Zone extender module
Part number: CEXT
Description
The CEXT clips directly onto the C225 CPU module to extend zone capacity from 8 to 14 zones. Required for any system with more than 8 damper zones. The C325# AC unit module connects to the CEXT rather than the C225 when a CEXT is fitted.
Installation guide
Installation steps
When stacking with CSL: C225 → CSL → CEXT → C325#
- Power off the C225 system completely before fitting the CEXT
- Align the CEXT clip-on pins with the female connector on the C225 and press firmly until fully seated
- Connect the C325# AC interface to the port on the CEXT (not the C225)
- Wire zones 9–14 consecutively starting at the Zone 9 port on the CEXT
- Power on and verify zones 9–14 appear in Setup
Specifications
| Entry | Description |
|---|---|
| Model number | CEXT |
| Power supply | Powered from C225 — no separate transformer required |
| Communications | Wired CAN Bus |
| Number of zones | Zones 9 to 14 (RJ11 or RJ12) |
| Dimensions | H: 32mm · W: 119mm · L: 65mm (when connected) |
| Weight | 113 g |
Included in
Related parts
Documents
Troubleshoot guide
Read more
Zones 9–14 not appearing
- Confirm the CEXT is fully seated on the C225 — remove and re-seat if uncertain
- Ensure the C325# is connected to the CEXT, not the C225
- Power cycle after fitting the CEXT for the first time
Firmware history
No firmware — the CEXT is a passive expansion module.