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Esky Mash Temps

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When I first started ag I had aquired some k type thermocouples which I tried to use for the mash temperature. I thought that they would be good because they respond instantaneously to temperature. But these have a poor absolute accuracy, can be out by more than a degree and I switched to a probe type thermometer which averages out the temp and made mashing much easier. But when I used the thermocouples, I noticed that there was quite a difference in temperature depending on where the thermocouple was in the mash.

So last weekend while heating the strike water I instrumented the mash tun with a broomstick and 6 thermocouples. The thermocouples went diagonally across the tun and were labelled A to F as per the photo. The tun is a 44 l willow esky with thinnish walls. I sit it on polystyrene to insulate from the pavers below, and usually wrap in a blanket, but didnt this time.

instrumented_tun.jpg
 

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I missed my strike temp so didnt get any readings in the first 10 mins while I frantically tried to lift the temperature a bit. But from 10 mins on I measured each thermocouple, plotted in the graph below. Ignore the absolute temperatures from the thermocouples, but the change in temperature is accurate.

mash_temp.jpg
 

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I also measured the temperature with a probe pushed into the centre of the tun. The change in temperature from 10 to 60 mins was
Probe -0.3 deg
A, 190 mm below top of mash, near the base -4 deg
B, 150 mm, +0.2 deg
C, 120 mm, +0.2 deg
D, 90 mm, +0.2 deg
E, 40 mm, -2.4 deg
F, 5 mm, -7.8 deg

So, from the probe I would have noted that I lost 0.3 degrees over the mash and had a stable temperature. But the thermocouples show that while this is true for the middle of the mash, there is a large temp drop at the surface, and a smaller drop at the base and edges. For the shape of the mash I had, if you work out how much of the mash is within 50 mm of the top or a wall, its close to 50% of the total volume. So in reality 50% of my mash was maybe 2 to 3 degrees cooler than I thought it was.

But the beer still tastes OK, just thought it was interesting. I guess if I was to then build a recirculating system which gave a more uniform mash temp, I might have to learn to brew all over again to get the same results.
 

AndrewQLD

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I have /had the same esky as you, and I too noted large temperature variations using a digital thermometer depending on where it was placed, I opted to open the lid and quickly stir the mash at about the halfway point.

I used to wrap a towel around mine to, until I started doing 40 lt batches, with the mash almost up to the lid I got very little drop in temps from then on
 

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Just curious Andrew. How big is your boiler? Are you squeezing 40L batches out using a 50L keg or do you have an 18G (80L) keg for your boiler. I'm looking to up size soon to double batches, well 40L would be good enough and was wondering if you get away with a 50L kettle. That only leaves about 5L(ish) head space. Keen to see anyway.

Cheers, justin
 

AndrewQLD

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Yeah Justin, I have a 50 lt keg with an 8 inch hole cut in the top, your not the first person to query this but I assure you it works. I only lose about 3.5 - 4 lt in the boil (same as a 20 lt batch). I do have to stay close to the boiler just as it reaches boiling, but a quick spray of water as it starts to foam knocks it back nicely, and I can leave it alone from then on.
 

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Thanks mate. I thought it would work ok. Actually the foam up on my last couple of beers has been really slack and I haven't had particularly good hot breaks either. A suggestion has been lack of calcium but I'm yet to try. Anyway that's another topic. Thanks for the reply.

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One of the reasons I don't like using pellets is the massive amount of foam they create, leaf hops are much more gentle due to less surface area (iI think)

Regards
Andrew
 

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ahh, you can count on Engineers can't you..... Well done GL - I must have missed this thread when it was first posted.

What technology are you using to record those thermocouples - does it go into a PC?

I've been grappling recently with a PC monitored 4-sensor unit which I bought through Ozitronics (there's a thread here somewhere on it). and have noticed about a 2 degree difference across the 4 sensors (did a boiling water calibration last weekend). The sensors are guarenteed to be within .5 deg of real temp, so I don't know quite what to do.

Part of my problem here is that I shove the sensor into a copper tube with a folded end and put that in the mash/HLT and there would ahve to be a drop depending on the contact etc between the sensor and the copper. Can you (with your hydro engineers hat on) think of anything that would waterproof the sensor and provide a more direct thermal connection with the mash/water? I was thinking of putting into resin, but I'm not sure...
 

