Missing Mash Temps at times

Appreciate any help for a noob.  I seem to have an issue hitting my mash temps - but only occasionally.  I pre-heat my mash tun with hot water and then am very meticulous with entering my grain temps and mash tun temps into Beersmith.  It then of course gives me the correct mash in temp based on the profile selected and I make sure I check the box.
I have a Blichmann Top Tier system and use a 15 gallon SS mash tun that is wrapped with reflective insulation.  It holds the temp very well +-1 degree, but the initial hit is off - usually low ever 3rd batch or so. 
I brewed a Pumpkin Spice Ale yesterday and planned on a little warmer mash to sweeten it a bit, 156 degrees.  Beersmith said to mash in at 166, we did and it came out 150 degrees and once again we rushed to add a gallon of hotter water to bring the temp up.
Ideas of what I may be missing or doing wrong?  Anyone else ever have this issue?

I gave up on trying to hit it that way.  The variables of the following:

Mash tun weight
Mash tun specific heat
Grain Temp
and
Strike Water Temp

had me spinning my wheels.

Instead, I put 0 degrees F in for my specific heat for my mash tun.  My garage is temperature controlled, so my grain temp is always 68F.  I put hot water in my mash tun at about 5F above my strike temp and then stir it until it drops to my strike temperature.  I then add the grain and I'm always dead on.

It sounds like the weight or specific heat of your mashtun may be off. This can be confirmed by looking at the grain weights of the low batches. Lighter weight grists are going to lose more heat to the mashtun.

I suggest letting the preheat water sit for a few minutes longer to let the heat diffuse more evenly.

Thanks for the replies.  Brewfun, as I think back - it is the lighter beers I have the most issues with, so you may be spot on.  I will try both suggestions and report back how it goes.  Thanks again.

gevans said:

I have a Blichmann Top Tier system and use a 15 gallon SS mash tun that is wrapped with reflective insulation.  It holds the temp very well +-1 degree, but the initial hit is off - usually low ever 3rd batch or so. 

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Blichmann?  With that fancy false bottom that is sliced rather than holed?  How big is the dead space under that? 

I have a Polarware drilled false bottom, and had trouble accounting for the hot water under the false bottom.  It's there, so it adds heat, but it does not help mix the grains.  So, I ended up with additional hot water under the bottom that was not helping me mix the grains up. 

Makes sense that lighter grain bills would be low, since a greater proportion of your strike water was under the bottom.  I would imagine brewers with false bottoms have a measurable temp difference between the unmixed water under the bottom and the grist. 

I eventually adopted a lower water ratio to accommodate for that extra heat. 

I think brewfun is on this correctly. With the insulation on the mash tun you have changed the specific heat of your mash tun.  I am not an engineer so I can't tell you which way to tweek the mash tun specific heat in the Equipment section. The dead space is only .19 gal so that is kind of insignificant. It doesn't sound like your doing RIMMS. You should plan to upgrade to the autosparge and a March pump to have a RIMMS system, so you can safely put heat to the mash if needed. I can't see the need for insulation in the summer, I do use it for late Fall thru March. brewing. But if you not doing RIMMS your insulation is cool, stick with it. Pumpkin Spice Ale... you are a newbie!

You do mention the word WE... Just remember one of you is the Head Brewer and one is the Assistant Brewer.

With your SS mash tun you can direct-fire it, and stir like crazy, to raise your temp or add ice to lower it. That's not as elegant as hitting the strike temp dead-on first try but there's no marksmanship badge to be earned.

I assume everyone else occasionally needs to add or remove heat after mash-in. The simple solution is to have ice and boiling water on-hand. Conventional wisdom (this week - and it will probably change next week) is that exceeding 170 F will extract tannens; however, most of us have gotten away with adding boiling water to our mash. One school of thought is that the brief excursion of a small part of the mash above 170 is insignificant; the other is that temperatures above 170 do not leach tannens if your pH is in an acceptable range. So says Denny Conn:  http://forum.northernbrewer.com/viewtopic.php?f=5&t=118609

Specific heat is the amount of energy required to change temps by one unit, so would added insulation outside the s/s affect that greatly?  It's still just the s/s in contact with the strike and mash.  I would think the insulation acts more on the retention of heat once it's stabilized.  Dunno. 

I think Brewfun is correct about the smaller grists having less "thermo inertia" to keep them steady, plus there's more dead air between the mash surface up to the lid that consumes heat. 

I use a circle of that stiff pink foam insulation board that rests on top of the mash to insulate it from the dead air. 

durrettd said:

...not as elegant as hitting the strike temp dead-on first try but there's no marksmanship badge to be earned. I assume everyone else occasionally needs to add or remove heat after mash-in. The simple solution is to have ice and boiling water on-hand.

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+1 to that! Happened to me on yesterday's brew. I normally come within a degree or two, but this one missed by a long-shot. I errantly left the heat on the HLT - forgot to shut it down after I hit my strike temp - just opened the valve and by the time I was done stirring it in, my mash temp was 158F! I wanted 151!! Luckily I had a bunch of ice on hand and tossed some in, stirred, and hit 151 - disaster averted.

