Electric brew in a bag - where to place temp probe?

[Rivenin]

I've been electric brewing for a few years now, but as i have a 20 gallon pot, smaller batches are a bit of a chore. I had another 9 gallon kettle, so i decided to make that into a BIAB pot with a 240v element.
However, on the maiden voyage, i couldn't find a correct temperature anywhere.
i was recirculating the whole time, brought it to 155 for mash in with a rest around 149-150.
turned off the element, doughed in and did my normal stir for 5-10 minutes and plopped the temp prob into the bag mash area and started my pump to see where i was stabilizing at, which hit 150... thought, awesome!
However, once it got to 149, the element turned on... then stayed on for a good 2-3 minutes with no change with the pump on blast... made sure the pump was still moving wort, which was pumping around just fine. so i turned off the element to stop further heating.
dropped the probe outside the bag and the temperature was reading 155.
So i ended up shoving the temperature probe into the hose while it was recirculating and was reading 154. So i dumped some cold water into the brew pot to get it back down to 149.
at that point i kicked the element back on which seemed to hold the recirculating wort at 149, kicking the element on every like 2 or 3 minutes for a few moments.

So i guess i'm wanting to check what people are doing to overcome this.
There aren't many videos on the subject. The few commercial examples have the probe reading on the out path of the pump... which in my case of shoving the probe into the hose would "work"... But i would like to see what everyone else is doing before i attempt this again

Pictures, becuase why not....

20160705_110255 by Noah Scott, on Flickr

 

[thekraken]

Where is your temp probe now? I would think to put it inline with the kettle outlet to get a reading ASAP after the heating element.

 

[TexasWine]

My opinion, pump discharge is the best place for the probe. That's where I have mine.

 

[BeardedBrews]

I found you needed a few things to effectively control during re-circulation.

1. Space around the element - If the bag is laying on the element like a blanket then the heat is trapped right there. You'll get localized boiling (thump thump thump) on the element. Put something in there to hold the bag off the element and create some "dead" space under the bag so that the liquid can heat more evenly.

2. Put the temperature probe in the pump flow. I went with a Tee right on my pump inlet since it was pretty close to measuring the kettle outlet temperature and was less clutter for wiring.

3. Insulate the kettle. Even when you recirculate, the outside of the kettle will be colder or hotter if the whole thing isn't well insulated.


The last is a bonus bit of advice. Consider not heating during your mash.

 

[Rivenin]

Where is your temp probe now? I would think to put it inline with the kettle outlet to get a reading ASAP after the heating element.

it's a temp probe on a 6 or so foot cable, so i can place it anywhere mostly. it's not bolted into place so i can kinda just toss it where ever i need it to be, if that makes sense.

 

[Rivenin]

My opinion, pump discharge is the best place for the probe. That's where I have mine.

had a feeling on this as well, had the best readings when i stuffed it into the pump outlet.

 

[Rivenin]

I found you needed a few things to effectively control during re-circulation.

1. Space around the element - If the bag is laying on the element like a blanket then the heat is trapped right there. You'll get localized boiling (thump thump thump) on the element. Put something in there to hold the bag off the element and create some "dead" space under the bag so that the liquid can heat more evenly.

- No bag on the element, it's a bag inside of a basket with about 2 gallons or so under said basket​

2. Put the temperature probe in the pump flow. I went with a Tee right on my pump inlet since it was pretty close to measuring the kettle outlet temperature and was less clutter for wiring.

- this is close to what i finally settled on during brew day... well, shoved into the wort path that was going into the mash bag, so it was measuring the wort flowing back onto the mash right before hand. I think this is the best option but wantd to make sure with other peoples opinions as well ​

3. Insulate the kettle. Even when you recirculate, the outside of the kettle will be colder or hotter if the whole thing isn't well insulated.

- i'll try this next time - ripped off the insulation to drill all the holes​

The last is a bonus bit of advice. Consider not heating during your
mash.

- But if i don't heat during recirculation, i'll loose a ton of heat in the mash​

 

[thekraken]

it's a temp probe on a 6 or so foot cable, so i can place it anywhere mostly. it's not bolted into place so i can kinda just toss it where ever i need it to be, if that makes sense.

What I mean to say is that it would be most accurate to place the temperature probe inside a thermowell that is in side the kettle outlet's liquid flow. In between the hose and the ball valve you would put a tee with a compression fitting and a thermowell. The liquid would flow around the thermowell, in direct contact, quickly transferring heat energy to the thermowell/temperature probe giving you the quickest and most accurate reading. If you are worried about having an obstruction in front of the pump you could just as easily place this fitting/thermowell after the pump, you may experience a temperature drop from the kettle to the probe but it will most likely be negligible if it exists at all.

It's difficult to see but notice in this picture from Elco (brewpi) how it goes kettle -> tee fitting -> ball valve. Also, notice the cable coming from behind the tee fitting, that is his temp probe installed in the tee.

 

[BeardedBrews]

To add a bit of clarity on the "Put it in a Tee" discussion, check out what @The_Bishop did on his build:
https://www.homebrewtalk.com/showpost.php?p=7391275&postcount=83

The temperature probe is screwed into one end and then the quick disconnects mean you can attach it anywhere you want.

If you've already got a long straight temperature probe, you can use a compression to NPT fitting from @bobby_m
https://www.brewhardware.com/product_p/pcomp1.htm



As far as losing heat during the mash, yep, you are correct. For my keg kettle with insulation that's about 1-2F / hour which doesn't bother me too much. If you can get the recirculating and temperature control working without much overshoot, then I would say go for it!

 

[thekraken]

To add a bit of clarity on the "Put it in a Tee" discussion, check out what @The_Bishop did on his build:
https://www.homebrewtalk.com/showpost.php?p=7391275&postcount=83

The 'portable' temp probe with disconnects on the tee is a neat idea, at the very least for making cleaning easier.

 

[BeardedBrews]

The 'portable' temp probe with disconnects on the tee is a neat idea, at the very least for making cleaning easier.

http://www.theelectricbrewery.com/custom-temperature-probes
http://www.auberins.com/index.php?main_page=product_info&cPath=20_15&products_id=249

Both Auber and TEB offer a disconnectable probe that should work well.

 

[thekraken]

http://www.theelectricbrewery.com/custom-temperature-probes
http://www.auberins.com/index.php?main_page=product_info&cPath=20_15&products_id=249

Both Auber and TEB offer a disconnectable probe that should work well.

If only they sold them as thermowells (or DS18B20) then I could use em.