Issue
A failed IAC 400 controller requires replacement, but only an IAC 420 is available. This article provides guidance on using the IAC 420 as a substitute, including key differences and configuration considerations.
Product Line
Satchwell MicroNet, Satchwell Sigma
Environment
- IAC 400
- IAC 420
Cause
The IAC 400 controller is no longer manufactured or supported, making direct replacements unavailable. In legacy systems, the IAC 420 may be the only remaining compatible controller on hand, despite also being obsolete. However, differences in hardware and configuration between the two models can lead to confusion or improper operation if not addressed.
Resolution
Key Differences Between IAC 400 and IAC 420
| Feature | IAC 400 | IAC 420 |
|---|---|---|
| Input Types | 3 x Temperature Inputs 2 x Analogue Inputs 1 x Digital Input |
6 x Universal Inputs |
| Communication Cable Screening | Terminal 3 used for earthing the communication cable screen | Screen must be connected to a good earth, not to Terminal 3 |
| Tables & Offsets | Specific to IAC 400 input types | Different due to universal inputs—review updated tables and offsets |
⚠️ Important: Because the IAC 420 uses universal inputs, existing configurations from the IAC 400 will not directly transfer. You must update the input tables and offsets accordingly. Refer to the document: IAC Controllers – Tables and Offsets for detailed guidance.
Wiring Information
- IAC 400 Wiring Details: Download IAC400A.pdf
- IAC 420 Wiring Details: Download IAC 420 - DS2801A-1205.pdf
Recommendations
- Compatibility Check: Ensure the IAC 420’s universal inputs can be configured to replicate the IAC 400’s original input types.
- Documentation Review: Carefully consult wiring diagrams and configuration tables to avoid miswiring or misconfiguration.
- Testing: After installation, verify all inputs and outputs function as expected.
Additional Notes
- Both the IAC 400 and IAC 420 are obsolete. For long-term reliability, consider migrating to a supported controller platform within the EcoStruxure Building Operation suite.
