Party scale sous-vide

Has anyone had success at large scale sous-vide at home?

My scale was not quite as big as yours, but I cooked my Thanksgiving turkey for the extended family this year sous vide. Not only was the outcome a huge hit among the guests, but it was a huge relief for (your truly) the chef.

I want to go to party scale, say 30 to 40 servings, what are my chances of success?

In my experience, scaling up is one of the biggest advantages of cooking sous vide. Cooking 30-40 servings on a home stove would be a daunting prospect, to say the least. With sous vide, 15–20 servings is only marginally more work than 4–6. Again, I've not done 30–40, but it should scale accordingly.

Should I just get three or four chilly bins or just one large bin?

If your food will fit in one cooler, it will work, but I think you'll find it much easier to use more. The more water you have, the slower it will lose heat, and thus, the less you will have to pay attention to it. I also typically cook chicken and beef at separate temperatures, so I would probably have two coolers for chicken and two for beef.

The "chilly bin method" will work with small cuts of meat like individual sized portions. If you're just scaling up with individually sealed cuts, I would err on the side of caution with using more bins rather than a single larger bin (and even favoring multiple large bins since they will have higher heat retention). The reason for this is that in a large bin with a quantity of 30-40 cuts (or a small bin with 10+ cuts), you may be blocking water circulation and end up with temperature variations (cold spots) that will allow dangerous bacteria to breed. Make sure that you have plenty of "space" around each piece of meat with the "chilly bin method" and that you have a high enough water-to-meat mass ratio that you won't lose much heat during the cooking.

However, even with these warnings, I would never use the "chilly bin method" for a large cut of meat. Not even for a 2 lb pork tenderloin. The reason why is that doubling the circumference of a cut of meat can quadruple cooking time.

I have cooked 8 lbs of pork tenderloin (half of it fed 7 and the leftovers fed another large group meal) and a 10lb ham that would easily feed 15. Unfortunately as noted, large cuts of meat can take a long time to cook sous vide. It took 18 hours with my ham (thawed at 38F) and 10 hours with the tenderloins (from 23F).

Due to the time scale, you probably need active and controlled heating if you want to avoid falling into the "danger" zone for temperature when you are doing sous vide. It would be dangerous do do a 10 lb ham for 18 hours in any chilly bin or even 10 hours for the tenderloins (~2 lbs each x 4).

Active heating means a water oven or an immersion circulator or heater with air-bubble circulator. You can do sous vide on the cheap with PID controllers and a crockpot or many other cooking appliances.