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Emergency Generator Monthly Test - 30% Threshold

When are annual emergency generator load tests required?

Any examples are for illustrative purposes only.

When conducting the monthly test of a diesel-powered emergency generator as required by EC.02.05.07/EP 5; test of each emergency generator beginning with a cold start under load for at least 30 continuous minutes.

When conducting the monthly tests for diesel-powered emergency generators the dynamic load that is applied to the generator is at least 30% of the nameplate rating of the generator or meets the manufacturer’s recommended prime movers’ exhaust gas temperature. 

If either the dynamic load is less than 30% of nameplate rating or the recommended exhaust gas temperature is not reached during the monthly test, then the diesel-powered emergency generator must be tested every 12 months using supplemental loads either dynamic or static.

This annual test is conducted for a total of 90 continuous minutes as follows:
  1. 30 minutes with a connected load of at least 50% of nameplate rating
  2. 60 minutes with a connected load of at least 75% of nameplate rating
Static load is typically a load bank brought on-site and connected to the generator to increase electrical load in order to achieve the 50% and 75% of nameplate rating loading.

Cool down period is not part of the 30 and 90 continuous minutes test duration.

Tests for non-diesel-powered generators need only be conducted with available load.

Additional Resources:
NFPA 99-2012:
Last updated on March 26, 2021
Manual: Hospital and Hospital Clinics
Chapter: Environment of Care EC

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