Strike water temp

Hello.  I am mashing into a converted 15.5 gallon kegs that I have wrapped with insulation and also insulated the top and bottom.  I modified the brewtree mash system.  My mash tun weight is 32# and MT specific heat is .120. 

I add all my water to the mash tun and make sure it sits for 3 minutes to preheat the MT

I like to mash in at 1.2:1 so for my last batch of IPA I used 27# of grain and 32.4 quarts of water.  BS suggested either 165.2F if I do not adjust for equipment or 170F if I do adjust for equipment.  This was to try to hit 150F.

This seemed too hot to me and I used 162F water.  My mash temp was still too high at 154F

What am I doing wrong please?

What did you use for grain temp.  My calculator shows 165.2 using 27# grain at 55f.  If the grain is 70f, my calculator suggests 162.8. 

As for why you used 162f water and achieved 154f, I could guess the grain weigh was incorrect, grain temp was 100f or maybe your thermometer needs to be calibrated.  I use 3 floating ones and they can be 4F apart.  Really ticks me off.  I have a digital that seems to be accurate when it is not wildly inaccurate.  the more precise one has too small of a dial so I can tell 162 from 165.  Reminds me to buy a better thermometer.

Unrelated, I recently added a tool to both my web tools and BeerCalc android app to calculate the amount of water to add to adjust your mash temp up or down when you miss your target.

Jomebrew

"What did you use for grain temp."  50F  Its cool in Sacramento in the winter...

"the grain weigh was incorrect"  I weighed it out at More Beer.  Should I call weights and measures on them?  lol

"thermometer needs to be calibrated:  I used 2 digitals and the read the same temp.

Basically my calculator and Beersmith said the same thing.  It suggests some temp was not accurate for some reason or the grain weight was substantially off or really, really hot.  One last thought is that preheating the mashtun to 162 or so threw things off.  I preheat my cooler mash tun to my mash temp not my strike temp.  Good luck on your next batch.