Coolant System Maintenance

NFPA 110 calls for a weekly inspection, a monthly exercise run of at least 30 continuous minutes at 30% or more of nameplate kW (or the manufacturer’s minimum exhaust gas temperature), monthly operation of each transfer switch, annual fuel quality testing, and, for Level 1 systems, a 4-hour run at least once every 36 months. The edition that applies is the one adopted by your local authority having jurisdiction, so confirm it with your AHJ.

Generators typically need full service annually or every 200 to 500 hours of operation, whichever comes first. We also recommend weekly visual checks and monthly exercise runs. A tailored plan can include breaker testing, fuel tank cleaning, and engine maintenance to prevent issues before they start.

The most common cause we find is a dead or weak starting battery, which is why batteries get tested monthly and replaced on a schedule. After that: contaminated fuel that clogs filters, a transfer switch that did not transfer, and coolant or block heater problems that keep a cold engine from starting. A generator that only runs under light load can also wet stack, leaving unburned fuel in the exhaust that chokes the engine when real load arrives.