09 Low secondary (control) voltage

What the control is telling you

Voltage between R and C at the ICC is below 18VAC. Reported as 9 flashes on the L terminal.

Applies to: (-)PRL-JEC 2-stage 16 SEER heat pumps: RPRL/UPRL-024JEC, -036JEC, -048JEC, -060JEC

Likely causes

• Control transformer overloaded
• Low line voltage

Test and repair steps

1. Measure 24VAC at R-C on the ICC with the system calling; it must be at least 18VAC.
2. Check the indoor unit transformer size 40VA minimum (communicating air handler/furnace uses 50VA).
3. Disconnect accessories one at a time to find an overload.
4. Check thermostat wire gauge/length (no smaller than 18 AWG; see Table 6).
5. Check incoming line voltage at the indoor unit.

Settings for these units

Outdoor unit clearances · Rheem/Ruud PRL-JEC heat pump (Comfort Control2 ICC)

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

• 6 flashes (L terminal) L-terminal fault output: Open start circuit
• 07 Compressor open run circuit
• 7 flashes (L terminal) L-terminal fault output: Open run circuit
• 8 flashes (L terminal) L-terminal fault output: Control mis-operation
• 9 flashes (L terminal) L-terminal fault output: Low control voltage
• 21 Low pressure control (LPC) open
• 27 Low line voltage or no line voltage
• 28 High line voltage