todd wrote:KnowItAll,
The inner two rings will bring the pot to boil without a boil over, it just will take longer. You are correct that I may or may not boil at 212F and what my idea of a boil is different than yours.
Gas is a different animal than electricity, once it's off it's off and no btu transfer.
No needle valves just one setting for every boil.
Can you explain why 50 gals is the practical limit of direct fire, please. Todd
Do you have any background in control systems?
There are limits to what you can automate practically/economically using your type of equipment. I am not saying a control system can't be designed for it. The limit to what can be controlled is only limited by your wallet. There are also limits to how large you can scale home brew style equipment before energy costs impact your wallet. You are talking about directly scaling your current setup to a ~2BBL size. There are some companies marketing these types of systems to aspiring homebrewers, but I am highly dubious of them. Take a look at any small commercial 2BBL brewery/pub and see how many Andy Warholesque home brew systems you see being used.
The idea of a boil is pretty standard- some steam needs to break the surface.
For standard stock pot type kettles-
Choosing a temperature that will repeatably shut off the extra burner "just" as boil is reached is not feasible. It will also be impractical to have a single fixed heat input that will provide the desired boil rate for every batch. The tricky part is the difference in heat input between barely boiling, and boil over can be vary small. The variations caused by hot break (foam) insulating the top; ambient temp and drafts; and even small batch size differences, prevent a single heat input setting or simple temperature only setting to manage boil. It would need some kind of surface boil sensor (or something) to automate an open top kettle with a normal head space (why breweries have capped/chimney kettles)
If your system can really be set (after boil is reached) to one fixed heat input, even with batch variation, hot break insulation, drafts, etc., and still provide the desired boil rate, I would be very surprised. Once hot break has subsided, and if there are no draft issues, a fixed heat input could maintain a steady boil. The big difference with most systems though, is that heat input is usually slightly different based on ambient temp, beer style, slight batch size differences, etc. Breweries use the "funnel top" style kettles to help deal with this, among other things. Are you morally opposed to using a valve to get some adjustability?
There is only so much heat you can get into a vessel using a direct flame, not to mention the energy costs. Heat shrouds to direct/contain the heat around the sides of the vessel, steam jackets, calandrias, etc., are used for larger batches. Larger breweries don't use large versions of kitchen pots, although there could be some freak brewery out there. I just isn't practical or energy efficient. The jacketed kettle the other guy referred to may be a "dry" jacket, but more common jackets are steam powered. These steam devices are sometimes called "direct steam", but it is just a technical/marketing term meaning the steam is not supplied in a self contained package, but instead from a central supply.
A big reason why there is a practical limit to a direct fired kettle is the time required to get to a boil. You don't want to spend 2 hours just getting to a boil. The energy efficiency is another major factor.
