Steam boiler pressure on PID'd HX espresso machines?

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dright
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#1: Post by dright »

Hi,

I recently bought an Izzo Alex II with PID when Chris' Coffee had it on sale a couple of weeks ago. I like the machine over all, but I do not understand the interaction between the boiler temperature and the pressure, now that the heating element is controlled by the PID and not the pstat.

The machine operates normally: it auto-refills the water when necessary; it buzzes when the reservoir is empty; brew head is hot; etc. The only thing that's not so normal is the boiler pressure. The PID is set to keep the boiler at 255 degrees F. It should keep the boiler pressure at 1.1 - 1.2 bars. But on my machine, the pressure approaches 2 bars while the PID only shows a little bit over 240 degrees and keeps the heat going up. If I don't release some steam from the steam wand, eventually the pressure release valve will activate when the temperature is around 250. (My wife described it as coffee machine farting.) After the "farting", the pressure is still at 2.2 bar or so.

But if I release some, just 2-3 seconds of steam out of the steam wand, the pressure will go back to normal. The temperature will be kept at 255 degrees. Sometimes I kept the machine on for 5, 6 hours and the pressure would be kept at around 1.2. So if I remember to release some steam several minutes after I turn on the machine, everything will be fine. Still unexpected machine farting early in the morning can be surprising.

I understand that there are few HX machines with PID. Is it normal for the boiler pressure goes so high when the machine is heating up? Or is there some problem with my machine?

Thanks!

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HB
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#2: Post by HB »

dright wrote:But if I release some, just 2-3 seconds of steam out of the steam wand, the pressure will go back to normal. The temperature will be kept at 255 degrees. Sometimes I kept the machine on for 5, 6 hours and the pressure would be kept at around 1.2. So if I remember to release some steam several minutes after I turn on the machine, everything will be fine.
Sounds like the vacuum breaker is sticking, so the gauge reading is incorrect due to false pressure (explanation excerpted below). Opening the steam wand allows the trapped air to escape and the boiler to be filled with saturated steam (i.e., only water vapor, no air), so the gauge reading returns to the expected range. The PID is reading temperature, so it is unaffected by the false pressure.
Billc wrote:One simple way I used to explain this to customers is:
Everything expands when heated. Gases expand faster than solids. In the case of a steam boiler with air and water; when heated the gas (the air) expands much faster than the solid (the water). The pressure in the boiler increases quickly due to the expanding air... Once the air is released and is replaced by water vapor then everything returns to normal.
Dan Kehn

dright (original poster)
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#3: Post by dright (original poster) »

Thanks Dan. I don't know much about the internals of the machine, but I think the circled part is the vacuum breaker. It looks different than the vacuum breakers sold on Chris' Coffee website though. I'll send an email to them and ask about the diagnosis of the problem. Thank you!


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erics
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#4: Post by erics »

The part that you circled is the boiler safety valve but, in any event, this is a simple problem to solve. Normally there is loads of clearance for the vacuum breaker valve to operate properly but . . . ya never can tell. Your vacuum breaker valve is one of the parts connected with the silicone tubing on the right of your pic.
. . . but I do not understand the interaction between the boiler temperature and the pressure,
See this: /downloads/ ... essure.jpg
Skål,

Eric S.
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E-mail: erics at rcn dot com

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erics
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#5: Post by erics »

Another alternative would be for you to lug your machine to the Friday morning's "get together" at Counter Culture where, I assure you, there is an abundance of knowledgeable nuts to explain every single nook and cranny in your machine.
Skål,

Eric S.
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E-mail: erics at rcn dot com

dright (original poster)
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#6: Post by dright (original poster) »

Another alternative would be for you to lug your machine to the Friday morning's "get together" at Counter Culture
Thank you for pointing out where the vacuum breaker is, Eric. Now you know how ignorant I am about the machine parts. This proposal is very attractive. I have seen the UNC TV program showing the Friday morning events at CCC. But Friday morning is difficult for me, being a regular 9-5 worker and all that. (My wife might kill me if I take 0.5 day off and leave her along with the fussy 1-year-old at home.) I have written an email to Chris' Coffee Service. Let's see what they say about the problem.