Ross

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GL,

You are having same problem as me - pictures that were correctly sized under the old format are now huge after the site upgrade - any chance of editing your pics?

Cheers....
 

Pumpy

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GL ,

hell of a copper manifold I notice the slots are upward !!!!

have I had mine upside down all this time !!!!!!

Pumpy
 

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Goat
Will get back to you

Ross
Yeah the photo was fine before will fix tonight/this weekend

Pumpy
Nope, slotted top AND bottom. My first ever mash stuck, so like most new brewers I went to the manifold instead of the grain, and built what I hoped would be an unstickable one. Slotted every 10 mm on top and every 10 mm on bottom. I also built a 3d accellerdrainer to help flow get through the mash. I empty a full 44 l esky in a few minutes.
 

Ross

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Ok GL -

I did search on "accellerdrainer" & just got this thread back, so I guess I'll have to ask - What is it?? ...
 

Pumpy

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Ross I cant upload pics anymore have i missed something Pumpy
 

Ross

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i don't think so Pumps - everything worked fine last time I uploaded - maybe drop Dane a line....
 

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Ross said:
Ok GL -

I did search on "accellerdrainer" & just got this thread back, so I guess I'll have to ask - What is it?? ...
[post="54309"][/post]​
The accelerdrainer is available on the Foxtel shopping channel and from all good brewshops, or you can purchase direct from my secure customer service site. Add $40 for stainless steel. I'll post the link, but I just know you are going to make me resize the photo again.
Order in the next 10 minutes and get a free steak-knife from GMK
 

Andrew

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ahh, you can count on Engineers can't you..... Well done GL - I must have missed this thread when it was first posted.

What technology are you using to record those thermocouples - does it go into a PC?

I've been grappling recently with a PC monitored 4-sensor unit which I bought through Ozitronics (there's a thread here somewhere on it). and have noticed about a 2 degree difference across the 4 sensors (did a boiling water calibration last weekend). The sensors are guarenteed to be within .5 deg of real temp, so I don't know quite what to do.

Part of my problem here is that I shove the sensor into a copper tube with a folded end and put that in the mash/HLT and there would ahve to be a drop depending on the contact etc between the sensor and the copper. Can you (with your hydro engineers hat on) think of anything that would waterproof the sensor and provide a more direct thermal connection with the mash/water? I was thinking of putting into resin, but I'm not sure...
Hi Goat,
I think I use the same oztronics sensors as you have bought, I also use them to control my ferment temps.
FWIW I use security cable to connect the sensor to the interface box. It's four wires, I just cut the unwanted wire out of the way, and solder the remaining three to the sensor. I then heat-shrink the three individual wires (very fiddly) then use a bigger diameter of heat shrink to cover the whole lot, sensor and all, leaving only the very tip of the sensor exposed. You can then circumcise the heat-shrink to your heart's desire (? what the...) depending on how far you want to risk leakage. I've found this effectively blocks all moisture out (you'll know if you have a short, your pc will register blank or negative temps). For longevity I then got some S/S tube from a hobby shop that had an internal diam EXACTLY the same as the temp sensor, squashed the end flat and slowly encouraged the sensor down to the end. so that the 'head' of the sensor is physically in contact with the metal probe. I've checked the accuracy of mine using 3 thermometers (1 digital, 1 brewing (least accurate) and 1 lab thermometer) at a variety of stepped temps between freezing and boiling, and the sensors are easily accurate to inside a degree (BTW those shop-bought brew thermometers are absolute crap).
Hope this might help you.
Cheers!
 

Ross

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I almost wish I hadn't asked - lol....
 

Andrew

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PS I don't know if GMK does steak knives, but he lathes an awesome wooden pen...
Cheers!
 

Goat

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Andrew - bloody brilliant !!

I used the 4-core security cable too - its about 4mm dia off white in colour. I also have done the double layer heat shrink thing on individual wires and then the lot - but I've stopped it short of the sensor by a couple of mil's.

The smaller diameter s/steel tube is the answer I think, 'cos it will eliminate the chance of an air gap between sensor & tube wall that I am getting with 1/2 in copper. Its also thinner so thermal conductivity will should as good. Thanks for that - an nice solution.... and I still love going to model shops !

What happens AFTER you get a short ? does it kill the sensor or damage it or does it come around if dried out?

What sort of variation are you getting across the 4 sensors? I'm getting up to 2.5 deg at the moment.
 
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