Heat loss issues

[ChemPaul]

Hi folks and Happy New Year! :

This is my first post here so here goes....

Ive been brewing AG with plastic kit and cooler-box style equipment for a while now and am building my first all metal (and 2x larger) mash tun. Im having a few problems with it though and im hoping you can help me a little with it.

The main problem I have is heat loss from the mash tun. It seems no matter how much insulation i put around the mash tun, it still bleeds far too much heat. Its a 50L aluminium stock pot which i got of flea bay a while back which ive fitted with tank adaptor, S/S mash filter screen and a copper pipe recirculation system powered by a totton pump.
The sides are insulated with: 1 layer of 10mm camping mat, 1 x cold water tank jacket, 1 x hot water tank jacket on its sides
The base has: 1 x 10mm camping mat layer, 3 x cloud9 carpet underlays (~8mm each i think) and 2 x foil layers for its base, and the mash tun sits on a wooden footstool
The (aluminium) lid has 2 cloud9 layers. 1 foil layer and two cylinder jackets folded on top of it.

The typical heat loss i am getting are like this:

0mins 84oC,
5 mins 79.9
10 mins, 78.4
15 mins 77.2
20 mins 76.8
25 mins 76.4 and then loses 0.4 oC every 5 minutes therafter, finishing at 70.3 at 90 minutes (!)

As you can see, this is far too much. I did the test with plain water but I have done a test mash on it (i made a cheeky little mild) and the grains made little difference to the heat loss (76.4 to 69.7 after strike, dropping to 67.0 after 90 mins (63 oC on edges)

Any ideas on what I could do? Ive tried all sorts of materials and combinations but i dont seem to be getting anywhere.
Im starting to suspect that the majority of the heat loss is through the lid. The insulation on the sides and base feels cold to the touch, so if anything, it must be that, although i cant feel any heat coming through the lid insulation either. How much insulation do people use and what material? plastic, wood, S/S? Is there a minimum mash volume to mash tun ratio? Im typically putting in 10-15L water to mash-in (as you do for a typical 23L batch) which means that nearly 3/4 of the tun is air. Do you think this is causing it? Did anyone else find this effect when you scaled up?

Any help would be appreciated. Ill try to post some pics tomorrow to illustrate all that :thumb:

Cheers

 

[prolix]

I would have thought that would have been enough lagging to keep the heat.

I use a thermobox and have no problems, prior to that I had a plastic tub with two layers of camping mat that was not bad.

If you can't find a solution maybe RIMS would be something to look at.

 

[unclepumble]

Have you tried a layer of Tin Foil on top of the mash.

If you have a lot of airspace between the top of the mash and the pot this may not be helping a layer of tin foil will.

UP

 

[Vossy1]

Hi Paul and welcome to the forum :thumb:

First off, the water test is relatively useless for info, ignore it.
The insulation you've got sounds MORE than adequate.

69.7 after strike, dropping to 67.0 after 90 mins (63 oC on edges)

That's 2.7 deg over 90 mins, it could be worse, and should be better due to your insulation.
keep in mind that most modern ENGLISH malts convert almost fully in 30-45mins, so you really need to keep an eye on the heat loss in the first hour. The 90 minute mash is really testament to less modified malt from the 70's, some brewers only mash for an hour as standard.

Did you stir the mash properly ? Did you take a few readings from the mash to ensure even heat distribution before slapping the lid on the tun?
How big a mash was it in how big a tun ? (thinking of up's advice above)
What ratio of water to grain did you use? You mention 'typical' but a mild uses less grain.

And at the end of the day there's nothing wrong with a few degrees drop during the mash, it may even give you a better tasting beer due to the range of temperature for conversion.
69.7 deg c is quite a high mash temp for a mild, though I suppose that depends what you're aiming for.

