Parallel Generators: Suggestions

Running Out of Gas

Don’t let your generator run out of gas while servicing a load. This can be non-beneficial to both the generator and any motorized (and especially any 240 VAC) appliances the generator is servicing. Repeated practice of this can also lead to a demagnetizing of the generator’s magnets. But in any case, forgetting once in a while is not going to be a big deal. These things happen.

Letting the generator run out of gasoline while under load is not to be confused with explicitly shutting the generator off under no load by shutting off the fuel supply. This is the recommended practice for shutting off a generator when it is known that it will then go into storage. This manner of shutting off power to the generator, before going into storage, is essential in that it removes gasoline from the carburetor where gasoline left over many months would gum up.

Losing One Phase

Let’s consider the case of a non-parallel configuration–one generator servicing the load. Some generators have three circuit breakers: one each for each 120 V phase and a third for the combination 240 VAC output. For these generators, it is possible to lose one of the 120 VAC phases leaving the generator powering the other 120 VAC phase. This is hazardous to the health of any 240 VAC appliances the generator is servicing in the home.

Bringing Online a Parallel Set

If you have parallel generator capability, try to structure placing the generators online as a paralleled set. That is, start and run both generators under no load, synchronize them to a parallel operation with no load, and only then connect them as a parallel pair to the load. The reason for this is the startup surge currents many appliances within the home will have. You can do it with one generator but you have a parallel set. Put that advantage to work for you allowing your motorized household appliances to startup more solid, which benefits their health and longevity.

Crankcase Oil

Remember to check the crankcase oil level periodically when running the generator for contiguous 8-hour shifts. This is especially important if you are using a consumer-grade generator and even more important if this is the first use of the generator. Generally for consumer grade generators, they will need additional crankcase oil every 24 hours of operation.

And, of course, for heaven’s sake, do not neglect to change the crankcase oil when recommended.


While not a big deal, it is beneficial nevertheless to close out a generator’s operation in such a way that it is able to cool down. When a generator has been maxing out on its power delivery capability for a lengthy time, it will build up an acceptable heat. This heat is a function of the large load being delivered. It is therefore beneficial (though not required) to let the generator run for a minute after switching off the load. If allowed to run for a minute under no-load, the armature will cool significantly in its rotation.