How I made My HERMS heat exchangers

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Vossy1

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The bits



These consist of:-

A stainless steel pasta jar which I bought from Debenhams in the sales for £4 (I think...long time ago now :roll: )
1 x kettle element
1 x 1/2" male to 10mm compression fitting
1 x anode
1 x roll of 10mm copper tube
2 x 10mm elbows

Tools required

A drill, a dremmel, 20 & 40mm hole saw bits, a 10mm hss bit,
a file, a hack saw, a blow torch, solder and wire wool.

The purpose of a heat exchanger

Wort is pumped from the mash tun, through the heat exchanger, and back to the mash tun.
As the wort passes through the HE coil, it absorbs heat from the water bath in the HE vessel which is heated by the kettle element.
The temperature of the wort is monitored by a PID, which regulates the water bath temperature by turning the kettle element on and off.
This means that you can maintain a stable mash temperature at whatever temperature you want.
It also means the system is ideally suited to temperature step mashes.

How I made my Heat Exchanger

The heat exchanger coil is 10mm copper pipe which was wound around a fire extinguisher to get a coil of copper small enough to fit inside the stainless vessel. I took the outlet feed off at a right angle, by soldering an elbow onto one end of the coil along with a small piece of copper pipe which exits through a 10mm hole at the top left hand side of the vessel.
At the other end of the copper coil I soldered another elbow to make the inlet feed vertical, again with a small piece of copper pipe

The first thing to do was to make a 40mm hole dead centre in the base of the vessel wall, where the element would be mounted.
To the outside of this I drilled a 20mm hole for the inlet fitting, being careful to allow room for the lock nut of the element, and the fitting.
I used a constant supply of cold water to cool the hole saw bit and vessel whilst drilling. Then I filed the burrs off which were left after drilling the holes, with a dremmel.



Next I had to prepare the brass fitting for the inlet.
The 1/2" male to 10mm compression fitting, has a collar inside it that prevents 10mm tube from going all the way through it.
To get the 10mm copper tube to pass through the fitting, I used a 10mm titanium drill bit to drill through the collar, thus removing it, using a vice to secure the fitting whilst drilling.

I then screwed the fitting into the 20mm hole in the vessel, from the outside, applying some JB Weld to make sure it sealed water tight.



Now it was time to insert the copper coil.
Before doing this I offered the copper coil to the vessel to see roughly where the outlet would be. I marked this position, then drilled a 10mm hole through the vessel wall, at this point.
The inlet tube of the copper coil passes through the brass fitting in the base of the vessel. Then I attached the 10mm olive and nut, and tightened. I coaxed the outlet tube through the hole at the top of the vessel and then fitted the element securing it with the lock nut





The reason for not sealing the area around where the outlet exits the vessel, is to allow any pressure generated by the heated water to escape, as the lid is fitted with a seal.
The anode was added to prevent any corrosion of items within the water bath due to the different metals it contains.

Ideally any parts that come into contact with the acidic wort should be stainless steel and at some point in the future I will be replacing any non ss parts. This will negate any possibilities of verdigris within the system.
 

BillyB

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Hi Vossy1,

How is the wort, that is recycling, having it's temperature taken? i.e. you say that the "temperature is being monitored by a PID", so where is the probe in your set-up? :?

Thanks. :)
 

Vossy1

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so where is the probe in your set-up?
The probe in a HERMS system should be mounted as close to the exit from the HE as possible...according to percieved wisdom :D
My PT100 (probe) is mounted in a elbow that fits onto the copper tube exiting the top of the HE.
In practice, I've found it's wise to have a probe in your mash tun also, as the loss of heat to the environment needs to be off set against the wort temp.

Ie, the tun temp can be 2 deg below the recircing wort, so you have to off set the PID using it's PSB setting, to take into account the thermal loss.

I have a piccy I'll insert ;)

 

Rabmaxwell

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Hello Vossi how do you go about off setting the PSB setting still trying to understand the PiD instructions. Cheers
 

Vossy1

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Hello Vossi how do you go about off setting the PSB setting
Hi Rab,

1st thing you need to do is calibrate your PT100 sensor (or whatever sensor you're using)
PT100's can be calibrated using only an ice bath, as opposed to other sensors, which may require calibrating at differring temps.

I used a flask, filled it almost fully with ice, and then topped it up with water.
Place your PT100 in the ice bath so it's not touching the sides or bottom of the flask and leave the bath to for a while for the temp to even out (stirring it will help but watch the probe)
Now check your PID display...it should be reading zero....but it probably wont be :roll:
To alter the PSB (Temperature Sensor Correction)

Press SET (to enter the setting mode)

Arrow across the 4 zero's on the display using the > button, until you reach the second 0 from the right (the zeros will flash as you select them) and change the 0 to a 8 using the ^ or v button. Then arrow to the far right 0 and change it to 9. You should now have 0089 in your display.

Press SET (to enter the menu)

You have now entered a settings menu
Use the ^ or v button until you have PSB in your display, then press set....you should get this on your display 000.0
The first zero on the left can be changed to a - symbol, if needed, by pressing the ^ or v button, ie, -00.0
Now you can enter the figure by which your PT100 is incorrect, into the display.
So if your PT100 is reading +1.4 deg c when it should be zero, set the PSB display to -01.4
If it's reading -1.4 when it should be zero , set the PSB to 001.4

Press SET to exit PSB settings
Arrow ^ or v to END...press SET and you should return to your display with the new corrected reading ie, 0.0.

