel-to-channel and user-to-system isolation are both tested at 1500 VDC for 1 second.

This isolation testing provides defined electrical separation between input circuits and between the field-side and system-side interfaces. The 1500 VDC test rating is an isolation test condition, not a continuous operating voltage.

Technical Specifications

Input Timing Characteristics

The published Experion LS technical specifications identify programmable input filtering for the TC-IDD321:

• OFF-to-ON filter settings: 0 ms, 1 ms, or 2 ms.
• ON-to-OFF filter settings: 0 ms, 1 ms, 2 ms, 9 ms, or 18 ms.
• Hardware delay: 1 ms maximum, plus the selected filter time.

The selectable filter settings allow input response to be configured according to the required signal characteristics. Longer filtering can help reject brief signal disturbances, while shorter settings provide faster recognition of input transitions.

Terminal Block Configuration

The supplied product information identifies a 36-position TC-TBNH terminal block for field connections. However, the Experion LS technical specification document lists TC-TBCH as the 36-position terminal block for the TC-IDD321.

The terminal block identifier should therefore be checked against the existing hardware configuration and module documentation before ordering a replacement.

Frequently Asked Questions

Q: How many digital input signals can the Honeywell TC-IDD321 monitor?

A: It supports 32 discrete input channels arranged as 16 points per common. The module accepts nominal 24 VDC field signals.

Q: What input conditions are required for reliable ON/OFF state detection?

A: The minimum ON-state current is 2 mA. For OFF-state recognition, the input voltage must not exceed 5 V and the OFF-state current must not exceed 1.5 mA.

Q: What terminal block is used with the TC-IDD321?

A: The supplied product information specifies TC-TBNH, while the published Experion LS technical specification lists TC-TBCH. Verify the required terminal block against the installed configuration before procurement.