Holding Mash Temps

[Minjin]

I am having issues with mash temp.
I use a 15 Gallon Sanke keg with reflectix wrapped around it.
I heat my strike water to the recommended temp, mash in and stir.

Here is the scenario....
Last weekend I mashed 1in had an issue with the temp dropping to like 147 and I needed to be at 152 -
So, I turned on the burner and heated to 152 - Turned off burner and was good.
Then about 20 minutes later I checked the temp and was at 157......

I have a laser thermometer, 2 digital thermometers, and a gauge on the front of the tun.

this has happened more than once and I'm not sure what I am doing wrong.
Do I need to wait longer before checking temp?
How long should it take to stabilize temp throughout the tun?

 

[NewJersey]

i dont even have the wrap on mine, but stir more and stop the flame a lil sooner. this has worked for me so far. not exact, but nothing short of automated recirculating setups are.

 

[WissaBrewGuy]

What temperature do you mash in at? Here is a quick run down of what is happening regardless of mash-in temp:

Reflectix is not a very good insulator (R=1.1). It is convenient and looks nice but it really doesn't do as much as one would like. For my setup I use R-6 duct insulation folded in half to make R-12 so it is almost 12 times better at insulating as Reflectix and I still have large temp drops over time. The kegs just have a lot of metal and they radiate heat really quickly.

This is also related to why you overshot: Stainless steel is not a very good heat transfer metal so it is going to heat itself up way before it heats up your wort. Also the design of the sanke includes a nice large heat trap ring at the bottom and your burner holds in some heat. If you turn on the burner and heat to 152F, then turn off the burner you will overshoot because all of the metal around your system is still hotter than 152F. If you turned off your burner at 147F then you might hit 152F dead-on. It shouldnt take 20 min to increase that extra bit but that will really depend on how much volume and grain you are heating. Ideally you would stir the liquid around to distribute heat better but that would ruin your nice grain bed and we don't want that!

 

[Minjin]

Thanks Wissa! That was kinda what I needed to know. The metal was heating up very hot then after turning the burner it continued to distribute the heat to the mash. Overshooting it.

 

[WissaBrewGuy]

No problem Minjin! Good luck with your next brew. It'll take some trial and error to get it to work just right but what else is new...

 

[Phunhog]

I have the exact same setup. It's not perfect but it works well. You really just have to brew a lot to learn the nuances of your system. I usually will turn on the burner at a low setting for 1 minute and then shut it off. I have the pump recirculating the whole time.

 

[GuldTuborg]

A better approach would be to heat an extra gallon before you mash in. If your temps drop, add some more hot water, stir, and take the temp again. With a little practice, you'll keep that temp dialed in easily.

Moral of the story: always keep extra hot & cold water on hand when mashing. You never know when you'll need it.

 

[LKABrewer]

We have a thermometer between the sanke keg and the insulation near the bottom to measure the 'system temperature'. Once that thermometer hits your mash temp back down the heat.