# Crazy thoughts about actively cooling a La Pavoni grouphead



## GlenW (Sep 7, 2013)

So I've just got back into trying to make espresso (posted my new setup here) and looking for ways to improve my setup without spending loads on a new machine.

I'm loving my la pavoni europiccolo - just wish the grouphead didn't overheat so quickly. Its a millenium version with a brass piston.

Whilst I've been standing with a wet cloth cooling it down, I've been thinking of ways to actively cool it... 3 ideas so far

1) Use a heatpipe based laptop cooler. My thinking is you can cut wrap the heatpipe around the grouphead with some thermal tape sandwiched between the heatpipe and the grouphead. The heatpipe would then transfer the heat to the heatsink to be cooled by the fan. I'll have to fgure out how to remove the other bits stuck on the heatpipe, and then straighten and rebend it.

I've bought one of these off ebay last night for £3 to experiment









I've no idea if it will work, but cheap enough to give it a go. It comes off a laptop with a 35W CPU. If I guess the grouphead is made of 500g of brass which has a specific heat capacity of 0.38 J/g K, then if I want to cool down the grouphead by 10C after a shot then I estimate it will take 54sec. 0.38*500*10/35.

This ignores the fact there is more heat coming from the bridge to the boiler. No idea if this will work at all but I'll give it a go as the total cost of the heatsink and some tape ~£5. I think this is fairly unlikely to work, a 35W cooler seems pretty wimpy compared to a ~1KW boiler.

2) Similar to above but fashion something DIY out of heatpipes and a PC heatsink fan combo. If the principle works but the laptop cooler is not powerful enough, you can build something more meaty. You can get 200mm long heatpipes for £5 on ebay I'm thinking you could wrap two of those round the grouphead and then attach the other end to a poweful heatsink+fan. Not sure how you'd attach it - some kind of thermal epoxy or solder?









3) Watercool it. You can get 1m of thin 4 or 5mm diameter copper tubing for around £5 on ebay I have a tiny pump somewhere from some random project I could use to pump water through it. I'm thinking put thermal tape round the grouphead and then wrap a few loops of the copper pipe round. Join to some flexible plastic pipe and then pump cold water through. To start with could just have a cold and warm water tank without bothering with a fan and cooler. No idea if you can get enough water down a tiny pipe and enough thermal transfer between the pipe and the head to actually cool anything.









All of these you could then couple with a PID controller to keep the grouphead at a fixed temp. On my ebay adventures I was amazed to find you can get a PID controller with a thermocouple for £10!

I think if 1 works that would be pretty easy and very cheap - but look pretty horrible. I think you could get 3 to look pretty nice if you can wrap the copper tubing neatly, and I could have the controller pump and tank under the bench put of sight.

Anyone tried anything like this - is there any chance of any of this working?


----------



## HowardSmith (Jan 21, 2018)

I have been playing with cooling the e61 group on my rocket appartamento with a fan. The group head temp pretty much determines brew temp when HX water is within 'normal' parameters.

I installed a small brush less DC fan with a 'PID' controller and a thermostat. I am able to control the group head temp to cycle within less than 1°c and no cooling flushes are required.

Airflow is very effective at cooling the group so I would consider simply buying a small battery operated fan and see how you get on. If you like the process then you can play with automating the temperature management.

Sent from my SM-A405FN using Tapatalk


----------



## HowardSmith (Jan 21, 2018)

This video shows the basic set up. This is an ugly solution but it is more to prove he concept than look pretty for now.

The 'PID' can be programmed to have an offset so hitting target GH temp can be managed easily.

FWIW with this set up on an E61 HX machine the theory is similar to the 'Flush and wait' method of hitting brew water temps where you flush the GH below target brew temp and initiate the shot at around 1-3°c below target brew temp. However since the thermosyphon is going to be at a constant cooler temp as in theory the Idle temp is now lower you can almost initiate the shot when GH temp matches target brew temp to get about the correct temp.

