Heat pumps · Error codes · Hitachi
b5Hitachi
b5 on a Hitachi heat pump: Incorrect setting of indoor unit number for H-LINK type
Short answer
On a Hitachi heat pump, b5 means: Incorrect setting of indoor unit number for H-LINK type. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Incorrect setting of indoor unit number for H-LINK type.
Part involved: outdoor PCB address setting.
Likely causes:
- Number of indoor units connected to one H-LINK II system is 17 or higher.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Correct setting then restart.
What you can check
- Read and note the alarm code and any retry code (e.g. P70) shown on the unit controller.
- Check the heat pump supply breaker/isolator at the consumer unit is ON.
- Call the installer - this is a commissioning/setting fault.
What the engineer will check
- Follow SMGB0146 section 6.7 troubleshooting flowchart for alarm b5.
- Check DIP switch capacity/model settings on indoor and outdoor PCBs.
- Check unit controller installer configuration.
Who to ask for: Commissioning engineer / MCS heat pump installer.
What you might notice
Sources
- Installation & Operation Manual - YUTAKI series and YUTAKI Cascade Controller (R410A series / R32 series) ↗ · PMML0510 rev.1 - 10/2019 · page p.149 (PDF p.160) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026