20 quart mixer

how many pounds can we do in a 20qt? 10lb of flour?

Yep, about 10-pounds. With a used mixer it is hard to say exactly how much flour can be used but satrt at 10-pounds and if the mixer seems to struggle, or if the agitator begins to stall back off 2-pounds of flour. If you are mixing multiple batches feel the top of the mixer occasionally to make sure the motor isn’t getting too hot. Warm is ok, but hot is not so good.
Tom Lehmann/The Dough Doctor

We’ve been using 20Q mixers for our mobile operation for a number of years.
The maximum weight of flour is partially a function of hydration level.
The receipt we use is 1 gallon of water to 13.5# of flour along with salt, oil, and yeast. This gives a 62% hydration level.