Formula for strike water temp using HERMS

[BrewRunning]

For those of you using a HERMS system, how do you calculate your strike water temp?

I just did my first brew on my 30g Spike system. I used the standard formula that I've always used;

(.2/R)(T2-T1)+T2 Where R=water/grain ratio T1=grain temp and T2= target mash temp

For this brew I used a 1.40 water/grist ratio. My target mash temp was 154 and grain temp was at 88 degrees from sitting in the garage.

(.2/1.4)(154-88)+154

(.1428)(66) = 9.42 degrees of expected drop in temperature after mash + 154 = 163.42 for strike water

I got the MT to 164 and mashed in but the temp settled too high at 157. So approximately only a 7 degree drop in temp. I'm assuming this is due to the MT already being heated up so no loss for MT temp.

I'm looking to more accurately predict the strike temp in the future. Does the following make sense?

If I use the 7 degree drop in temp I experienced and divide by 66 = .106 and multiply that times the ratio (1.4) I come up with 0.148.

Is it as easy as taking my original formula and changing the .2 to .148 for future brews? Am I off on the math?

Hope this post isn't too confusing. I'm no math whiz so I could be over thinking this.

Thanks,

 

[day_trippr]

fwiw, while I respect the effort to generate one's own tools, I use BeerSmith3 with an equipment profile carefully tuned to my 3v2p herms rig and it tells me what the strike water temperature should be.
It's one of the things BS3 is very good at - IF you generate a high fidelity equipment profile. I'm rarely off by more than 1°F after underletting the strike volume, giving the mash one good stir, then lidding it and letting it sit for five minutes before measuring temperature, whether the dead of winter or dog days of summer...

Cheers!

 

[BrewRunning]

Thanks, I do use Beer Smith 3 but unfortunately I don’t have the number dialed in enough to trust it. Looking to verify/supplement that info with calculations to double check myself until I get it all down pat.

 

[kevin58]

Thanks, I do use Beer Smith 3 but unfortunately I don’t have the number dialed in enough to trust it. Looking to verify/supplement that info with calculations to double check myself until I get it all down pat.

It would greatly be to your benefit to take the time to make the weights and measures you need to build a fully customized equipment profile.

 

[hottpeper13]

I figure my temps the same way. I call it Brew Palmer, because I use the formulas from How to Brew. I have the 15 gal Spike kettle and the markings are off by .5 gal at the 4.5 gal volume mark. May i suggest you take a 1 gal measure and check your markings.