Sent from my SM-A405FN using Tapatalk


----------



## GlenW (Sep 7, 2013)

Good idea - I have one of these I use to get my little pizza oven going - I'll try it out.









What kind of fan is that you have - is it a little centrifugal fan blowing out of the side onto the grouphead?


----------



## HowardSmith (Jan 21, 2018)

GlenW said:


> Good idea - I have one of these I use to get my little pizza oven going - I'll try it out.
> <img alt="MVIMG_20200414_102344.thumb.jpg.7949609aa25de505764079b5861165d6.jpg" data-fileid="38062" data-src="<fileStore.core_Attachment>/monthly_2020_04/MVIMG_20200414_102344.thumb.jpg.7949609aa25de505764079b5861165d6.jpg" src="https://www.coffeeforums.co.uk/applications/core/interface/js/spacer.png">
> What kind of fan is that you have - is it a little centrifugal fan blowing out of the side onto the grouphead?


If you look through my other YT vids you will see one where I cool the GH with a mini fan, just like you I brought the fan first my pizza oven, UUNI 3

Sent from my SM-A405FN using Tapatalk


----------



## HowardSmith (Jan 21, 2018)

And yes, it is a small 12V dc 'blower' fan. It takes very little airflow over the GH to drop the temp.

Sent from my SM-A405FN using Tapatalk


----------



## johnealey (May 19, 2014)

Am sure Frans would be ok linking to his blog the below from 2015 so may require some further searching for anything more up to date:

http://kostverlorenvaart.blogspot.com/2015/01/time-to-pid-pavoni.html?q=PID

Some really interesting reading on his blog

Hope assists

John

p.s. and please take this as not being flippant, but could you not just turn off between shots given the quick heat up time? would save electricity as well as extend life of your la pav (is what I do on the G105 which is basically a la pav in different clothes and a hat fetish  )


----------



## GlenW (Sep 7, 2013)

johnealey said:


> Am sure Frans would be ok linking to his blog the below from 2015 so may require some further searching for anything more up to date:
> 
> http://kostverlorenvaart.blogspot.com/2015/01/time-to-pid-pavoni.html?q=PID
> 
> ...


 Thanks - will have a read!

On - 'why not just turn it off' - good question. My perception is if the head is overheated to 90+ it takes a long time to cool down to ~80 even if turned off, and I want to minimise shot to shot time. M

My use case is typically making too shots back to back. Generally two things happen. First - I switch the machine on, get distracted and when I come back the head is overheated. Putting a PID with the thermocouple on the group-head and switching the main heater might solve this, but I'd be worried how long the feedback loop would be from heater to group-head temp. After pulling a shot and temp spiking up to 90, how long would it talk to come down to temp, and then for the boiler to reheat?

I could definitely experiment with this - with me pretending to be a PID controller, switching off and seeing how long it takes to come down to temp using an IR thermometer.

Second typical thing I'm solving for is after a shot, trying to get the temp down quickly for a second shot.

Just did my first experiment with the fan - this was my sophisticated setup:









Actually worked pretty well. Eyeballing the temperature strip - took 2-3min to bring the temp drop from 90ish to 80ish, which is also roughly the time it take me to dose, grind and tamp a shot. Should also have a much faster feedback loop than the heatpipe setups, so might work well on a PID controller. Now how do I make it look vaguely attractive?!?


----------



## HowardSmith (Jan 21, 2018)

GlenW said:


> Thanks - will have a read!
> On - 'why not just turn it off' - good question. My perception is if the head is overheated to 90+ it takes a long time to cool down to ~80 even if turned off, and I want to minimise shot to shot time. M
> My use case is typically making too shots back to back. Generally two things happen. First - I switch the machine on, get distracted and when I come back the head is overheated. Putting a PID with the thermocouple on the group-head and switching the main heater might solve this, but I'd be worried how long the feedback loop would be from heater to group-head temp. After pulling a shot and temp spiking up to 90, how long would it talk to come down to temp, and then for the boiler to reheat?
> I could definitely experiment with this - with me pretending to be a PID controller, switching off and seeing how long it takes to come down to temp using an IR thermometer.
> ...


