Daikin VRV 5 Heat Recovery Aircon CH-21 Error Code

What does Daikin CH-21 mean?

Daikin VRV 5 Heat Recovery CH-21 is listed as r32 sensor malfunction in a BS unit and r32 sensor malfunction in a SV unit in the VRV 5 Heat Recovery REMA / REYA R32 and VRV 5 Heat Pump RYMA / RXYA R32 fault lists. This meaning comes from the manufacturer's own diagnostic material. Do not collapse this code across model families; use the model, series, or system type to choose the right row. Confirm the exact model, series, or signal row before accepting a parts quote.

What to do now

Use these steps to record evidence and match the installed model to its service manual before diagnosis or a repair quote.

Record CH-21 and match the service manual
Record CH-21 and stop there; the manufacturer gives no customer reset procedure. Arrange diagnosis with the matching service manual.
No manufacturer reset steps listed for CH-21
Capture the complete CH-21 error code and model stickers first. The manufacturer lists the meaning but no customer reset procedure; do not treat a generic power-cycle as manufacturer guidance.
Send these to us
CH-21 error code, a clear display photo, Daikin VRV 5 Heat Recovery indoor and outdoor model stickers, the controller, gateway, or unit that reported the code, operating mode and affected area, and any power or setting changes made after the code appeared

Choose the listing that matches your unit

The same code has more than one listed meaning. Match the model family, the system type and the unit that shows the code before approving parts.

Code, what it means, and what to check first
Code	What it means	What to check first
VRV 5 Heat Recovery R32 - CH-21	R32 sensor malfunction in a BS unit	Check the BS-unit R32 sensor connection at the PCB or actuator.
VRV 5 Heat Pump R32 - CH-21	R32 sensor malfunction in a SV unit	Check the SV-unit R32 sensor connection at the PCB or actuator.

Code
VRV 5 Heat Recovery R32 - CH-21
What it means
R32 sensor malfunction in a BS unit
What to check first
Check the BS-unit R32 sensor connection at the PCB or actuator.
Code
VRV 5 Heat Pump R32 - CH-21
What it means
R32 sensor malfunction in a SV unit
What to check first
Check the SV-unit R32 sensor connection at the PCB or actuator.

Guidance for your model

Notes that match the code to your exact model. Electrical, refrigerant, wiring, resistance and component checks are for a technician.

Guidance for your model
Detail	What it says
Singapore / model note	Official Daikin 4P687640-1D row for the REMA5A7Y1B and REYA8~20A7Y1B VRV 5 Heat Recovery R32 family. Confirm the exact model and displayed punctuation before using this interpretation.
Singapore / model note	Official Daikin 4P749918-1B row for the RYMA5A7Y1B and RXYA8~20A7Y1B VRV 5 Heat Pump R32 family. Confirm the exact model and displayed punctuation before using this interpretation.

Detail
Singapore / model note
What it says
Official Daikin 4P687640-1D row for the REMA5A7Y1B and REYA8~20A7Y1B VRV 5 Heat Recovery R32 family. Confirm the exact model and displayed punctuation before using this interpretation.
Detail
Singapore / model note
What it says
Official Daikin 4P749918-1B row for the RYMA5A7Y1B and RXYA8~20A7Y1B VRV 5 Heat Pump R32 family. Confirm the exact model and displayed punctuation before using this interpretation.

What to check before repair

The manufacturer's fault table gives the code's meaning, not a repair procedure. Capture evidence first; model-specific tests belong to the matching service manual.

Homeowner checks and technician confirmations
You can check	Technician should confirm
Photograph the complete CH-21 error code before taking any action.	Confirm CH-21 exactly and record which controller, gateway, or unit reported it.
Capture the Daikin VRV 5 Heat Recovery indoor and outdoor model stickers and identify which controller or unit reported it.	Match the indoor and outdoor model stickers, installed family, and reporting equipment to the source scope.
The manufacturer provides no customer reset procedure. Preserve the evidence and use the matching service manual for any system action.	Follow the matching service-manual procedure and keep measured test evidence before naming a failed part.

You can check
Photograph the complete CH-21 error code before taking any action.
Technician should confirm
Confirm CH-21 exactly and record which controller, gateway, or unit reported it.
You can check
Capture the Daikin VRV 5 Heat Recovery indoor and outdoor model stickers and identify which controller or unit reported it.
Technician should confirm
Match the indoor and outdoor model stickers, installed family, and reporting equipment to the source scope.
You can check
The manufacturer provides no customer reset procedure. Preserve the evidence and use the matching service manual for any system action.
Technician should confirm
Follow the matching service-manual procedure and keep measured test evidence before naming a failed part.

Source-bounded repair decision

Daikin VRV 5 Heat Recovery CH-21 confirms the fault label the manufacturer lists, not a failed part or repair procedure. Match the installed model to its service manual and require measured diagnostic evidence before approving parts, settings, or refrigerant work.

Whether the reporting controller or unit and exact installed model are confirmed.
What the matching service-manual procedure and measured tests show.
Whether the proposed repair names the evidence for the failed part or condition.

Daikin CH-21 questions

What does the Daikin CH-21 error mean?

Daikin VRV 5 Heat Recovery CH-21 is listed as r32 sensor malfunction in a BS unit and r32 sensor malfunction in a SV unit in the VRV 5 Heat Recovery REMA / REYA R32 and VRV 5 Heat Pump RYMA / RXYA R32 fault lists. This meaning comes from the manufacturer's own diagnostic material. Do not collapse this code across model families; use the model, series, or system type to choose the right row. Confirm the exact model, series, or signal row before accepting a parts quote.

Can I fix a Daikin CH-21 error myself?

No. CH-21 needs a technician's measurement before parts are decided. Photograph the complete CH-21 error code before taking any action. Capture the Daikin VRV 5 Heat Recovery indoor and outdoor model stickers and identify which controller or unit reported it.

Is it safe to keep running the aircon with a CH-21 error?

Record CH-21 and stop there; the manufacturer gives no customer reset procedure. Arrange diagnosis with the matching service manual.

What causes a Daikin CH-21 error?

Daikin CH-21 has a listed meaning that depends on the exact model and on which unit shows the code. Use the decoder on this page before assuming a specific cause.

Will a Daikin CH-21 error need a repair or a full replacement?

Daikin VRV 5 Heat Recovery CH-21 confirms the fault label the manufacturer lists, not a failed part or repair procedure. Match the installed model to its service manual and require measured diagnostic evidence before approving parts, settings, or refrigerant work.

What should I send a technician about a Daikin CH-21 error?

Before booking, send: CH-21 error code, a clear display photo, Daikin VRV 5 Heat Recovery indoor and outdoor model stickers, the controller, gateway, or unit that reported the code, operating mode and affected area, and any power or setting changes made after the code appeared.

Where to go next

Confirm the fault

Share the error code, model number and symptoms so we can assess the likely cause.

Not the right code?

Browse the full Daikin list or check a few codes in the same fault category.