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:
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: 6.4.4.1
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:
- 30 minutes with a connected load of at least 50% of nameplate rating
- 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: 6.4.4.1
Manual:
Laboratory
Chapter:
Environment of Care EC
First published date: April 11, 2016
This Standards FAQ was first published on this date.
This page was last updated on November 15, 2021
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