It's well worth letting the ice bath stabilise for at least 10 mins before altering settings.
I've assumed above that you're using PT100's and that you've set the PID to PT10.0

Hope that helps :thumb:
 

MEB

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MMM, i'm liking this HERMS set-up. The more i find out the more i'm liking...
 

Rabmaxwell

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Hello Vossie i have already calabrated the PT 100 probe it's how to off set the temperature between the herms exit & mash return temperature cheers
 

Phil

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You don't set an offset between the exiting and returned wort. All you need to be concerned with is the temperature of the return manifold. If that matches the temperature shown on the PID then you're good to go.

Then, if you have a good enough flow in the system, the exiting wort will eventually match the temperature of the returned wort.

/Phil.
 

Rabmaxwell

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Herms water trial



When trying last night i got wild jumping read-outs until i set the Filt setting to 3 set temperature at 65oc & pid read-out was quite stable at 65oc but another temperature probe inside the mash-tun was showing a steady 60oc.Think i need to calabrate both probs with ice again shouldn't be 5oc difference with my fairly good insulation.Anyone using a totton pump like mine in there herms doesn't sound to good when trying to reduce the out-flow speed
 
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BrewStew

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even if you're having problems, i'm loving that wood clad set up mate :thumb: ... so jealous :mrgreen:
 

Vossy1

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When trying last night i got wild jumping read-outs until i set the Filt setting to 3
I had the same problem Rab...I have an Auber PID.

I think your readouts will be right, I had exactly the same problem. I think I remember Phil saying his HE to mash difference is 6.5 deg c.

FWIW Rab, I'd go with the mash probe. Off set your HE PID by the 5 deg c difference between the two probes.
Monitor your next few mashes using the probe in the mash and make adjustments if needed.
This is how I've overcome the problems I've been experiencing on my new larger system.
 

Vossy1

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As part of my drive to eliminate copper and brass from my system, today I replaced the copper coil in my heat exchanger with a new coil made of stainless. The coil is an exact replica of my existing coil, however the existing conatiner was such a snug fit that I couldn't manipulate the heat exchanger outlet into the existing stainless container. Wishing to brew soon, and not wanting to trawl for a stainless replacement (yet), I decided to use a acrylic container from John Lewis (£12).
The brass fitting on the coil inlet has been replaced with a cable gland, and I've uprated the element from 2.4kw to 2.75kw.So here are the pics


I can't decide if I really like it as opposed to the previous stainless jar..but it's growing on me :lol:
It's all tested to boiling and bar a few parts which should arrive tomorrow I should be brewing at the weekend.
If the acrylic clouds up, I'll replace the container.
 

Screwy

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In my original HERMS design mash temp was monitored by a through the wall dialface thermometer in the grainbed. Temp of the wort out at the HE was a good 6°C higher for much of the ramp time and this resulted in lower attenuation. After seeking the advice of some commercial brewers and some celeb brewers the advice was to use the temp at the hottest part of the system as my mash reference temp. Now the only temperature I'm interested in is the temperature of the wort out of the HE, this is where the control probe is mounted, so once the desired mash temp is reached at this point the mash timer is set. Thought I would pass along the finding it works for my system and low attenuation is no longer a problem due to this change in process.

Screwy
 

Vossy1

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Great advice S.
I find it's still very important to measure the mash temp itself. Ideally the temp should be measured, as you say, as close to the outlet of the HE as possible, but the mash temp can vary by quite some bit from the HE output. It may take some time for the mash temp to reach the HE outlet temp, if the strike temp resulted in a low mash temp initially, even when the HE return is relatively stable.
 

Bionicmunky

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Now your confusing me.

So when I set my HERMS up do I set the PSB value on the HE PID to reflect the temp of the mash probe reading? or do I start the clock when they have equalized?

cheers,

John
 

Vossy1

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So when I set my HERMS up do I set the PSB value on the HE PID to reflect the temp of the mash probe reading?
On initial set up, yes. Check the difference between the HE return and the mash temp once settled, maybe 30 minutes into the mash(though it should be settled well before then), or whatever you prefer. Once the PSB has been set, and your happy the mash is tracking the HE return, just re-check it every other brew or whenever you want to.
I'm nosy so I always have a PT100 in the mash. Just because the runnings exiting the HE are at say 65 deg, doesn't mean they are at 65 deg when they enter the mash. How much heat you lose will depend on various factors, air temp, length of piping, insulated pipes etc and you may also lose heat from the mash surface to the environment.
Eg, you may lose 1 deg to the piping/atmosphere which means the mash will track at 64 deg c, even though the HE is returning the runnings at 65 deg c.
I keep the return piping as short as possible and insuate it to aid in heat retention.
Before I insulated the HERMS piping if brewing outside in winter, I'd have to change the PSB from it's 'normal' setting by about 2 deg c to compensate/off set for losses. Now the pipework is insulated there's not as drastic a difference.
I've spoken to a few HERMS users who didn't have this problem, but they all brewed in a kitchen or heated garage, lucky buggers :mrgreen:
 

Phil

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I don't really find that I lose any temperature between the HE and the mash tun. Possiby because the silicone tubing is a good (enough) insulator. Possibly because the flow rate is fast enough that it doesn't have time to lose much heat. Whatever.

For me, the PSB parameter is only really used to calibrate the PID and thermocouple to my chosen baseline thermometer.

/Phil.
 
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