1.

Set the coffee boiler temperature 96C, grouphead 96C, needle valve full open, and got the water temperature about 92C.

How much time did it take between open needle valve and take the temperature? I wonder if this is a steady state temperature?

When measuring temperature, do you use RTD or a thermal couple or other?

2. Still 96C/96C, needle valve dialed to slow flow rate, and got the water temperature about 93C.

Doesn't this tell us the group heater is heating up the water? Which means the group PID set point could be correct?

If the group PID is not kicking in, slower flow should result larger temperature drop, we should measure lower temperature comparing to step 1. My opinion.

macaber8 wrote:1.
How much time did it take between open needle valve and take the temperature? I wonder if this is a steady state temperature?

When measuring temperature, do you use RTD or a thermal couple or other?

K-Type thermocouple like this


Of course it is a steady state temperature. The time and how to measure It depends on the machine and thermofilter you use. When the needle valve is full open, the flow rate is high so the grouphead cannot be filled. If the time is too long, the boiler will be cooled down and you will find the water temperature is decreasing.

macaber8 wrote: Doesn't this tell us the group heater is heating up the water? Which means the group PID set point could be correct?

Yes, the water is heated by the grouphead or the grouphead heater, so the PID setting for the grouphead temperature is too high. My target is that the grouphead temperature matches the water temperature.

macaber8 wrote: If the group PID is not kicking in, slower flow should result larger temperature drop, we should measure lower temperature comparing to step 1. My opinion.

Yes, but it is only based on the grouphead temperature is lower than the water temperature. If the gouphead is too hot and higher than the water temperature, the water will be heated.

I'm not sure we can trust a thermal couple in this case. So much error. The PID probably uses a RTD, which is slower but could be way more accurate (+-0.1C).

I think it is the group temperature displayed in the PID not reflecting the real temperature of the entire group head. The actual average group head temp is lower than the PID, that is why water temp is lower than 96C when you run fast water. When you run slow, sensor pickup the temp drop, and group heater is actually heating up the water before it runs out.

I am still not convinced there is enough evidence to say group PID is overheating.

Macaber8, Mate can I ask what actual experience you have with espresso?
What machines do you have experience with using?
What shots have you tried, either at cafes or at home?
What sort of coffee do you lust after?

I ask because you seem to be extremely caught up in the finer technical aspects of espresso from a theoretical perspective.

A lot of these points may be totally irrelevant to a machine that delivers the elixir that you desire.

Macaber8, Mate can I ask what actual experience you have with espresso?
What machines do you have experience with using?
What shots have you tried, either at cafes or at home?
What sort of coffee do you lust after?

I ask because you seem to be extremely caught up in the finer technical aspects of espresso from a theoretical perspective.

A lot of these points may be totally irrelevant to a machine that delivers the elixir that you desire.

I have little to none experience with espresso machines. I liked rich and chocolate suggesting taste in milk based drinks. I am about to put in an order for Vesuvius, therefore I want to learn as much detail as possible about machines.

Please shin some lights.

Hi Ray.
I have read your posts with interest as you have been getting down and dirty into various machines, some that I own and some I am considering purchasing.
However, I have been playing around with these things for about forty years.
That doesn't mean I know more about the machines but it does mean that I know what I like to drink and how to make it.

I can understand your desire to find the best machine for your purposes but...I believe that first you must discover your preferences.
If you prefer milk based drinks then the discussions over stable, descending or rising temperature profiles during extraction are mostly irrelevant as the milk will hide many imperfections.
If you prefer "Third Wave" light roasted fruity brews you might not even want a machine.
I think you need to get out to various cafes, visit other HB coffee elitists and find out what you like to drink.

If you like chocolate, syrupy thick mouthfeel old school espresso then the Vesuvius or EVO will give it to you in spades if you throw the right beans at it.
So will many other machines.

Don't get too bogged down in the minutia about machines.
Your three biggest problems once you buy a machine will be,
1. finding good roasted coffee that you like,
2. finding a grinder that suits your preffered taste profile,
3. learning how to tie those three into something you like to drink.
Good Luck and I'm looking forward to hearing about your journey.

macaber8 wrote:image
I'm not sure we can trust a thermal couple in this case. So much error. The PID probably uses a RTD, which is slower but could be way more accurate (+-0.1C).

