Need help on some steam calcs for my new brewing system

Josh_10

So I'm getting ready to build a new homebrewing system. Upgrading from the ol' 6 gallon stovetop to an all grain 15 gallon system.



I'm pretty good at working on steam heating systems but have no experience in sizing steam to liquid heat exhangers.



Here's what I'm wanting to do. My wort boiler requires me bring 15 gallons of wort to a rolling boil for up to 90 minutes. I'd like to install a stainless steel coil inside the kettle for steam to boil the surrounding wort. How do I size that coil?



Also, is anyone familiar with a very small electric steam boiler? I worked on a 10K a few years back but can't remember for the life of me who made it.



Thanks much,



Josh