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RS home standby display

15

Underfrequency

Electrical · Shutdown

Fault code 15. The RS20 manual tells you to reduce the number of connected loads, especially loads with high starting current such as air conditioners, and then to have an authorized dealer service the set if that is not the end of it. Causes listed include loads, governor, fuel, air-fuel mixture, exhaust, choke, demand regulator, carburetor, windings, ignition, and connections.

Seen on: Cummins RS-series home standby sets covered by the RS20 operator manual. QuietConnect RS13A–RS20AC operator manual A053X174 repeats these fault code numbers.

Likely causes

  • Too many loads, particularly motors that pull frequency down while starting.
  • Fuel, governor, or ignition problems the manual still sends to a dealer.

Checks an owner can do

  1. Turn off air conditioners and other large motors, then try one restart.
  2. If it holds frequency with the heavy loads off, leave those loads off until the set is sized or repaired for them.

When to call a pro

If frequency collapses with the breaker unloaded, stop and call Cummins.

Source

Cummins RS20 home standby operator manual, section 5 (fault codes and blink pattern). The same code numbers are listed in operator manual A053X174 for the RS13A, RS17A, RS20A, and RS20AC QuietConnect sets.

Wording follows that document. Firmware can change a threshold. If this page and the manual shipped with your unit disagree, follow the manual.

What fixed mine

No approved reports for this code yet. Send one. It stays in the review queue until it is approved.

Related Cummins codes

https://generatorcodes.com/brand/cummins/15