Electrical Question

Jw I'm wondering if the two gages are on separate circuits, which might complicate things

At 15 kw you might be pushing things, but heck, try it. Worst thing that could happen, you burn down your house

Con we need an expert

Need to know the current rating (amps) of the transfer switch, and the supply voltage.

Regardless of volts and amps it might be interesting to know the present readings on those two gages when the lights begin to dim

If a 10,000 Watt (or does he mean kVA?) generator is struggling to supply the load and he has "gauges" with a max reading of 7,500 watts, they are going to be hard against the stops. Bad signs: he thinks that 2 x 3750 is 7000, and also does not bother to specify what the "various items" are. I do not hold out much hope for enough information, or that an answer will be understood, and will repeat the advice I usually give: don't monkey around with electricity if you don't understand it, get a professional!

Additionally consider getting the generator serviced, and check the wiring is thick enough for the load and suitable in every way.

A good point.

The point I was trying to make is that the generator has two parts -

1. An engine (like a car or motorcycle engine only smaller) which runs on gasoline or diesel fuel. If the generator is failing to deliver its full rated load it could be because the engine needs attention. It could be overheating or starved of fuel or the lubricating oil could be low or it could have some other problem that needs fixing.

2. A generator driven by the engine. Some of these have parts that wear and need replacing periodically (e.g. brushes).

We do not know at what power level the brownouts occur. It could be that the generator needs a service.

Excellent advice.