Strike water temperature

[RoadKing]

  Hi.  
 My strike water temp calculation never seems to be right.  I am using a direct fired 15.5 gal Stainless tun and heat the water in it then add grains.
 It seems the calculations are for adding strike water to a cold tun.
For example my last recipe , it said to add X amount of water at 173 to give me 154 when I really needed around 160.
 Is there a correction for this or am I just missing something?
Thanks..

[ghwren]

Using the following conditions and the strike/infusion calculator:

Calculation - initial strike
Target Step Temperature - 154
Water to add - 36.2 qt
Mash Tun Volume Required - 10.97 gal
Starting Water Volume - assumed to be zero for initial strike
Weight of Grain - 24.5 lb
Initial grain Temperature - 65
Mash Tun Weight - 0.00 lb because you have already heated both the water and mash tun by direct fire.
Calculation gives me - 165.0 with a water/grain ratio of 1.48.

Note for my system I use a water/grain ratio of 1.25, BUT, I have to add the false bottom space back into the strike temp equation or my mash will be way to high. My false bottom is 5.6 qt which I add to 30.6 qt for my usual 1.25 qt/lb. I'm still getting my desired thickness and correcting for extra thermal mass. So far the numbers are right on in both BeerSmith and ProMash.

[stadelman]

I think your problem is the hot mash tun.  I don't know of any formula that takes into account picking up heat from the mash tun.  I'm sure you could adjust current formulas to do this.

I use a standard formula (palmers) and then I have an offset value for temp loss due to my mash tun.  When I put strike water into my cooler mash tun I lose about 4 degrees if the mash tun is at room temp.  I come very close to hitting mash temps with this.

You could do the same to account for temperature pickup instead of loss.  Figure out how much temp your water gains after being poured into mash tun and put that in your formula.

Or, start out cool and come up with an offset to account for that.  That seems more reliable to me, but either way would work.

A couple other areas to look at- are all your thermometers right?  Also, are you stirring strike water to get a consistent temp to measure?

[ghwren]

Unlike a cooler mash tun, a direct fire stainless mash tun needs no correction as long as the vessel and water are the same temperature prior to adding your grains. Stirring your water as it nears the desired temperature will help with overshoots. The biggest problems seem to come from not accounting for the extra thermal volume of water under the false bottom.

[stadelman]

Dohh... Great point.

Obviously, I have a cooler mash tun.

Unlike a cooler mash tun, a direct fire stainless mash tun needs no correction as long as the vessel and water are the same temperature prior to adding your grains. Stirring your water as it nears the desired temperature will help with overshoots. The biggest problems seem to come from not accounting for the extra thermal volume of water under the false bottom.

[RoadKing]

   Thanks everyone for replies,  Ghwen I think you pointed out my biggest problem...not adding in the water under the false bottom, and to make it worse I have a 2 gallon space!
    I tried some trial calculations adding that water and it brought my temperatures down to where I think they
should be.
Thanks again, RK.

[MaltLicker]

There is also that "check box" that says "Adjust Temp for Equipment" 

If you check that, it makes Bsmith assume your MLT is cold, so it adds a couple degrees to the strike needed. 

Since you preheat with hot water, you could leave that unchecked.  But your dead space with two gallons is the bigger factor.