Compliance News: Weekly Generator Run Tests

By David Stymiest, PE, CHFM, FASHE



A question that I am commonly asked is whether weekly generator run tests are required. This question occurred almost a half dozen times at the recent ASHE Annual Conference.

NFPA 110 requires weekly Emergency Power Supply System (EPSS) inspections as stated in this excerpt from NFPA 110-2010 (The EPSS consists of the generators downstream to the transfer switch load terminals, inclusive):

“8.4 Operational Inspection and Testing.
8.4.1* EPSSs, including all appurtenant components, shall be inspected weekly and exercised under load at least monthly.”

However NFPA 110 does not require weekly emergency generator run tests. In fact NFPA 110 clarified this issue in the 2010 edition Annex as stated below:


“A.8.4.1 Weekly inspection does not require running of the EPS. Running unloaded generators as part of this weekly inspection can result in long-term problems such as wet stacking. See Figure A.8.4.1(a) and Figure A.8.4.1(b).”

Some state and local Authorities Having Jurisdiction (AHJs) do require weekly generator run tests. Some major diesel generator manufacturers do recommend weekly generator run tests, particularly if the generators are used in Level 1 applications such as hospitals.

NFPA 110 gives the default guidance for routine EPSS maintenance and operational testing:

“8.1.1 The routine maintenance and operational testing program shall be based on all of the following:
(1) Manufacturer’s recommendations
(2) Instruction manuals
(3) Minimum requirements of this chapter
(4) The authority having jurisdiction”

The referenced NFPA 110 Annex Figure A.8.4.1(a) and Figure A.8.4.1(b), like all informational Annex material, are not “minimum requirements of this chapter” but do provide guidance for items to be inspected that can be used in the absence of detailed manufacturer recommendations on inspections.

If you must run your generator unloaded and do not have a mandatory minimum run time, considering starting it, operating until the water temperature and the oil pressure have stabilized (basically so that it is warm and fully lubricated) and then shutting it down. This can help minimize the potential for wet stacking from running the diesel generator unloaded.


NFPA Disclaimer: Although the author is Chair of the NFPA Technical Committee on Emergency Power Supplies, which is responsible for NFPA 110 and 111, the views and opinions expressed in this message are purely those of the author and shall not be considered the official position of NFPA or any of its Technical Committees and shall not be considered to be, nor be relied upon as, a Formal Interpretation. Readers are encouraged to refer to the entire text of all referenced documents. NFPA members can obtain NFPA staff interpretations of NFPA 110 at www.nfpa.org/110.