Install a small blower fan in the base of the la pav and use small diameter copper pipe to get the air where you want it.

You could polish the copper pipe and lacker it or have it chromed.

Temp controller in the base also or cut into side.

I don't have a la pavoni but u suspect temperature management is somewhat similar to an e61 HX machine where brew boiler temp is above brew temp and group temp needs to be at or below brew temp to buffer the incoming hot water.

Assuming this is the case a temp controlled fan would do a good job of maintaining the GH at a constant temp, whatever that may be. Considering my controller shows target temp and also live temp this set up could be great on la pav as you will see a sudden rise in temp as you draw the hot water into the group and then you will monitor the temp drop as the cooler GH buffers the water temp. You could be very consistent with this set up.

Sent from my SM-A405FN using Tapatalk


----------



## GlenW (Sep 7, 2013)

HowardSmith said:


> Install a small blower fan in the base of the la pav and use small diameter copper pipe to get the air where you want it.
> 
> You could polish the copper pipe and lacker it or have it chromed.
> 
> ...


 Nice idea with the pipe. Rather than cutting into the base - in case it doesn't work - I could drill a hole into the worktop (it's just 12mm ply), mount the fan and controller underneath and then just have a nice chrome pipe coming out of the bench


----------



## GlenW (Sep 7, 2013)

So the PID controller arrived and I've cobbled together a 12v transformer and PC Case fan I found in my magic box of bits.

Works surprisingly well, it's a pretty stable system, so no trouble keeping the PID temp reading pinned on the setpoint. This fan isn't that powerful - so takes a bit longer to bring the temp down after a shot - approx 2.30.









Main issues I've had so far are
1) Configuring the PID controller. Tried the autotune function but didn't do anything useful. Tried a bunch of combinations, read a lot of articles, in the end I have P=1, I=0, D=0 which seems unconventional but works just fine. Think it's basically acting as a on/off controller, but as the fan is really not that powerful it seems to work great. After a shot the fan is on 100% until temp gets down, it doesn't overshoot v much and then when stable sits nicely pulsing every few seconds

2) Measuring temperature. Three thermometers - the K type thermocouple on the PID, a cheap refrigerator thermometer and an IR temp gun. All have different lags, all read different things, different quality of contact to the grouphead, probably different susceptibility to the breeze from the fan as well, I seem to have no idea what any temperature actually is. So far, I'm using a rubber band to keep the thermocouples against the grouphead.

What I'm trying to optimise for is to set a group head temp on the PID which results in an appropriate brew temp - 93 deg seems to be the established number. I've stuffed the a bit of sponge into the bottom of the naked portafilter with the fridge thermometer above it. With the PID reading 76, the measured water temp when I do an extended (20s?) preinfusion pull has the temp spike up to around 93 which seems about right. Its all pretty hit and miss, the sampling rate on the thermometer is only every couple of sec, and the reading moves a lot in between samples. The extended flush into a sponge isn't representative of a normal espresso pull, so I don't have a lot of faith in it. The other method I've seen recommended is pull some water into a polystyrene cup - but its kinda hard to get hold of one right now. I tried just using a preheated normal cup, but with water straight out of a boiling kettle I couldn't get a reading above 90deg so didn't trust that much. I've seen the SCACE things - they look pretty awesome but cost way more than the La Pavoni! Coffee tasted good so maybe that's what counts.









I've ordered a pt100 temp sensor which the internet tells me is more accurate and faster response time than the K type thermocouple currently have which hopefully will make temperature measurement less frustrating. If what I read is correct, the PID controller will also work with 0.1deg accuracy rather than 1 deg when I use a pt100. It also has a cylindrical barrel which will make it easier to hold against the group-head, as opposed to my current one which has a thread and nut so you cam't hold the body flat against the grouphead.

