HVACopediaICP · Heat pump
9 Low voltage
What the control is telling you
Control circuit voltage below 17 VAC.
Applies to: ICP N4H3 R-410A split heat pump (manual 428 01 5103 02); Comfort Alert codes apply only to units factory-fitted with the Comfort Alert module
Likely causes
- Control transformer overloaded
- Low line voltage
Test and repair steps
- Measure 24 VAC at R-C on the module; must be above 17 VAC.
- Check transformer load and its VA rating.
- Check line voltage; contact the utility if low at the disconnect.
Settings for these units
Outdoor unit clearances · ICP N4H3 Heat Pump
| Location | Minimum |
|---|---|
| Above unit (discharge) | 48 in. (1.2 m) |
| Each coil side (intake) | 18 in. (457 mm) |
| One coil side, reduced (unit to structure) | 6 in. (152 mm) |
| Control box corner and service panel | 24 in. (610 mm) |
| Between side-by-side units | 18 in. (457 mm) |
| Roof overhang above unit (with gutters) | 48 in. (1.2 m) vertical |
Small objects (post, fence end): clearance about equal to the object width.
Do not install under an overhang without gutters.
Models that show this code
1 model in ICP N4H3 Heat Pump
Other codes on the same units
- 3 Short cycling
- 4 Locked rotor
- 5 Open circuit
- 6 Open start circuit
- 7 Open run circuit
- 8 Welded contactor
- Red TRIP LED Comfort Alert TRIP - Y1 call but compressor not running
- TRIP + ALERT flashing together Control voltage too low
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Source: ICP N4H3 Installation Instructions 428 01 5103 02, Comfort Alert Diagnostics Codes (Figure 18), p.20. 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.