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pstat to thermocouple mod - entry questions
Hi everyone,
I'm planning to do what I've done on my Elektra T1 in the past, swap the noisy / clicky pstat with a thermocouple and a PID in order to control the pressure in the boiler. A few questions before I start and order parts:
- what's the standard boiler pressure the L1 operates at?
- what's the thread size on the boiler pstat fitting?
The mod is rather simple, all you need is a Swagelok tube adapter with the correct female thread (that goes where the pstat sits currently), a long-ish mineral insulated sheathed thermocouple probe (you can bend those), a PID and an SSR. I'll post photos as I go along to document the process, you never know someone else might be mad enough to do the same!
Regards,
Tom
I'm planning to do what I've done on my Elektra T1 in the past, swap the noisy / clicky pstat with a thermocouple and a PID in order to control the pressure in the boiler. A few questions before I start and order parts:
- what's the standard boiler pressure the L1 operates at?
- what's the thread size on the boiler pstat fitting?
The mod is rather simple, all you need is a Swagelok tube adapter with the correct female thread (that goes where the pstat sits currently), a long-ish mineral insulated sheathed thermocouple probe (you can bend those), a PID and an SSR. I'll post photos as I go along to document the process, you never know someone else might be mad enough to do the same!
Regards,
Tom
Comments
from memory that thread size is 1/4"BSP
the pressure switch is typically set to open at 1.3 bar, +/- 0.2 to adjust for ambient conditions
kind regards
reiss.
I look forward to your illustrated narrative. I just may be mad enough to follow your example.
Matt
The Londinium machine is so stable that I don't see the advantage for a PID (except the fun in tinkering) and in terms of simplicity and robustness the p-stat wins hand down. It's a simple device that has been in the industry for dozens of years for a reason.
If I'd want to add a PID, I'd just stick the probe on the outside of the boiler and keep the P-stat as it is so I could use a simple switch to revert back to the p-stat for any practical reason.
The clicking of the p-stat is for me so trivial, i could not bring myself to bother about it.
If I could get one, I would like a vintage mercury switch / p-stat like ancient machines have.
Rgds,
Tom
Matt
In your unusual 'kitchen climate' a probe on the group would be more effective I think.
The boiler temp is stable enough with the p-stat as I have measured, logged and published extensively and a quick change in kitchen temperature will hardly change the boiler temp but it will affect the group temp if you have all seasons in one day. With a pid probe on the boiler you would be chasing a tail all day, manually changing the pid target temp to get the group temp 'right'.
Do let us know how you did it when ready and I would like to see your pictures and temp results!
In your unusual 'kitchen climate' a probe on the group would be more effective I think.
The boiler temp is stable enough with the p-stat as I have measured, logged and published extensively and a quick change in kitchen temperature will hardly change the boiler temp but it will affect the group temp if you have all seasons in one day. With a pid probe on the boiler you would be chasing a tail all day, manually changing the pid target temp to get the group temp 'right'.
Do let us know how you did it when ready and I would like to see your pictures and temp results!
Thank you for your observations, Frans. I'm not dogmatic about this idea, but here is the 'problem' I'd like to resolve. Yesterday afternoon, I pulled a shot when the group temp read 92C on my Amprobe TMD-50. The crema was thin and the drink flat. I pulled another at 78C and the result was a golden crema and a subtle and layered taste. (The coffee is a medium-roasted SO from Costa Ricca.)
Had I reset the boiler pressure via the p-stat to bring the group temp down 10C or so, it would have been a disaster this morning when the group temp is hovering around 72C (which should be fine but wouldn't be if it were much lower).
When needed, I adjust the group temperature up or down by small flushes or the insertion of a room-temperature portafilter. In a way, I prefer this method to an electronic one, as it seems appropriate for a manually operated machine. But I can't help wondering if there is an automated way to achieve the same result. Could you PID the group?
Matt
As for group temps, the relation stays the same as on a stock machine as this is mostly affected by the design.
T.
I did that on my La Pavoni. On that little 'hothead' it does make a difference and it makes life easier but I don't see the use on a professional brew group like we have on our Londiniums.
