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Rheem · Heat pump

09 Low secondary (control) voltage

Medium severity Rheem/Ruud PRL-JEC heat pump (Comfort Control2 ICC)

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.

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Source: Rheem (-)PRL-JEC Heat Pump Installation Instructions, 12.6 ICC Diagnostic Codes, p.29. Summarized in our own words; check the original manual for your model.

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