HVACopediaMidea · Heat pump · Defrost
Multi-zone defrost entry and exit
What happens, in order
- After the compressor settles into normal running, the lowest T3 reading between minute 10 and minute 15 is stored as T30
- Defrost starts if any of these is true 29 min cumulative run and T3 below TCDI1 and T3 plus offset is at or below T30; 35 min run and T3 below TCDI2 with offset; 40 min run and T3 below -24 C for 3 minutes; 120 min run and T3 below -15 C
- Four-way valve and fans follow the defrost action profile
- Defrost ends when T3 passes the quit temperature, or after 10 minutes, or when the mode changes or the unit is turned off
- Heating resumes in normal heating mode
Timings and thresholds
| Item | Value |
|---|---|
| Check window for T30 | minute 10 to 15 |
| Run time conditions | 29, 35, 40 or 120 min |
| Max defrost time | 10 min |
| Four-way valve closes after heat stops | after 2 min compressor off |
Applies to: Midea / Carrier / Viessmann DLCMRBH and DLCMHBH multi-zone outdoor units (Vitocal 200-S)
Models
More Midea heat pump sequences
- Compressor start and system protections · Startup
Related
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Source: Midea-Carrier-Viessmann DLCMRBH / DLCMHBH service manual (Viessmann Vitocal 200-S 6225551-03), Defrosting Control; Four-way valve control. Written in our own words; timings can differ by model and software version, so check the manual for your exact unit.
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.