Adding a PID to a non-PID Aurelia?
Replies to This Discussion
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Permalink Reply by R. Justin Shepherd on
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Yes I've googled it. No dice.
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Permalink Reply by Scott on
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Try calling the tech line at NS. Or if you are up to the challenge you could DIY it with parts from these guys - http://www.auberins.com/.
I would ask, what problem are you trying to solve?
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I guess what I'm wondering is... OK it has a pressurestat like every other HX. And if I adjust the pressurestat then my brew temps change. A PID is just a fancy pressurestat, right? Or am I understanding how PIDs work wrong...
In other words, if one can PID a Silvia or a Linea or whatever, would it just be the same function, or might there be some reason such a mod wouldn't work?
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Permalink Reply by Mike Sabol on
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Alright. The PID is a computer controlled way of deciding when to turn on the elements, so in this way it is the same as a P-Stat. Now in the Aurelia the thermal stability has to do with the mass of the group head, which is enormous. If you PID'ed the Aurelia you would be very closely controlling the temp of the water in the steam tank, which is only coupled to the group head via the thermosyphon from the hX. So it really depends on what you are trying to do. The Linea greatly benefits from PID because the coffee boiler can really fluctuate when the cold water hits it and you can see temp swings in excess of 15 degrees pretty quick. But the Linea directly heats the water for the espresso. The benefit for the Aurelia is a little more abstract and more likely to be seen in steam performance rather than extractions. And the Aurelia doesn't really suffer from poor steam performance, anyway, it's actually one of it's strong points. A more direct way of manipulating Aurelia extractions is in changing the flow restrictors at the top of the group head and in the bottom of the hX. It really depends on what you are trying to do. PIDing things just because it can be done is possible. Getting some return on your time and money is another issue.
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Thanks Mike! This is really helpful.
I have been able to raise/lower the brew temps through the pressurestat, but in comparison to the Astoria Argenta I used to own, it takes a much more drastic change to the pressurestat to get the temps I want. Right now, based on the gauges, I'm below the "1", which I know is supposed to be the optimal operating point, but the coffee is tasting better at a lower temp. It hasn't affected the steaming much, if at all... but like you say, the steaming wasn't an issue anyway.
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Heat exchanger machines run hot because the water in the steam tanks is hotter that 212 which therefore heats the water in the hX beyond 212. PIDing the Aurelia will only make the source of the thermal energy more consistent, though it will still be quite a bit hotter than boiling. The only way of really dealing with exact temperatures at the grouphead is to manipulate the flow of the thermosyphon. The Aurelia address this with little jets installed in the grouphead and the bottom of the hX. The E-61 Legend and Key Van DerWesten use needle valves at the top of the hX to adjust the thermosyphon flow. With a hX machine you can get good results by getting very scientific with flushing the group before pulling a shot. But you will not get the kind of temperature exactitude with the Aurelia as you can with the Linea because the water for extraction is indirectly heated. Everyone's strength is also their weakness. The same holds true with espresso machines. The Aurelia, specifically uses a massive grouphead to achieve it's thermal stability, which makes it very unresponsive to slight fluctuations in the environment. This is the same property that makes the benefits of PID not so applicable to the Aurelia. The Linea is a different story and it really becomes a different machine once you PID it. And the Silvia is a home machine without much thermal mass, which makes it very susceptible to environmental temp fluctuations. The Aurelia's grouphead probably weighs more that the entire Silvia. So if you are looking for results in the cup by PIDing an Aurelia you might not find them. However if you change the jets in the thermosyphon you really change what you get in the cup. But you can never achieve the "change the temp real quick" kind of thing people can do with their PIDed Lineas because the mass of the grouphead won't allow that kind of quick response. If you're looking to change machine temp to suit any arbitrary SO or tweak a new espresso blend the Aurelia is not the machine to do that with. You can eventually arrive at the temp you want but it will always take some time and some experimentation to get there. The Aurelia is more of a "set it and forget it" kind of machine. Hope this helps. Let me know if this is not the info you were looking for.
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Permalink Reply by Brady on
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Justin, I've noticed the same thing when adjusting the Aurelia. Getting to a cooler temp does take you below 1 bar. I'm not sure this is such a big deal... especially since you are running a more restrictive steam tip. To Mike's point, if you'd like to achieve lower brew temps at more customary boiler pressure settings you can have the jets changed.
I will say that I believe there is some benefit to electronic temperature control on the Aurelia. Regardless of how directly or indirectly the control effects the outcome, repeatability is our friend. In any case, PID control is utilized on the Competizione machine, as well as their newer Digit model. It looks like on-the-fly temp adjustment is much more straightforward on this model. I doubt that implementing this on your machine with OEM parts would be terribly cost effective though.
Kind of rambling, but wanted to add a couple of thoughts to Mike's already very thorough post on the matter. Hope all of this info is helpful.
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Permalink Reply by Troy J Mallett on
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Brady, the newest Aurelias use a PID to control boiler pressure electronically, and not the temperature directly. Even at that, the controls step at intervals of 0.05.
I have been working on putting a PID into my appia, but there are much more significant problems than just replacing the pressostat with a PID. Each measure completely different things. The pressostat manages the pressure in the boiler, thus the brew water temp indirectly). A DB machine with a PID regulates the temperature of brew water (in the brew boiler) by adjusting the on/off cycle of the heating element. The two things that you will have to overcome if you are to consider putting in a PID is how to quickly adjust the water temperature inside the HX without creating too many problems with steam generation, and where you will put the thermometer probe that will work the PID.