I'm not sure if it was from Matt Perger or Gwilym Davies (probably the latter) that I read a blog posting, a while ago, about all the stuff you can do to get your extraction right with different beans (light, dark, fresh, older). Changing the boiler/brew temp was the very very last resort ever as there is so much you can do with grinding, dosing and timing of the shot.
If the room temp changes dramatically all the time during any day, I'd probably set the boiler temp/pressure so that the brew temp would not be too high in any circumstance and work with that. I also believe the constant boiler temp would ensure that any temporary coolness in the heavy brew group is slightly compensated.
Similarly when using my pour over devices (Portaspresso, EspressoForge, etc.) the difference between matching the bean to the brew water is the difference between being drinkable and sinkable...experimented with this ad nausea.
So for me having the ability to reference and easily adjust the effective brew temp is worthy of the experiment...and one I plan to play with soon.
http://europeancoffeetrip.com/pdf/5-LCwG-handling-and-dailling-in.pdf
• A fast flow brews hotter in the filter basket • A slow flow brews cooler in the filter basket
Temperature from the grouphead is the last variable I change, I generally have my machine at 92.5c and leave it there.
• Reduce temperature if it tastes bitter
• Increase temperature to reduce sour acidity
• Very unripe or underdeveloped coffee can benefit from a drop in temperature below 90c
• If you cannot get a coffee to taste good try it at 80c, sometimes it creates a simple uncomplicated espresso.
You are right, mounting a pressure transducer directly on top of the boiler is probably not a good idea.
Specification for the pressure transducer I use states 105*C thermocompensated range (that means accuracy is not the same above that)
There is an elegant solution for a pressure transducer mount for a second generation L-1 (where pressure gauge positioned under the power switch)
>>https://www.pegasusautoracing.com/productdetails.asp?RecID=11217<<<br />You simply unscrew the tube from the gauge and insert the adaptor.
It didn't work in my case as I have first gen machine where gauge positioned under the steam valve - steam tube gets in the way.
Another thing is its made of aluminum - not sure how it would play in contact with brass long term. If they can make it from brass that would be ideal.
Ended up using a long tube (that I have left from over-pressure valve set-up that Reiss did for a small number of early machines) on the p-stat port. Running it since late June with no single hiccup.
The main advantage for me is ability to change the boiler pressure (0.8 - 1.5 Bar) without unscrewing top panel (panels on early machines are secured with screws - not clip-on). I never thought I would need an adjustment until I modded my machine for direct HX feed recently (my machine is plumbed in). It seems to me that direct feed setup requires lower temp / boiler pressure (I run it just below 1 Bar) but I didn't bother measuring grout surface temp.
Reiss have you got any cross-section drawings showing how the heater is coiled up in the boiler? I need to know this in order to get the right thermocouple length. Also, how high does the water level go on a factory set level probe?
Cheers,
Tom
If you are interested in a fitting and TC let me know and I can send you a set. We are talking around £30 for both. All you need then is a PID controller (you can find used Omron's on ebay for £30-£50) and an SSR (£20) and you are good to go.
T.
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Thanks for doing this! This surely will make it easier to get the flavor profile I'm after with the variety of beans I pull...with more accuracy/predictability. And if not, well then, it was a learning exercise
Same goes for thermocouples, I'll post some photos and a short tutorial when I get all the parts.
Cheers,
Tom
T.
Sent from my Hudl 2 using Tapatalk
T.
Sent from my HTC One_M8 using Tapatalk
I also had to drain the boiler and remove the heater as I had to change the heater gasket, but mostly due to the reason of dropping a BBQ stick into the boiler when doing some dimenson checks for the TC. So a simple mod turned into a massive task of dismantling half of the machine only to fix a few silly mistakes. Will post some photos soon...
Cheers,
Tom
T.
Attached files
The modification will be similar to that done by Victor Sherman
I'll play around with the TC still as I do think I can bend it so that it goes around the HX, but I need to try it first with some 3mm rod (or tubing as a solid rod is fairly hard to bend).
Cheers,
Tom
T.
Rgds,
T.
Yes, still working, still happy. Dead quiet which is great although the discrepancy between the on-board gauge and the PID also worries me. Will need to have a look at calibrating the PID and checking if it's real or an error.
Rgds,
T.