Have you checked your thermometers?  The dial thermometers should be checked often against a floating mercury thermometer.  I recently visited with a brewer that found his thermometer off by 10 degrees.  I typically have two thermometers in every vessel.

+1 to bad thermometers; just went through that. 

And I forgot to mention volumes:  that is usually the easiest way to miss mash-in targets.  In a 5-gal batch, with a small grist of 10-11 lbs, a quart or two of extra hot water could be more than 10% error in volumes, depending on the water ratio. 

A lot of good info here guys, thank-you.  To answer some of the questions:

I do not have a RIMS system yet - it is coming, probably not a direct fire, but a SS tube with a element and controller.
I do have a Blichmann Auto Sparge system.
I do calibrate my thermometers regularly at the Temperature they are mostly going to be used it.  I learned long ago that even if it is calibrated at boiling, it may not be at 154 degrees.  I do verify numbers with a second digital thermometer.
My weights were off on the Mash Tun, after punching that number in, it did change the temps.  But, changing the Mash Tun specific heat seemed to take the numbers the wrong way.  I.e.  .12 lowers the initial strike water Temp, whereas, .30 - such as used on a cooler, raised the water Temp.
I've thought about using a piece of insulation on top of the mash, but wasn't real keen on that touching my grains.
I use the term 'We' as I brew with a couple of my adult sons.
Good point on the volumes, I normally follow Beersmith's numbers to the letter.
LOL, how does brewing a Pumpkin Spice identify me as a newbie.  :


I will play with the numbers a bit more and see how it comes out, and will have Ice and Hot Water standing by.  I may also go back to my Igloo 10 gallon cooler for the smaller beers.  11 gallon batches and it often gets pretty full, that's why I opted for a 15 gallon SS unit, and to be flexible for a RIMS/HERMS system down the road.  Brewing again tonight, so we will see.

Cheers!

gevans..... I wouldn't worry about that occasional off batch. You are doing things right. With the auto sparge and Blichmann false bottom, which are both designed for recirculation, you are one March pump away from being a RIMS direct fire system. < $200, pump, fittings, silicone hose.

I am jealous, I wish  I had two assistant brewers.

pumpkin spice beer- Seasonal hype by brew pub & LHBS. I have had over a dozen different samples of this recipe. The question I always ask my samplers is,
" Would you BUY this beer at a pub?" I would give you a NO, but you will have to answer that yourself. Seasonal to me is lighter in the Summer and heavier in the Winter, and a Maibock in the Spring.... an IPA on tap year round! To each his own! My palate has one basic rule, "If its got spice. its not nice!!"

I hope you are slowly adding the grain to the water, not the other way around! You need to let the grain fully absorb the water, dough in. It takes about 10 minutes, then check temp. If your checking at different initial intervals you are not consistent and you will have a problem dialing in the strike temp. Wait 10 minutes for the first check every time. You won't destroy your mash in waiting 10 min. It is a forgiving process.

As for going back to the cooler, stick with your SS and learn how to adjust temps. Mashing is a 45-60 minute wrestling match with temps. Twenty batchs from now you will have a different perspective on priorities and techniques. Every post should tell you we all have are own way of brewing. I like it when I hit my numbers, but it doesn't make the beer taste better! Software is just a brewer's recipe guide.

Well, getting ready for brew last night, making the weight changes, etc. as recommended here, I discovered an issue with Beersmith that may be the main source of my issue all along.

I like to add mash steps into the program to remind me to check PH, start the HLT, etc. while the timer is running.  When you add steps in, then copy from my recipes and move it to the 'Brewing Currently' folder, it moves the order of those around, when it does this it changes the strike temperature! 

When I first looked at it, I thought the numbers looked odd, then verified with my printed copy and sure enough it was wrong.  It was only off a couple degrees, but it doesn't take much.

Needless to say, we hit our numbers dead on all night long after discovering that.

I see what you mean on the Pumpkin Spice.  We have a local brewery here that makes 'Ichabod' and is one of my sons and his wife loves that beer, so when in Rome.

I bought a SS Chugger pump on special for $100 at the AHA conference in Philly and am discovering the freedom it gives me over gravity.  RIMS system is close, but finishing a few other projects first.

Cheers and thanks for all the input.

This is somewhat related and thought I'd post it to help others. I'm not a newbie but what I did on my last brew made me feel like one. I was christening my new tun and worried about hitting temperatures. After I added the mash water my temperature was high so I added some cold water to hit it. Then when I measured it again in about 5 minutes it was too low so needed to add some hot water. Later I had the duhhh moment - I didn't let the tun and grain come to temperature after a added the initial water. Oh well, I still made beer!

Mike

gevans said:

I discovered an issue with Beersmith that may be the main source of my issue all along.

I like to add mash steps into the program to remind me to check PH, start the HLT, etc. while the timer is running.  When you add steps in, then copy from my recipes and move it to the 'Brewing Currently' folder, it moves the order of those around, when it does this it changes the strike temperature! 

Click to expand...

Gevans, I saw this from you in another forum. I had some thoughts for you. http://www.beersmith.com/forum/index.php/topic,9137.0.html