I'm sure your beer will taste great anyway :drink:

 

[Springer]

Welcome Paul and don't worry you have nothing to panic about.
2.7 degrees is not a lot and if your mash temp was aimed a shade lower the loss would have been slightly less :?
I think the most likely cause for your concern was not enough mixing resulting in false readings, as V suggested, it is amazing how you can get heat differences within a mash if you don't dough in thoroughly
I'm surprised you could find your mash tun in 90 minutes under all that insulation. :lol:

 

[ChemPaul]

Hi Paul and welcome to the forum :thumb:

First off, the water test is relatively useless for info, ignore it.
The insulation you've got sounds MORE than adequate.

69.7 after strike, dropping to 67.0 after 90 mins (63 oC on edges)

That's 2.7 deg over 90 mins, it could be worse, and should be better due to your insulation.
keep in mind that most modern ENGLISH malts convert almost fully in 30-45mins, so you really need to keep an eye on the heat loss in the first hour. The 90 minute mash is really testament to less modified malt from the 70's, some brewers only mash for an hour as standard.

Did you stir the mash properly ? Did you take a few readings from the mash to ensure even heat distribution before slapping the lid on the tun?
How big a mash was it in how big a tun ? (thinking of up's advice above)
What ratio of water to grain did you use? You mention 'typical' but a mild uses less grain.

And at the end of the day there's nothing wrong with a few degrees drop during the mash, it may even give you a better tasting beer due to the range of temperature for conversion.
69.7 deg c is quite a high mash temp for a mild, though I suppose that depends what you're aiming for.

I'm sure your beer will taste great anyway :drink:

Ok thanks vossy, thats quite reassuring

The test mash was probably the worst example to use acually :lol: . It was a simple mild. 3kg mild malt, 500g muscovado sugar and 150 g black malt in 9.1 L water at a target mash temp of 69 oC (strike was 76.3). The idea was to get a thin, light yet sweetish drinkable mild with rum-like notes. Im drinking it now as i write this and its ok, so something went right ( :) : ) but that heat loss is a bit worrying still, especially as this is a weak beer and I need to maintain the high temp for the extra body (the OG was 1.039 with a final of 1.012 using S-04)

I normally mash in and give it a good stir until i cant find any more doughballs. I then do a few tests in different places to see if ive hit my target temp then bury the temp probe in the middle of the mash and seal it in. (i have one of those cheap electronic temp probes on a wire btw)

As for the mash volume, it was 9.1L of water in a 50L mash tun. The S/S screen has a 5L deadspace under it so hardly any of the grain was sitting in the water ( :grin: ). Im starting to think sod it and go for a much bigger mash and see how that compares to the smaller mashes. I just didnt want to make a 40L mash and find that the beer isnt anything like what im aiming for -- or worse -- nice but unrepeatable.

Btw, have u found that there is a minimum mash volume you can do in your kit before your heatloss becomes too great? Im starting to think that 23L scale is too small for a 50L mash tun (or at the very least, use 5kg of grain in the MT)

ill also try the tinfoil trick (thanks unclepumble). Im going to make the new beer tomorrow (a golden ale) so ill take pics and post later :party:

 

[timbowden]

Hi Chem Paul
i was also getting quite a lot of heat loss but with loads of lagging all over the place! I tried the tin foil on top of mash trick and it worked a treat!! Seeing as i also use the tin foil for my sparging (after poking holes in it) it makes a lot of sense!

tim

 

[Aleman]

Have you found that there is a minimum mash volume you can do in your kit before your heat loss becomes too great? I'm starting to think that 23L scale is too small for a 50L mash tun (or at the very least, use 5kg of grain in the MT)

I certainly wouldn't try and do a 3Kg mash in my 80L mash tun! . . .Or my 50L one for that matter. for my experimental brews I have a 24L Thermobox which I use to make 18L batches . . . Of even quite strong beers (Like the Durden Park ones) . . . Heat loss is negligible . . . although my last beer, a mild mashed at 69C, did drop 1C over the 90 minutes, mashing outside at a temperature of 2C . . . still didn't affect the final gravity . . . chewy :thumb: RDWHAHB :thumb:

 

[Vossy1]

Btw, have u found that there is a minimum mash volume you can do in your kit before your heatloss becomes too great?

I can't really answer that question as I use a HERMS system so heat loss isn't an issue for me.
I would be more concerned that the grain bed depth isn't great enough.

