Ideal temp rise in kettle

[TwelveBarBrews]

Hi All,

I have a 15-bbl DME system with an Economite 400-33 burner. Pretty typical from the look of things. I'm just doing hot-water dry runs now, but I'm seeing a temp rise of 1 degree every 4 minutes on a full batch of water, which seems quite low to me. After sparge it would take hours to get to boiling at that rate.

We've been playing with the output baffle (currently set 70% closed) and the gas tester says the burn is actually pretty good.

What kind of temperature rise should I be seeing on the way to hop boil?

Also the tech is asking about the stack temperature? It's a used system, no manual, no tech sheets, etc.

[TwelveBarBrews]

Update:

We timed the gas flow at the meter and came to 200,000 BTUH, which is half the flow rating required by the burner. A bit more research and the gas regulator (which came with the kettle from the old brewery) is rated max 250,000, AND it necks down to 3/4" pipe diameter. The fix is to get a 1" ventless gas regulator rated for > 500,000 BTUH.

I'm still interested if anyone happens to know what the exhaust stack temperature range should be for a mid '90's DME direct fired kettle.

[brewmaster 2011]

with a direct fire kettle you should turn on the burner when you get to a set volume during runoff so that at the end of runoff you are right around boil then trim back the fire so as to not scorch the bottom of the kettle. all of it will be trial and error until you learn your new system

[monkeybrewer]

stack temp

I have a mid 90's 7 bbl DME that we recently reinstalled after a fire in our hotel. We also have an economite but its just 183K BTU...definitely takes me an hour to boil after run off is complete but boils well after that. The stack temp we tried to achieve was 600F. We used a barometric damper to get the temp down from the 1300F that was going up the stack. Our metalasbestos was rated for 2200F max temp with a 1400F constant operating temp max. The bottom 90 degree on the stack still gets the 1300F but it hasn't shown any signs of damage or wear after many brews and CIP's. All of this was done by a professional and checked with the appropriate meter. Hope that helps...
Cheers

[South County]

We have a smaller direct fired kettle that we built, uninsulated (yeah I know) with a baffled firebox and 300K btu economite. Our wort temp from the mash comes in at about 145 degrees and takes 45 mins to come to a boil. We start our flame at 2 bbls and run it pretty hot and then pull it back when gets to rolling boil. We also find that we have to purge our bottom kettle drain periodically to keep that 15 inches tube from hot vaoprizing into acrid wort sugar, we even have a baffle to block it from to much flame. We have a damper at 75% that helps hold heat in the fire box, Flu temps on double wall type B are 800-1000°. Which drops quickly as we only have 4ft of vent in the building, the rest is outside.