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Adjustments needed after insulating boiler?
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Discussions > Espresso > Espresso Mods > Adjustments...  
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davethebrewguy
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davethebrewguy
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Posted Wed Apr 7, 2010, 9:28pm
Subject: Adjustments needed after insulating boiler?
 

I usually run my Bric 24/7 but I was away last week so I shut it off. While I was away I ordered a piece of melamine foam to insulate the boiler and since the machine was already cool when I got home I figured I'd just jump into the project. It took longer than expected but I descaled it and did a few other minor tweeks while I was in there. One of the tweeks was lowering the pressurestat a hair, I'd been running a little hotter than I'd like and I had hoped to knock 3-4 degrees off of it.
Previously, the PS was shutting off at 1.25 BAR and my grouphead thermometer would read 206-206.5 after extended idling. After turning it down the smallest increment I could manage (and insulating the boiler) the PS would now shut off at 1.15 BAR but the grouphead temp was only around 196. I turned it back up that tiny hint of a turn and the boiler pressure came back up to 1.2-1.25 but the temp still only came up to 199, a second adjustment brought the temperature up to 202.5 but the pressure is now 1.3 bar.
I did descale the machine during this process but there was very little scale (very soft bottled water, very low use, descaled annually whether it needs it or not) so I don't think that this is a factor. I am currently running the machine with the top cover (cup warmer) off so there may be more air flow over the tubing in and out of the thermosyphon loop. Am I missing something here? Evidently, I have to keep the boiler hotter and the grouphead is still cooler than it used to be. I wouldn't expect insulating the boiler to have this kind of effect on the group temperature. Is this normal?
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JamesWarren
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Posted Thu Apr 8, 2010, 11:45pm
Subject: Re: Adjustments needed after insulating boiler?
 

Inspect the heat-exchanger loop to ensure scale has not inhibited the flow, in addition replace the diaphragm on the pressure-sat as they get rigid over time creating lager hysteresis.
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fnacer
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Posted Fri Apr 9, 2010, 10:25am
Subject: Re: Adjustments needed after insulating boiler?
 

Googling didn't help. Or rather, I am feeling too lazy to read what I am sure in an enlightening and very relevant discussion in  "Electrical Property of a Layered Non-Centrosymmetric Self-Assembly" or "Study on advanced multilayered magnetostrictive thin film coating techniques for MEMS applications".

So I thought I'd just ask. What is lager hysteresis?

F.
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davethebrewguy
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davethebrewguy
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Espresso: Fiorenzato Bricoletta,...
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Roaster: Behmor 1600
Posted Fri Apr 9, 2010, 11:30am
Subject: Re: Adjustments needed after insulating boiler?
 

JamesWarren Said:

Inspect the heat-exchanger loop to ensure scale has not inhibited the flow, in addition replace the diaphragm on the pressure-sat as they get rigid over time creating lager hysteresis.

Posted April 8, 2010 link

I look into the heat exchanger loop. Checking the PS seems counter intuitive, how could it cause the group to run cooler while the boiler that it controls is running hotter? Could the diaphragm harden noticeably after only 5 days?

fnacer Said:

Googling didn't help. Or rather, I am feeling too lazy to read what I am sure in an enlightening and very relevant discussion in  "Electrical Property of a Layered Non-Centrosymmetric Self-Assembly" or "Study on advanced multilayered magnetostrictive thin film coating techniques for MEMS applications".

So I thought I'd just ask. What is lager hysteresis?

F.

Posted April 9, 2010 link

Lager hysteresis is what happens when I've had too many beers and think everything is funny. I think he meant larger hysteresis, an increase in the lag between change in the input vs. change in the output resulting in greater swings during each cycle.
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JGG
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Posted Fri Apr 9, 2010, 12:45pm
Subject: Re: Adjustments needed after insulating boiler?
 

This Home-Barista.com thread might give you some new ideas.

Seems unlikely to me that insulating the boiler would cause a thermosyphon stall.  There are too many insulated steam boilers out there on HX machines for the insulation to be the bad guy.

Jim
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davethebrewguy
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davethebrewguy
Joined: 31 Jul 2008
Posts: 1,228
Location: The Brewery
Expertise: I live coffee

Espresso: Fiorenzato Bricoletta,...
Grinder: Compak K-6, Baratza Maestro...
Drip: Saeco Renaissance
Roaster: Behmor 1600
Posted Fri Apr 9, 2010, 4:01pm
Subject: Re: Adjustments needed after insulating boiler?
 

JGG Said:

This Home-Barista.com thread might give you some new ideas.

Seems unlikely to me that insulating the boiler would cause a thermosyphon stall.  There are too many insulated steam boilers out there on HX machines for the insulation to be the bad guy.

Jim

Posted April 9, 2010 link

Thanks for the link... I think...
At just a couple degrees lower than expected, I wouldn't call it "thermosyphon stall," but a restriction is a possibility. Between JamesWarren's suggestion of a restriction due to a chunk of scale and some of the info in the link, I decided to open up the group.
I pulled the gicleur screen and there was a small amount of chrome stuck to it. I cleaned it out, along with the bits I found around the gicleur once I pulled the screen out and then decided to pull the whole mushroom. Once the mushroom was out I found a surprising quantity of chrome buts inside the group (watchmaking tools come in handy, especially Rodico which picked up the chrome bits nicely). The good news is that the chrome is out, the bad news is that the group is now leaking after pulling blank shots. I also backflushed the heck out of it with Joe-Glo once I put it back together but that didn't help.  I guess the seals are getting hard so I'll have to order a rebuild kit and learn how to dismantle the rest of an E61 group. Any tips? I've got it idling now to see where the temp settles.

BTW, how is "gicleur" pronounced?

Edit: Well this isn't good...after an hour my group is up to 235F! I guess it's dripping enough to empty the thermosyphon loop and I'm just reading steam. Never had that happen before!?!
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ThomasK
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Posted Tue Jul 23, 2013, 6:39am
Subject: Re: Adjustments needed after insulating boiler?
 

davethebrewguy Said:

I look into the heat exchanger loop. Checking the PS seems counter intuitive, how could it cause the group to run cooler while the boiler that it controls is running hotter? Could the diaphragm harden noticeably after only 5 days?

Lager hysteresis is what happens when I've had too many beers and think everything is funny. I think he meant larger hysteresis, an increase in the lag between change in the input vs. change in the output resulting in greater swings during each cycle.

Posted April 9, 2010 link

An old thread but I thought I should correct/clarify this.

"Hysteresis" is the error (delta) when you try to reach a setpoint from one side of a range of movement versus from the other.  "Where you came from influences where you will arrive."  HVAC systems that shed temperature will reach a set degree in a different fashion than when heating toward the same temperature.  Industrial robots trying to land at a spot coming from one side versus reaching the same spot while approaching from the opposite side of its range.

Lag in response between input versus output (that is not inertia related) is called "deadband" - for example, the house HVAC is set to 74 degrees - and behind the scenes (in the control box) you have at least a 2 degree deadband - meaning that cooling kicks in when measured temp hits 75 and turns off when it reaches 73.  In this case the deadband should be set to create sufficient runtime - to allow proper dehumidification.

Control problems arise if you try to tweak your system so that the deadband becomes narrower than the hysteresis - then you can get oscillations depending on the type of system.

Inertia only compounds issues.

Modern PID control aims to compensate for all of the above - tweaking the settings to arrive at an optimal state - where the weakest link in the chain will be the limiting factor.
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