I have been doing generator maintenance on and off for most of my life and part of plant maintenance. Ours have always been diesel, except the few that were natural gas, and the one that was CNG, but only because we had a CNG plant on site that we maintained as well.
Some of the loading/exercising is to keep the engine working properly. As you probably know idling a stored car once a month is better than never starting it but not really keeping it in good shape. You need to exercise all the systems to make sure they are working and keep them in operational state. Basically any load that will idle it up and cause it to work is good. If you are wanting hit a certain amount of load heaters are good. So are compressors. Just make sure that your gen set can handle the inrush of starting a large compressor if you have one. It can be really rough on the motor for the compressor. (Massive lighting loads are also good, not everyone has a few hundred thousand square feet of office space to use as load tho) You can measure the load using amp meters. If you know your gen set can handle 200 amps total at 220 volts you need to be able to load it at 100 amps on some 220 circuits. Any load is better than no load, you want to see it work, not just sit there and be ready to work.
As for loading keeping the moisture out, or maintaining the magnetics... The magnetic fields are for the most part created under run conditions and induced from one set of windings to another. The iron cores and the windings should be encased in resin to keep dry. If you are getting moisture in the iron cores at a rate significant enough for corrosion periodic run times are not going to keep them dried out. My generator for camping gets exercised right before leaving once every year or three. It works flawlessly, just as good as the ones that I tend to that get exercised weekly. Albeit on a much smaller scale, and minus a phase.
The current place of employment has a few 3 phase generators on site. We have them set to exercise one per week for an hour. 15 minute start up, 30 minute load and 15 minute cool down. We have them set to transfer the whole building UPS systems from city to generator power for that 30 minutes. During these regular automatic exercise cycles the generators and transfer switches are observed.
At the end of the day the main reason you want to exercise your generator has to do with fault detection. Any abnormal run condition or lack or run condition, be it during start up or during transfer/load is best detected while normal power is available so that repairs can be done while normal power is available. It is inevitably harder to source a back up generator or get generator repairs while there is no power as you are probably not the only one in need.
So, how much load? Enough to know that the gen set is going to do it's job when it is needed. How often? Professionally we like to do it weekly but at a minimum monthly.
As for the last generator maintenance run. Oil and fuel filters changed with the oil yearly. Air filters changed when needed. Oil analysis done once a year.
My own personal ones.... Oil changed when it looks bad, never analyzed. Air filters changed when they can't be blown out any more... lol.
Welcome to TBN CB, and thanks for stopping by.
Good input - IMO one of the best uses of these forums is listening to other peoples direct experience. In another recent thread I cited Will Rogers quote about Learning and Electric Fences...... I've had enough "Learning Experiences" over the years to provide me some incentive to sharpen my listening skills
.Good analogy about cars sitting around - that is the mechanical system that the most people will be familiar with. In the back of my mind, I'm thinking of PM motors.... your comment on magnetics reminds to me add looking at actual modern day generator design to my rainy-day list.
While I do detect some humour
in your comments on your personal generator, I do want to ask - Is the much lighter exercise on your camping gen simply because it serves a less critical function than the facility generators, or are there technical reasons for that difference in approach ?Rgds, D.
