HVACopediaCarrier · Mini-split troubleshooting
Multi-zone: one room heats, another will not cool - DLC multi-zone
What is going on
On a multi-zone system the indoor units cannot heat and cool at the same time.
Likely causes
- Mode conflict between indoor units
Check in this order
- Heating has priority. If unit A is cooling or on fan and unit B is set to heat, A shuts off and B heats.
- If A is heating and B is set to cool or fan, B goes to standby and A keeps heating.
- Set all running indoor units to the same mode (fan with cool is fine).
Applies to: DLCM(R/H)B multi-zone outdoor units with DLFSHBH high wall indoor units (Midea, Carrier, Viessmann)
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Source: DLCMRBH/DLCMHBH Multi-Zone Outdoor Service Manual (sold as Midea, Carrier and Viessmann Vitocal 200-S; Viessmann doc 6225551-03, 12/2024), Indoor units mode conflict p.44. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.