Im starting to think that 23L scale is too small for a 50L mash tun (or at the very least, use 5kg of grain in the MT)

I'd be happy to use my tun (80ltr) only a third full. I used to have a 50ltr mash tun and regularly made 23ltr batches without issues.

 

[mr_spin]

the tin foil on top of the mash indeed works well. I also put in rolled up balls of foil on top of the sheet to reduce the airspace further

 

[ChemPaul]

Ok here are the photos i promised.

I made a golden ale today. Thought i would try again with more grains and with two layers of tin foil (as suggested by UP) on top to see if that helps (it did)
Oh, the recipe used about 3.9 kgs of various grains. Hmmm still a bit low maybe.

Heres the offending beast. Believe it or not, there is a mash tun in there somewhere!

Mash tun with its hat off

Grains in and well stirred. Temp was 63.0 (aiming for 65.5 but missed, grrr, but im not too bothered about that on a golden ale)

The hat up close

Temp start - 63.0 oC (bit blurry for some reason)

Temp end - 57.3 oC after 75 mins -- grrrr -- help!

The ambient temp today was 4 oC which wont have helped much but i think its still too much heatloss. I noticed the aluminium lid of the mash tun was a lot cooler than before, with the tin foil in there, which just goes to show that it really helps stop the convection in the airspace. Shame i cant seem to get that last degree or two. Any thoughts? Heat up the greenhouse??? New shed???? lol :hmm:

 

[mr_spin]

yep still losing too much heat IMO. where does the pot feel warmest after the mash?

Also, did you preheat before dumping the grist in? I put two pans of boiling water in mine to preheat for 10 mins then empty out seconds before putting the grist in (I underlet).

 

[Stone Cold]

I had heat loss issues when starting I use tin foil on top of the grain bed and seems to work well. but what i do aswell now is pre heat the mash tun with boiling water from kettle and then ditch the water when strike temp is ready. and just a thought if its an ally stock pot i imagine the metal is thicker than stainless pot would be and the ally could be soaking up the heat from the water?? or is that a bit far fetched?

 

[Springer]

I had heat loss issues when starting I use tin foil on top of the grain bed and seems to work well. but what i do aswell now is pre heat the mash tun with boiling water from kettle and then ditch the water when strike temp is ready. and just a thought if its an ally stock pot i imagine the metal is thicker than stainless pot would be and the ally could be soaking up the heat from the water?? or is that a bit far fetched?

Agreed, especially getting the mash tun up to temperature is very important, it will continue to draw in heat from the mash. If you have lots of "lower temperature" mash tun and only a small amount of heat theres only one way for the temperature to go.
During this cold weather I have started to leave my grain in the house to get it up to 20 ish, to help mashing. We are all keen to get doughed in and get the lid on quickly to save heat, but it is easy to do it to quick

 

[Vossy1]

Some sound advice in the posts above :thumb:
Out of interest what was the temp of the liquor before adding the grain.

I had to make adjustments to my strike temps depending on time of year due to my grain and gear being at the mercy of the outside temps. I changed that by storing my grain indoors, under the stairs where it's nice and cool/dark, as per Springer.

I also use Beersmith to calculate the strike temps based on grain temp and vessel being used.
If you don't have Beersmith download the trial version, it's well worth a play. Even using Beersmith, at certain times of year to avoid pre heating the tun, I'd have to add a few degrees to liquor to get the desired strike temp in the tun. I got to know my system so I could get it quite accurate, it takes time.

 

[Springer]

Some sound advice in the posts above :thumb:

I also use Beersmith to calculate the strike temps based on grain temp and vessel being used.

Right on the mark V and yes "investigate Beersmith" has been on my to do list for a while. :hmm:

Think I read somewhere that it works on Ubuntu using wine or crossover :?

 

[ChemPaul]

yep still losing too much heat IMO. where does the pot feel warmest after the mash?
Also, did you preheat before dumping the grist in? I put two pans of boiling water in mine to preheat for 10 mins then empty out seconds before putting the grist in (I underlet).

