NFPA 110, 8.4.2* Generator sets in service shall be exercised at least once monthly, for a minimum of 30 minutes, using one of the following methods:
(1) Loading that maintains the minimum exhaust gas temperatures as recommended by the manufacturer
(2) Under operating temperature conditions and at not less than 30 percent of the EPS standby nameplate kW rating
Several questions have arisen recently regarding the “exhaust temperature option” during monthly generator tests as per NFPA 110, 8.4.2 (1). Unfortunately, some of the manufacturers do not/have not published their minimum combustion temperature recommendations. However, NFPA 110, 8.4.2 (2) gives us a hint since it states: “…30% of the EPS standby nameplate KW rating.”
I think we could conclude that if we “measured” the exhaust gas temperature while the generator set was running, at 30% of its kW load (may need to use a load bank), we could use this as the minimum temperature. Measurements can be made with an infra-red gun at most any place along the exhaust route starting at the exhaust manifold up to the silencer. The key is being consistent as to the same spot along the exhaust route each month. Using a thermocouple is a tad more expensive but less prone to question by a surveyor.
As a side note, several stock car teams use an infrared gun to see if all cylinders are burning at the same temperature.
Dan Chisholm, Sr., CHEPP®
Certified Healthcare Emergency Power Professional
Chairman, NFPA 110 and 111, Emergency and Standby Power Systems, Technical Committees
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