Temperature control issues

[dazsnow]

I'm testing out a brand new 200L system and found a couple of potentially disastrous but potentially easy-to-fix issues:

1) While mashing the temperature indicated on the thermometer which sits near the bottom of the tun was fluctuating wildly between 60 and 70 degrees. It might go from 62 degrees to 70 degrees in a matter of seconds, then a few minutes later fall back down, even without any additional heat from the stove or from hot water additions. Other times when adding heat from the stove the temperature would remain in the low 60s. Obviously this is still in the desirable temperature range for mashing but means it's difficult to control the mash temperature for repeat recipes. There is a sight gauge with an inlet near the bottom and outlet at the top. The tun has no insulation, just a stove for heating/maintaining temperature.

Any ideas what could be going on? Some crazy convection current? At the moment I'm thinking my only option might be to get a jacket to insulate the tun once it's at the desired mash temperature. Anyone have any other suggestions?

2) My boil kettle is the same size, also with a sight gauge and thermometer near the bottom, as well as an in-place immersion cooler fixed inside. I found that after the boil I cooled for an hour and saw the temperature drop to 20 degrees so began filling the fermenters. However by the time I was drawing the last 3rd of the batch the temperature reading was back up to 50 degrees! Sadly, I didn't realise until I'd already aerated the wort in the fermenter :smack:.

My best guess is that the hot wort rose to the top and sank down to the bottom as I was gradually drawing it off. With less wort in contact with the immersion chiller it wasn't cooled properly. Should I carry on chilling for another hour? Or maybe draw the wort off in batches while continuing to chill? Or plump for a plate chiller?

Thanks

 

[day_trippr]

For the BK chiller issue: are you not keeping the wort moving the entire time that you're running cold water through the chiller? If the wort is just sitting there the time to chill it will be dramatically higher - multiples of the time it would take if the wort was in motion.

And of course that whole stratification thing would disappear with the stir of a spoon or switching on a pump.

The MLT problem is likely typical of direct-fired tuns. Other than stirring, not sure what you can do about that...

Cheers!

 

[dazsnow]

Other than stirring, not sure what you can do about that...

So you reckon stirring continuously while mashing will effectively maintain the temperature and prevent those crazy fluctuations on the thermometer?

 

[dazsnow]

And of course that whole stratification thing would disappear with the stir of a spoon or switching on a pump.

How about recirculating the wort from bottom to top using a pump?

 

[Spellman]

Wow, that's a big setup you got there! For the mash I would think at least a pump to recirculate. Others may be able to chime in here, but you might be big enough to need a mash rake to constantly stir to keep the temps consistent. If you go the pump route, maybe place your temp probe inline with the pump so you don't measure any pockets of temp stratification. For the BK, pumping should help a lot, but that is a lot of volume to cool with an IC, you might need to think about a counter flow setup.

 

[dmcman73]

Stratification is what's happening.

For cooling, you need to stir the wort to cool evenly or use a re-circulation arm setup. If you just rely on the immersion chiller to cool then it will chill the wort around it but the wort below and above it will not cool as fast and it will rely on the cooler wort to chill it slowly. Easy fix, stir it or recirculate by building a recirucation arm inside your immersion chiller, similar to this:

.

It's just a tube that is in the interior coil of the chiller. You then hook up the outlet of your brew kettle to the inlet of a pump and the outlet of your pump to the re-circulation arm in the center of your chiller and you won't have any more cold spots. You'll also find that it chills faster too. Just turn on the pump a few minutes before you turn off the heat to sterilize everything.

As for the mash tun temp differences, same type of thing. Having the temp sensor at the very bottom of the mash will fluctuate. Most brewers will state that it's useless to have a temp gauge inside the mash tun as temps will differentiate at different levels of the grain bed. Some will actually place the temp gauge on a "T" fitting right off the outlet of the mash tun to read the temps as it recirculates back into the mash tun. Or as a good majority do, just take the lid off and take a few temperature readings at different depths of the grain to get a good average of your temps. It seems that a good portion of brewers swear by the thermoworks thermopen as it is very fast at taking readings and it's one of the most accurate digital thermometers out there on the market: http://www.thermoworks.com/products/thermapen/

 

[Chrisl77]

How about recirculating the wort from bottom to top using a pump?

That is what I would do if I had that setup. Do you have a false bottom in the mash tun to keep the grains from making direct contact with the bottom?

 

[AleForce1]

Is the heating plate in your photo an induction ? If so maybe it's creating magnetic interference with your temp probe?

 

[dazsnow]

@spellman what do you mean by having the temperature probe in line with the pump? Just have the thermometer on the outlet going into the pump? I tried using a pump to recirculate last time but that resulted in big (+-15 degrees fluctuations on the thermometer).

 

[dmcman73]

@spellman what do you mean by having the temperature probe in line with the pump? Just have the thermometer on the outlet going into the pump? I tried using a pump to recirculate last time but that resulted in big (+-15 degrees fluctuations on the thermometer).

Are you sure you don't have a defective thermometer? It should not fluctuate that much!

 

[dazsnow]

Thanks @dmcman73. I managed to solve the chilling issue but controlling the mash temperature is still a bit challenging. If the temperature throughout the mash can fluctuate the mash how do you maintain control? i.e. how do you know what temperature you're actually mashing at? Would you recommend insulating the tun to try and maintain a constant temperature?

 

[dazsnow]

@Chrisl77 yes, there is a false bottom

 

[dazsnow]

@AleForce1 The heater isn't electric, it burns liquified petroleum, so I don't think magnetic interference is the issue, although there could be a problem with the thermometer

 

[dazsnow]

Firstly, thanks everyone for your help and suggestions. Progress is being made - I brewed another batch yesterday and it went more smoothly.

