Honeywell 621-6700 (6216700) Product Description

621-6700 (6216700) is an 8-channel, relay-type digital output module (DO) of the Honeywell 621 series I/O. It uses dry contact relays for output and is compatible with both AC and DC loads. It is compatible with traditional DCS systems such as 620/621 and TDC 3000. 

I. Basic Information

Brand: Honeywell (Honeywell / ISSC)

Full Model: 621-6700 (6216700)

Series: 621 Series I/O Module (IPC 620/621, TDC 3000, UCN)

Type: 8-channel Relay Dry Contact Digital Output Module (DO)

Production Status: Out of Production (Second-hand / Repaired / Reconditioned Channel)

Weight: Approximately 0.6 kg

Dimensions: Approximately 11.8 × 4.7 × 9.4 cm

Installation: Inserted into the 621 Series I/O Rack

Isolation: Channel - System Side Relay Electrical Isolation

Common Suffix:

621-6700R: Supports Hot Swap

II. Core Functions

8 Channels Relay Dry Contact Output: Passive Contacts, Switchable AC/DC Load

SPDT (Single-Pole Double-Throw) Relay: Each Channel Contains NO/NC Contacts, Flexible Wiring

Wide Voltage Compatibility: Supports 30V DC and 250V AC Load Control

High Isolation Voltage: Relay Contacts - System Side Strong Electrical Isolation

LED Status Indication for Each Channel: Real-time Monitoring of Output On/Off

Overcurrent and Overheat Protection: Built-in Protection Circuit, Enhances Reliability

Compatible Systems: IPC 620, IPC 621, TDC 3000, UCN, etc. legacy DCS

III. Electrical Specifications

Output Type: SPDT Relay Dry Contact (Passive)

Channel Number: 8 Channels (Independent)

Contact Specifications:

Resistive Load: 2A @ 30V DC / 250V AC

Inductive Load: 1A @ 30V DC / 250V AC

Isolation Voltage: 2500V AC RMS (Contacts - System Side)

Action Time: ≤ 5 ms

Release Time: ≤ 3 ms

Contact Life: ≥ 1000,000 Times (Rated Load)

Power Supply: 5V DC (Backplane Bus Power Supply)

Protection Functions: Overcurrent Protection, Overheat Shutdown, Reverse Polarity Protection

IV. Environmental Parameters

Operating Temperature: 0°C ~ +60°C

Storage Temperature: -40°C ~ +85°C

Humidity: 5–95% RH (No Condensation)

Anti-Vibration: 10–55 Hz, 0.7 mm Double Amplitude

Protection: IP20 (Installed in Cabinet)

Certifications: CE, UL, CSA

V. Interfaces and Status

Field Interface: 50-pin D-Sub / European Terminal Block

LED Indicators:

PWR: Green (Normal Power Supply)

8 Channel LEDs: On = Bright, Off = Off

COM: Red (Common Terminal Abnormal / Bus Fault)

Bus Interface: 621 Rack-Specific Parallel Bus

VI. Typical Applications

AC/DC Mixed Load Control: 220V AC Contactors, 24V DC Valves

High-Power Circuit Switching: Motor Start/Stop, Heater Control, Large Current Valve Island

Safety Interlock Circuit: Emergency Stop, Fault Protection, Safety Door Interlock

Old System Upgrade: IPC 620/621, TDC 3000 System Relay Output Replacement

Industrial Automation Standard Scenarios: Production Line, Packaging Machine, Machine Tool, Chemical Plant

VII. Model Comparison (621 Series DO) Table

Parameters: 621-6700, 621-6550, 621-6650, 621-6503

Number of channels: 8 channels, 16 channels, 16 channels, 8 channels

Output type: Relay dry contact, 24V DC source type, 48V DC source type, 24V DC source type

Load voltage: 30V DC / 250V AC, 24V DC, 48V DC, 24V DC

Single channel current: 2A (resistive), 2A, 2A, 2A

Isolation method: Relay isolation, photoelectric isolation, photoelectric isolation, photoelectric isolation

Features: Passive contacts, applicable to AC and DC, 24V high density, 48V high voltage, large current self-protection

VIII. Common Faults and Troubleshooting

Relay does not act (LED does not light up)

Reason: Loose wiring, abnormal power supply on the backplane, module not plugged in tightly, bus fault

Troubleshooting: Measure the 5V on the backplane, reinstall the module, check the bus communication

Contact without output (conduction failure)

Reason: Contact oxidation, overload of the load, damage to the relay coil

Troubleshooting: Clean the contact, reduce the load current, replace the module

Output stuck (unable to disconnect)

Reason: Load short circuit, contact burnout, module overheating

Troubleshooting: Disconnect the load, check for short circuit fault, replace the module

IX. Related Models

8-channel relay output (hot-swappable): 621-6700R

24V DC source type output (16 points 2A): 621-6550

48V DC source type output (16 points 2A): 621-6650

24V DC source type self-protection output (8 points 2A): 621-6503

24V DC source type output (8 points 0.5A): 621-6500

Digital input: 621-4500, 621-4502, 621-4550

Analog input: 621-4000, 621-4001

Analog output: 621-5000, 621-5001