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PTI-25-30-T4F Operators Manual
Wet Stacking
Diesel engines are designed to operate with a load. When a diesel engine operates considerably below
the rated output level the engine can start to over fuel or “wet stack”. Diesel engines perform moste
efficiently at 70-80% of the rated output. When an engine operates for a prolonged period of time below
40% of its rated out it begins to over fuel. This occurs because the injection tips begin to carbonizes and
disrupt the fuel spray pattern. In commercial generator standby/ emergency where loads can vary and low
output conditions can occur more frequently because of the diverse load applications, an automatic load
bank is sometimes used. A load bank will place a “false” load on the generator system to keep the diesel
engine properly loaded to prevent a “wet stack” condition and automatically adjust the “false” load to the
real load.
In smaller applications a “false” load can be provided by an electric heater or other high load appliances
to ensure that the generator operating at an acceptable level. Once an engine begins to wet stack the
only way to correct the problem is to provide a high level load for an extended period of time depending
on the severity of the condition. Today`s newer emissions common rail electronic fuel injected engines
are very unlikely to create a wet stack condition, but it is possible. This is why sizing a generator for a ar
