Ordering a Blichmann Floor Burner this month in a slow build up to going all grain by the fall. Trying to decide whether or not to get a 15g Kettle or a 15.5g converted keg.

Main question is, how hard is it to add a sight glass to a keg, cause it seems like it'd need to be different than adding it to a kettle cause of the ridges in the sides of the kegs.

Easy. I bought this, and he has weldless versions too. It was kind of dark when I took the photos:

Although not what you asked, if you are planning 10 gallon batches, I would get at 20 gallon brew pot instead of the 15. Boil-overs are a pain, so for an extra $30 get the bigger kettle.

$30 is based on prices of boilermaker kettles at Northern brewer

+1

I brewed with a 15 gallon pot for years, finally bought a 20g Boilermaker last fall, I wish I would have done this 10 years ago!

I'm happy with my 15.5 gallon keg for 10 and even 11-12 gallon batches, starting the boil with 13. I've had a boil over or two, but it has been a while and the price was right.

There are definite advantages to going with the kettle and it all hinges on the diameter.

A 15g kettle will have a larger diameter than the half barrel converted keg. That means that the boil off will be slightly better and the ability to keep the trub in the center of the pot after whirlpooling will be better which allows you to drain off more clear wort around the periphery. Of course, you have to set up your wort drain to draw around the periphery and not the center. The center is where all the trub is if you're doing it right and you don't want to draw off there. The final reason is that the larger kettle diameter improves the transfer of heat from the flame to the wort.

I think I'm going to go with a converted keg. The price difference between a 15 or 20g kettle and a keg with fittings, is a 2nd keg with fittings, seemingly.

As for trub settling, I can see the larger diameter being helpful. On the flip side, I can see the shape of the keg being more favorable as well.

For heat transfer, I thought the chimb on the keg would help keep some heat in that is lost to the outside of a kettle. Or the chimb might just heat up and radiate more heat away. As for size, if the size of the burner isn't huge, I wouldn't expect the big kettle to really help there either. Now the kettle could have thicker bottom or a different metal sandwiched between layers of stainless to help distribute the heat. I think we really have to do a test to resolve this one. Two pots, same burner configuration, which boils faster?