Mixing boiling water with room temp water get right temp?

[AinBritain]

Hey all,

I just completed my first all-grain brew, and counting setup & cleaning it took a whopping 10.5 hours. A lot of this was due to my unfamiliarity with my equipment, (ex, I decided to cut more slits in my manifold before putting anything in the mash tun, lol) but I think the most trouble I had was heating my water to the desired infusion temperature.

So I had an idea: why not avoid having to watch my thermometer and play with the heat dial, and instead just use physics: given my desired volume and temp, and the temp of my 'cool' water, I can determine what volumes of boiled and cool water to add together to get the exact temp I want.

(Cool water would be tap water, or bottled water.)

This allows me to plug in some numbers in a spreadsheet program, measure, simply wait until the water boils, then pour in the measured-out cool water to the boil-pot. There is not really possibility of overheating and having to wait to cool, or underheating and waiting a long time to get up to my temp.

Has this been done? Do you think it's advisable? Obviously, I would also have to account for the temp drop from the grist etc, but I have BrewTarget software for that!

The 2-part formula is just:
V1 = ( (Vtot*(Tf-T2) ) / (T1-T2)
V2 = Vtot - V1
where V1,T1 is for boiling water, and V2,T2 is for tap water.

 

[cvstrat]

Or use a thermometer.

Seriously though people do it all the time when mashing out. You add a specific amt of boiling water to raise your mash temp to a specific temp. You could use it with any substance/temp. Still why not just heat the entire volume up to the right temp?

 

[wilserbrewer]

With a little practice it is relatively simple to adjust the temperature downward to hit your strike temperature. Either slowly pouring in cool water or a few ice cubes at a time while monitoring the drop.

Or another trick is to simply stir to vent a little heat. Or sometimes I will simply take a pitcher and sc0op and pour the overheated water repeatedly to release some heat.

 

[bad coffee]

Why spend all that energy (and time) to get the water up to boiling if you only want it at 154~?

B

 

[Northcalais40]

You want the final temp much nearer boiling than tap temp. So a small variation in tap water volume is going to have a big effect on the final temp. It's easier to just heat the mashin water to a single temp. Its better to limit the number of links in the chain that can bone you. Sorry for the mixed metaphor.

 

[MrManifesto]

you're thinking waaaay too hard about this. just heat up your water to 20 deg higher than your mash temp. pour into your mash tun, stir until it drops 10 deg (preheating your mash tun) and dump in your grain. by the time you've stirred enough, you're down to your mash temp.

 

[pedrovic]

Hey all,

I just completed my first all-grain brew, and counting setup & cleaning it took a whopping 10.5 hours. A lot of this was due to my unfamiliarity with my equipment, (ex, I decided to cut more slits in my manifold before putting anything in the mash tun, lol) but I think the most trouble I had was heating my water to the desired infusion temperature.

So I had an idea: why not avoid having to watch my thermometer and play with the heat dial, and instead just use physics: given my desired volume and temp, and the temp of my 'cool' water, I can determine what volumes of boiled and cool water to add together to get the exact temp I want.

(Cool water would be tap water, or bottled water.)

This allows me to plug in some numbers in a spreadsheet program, measure, simply wait until the water boils, then pour in the measured-out cool water to the boil-pot. There is not really possibility of overheating and having to wait to cool, or underheating and waiting a long time to get up to my temp.

Has this been done? Do you think it's advisable? Obviously, I would also have to account for the temp drop from the grist etc, but I have BrewTarget software for that!

The 2-part formula is just:
V1 = ( (Vtot*(Tf-T2) ) / (T1-T2)
V2 = Vtot - V1
where V1,T1 is for boiling water, and V2,T2 is for tap water.

This formula appears good But I don't understand the variables; Someone could explain in practice, with real values?

 

[pvtpublic]

I have a three year old, so the mixing works great for me. Both my BK and my MT have volumes etched inside. So I fill them so far with water depending on how much grain I'm using. Then I put the kettle on, and hang out with the kiddo until it boils. I simply mix them in the MT until I get the temp I want and then open the ball valve to bring it down to the volume I want. Then the water in the kettle is used for sparge water later.