Then need to clean everything us somehow - my nice new tidy coffee bench isn't so tidy right now. Plus I've already taken a small chunk out of my finger sticking it into the spinning fan. Its all worth it in the search for temperature stability!


----------



## MediumRoastSteam (Jul 7, 2015)

I'm going to read this thread with interest. I was thinking of attaching an external PID to the machine to increase/decrease temp (in consequence pressure) as I wish.

I'm bored, this lockdown is killing me!


----------



## jimbojohn55 (Jan 15, 2016)

You could turn the pressurestat down a bit - depends if you steam milk or not

Im running a Pav at 0.6 bar at the moment,


----------



## GlenW (Sep 7, 2013)

jimbojohn55 said:


> You could turn the pressurestat down a bit - depends if you steam milk or not
> 
> Im running a Pav at 0.6 bar at the moment,


 How do you find the preinfusion? From what I've read people say generally it's better to have a bit higher pressure?

I also don't have a gauge to measure the pressure, but if I dredge up the remnants of a long distant engineering degree I can probably figure out a steam table to roughly estimate the pressure from temperature.


----------



## MediumRoastSteam (Jul 7, 2015)

jimbojohn55 said:


> You could turn the pressurestat down a bit - depends if you steam milk or not
> Im running a Pav at 0.6 bar at the moment,


I do steam milk. I was toying with the idea of having a temperature monitor where I could set it to "brew friendly" or "steam friendly".

In my case, it would be steam friendly in the morning, and brew friendly after lunch.


----------



## jimbojohn55 (Jan 15, 2016)

GlenW said:


> How do you find the preinfusion? From what I've read people say generally it's better to have a bit higher pressure?
> 
> I also don't have a gauge to measure the pressure, but if I dredge up the remnants of a long distant engineering degree I can probably figure out a steam table to roughly estimate the pressure from temperature.


Fit a gauge, it's the only way to know if you pstat is correct, most are out after a few years of use.

For pre infusion, as I understand it at the moment I leave the lever fully raised this lets about 10 seconds of water at 0.6 bar to infuse the puck. After this I bring the lever down but gently with less pressure than the main stroke to pre infuse further, once the first drops fall in the cup I then extract for 30 seconds ,. Works for me anyway

As for getting the group up to temp as the boiler has less heat in it, I do a couple of flushes and judge the heat in the group with my hand, less than scientific but I am happy with most shots ,

Sent from my moto g(6) using Tapatalk


----------



## GlenW (Sep 7, 2013)

jimbojohn55 said:


> Fit a gauge, it's the only way to know if you pstat is correct, most are out after a few years of use.
> 
> For pre infusion, as I understand it at the moment I leave the lever fully raised this lets about 10 seconds of water at 0.6 bar to infuse the puck. After this I bring the lever down but gently with less pressure than the main stroke to pre infuse further, once the first drops fall in the cup I then extract for 30 seconds ,. Works for me anyway
> 
> ...


 Using https://www.efunda.com/materials/water/steamtable_sat.cfm my boiler temp is 117deg which equates to approve 0.8 bar so I think I'm probably in the right ballpark. I know I should probably get a gauge but I've been buying a lot lately! I think you're right though a slightly lower boiler temp will help with the group-head overheating and I drink my coffee black.

I'm curious about trying the 'assisted preinfusion' with a bit of lever pressure if you have a lower boiler pressure. I understand that for very light roasts, higher preinfusion pressure is meant to be better for reasons beyond me. Will have a play

Here's the latest fan iteration - cheap ebay usb fan - I like it. Looks neater than the case fan, is easily positionable, and doesn't take a chunk out of your finger if you put your finger in it.

I'll stick with this setup for a bit, and if I like it will drill a hole in the bench and put in a small cigarette lighter socket USB charger


----------



## MediumRoastSteam (Jul 7, 2015)

GlenW said:


> Using https://www.efunda.com/materials/water/steamtable_sat.cfm my boiler temp is 117deg which equates to approve 0.8 bar so I think I'm probably in the right ballpark. I know I should probably get a gauge but I've been buying a lot lately! I think you're right though a slightly lower boiler temp will help with the group-head overheating and I drink my coffee black.