I think that you might want to invest in a more sensitive P-stat (or maybe an electronically controlled one vis WBC aurelia) or maybe get a DB system if you are bent on PID. While it might be neat to have an orange coloured apple, maybe it is better to leave apples and oranges apart.
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True, the temperature control on the Digit is by pressure transducer, not thermocouple. However, with the relationship between pressure and temperature being direct, do you feel like that distinction is relevant? If you think about it, even electronic "temperature" control using a thermocouple relies on the direct relationship between temperature and sensor electrical resistance... maybe I'm splitting hairs.
The point I was attempting to make was that there was benefit to electronic boiler temperature control on an hx machine... hence its use on the Competizione model to enable it to meet the WBC spec. The fact that this machine meets WBC spec and the standard model doesn't kind of makes that point, doesn't it?
Also, I wouldn't say that this approach changes the fact that this is a hx machine - it just makes it more predictable. As a friend of mine once said, all they've done is make a hx that actually works properly. To suggest that improving temperature control on an hx machine is making an apple into an orange is kind of silly - especially considering how many DB machines don't use PID, and how many stock HX machines use temperature transducers.
You are correct, too, that it would be difficult to directly control brew water temp on a hx machine... impossible on a multiple-group machine. So you definitely need to understand the limitations of the configuration. That doesn't mean you can't make your brew water temperature stable though.
Troy L Mallett said:
Brady, the newest Aurelias use a PID to control boiler pressure electronically, and not the temperature directly. Even at that, the controls step at intervals of 0.05.
I have been working on putting a PID into my appia, but there are much more significant problems than just replacing the pressostat with a PID. Each measure completely different things. The pressostat manages the pressure in the boiler, thus the brew water temp indirectly). A DB machine with a PID regulates the temperature of brew water (in the brew boiler) by adjusting the on/off cycle of the heating element. The two things that you will have to overcome if you are to consider putting in a PID is how to quickly adjust the water temperature inside the HX without creating too many problems with steam generation, and where you will put the thermometer probe that will work the PID.
I think that you might want to invest in a more sensitive P-stat (or maybe an electronically controlled one vis WBC aurelia) or maybe get a DB system if you are bent on PID. While it might be neat to have an orange coloured apple, maybe it is better to leave apples and oranges apart.
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Just to split a few more hairs, the PID is not the only difference between the WBC and stock model Aurelias. The jets I mentioned earlier are also different, as well as, there being a plug in the preinfusion chamber. The jets are quite a bit smaller than on the stock machine, which really slows down how fast the water moves through the group head. Both in the thermosyphon cycle and when trying to pull a shot. Simply changing these parts will make your stock Aurelia behave quite differently. It even sounds different. And the espresso is quite different as well. I think it's a little sweeter and the texture is lighter. I've switched a couple of stock Aurelias over to this WBC jetting with out adding the PID and have achieved great results.
Brady, your point that the PID will make the system more stable, I agree with. But to reiterate my earlier point the jetting in the flowmeters and groupheads on the Aurelia actually have a bigger effect on the coffee than PID does. And it would be hard to tell, without talking to Ben at NS, about which part of that system allowed the Aurelia to pass WBC muster. They are probably both interdependent although I would imagine that the PID was necessary to allow tighter control of the highly restricted hx.
Brady said:
True, the temperature control on the Digit is by pressure transducer, not thermocouple. However, with the relationship between pressure and temperature being direct, do you feel like that distinction is relevant? If you think about it, even electronic "temperature" control using a thermocouple relies on the direct relationship between temperature and sensor electrical resistance... maybe I'm splitting hairs.
The point I was attempting to make was that there was benefit to electronic boiler temperature control on an hx machine... hence its use on the Competizione model to enable it to meet the WBC spec. The fact that this machine meets WBC spec and the standard model doesn't kind of makes that point, doesn't it?
Also, I wouldn't say that this approach changes the fact that this is a hx machine - it just makes it more predictable. As a friend of mine once said, all they've done is make a hx that actually works properly. To suggest that improving temperature control on an hx machine is making an apple into an orange is kind of silly - especially considering how many DB machines don't use PID, and how many stock HX machines use temperature transducers.
You are correct, too, that it would be difficult to directly control brew water temp on a hx machine... impossible on a multiple-group machine. So you definitely need to understand the limitations of the configuration. That doesn't mean you can't make your brew water temperature stable though.
Troy L Mallett said:
Brady, the newest Aurelias use a PID to control boiler pressure electronically, and not the temperature directly. Even at that, the controls step at intervals of 0.05.
I have been working on putting a PID into my appia, but there are much more significant problems than just replacing the pressostat with a PID. Each measure completely different things. The pressostat manages the pressure in the boiler, thus the brew water temp indirectly). A DB machine with a PID regulates the temperature of brew water (in the brew boiler) by adjusting the on/off cycle of the heating element. The two things that you will have to overcome if you are to consider putting in a PID is how to quickly adjust the water temperature inside the HX without creating too many problems with steam generation, and where you will put the thermometer probe that will work the PID.
I think that you might want to invest in a more sensitive P-stat (or maybe an electronically controlled one vis WBC aurelia) or maybe get a DB system if you are bent on PID. While it might be neat to have an orange coloured apple, maybe it is better to leave apples and oranges apart.
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