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NS Ellimatic temperature way too high.... :(
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Discussions > Espresso > Espresso Mods > NS Ellimatic...  
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jannus
Senior Member


Joined: 19 Mar 2013
Posts: 71
Location: South Africa, Cape Town
Expertise: I like coffee

Espresso: NS ElliMatic & few...
Grinder: mazzer sj
Vac Pot: nope
Drip: yup
Roaster: nope
Posted Sun Oct 13, 2013, 8:04am
Subject: NS Ellimatic temperature way too high.... :(
 

Hello Everyone,

This is basically a continuation of my previous post  -
"NS Ellimatic cooling flush question"

I've now done several things to get a handle on what's going on:
- I've managed to get hold of a very precise digital pressure gauge to check my boiler pressure, deadband, etc.
- I've reworked my temperature measurement technique to improvise a "scace" type device (Thanks NSElliIterator!).  This gives me way better measurements than the foam cup, and I'm able to keep pretty close tabs on what happens.  See attached pic.  

For the temp measurement the thermocouple is lying inside the portafilter handle like pictured, and the basket goes on top.  The basket keeps it nicely in place, and I get the measurement off a digital readout.  Basically under no pressure, but at least the measurement is stable and not affected by air, etc.

My boiler pressure is now very close to where it was when I received the machine.  I've noted the position, and ended up adjusting it to basically 40 degrees out from where it was.  Pressure runs from 1.28 bar to 1.08 bar as the pressurestat cycles.  Yes, the deadband is probably a bit wide, but I'll attend to that once that's the problem.

So I'm getting a beautifully stable temperature.  Shot after shot after shot it remains almost perfectly stable.  Problem is it's sitting at 102.2 degrees C!  This puts me right back where I started...only last time I didn't have a pressure gauge, and just blindly started lowering pressure.  It ended up at about 300mbar (so I know now) before the temperature was ok...but that can't be right, can it?

As quick background again - Machine is a Nuova Simonelli ElliMatic.  Basic HX with 1.3 litre boiler.  I've completely stripped and cleaned the machine.  It wasn't too scaled up, just had milk in the boiler.  All that is now gone, the copper is shiny, and no leaks.  I've fitted an  adjustable OPV on the pump, although not adjusted much there.  I also fitted a vacuum breaker on the steam line, which works very well.

I considered the OPV, but with just the basket there's almost no pressure involved, so doubtful.  I also checked the flow rate of the pump, and at no pressure it pushes out about 650ml per minute.

What am I missing!?  Anybody got any ideas on this one?  :)  

Thanks in advance!
Jan

jannus: portafilter-thermocouple.jpg
(Click for larger image)
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jonr
Senior Member


Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Sun Oct 13, 2013, 10:58am
Subject: Re: NS Ellimatic temperature way too high.... :(
 

300 mbar equals 107C.   So a 5C drop from the boiler temp.

I expect that any temperature measuring device short of a bare RTD or bare thermocouple wires has a slow response and makes the temperature profile look a lot smoother than it really is.  And the electronics need to be fast.
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jannus
Senior Member


Joined: 19 Mar 2013
Posts: 71
Location: South Africa, Cape Town
Expertise: I like coffee

Espresso: NS ElliMatic & few...
Grinder: mazzer sj
Vac Pot: nope
Drip: yup
Roaster: nope
Posted Sun Oct 13, 2013, 11:26am
Subject: Re: NS Ellimatic temperature way too high.... :(
 

Hi Jonr,

The pic doesn't show much detail, but the tip of that thermocouple is actually bare.  The heatshrink you see just covers the bit before then, the last 1mm or so plus the tip is completely open.  I measured by running a few seconds, switching off a few seconds, running again, switching off, and it was pretty smooth around 102.2 deg C.

I'm under the impression that steam pressure for an HX should be 1.1bar to 1.3bar.  Is this right, or am I missing the plot (or pot!) somewhere?

Sorry in advance for the stupid question, but what do you mean with the 5 C drop from boiler temp?

I'm getting a sneaky feeling that I'm misunderstanding something basic, which is great, because that means that resolution is nearer than it felt earlier today! :)
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jonr
Senior Member


Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Sun Oct 13, 2013, 1:51pm
Subject: Re: NS Ellimatic temperature way too high.... :(
 

.3 above atmospheric is ~1.3 bars absolute. I think that is the cause of confusion.

For any of these pressures (1.1 bar, 1300 mbar, etc) you can look up the corresponding temp here:

http://www.csgnetwork.com/h2oboilcalc.html

A good test for a temp probe is to drop it in hot water and make sure it rises to the full value in 1 sec.
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jannus
Senior Member


Joined: 19 Mar 2013
Posts: 71
Location: South Africa, Cape Town
Expertise: I like coffee

Espresso: NS ElliMatic & few...
Grinder: mazzer sj
Vac Pot: nope
Drip: yup
Roaster: nope
Posted Mon Oct 14, 2013, 4:19am
Subject: Re: NS Ellimatic temperature way too high.... :(
 

jonr Said:

.3 above atmospheric is ~1.3 bars absolute. I think that is the cause of confusion.

