My brewing rig teething issues

[Daniel]

Hey guys, first time posting really.  I've been working on a new rig in the attempt to control my mash temp better than the chilli bin with dishwasher stainless hose manifold.  I did some searching and found this article that had a setup I liked. 

https://byo.com/mead/item/2799-build-a-heated-mash-tun-projects

First of all this new setup wasn't going to work on the kitchen bench like I had been doing.  At the same time my BBQ was getting a bit tired.  The side plate brackets seem to be made from recycled cans and cheap plastic and were long pas their use by.  I fabricated some new side plated from 25mm box steel.  Topped these with some kwilla decking which is mounted on it's on frame.  This frame then sits inside the side plates and fixes with a counter sunk bolt in each corner.  Turns from BBQ to brewing duty in a few minutes.  

I've got a MKII High Temp Magnetic Drive pump from KegKing mounted on a removable bracket.

Ive since replaced this cheap 2 ring burner with an italian spiral style one from Brewtopia but its mounted the same way

More good luck than good management as I built the new frames from the BBQ size and my current pot not kegs.  turns out the keg fits perfectly in the frame.

The mash tun

Inlet and outlets for the heat exchanger coil on the right with the temp probe beneath. Dip tube drain from below the false bottom on the left.

Heat exchanger coil. 1/2 copper tubing. It's pretty much the full roll, about 20m i think.

Temp sensor

I still need to mount the PID and SSR in a nice housing

How it works.  The HLT on the right of the BBQ is heated to above the desired mash temp.  If the temp in the Mash Tun drops below the desired temp the pump kicks in and and pumps the heated water through the coil to heat the mash.  It should therefore allow me to do step mashes and maintain temp better.

So the first brew I did the inital mash sat pretty much bang on temp with the pump only coming on sporadically to maintain temp.  The sparge I think i got the temp wrong for the sparge water and it just couldnt heat it up.  I put this down to a temp differential that was too low.  I got a new burner and thought that will get it higher and help.

Second brew on Labour day the strike temp was too low.  My manual temp readings were lower than my desired 68 degree and the mash tun sensor read about 5 degree lower than that.  Pump ran full time and still wouldnt heat the mash even though the HLT water was about 88 degrees.

I'm no expert in fluid or thermal dynamics but my theory's are:

1) Temp differential is still too low.  Though i think 20 degrees should be enough and id be worried about scorching the grain if its too much.

2) The coils are too tight and not allowing the water to transfer/move easily around.  The temp readings inside the coil are up to 10 degree hotter than the outer edges of the tun.  The few forum threads i found with people asking about similar setups said that constant stirring may be required to circulate the heated wort better.  That would be a giant pain and i'll convert it to a different setup before i resort to that.

Any thoughts/opinions welcome before I chop some coils off and spread them apart a bit for the next brew.

[Druid]

I reckon you should remove the coils from the mash tun. As you've noted, it's completely distorting the temp distribution In the mash tun. If you move the coil to the HLT and maintain the HLT to your target temp (step, mash out, sparge temps etc), you can recirc your wort, sparge or strike water through it just before introducing it to the mash tun using a more traditional fly sparge method. This way, you won't have to stir your mash constantly to distribute the introduced heat.

I'd also insulate the mash tun - the less temp lost, less aggressive you'll need to be to maintain the temp. Once you get on top of what strike temp you need to hit your mash temp, you'll have solved most of your problem.

With the coil in the HLT, I'd also get some way of mixing the water in the HLT to eliminate temp stratification, like an impeller on a cheap 12v motor - but this is probably only an issue if you are using automatic temp control in the HLT, which will need accurate readings for the whole mass of water in the HLT, not just around the probe.

If I sound overly confident about this, it's because that's the system I use, except that my HLT temp is maintained by a 2kw electric element controlled by a PID and it works a treat.

[Peter Church]

Nice looking setup but for a few teething problems, It seems that the heat is getting into the mash, the circumference of the coil looks like there is much higher volume outside the coil than inside, so you will heat the portion inside much quicker, and it looks challenging to get mixing between the inside and outside, do the maths to work out the diameter of the heat exchange coil so that 50% of the volume is on the inside and 50% on the outside then recoil the heat exchanger

failing that you may need a 2nd pump to recirc the wort

[Daniel]

Thanks for the input

The coil size is the best compromise between even heat contact to the mash vs being able to get a spoon between the outer edge of the coil and the mash tun wall.  It would be easier if i cut the hole bigger i guess.

I think for the next brew i'll try as you say Druid and change the Mash tun to be the HLT and move the false bottom to the other keg.  I'll throw another temp probe in that and just pump the wort through the heated coil when it drops below target temp and needs heating.  Low burning flame should keep it with enough differential to heat it up on its way through.

That article said he wasnt found of the aeration in pumping wort but it seems heaps of people do it this way and it does filter trough the grain bed again doing this.  Costs me nothing to try it this way and i don't have to spend much time in swapping over.

[Druid]

If you can reduce your heat loss from the mash tun by insulating it, you'll find you won't need to recirc your wort continuously which will minimise the abusing its gets from the pump. I made an automatic grant for recirculating my wort so that I could minimise this.

For what it's worth, you don't really want to use too much of a temperature differential when raising the temp of the mash unless you've got some way of quickly dispersing the extra heat through the mash - otherwise you'll be destroying the mash enzymes in those places in the mash which are hotter. After all, one of the functions of. a mash out step at 75*c is to raise the temp enough to stop the enzymes working on the mash by denaturing them.

[Max Ballbagz]

Hey Daniel, that's a pretty impressive set up! How easy are the PIDs to wire up? I'm thinking that might be the go for my electric HLT to keep constant temp for mashing and sparging.