Thats the odd thing. It doesnt feel warm anywhere on the outside, and you have to go rummaging underneath to find warm layers closer to the pot. I would say the bottom and sides are lukewarm (maybe cooler) at most, however the lid does gets red hot. The black tank jacket on the lid gets quite warm but the red jacket stays cold. Maybe there isnt enough on the lid perhaps?? (or better sealing insulation maybe)

Yes, I put 15L of near boiling water in it and left it for 20 minutes. It dropped to about 85 oC or so, and was slowly dropping still when i dumped it and added the strike water. The strike was 71.9 in the boiler (aiming for 65.6 after strike) but ended up as 70 in the mash tun and 63 after strike (guess that explains the missing 2 degrees then ). Its obvious now, looking back on the notes, that it must have been lost heating up the transfer line. I'll preheat it next time.

I had heat loss issues when starting I use tin foil on top of the grain bed and seems to work well. but what i do aswell now is pre heat the mash tun with boiling water from kettle and then ditch the water when strike temp is ready. and just a thought if its an ally stock pot i imagine the metal is thicker than stainless pot would be and the ally could be soaking up the heat from the water?? or is that a bit far fetched?

It is really chunky ally, good 3mm sides and more for the base, probably 4 or 5. Its one of those Vogue aluminium cooking pots so fairly decent quality (for ally). Certainly a possibility. Ill try a long preheat (~1 hour) with all the jackets on and see if that helps.

I had heat loss issues when starting I use tin foil on top of the grain bed and seems to work well. but what i do aswell now is pre heat the mash tun with boiling water from kettle and then ditch the water when strike temp is ready. and just a thought if its an ally stock pot i imagine the metal is thicker than stainless pot would be and the ally could be soaking up the heat from the water?? or is that a bit far fetched?

Agreed, especially getting the mash tun up to temperature is very important, it will continue to draw in heat from the mash. If you have lots of "lower temperature" mash tun and only a small amount of heat theres only one way for the temperature to go. During this cold weather I have started to leave my grain in the house to get it up to 20 ish, to help mashing. We are all keen to get doughed in and get the lid on quickly to save heat, but it is easy to do it to quick

I keep my grains in the house also, but prior to mashing in, mix them all well in a bucket and then add them slowly to the strike water. Come to think of it, they were hanging around for a fair bit (at 4 oC) before i mashed them in (at least 20 minutes while i was preheating the MT) so i suppose another chunk of heat would have been lost then

Some sound advice in the posts above :thumb:
Out of interest what was the temp of the liquor before adding the grain.

I had to make adjustments to my strike temps depending on time of year due to my grain and gear being at the mercy of the outside temps. I changed that by storing my grain indoors, under the stairs where it's nice and cool/dark, as per Springer.
I also use Beersmith to calculate the strike temps based on grain temp and vessel being used.
If you don't have Beersmith download the trial version, it's well worth a play. Even using Beersmith, at certain times of year to avoid pre heating the tun, I'd have to add a few degrees to liquor to get the desired strike temp in the tun. I got to know my system so I could get it quite accurate, it takes time.

Yes, ive been using it for about a year now. Very handy program that. Takes all the headache out of the calculations and has made a massive difference to the quality of my beer :thumb:

 

[Stone Cold]

insulating the bottom could help aswell? I think thick walls cant help, does the heat have a more rapid loss at the start than at the end of the mash?

 

[ChemPaul]

yes it does bt it eventaully tails off as the whole setup meets equilibrium, just at an annoying rate of 0.4 oC per 5 mins (ive got it to 0.3 now by adding another camping mat layer to the sides, lid and base). It just seems so mysterious where the heat is going. there is a 1 1/2 ft T-shaped copper pipe drain assembly underneath the mash tun that u cant see on the photos, which also maybe adding to the heat loss, but im starting to think its a combination of several factors.

Ive just glued two layers of camping mat to the lid in an attempt to slow down the heat loss. There is still a approx 1 inch rim around the sides of the lid which is not covered by mat which im starting to suspect is the major source of the heat loss.

Still trying lol :