HVACopediaRheem · Heat pump
27 Low line voltage or no line voltage
What the control is telling you
The ICC detects low or missing line voltage.
Applies to: (-)PRL-JEC 2-stage 16 SEER heat pumps: RPRL/UPRL-024JEC, -036JEC, -048JEC, -060JEC
Likely causes
- Low utility voltage
- Tripped breaker/fuse or open disconnect
- Loose or undersized power wiring
Test and repair steps
- Measure line voltage at the disconnect and at the unit; operating range for 208/230V units is 197-253V.
- Check fuses/breaker and disconnect.
- Check and tighten wiring connections at the ICC L1/L2 lugs (torque per wire size, check annually).
- If the utility supply is low, have it corrected before further diagnosis.
Settings for these units
Outdoor unit clearances · Rheem/Ruud PRL-JEC heat pump (Comfort Control2 ICC)
| Location | Minimum |
|---|---|
| Above unit (fan discharge) | 60 in. [1524 mm] |
| Coil air inlets (3 sides) | 6 in. [152 mm] |
| Service access side | 24 in. [610 mm] |
| Between two units (grille sides aligned) | 12 in. total (6 in. per unit) |
Do not reduce the 60 in. discharge or 24 in. service clearances.
Inlet clearances under 6 in. reduce capacity and efficiency.
Models that show this code
4 models in Rheem/Ruud PRL-JEC heat pump (Comfort Control2 ICC)
Other codes on the same units
- 8 flashes (L terminal) L-terminal fault output: Control mis-operation
- 09 Low secondary (control) voltage
- 9 flashes (L terminal) L-terminal fault output: Low control voltage
- 21 Low pressure control (LPC) open
- 28 High line voltage
- 29 High pressure control (HPC) open
- 30 ICC fuse open
- 80 Low airflow
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Source: Rheem (-)PRL-JEC Heat Pump Installation Instructions, 12.6 ICC Diagnostic Codes, p.30. Summarized in our own words; check the original manual for your model.
Homeowner looking at this code? See what it means for you and when to call a technician.
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.