I don't think so. The K-Type thermocouple is not very accurate in some cases. For example, the temperature range is very big, or use different sensors to measure the same thing. But in this case the temperature range is really small and use the same sensor. You can try to measure a kettle of boiling water with the same K-Type thermocouple many times to see the readings are stable or not. The PID also uses thermocouple which is written in the user manual, not knowing what type though.

macaber8 wrote: I think it is the group temperature displayed in the PID not reflecting the real temperature of the entire group head. The actual average group head temp is lower than the PID, that is why water temp is lower than 96C when you run fast water. When you run slow, sensor pickup the temp drop, and group heater is actually heating up the water before it runs out.

I am still not convinced there is enough evidence to say group PID is overheating.

When the water goes out from the boiler, it is not heated and starts to cool down. That's why the PID of pump coffee machines has the "offset" setting about 10C. If you set the boiler 92C, the real boiler temperature is 102C. The La Marzocco Leva X default offset is 3.5C. The Nurri Leva default offset is 0 which is unreasonable.

The Nurri Leva has only 2 150W cartridge heaters in the grouphead, so the grouphead should have hotter and cooler spots. If the sensor is near the heater, when it measures 96C, the temperature of other parts far from the heaters is lower than 96C. But I don't know its real temperature, so I have to use some methods to test it. Of course there are some more accurate methods. For example, take out the shower screen, stop the pump, pull the lever, and measure the surface temperature from the inside of the grouphead chamber.

In addition, there is an interesting thing. Due to the 2 150W cartridge heaters are too weak, or without a dedicated PID for the grouphead, the grouphead temperature showed on the PID is always 1C to 2C lower than the setting (If I set it 98C, it can reach 96C to 97C, but never 98C). The grouphead temperature that I mentioned previously are the readings showed on the PID, not the setting (For example, when I said the setting is 96C, the reading on the PID is 96, and the setting is 97). The heaters are weak so they cannot heat the water quickly. It must be the grouphead which is hotter than the water. Anyway, it is the situation of my Nurri Leva. If you choose other machine, or the Nurri Leva has some improvements, it would be different.

Thanks Amberale!

Already find a good coffee. Papachay Medium Roast. Reasonably priced. Local roaster. After trying many other beans lately, I think I am sticking to it for a now.

Currently owning a Niche Zero, and Acaia pearl scale. Running them with my Aero Press, and making latte every day with a handheld milk frother. I have been enjoying the drinks, but our company's 3 year old beat up Breville makes better drink. I am not rich, but, referring to my other hobbies, a Breville at home just wont settle this obsession. So the goal is go straight from 0 to 100. I am going to own only one espresso machine. No playing around, no upgrades, no back up manual machines on the side or for fun. Hopefully, Vesuvius is the one.

I have been visiting coffee shops around the bay area. Surprisingly, the latte art is better than the taste from most places I went so far. Going to expend the trip to SF and Oakland.

You can try to measure a kettle of boiling water with the same K-Type thermocouple many times to see the readings are stable or not.

I think this only tells us the measurements are precise but not necessarily accurate.

Thanks for sharing this experience. Are you getting consistent shots? How many consecutive shots can you do in a row without compromising the taste?

bakafish wrote:K-Type thermocouple like this
image

That thermocouple will take some time to react to changes in water temperature. A thin-wire thermocouple will react faster. A thin-wire T-type thermocouple is even better because its temperature range is closer to espresso temperatures so it is more sensitive to smaller changes in temperature. The speed matters when looking at how fast temperature changes during a shot.

The conclusions I have come to in this thread is that like most espresso machines the temperature settings and displayed temperatures of the boiler and the group head aren't absolutely correct. Also, the temperature control of the group head is far enough from the water flowing through it to react during a shot.

Based on this the open questions are more related to the difference between the settings and the real temperatures. Further, I think figuring out what the difference between the boiler and group head temperature settings does to shot temperature is the most important thing to understand. Once this is known then users can set things up to get what they want.

The only two ways I have found to do this after much experimentation is 1) to put a thin-wire surface mount thermocouple on the side of the group cylinder near where water flows into the cylinder and 2) to use a preheated device like a scace that also uses a thin-wire thermocouple. Recording those temperature readings from steady state through the start and end of a shot and ending only when the temperatures settle back to steady state is what I have found necessary to understand the temperature behavior of a lever machine.