Posted October 13, 2013 link

Indeed.....I think the confusion comes from several sources.  Firstly, my machine was set completely incorrectly (1.3bar gauge pressure, not absolute)  from the day I got it, hence the problem there.  No idea who did the setup, unfortunately.  Secondly, my idea of 1 bar is 1 bar gauge pressure, ie what the gauge on the pump says when you pump your tyres at the fuel station.  What I got from the machine reinforced that idea....which didn't help much in clarifying the situation!  :)

jonr Said:

A good test for a temp probe is to drop it in hot water and make sure it rises to the full value in 1 sec.

Posted October 13, 2013 link

I tested my thermocouple, response was about 1-1.5 seconds, so I guess it's ok?

jonr Said:

For any of these pressures (1.1 bar, 1300 mbar, etc) you can look up the corresponding temp here:
http://www.csgnetwork.com/h2oboilcalc.html

Posted October 13, 2013 link

I'll set the machine to cycle around .300 - .100 when referenced to atmospheric.  I live pretty much at sea level, ambient pressure is about 1022mbar at the moment, so I guess it should be fine.  From what I've read, 0.2bar deadband is pretty much in range for my pressurestat, so I'll play a bit around those readings and see how it runs.

Thanks very much for taking the time to explain another newbie mistake my part.  I live and learn, and will ultimately score a better cup of coffee from the deal.  :)
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NSElliIterator
Senior Member


Joined: 30 Jul 2010
Posts: 26
Location: Surrey, BC
Expertise: I like coffee

Espresso: NS Ellimatic
Grinder: NS MDXA
Drip: Bodum
Posted Mon Oct 14, 2013, 7:49am
Subject: Re: NS Ellimatic temperature way too high.... :(
 

What happens to the measured temp during a long flush?  I would suspect that as the HX gets emptied the temp should drop to your desired extraction range and below.  That's what is supposed to happen.  I know, the reservoir is small.
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NSElliIterator
Senior Member


Joined: 30 Jul 2010
Posts: 26
Location: Surrey, BC
Expertise: I like coffee

Espresso: NS Ellimatic
Grinder: NS MDXA
Drip: Bodum
Posted Mon Oct 14, 2013, 7:49am
Subject: Re: NS Ellimatic temperature way too high.... :(
 

What happens to the measured temp during a long flush?  I would suspect that as the HX gets emptied the temp should drop to your desired extraction range and below.  That's what is supposed to happen.  I know, the reservoir is small.
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jannus
Senior Member


Joined: 19 Mar 2013
Posts: 71
Location: South Africa, Cape Town
Expertise: I like coffee

Espresso: NS ElliMatic & few...
Grinder: mazzer sj
Vac Pot: nope
Drip: yup
Roaster: nope
Posted Mon Oct 14, 2013, 11:36am
Subject: Re: NS Ellimatic temperature way too high.... :(
 

NSElliIterator Said:

What happens to the measured temp during a long flush?  I would suspect that as the HX gets emptied the temp should drop to your desired extraction range and below.  That's what is supposed to happen.  I know, the reservoir is small.

Posted October 14, 2013 link

That was part of how I tested it..  I ran the pump for about 30 seconds (yes it basically emptied the reservoir), and it stayed pretty much on 102.  I was pretty impressed, just too bad the temp was too high!  :)  I suspect that at the higher pressure it might be more stable than at lower pressure?

Do you know what absolute pressure your pressurestat is actually set at?
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GVDub
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Joined: 25 Jan 2008
Posts: 864
Location: Los Angeles, CA
Expertise: I live coffee

Espresso: Londinium I, Arrarex...
Grinder: Gaggia MD85, Dienes Mokka,...
Drip: Behmor Brazen, Abid Clever
Roaster: Behmor 1600+
Posted Mon Oct 14, 2013, 11:45am
Subject: Re: NS Ellimatic temperature way too high.... :(
 

Just a stray thought, but brass holds heat pretty well, and once the flow of overheated water has the portafilter up to temp, the pf will be retaining heat. It does look as if, with a basket in, you might be reading metal temperature as much, if not more, than water temperature.
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jonr
Senior Member


Joined: 25 Jun 2013
Posts: 298
Location: Americas
Expertise: I like coffee
Posted Mon Oct 14, 2013, 12:19pm
Subject: Re: NS Ellimatic temperature way too high.... :(
 

> I'll set the machine to cycle around .300 - .100 when referenced to atmospheric.

That's more that a 4C error.  I wouldn't tolerate such variation if it makes it to the brew basket.  But maybe HX users are used to it :-).
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