Where are you measuring the boiler temp?


----------



## GlenW (Sep 7, 2013)

About half way up the boiler with a IR gun and a piece of sticky tape. Was thinking of putting a few more bits of tape on so I can see how the temperature varies - it's just a pain getting the adhesive off.


----------



## MediumRoastSteam (Jul 7, 2015)

GlenW said:


> About half way up the boiler with a IR gun and a piece of sticky tape. Was thinking of putting a few more bits of tape on so I can see how the temperature varies - it's just a pain getting the adhesive off.


I measured mine with a K type probe and a multimetre inside the overpressure valve assembly.

It measured 114C pretty constant, but does not reflect the actual temperature of the water inside the boiler, just an approximation.

The pressure on my machine is between 0.85 and 0.93 or something like that.

I'm not sure how fast I'll notice change in temp if the probe is attached to the external part of the boiler like you did. For instance, if I turn the machine off, how long will it take until the temperature drop registers?

I keep toying with the PID idea as a project.... will keep this updated If I go ahead.


----------



## GlenW (Sep 7, 2013)

MediumRoastSteam said:


> I measured mine with a K type probe and a multimetre inside the overpressure valve assembly.
> 
> It measured 114C pretty constant, but does not reflect the actual temperature of the water inside the boiler, just an approximation.
> 
> ...


 FWIW the reason I didn't go with PIDing the boiler was I didn't think it would solve the overheating grouphead issue.

Here's my thinking:

The brew temp (which is what I'm trying to control) is determined by the temp of the water coming from the boiler, the temp of the grouphead it comes Into comes into contact with, and how long its in contact with it.

Therefore to accurately control the brew temp, you need to control both the boiler water temp and the grouphead temp. The boiler water temp is already controlled reasonably well by the pressure stat, but the grouphead temp varies widely depending on how long the machine has been on for and how many shots you've made.

If you PID the boiler, you can either put the temp. sensor on the boiler or the grouphead. If you put it on the boiler, then you can control the boiler water temp but not the grouphead temp. If you put it on the grouphead, you can control the grouphead temp, but the boiler water temp will be uncontrolled.

This is how I ended up with leaving the pressure stat to control the boiler water temp, and then the fan on the PID controlling the grouphead temp. The need to do this would be reduced by reducing the temperature difference between the boiler and then grouphead - so I'll experiment with reducing the pressure stat.

If you actually want to change the temp in the boiler then I could see PID control be very useful - e.g. for steaming.


----------



## MediumRoastSteam (Jul 7, 2015)

GlenW said:


> If you actually want to change the temp in the boiler then I could see PID control be very useful - e.g. for steaming.


This is exactly what I want to do. You are absolutely right in your thinking.

Before I go anead, I'm thinking where's the best place to attach the probe. I don't really want to modify the machine, e.g: I don't want to replace the pstat with a tstat. For my case, maybe middle of the boiler is a good one, just unsure how accurate/responsive that will be.

Also the thermocouple which comes with those PID kits from eBay seems rather bulky.


----------



## GlenW (Sep 7, 2013)

Just to round out this thread - I've now replaced the big PID with a simple temperature controlled from ebay - it's much smaller, simpler, and works just fine.

Here's how the current setup looks like. Fast to warm up, once the boiler is hot, a few half pumps on the lever get the head hot. Then the fan keeps the temp between 74.5 and 75.5 consistently. Just need to figure out how I can accurately measure the brew water temp so I can figure out the optimal head temp.









If you're interested in the other bits - I've built a thing to draw graphs of pressure and coffee weight - I wrote about it here

What I'd love to do would be measure the grouphead and boiler temp/pressure in the arduino, and then write a simple algorithm to control temp both by switching on/off the boiler and the fan. The digital temp sensors I have seem slow to read, so slow down the whole system so bit of a roadblock there. Maybe I'll run it off a separate arduino.


----------