So the cooling issue seems sorted - I recirculated through a pump starting 10 minutes before the end of the boil and continued while cooling. When I drew off the wort this time it was all at 22 degrees - I stuck the fermenters in the freezer for a while to bring it down further before pitching.

For the mash temperature I still had a few issues. I tried stirring almost constantly. The reading on the thermometer near the bottom gradually dropped to about 61 degrees over the first 30 minutes. Meanwhile a digital thermometer at the top of the mash read around 70-75 - despite no heat being added and the strike water temperature being only 73. I decided this reading must be inaccurate. The tun has no insulation so I turned the lowest burner (which is really quite weak) on for about 10 minutes then stirred again. this time the temperature reading at the bottom suddenly went from 61 to 85 in about 60 seconds. Basically, I'm still baffled as to what's going on. At 40 minutes I gave up - just put the lid on the mash tun and left it.

I think my options now are

• 
  Step mashing - heat the strike water to around 62 degrees, mash in, stir, gradually heat to 76 then sparge out.

• 
  Alternatively, get some insulation (like a furniture blanket sandwiched between a couple of space blankets), wrap up the tun, including the top, strike at 72 degrees, mash in, and leave it for an hour.

Either way, I'm going to get a 1m long digital temperature probe to take readings in different parts of the mash - I suspect my thermometer might be faulty. Step mashing would still be difficult without accurate temperature readings.

Any other ideas?

 

[dmcman73]

Firstly, thanks everyone for your help and suggestions. Progress is being made - I brewed another batch yesterday and it went more smoothly.

So the cooling issue seems sorted - I recirculated through a pump starting 10 minutes before the end of the boil and continued while cooling. When I drew off the wort this time it was all at 22 degrees - I stuck the fermenters in the freezer for a while to bring it down further before pitching.

For the mash temperature I still had a few issues. I tried stirring almost constantly. The reading on the thermometer near the bottom gradually dropped to about 61 degrees over the first 30 minutes. Meanwhile a digital thermometer at the top of the mash read around 70-75 - despite no heat being added and the strike water temperature being only 73. I decided this reading must be inaccurate. The tun has no insulation so I turned the lowest burner (which is really quite weak) on for about 10 minutes then stirred again. this time the temperature reading at the bottom suddenly went from 61 to 85 in about 60 seconds. Basically, I'm still baffled as to what's going on. At 40 minutes I gave up - just put the lid on the mash tun and left it.

I think my options now are

• 
  Step mashing - heat the strike water to around 62 degrees, mash in, stir, gradually heat to 76 then sparge out.

• 
  Alternatively, get some insulation (like a furniture blanket sandwiched between a couple of space blankets), wrap up the tun, including the top, strike at 72 degrees, mash in, and leave it for an hour.

Either way, I'm going to get a 1m long digital temperature probe to take readings in different parts of the mash - I suspect my thermometer might be faulty. Step mashing would still be difficult without accurate temperature readings.

Any other ideas?

I would definitely insulate your mash tun as a first step, a lot of people like the reflectix insulation: http://www.homedepot.com/s/reflectix?NCNI-5

I read in a few places that the reflectix insulation needs some air gaps between each layer or it loses its R value, so as you wrap it, cut some strips to place between each layer to create those air gaps. The first layer should be right against the kettle, no air gaps there.

 

[Spellman]

I have mine in a T fitting on the output of the kettle. When you keep the liquid moving it helps keeps temps consistent throughout the entire mash. Having it on the output measures what the true temp is. While it may not apply entirely to your system, I would recommend checking out www.theelectricbrewery.com, Kal has some great tips on how and why some of the measuring theories work. And yes, that much fluctuation is high for a thermometer. One question, are your kettles 200L or are your batch sizes that large? If you get a chance a few more pics of your system may also help us zero in on how to make it run more efficiently.

 

[dazsnow]

ok thanks - I'll take some more pics next time. The tun capacity is 200L so I'm brewing 150L batches. Because it's quite tall and there's 7cm of dead space below the mash I wasn't sure if the temperature of wort coming out of the bottom would be an accurate reflection of the actual mash temp. Also, when you're recirculating does it matter where it's recirculated to, or just anywhere at the top of the mash?

 

[Gavin C]

ok thanks - I'll take some more pics next time. The tun capacity is 200L so I'm brewing 150L batches. Because it's quite tall and there's 7cm of dead space below the mash I wasn't sure if the temperature of wort coming out of the bottom would be an accurate reflection of the actual mash temp. Also, when you're recirculating does it matter where it's recirculated to, or just anywhere at the top of the mash?

I am in awe. That is one seriously large batch of beer.

 

[riderkb]

With a big mash like that you don't really need insulation, but you do need to circulate continuously and stir occasionally. I do 20 L batches this way. You can just lay the return hose on top of the grain bed if your recirc pump is gentle enough. You might need to make a flow diffuser out of aluminum foil if the return flow digs a hole in the grain bed.

With a system that big and relativly little experience, I'm wondering if you have a still . . .

 

[day_trippr]

Whoa. Easy now, big fella
Everything's above board until proven otherwise.

Anyway, insulation does in fact help any time you're trying to maintain a set temperature - recirculation only serves to equalize the mass, but it can't conserve thermal energy (quite the opposite, in fact - fitting and tubing losses must be accounted for in any herm/rims/etc loop).

The conflict is a fired MLT is generally incompatible with conventional insulators.
So, go unconventional: a fiberglass welding blanket makes for a decent thermal barrier when tightly wrapped around a vessel, and unless you literally place it so flames are licking at the bottom it will survive...

Cheers!

 

[riderkb]

Try it without insulation. You will probably only need to add heat about five times during the mash. I do it in a thin aluminum pot with a wimpy little pump and don't get any scorching.