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HB
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#7: Post by HB »

I hear you about the 9-5 duty, but don't confuse the 10AM cupping on Friday with the espresso lab from 7:30-9AM. I have helped organize the latter for the last 9 years: Friday mornings at Counter Culture Coffee in Durham, NC.
Dan Kehn

dright (original poster)
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#8: Post by dright (original poster) »

HB wrote:but don't confuse the 10AM cupping on Friday with the espresso lab from 7:30-9AM. I have helped organize the latter for the last 9 years: Friday mornings at Counter Culture Coffee in Durham, NC.
Thanks for the information, and the time works for me, too. I need to check it out sometimes. Unfortunately I cannot be there tomorrow.

And thank you, Eric, for pointing out where the vacuum breaker valve is. (I showed this thread to my wife, and she said you, me included, coffee geeks do help fellow coffee geeks out.) I opened the valve this evening. The valve is connected to a silicon tube which opens at the drip tray, and the rod is hidden inside. So I could not tell when the valve was closed when the machine was on. The rod was in the lower (open) position when I opened the valve though. So I connected everything back, and turned on the machine again. The valve squirted out some water and then stopped at a fairly low temperature, like 140 F. That should indicate the valve was stuck.

Then I took the valve apart, and scratched my head... The rod seemed very loose. How could it get stuck? Especially on a new machine. Not knowing what to do, I immersed the rod in some vinegar -- it would not hurt to clean it, even though it looked clean enough. And I gave the rod some scrub with an old tooth brush. So it is made of copper -- I thought it was made of aluminium because of the color. This seemed to fix the problem. I gave it some test. The squirted water did not make the valve stuck, and the valve was closed at 210 degrees. Looked good!

I noticed that while the machine was heating up, some 1-2 oz of water went out from there and flowed to the drip tray. From Google image, I saw that in most espresso machines, the vacuum breaker valves are not drained to the drip tray. Where do the water go? Or the valve is not supposed to let out so much water?

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erics
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#9: Post by erics »

I noticed that while the machine was heating up, some 1-2 oz of water went out from there and flowed to the drip tray. From Google image, I saw that in most espresso machines, the vacuum breaker valves are not drained to the drip tray. Where do the water go? Or the valve is not supposed to let out so much water?
1-2 ounces of water would be a lot . . . easy enough to measure in a cold, open jar.

On most espresso machines (older than ~ 2 years), the vacuum breaker spews the moisture laden mix of steam/air/water to the machine's internals. On some others, particularly machines which have been retrofitted, the output is led back to the water reservoir terminating above water level.
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Eric S.
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E-mail: erics at rcn dot com

dright (original poster)
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#10: Post by dright (original poster) »

erics wrote:1-2 ounces of water would be a lot . . . easy enough to measure in a cold, open jar.
This morning I tried the machine from cold. (Last night I tested when the boiler was at ~180 degrees.) On this machine (Izzo Alex II HX with PID) the vacuum breaker is mounted on the side of the boiler, a little bit lower than the steam wand outlet (see picture). As the machine was heating up, actually quite a lot of water came out from the vacuum breaker. Then the pump was activated to add more water into the boiler. After the pump stops, the vacuum breaker got stuck as well... The breaker could be open again if I let out some steam from the steam wand. But then the whole cycle would start all over -- water came out from the vacuum breaker; pump sucked in water; vacuum breaker got closed. If the vacuum breaker is closed before the boiler pressure reaches 1 bar, the pressure will be too high when the boiler reaches the set temperature.


In the picture, the boiler outlet on the left connects to the steam wand. It may be a little bit difficult to see, but the vacuum breaker is connected to a "hole" (what's the proper terminology of it?) lower than the steam wand.

Maybe the water level probe is not set properly that only water, rather than air, comes out from the vacuum breaker? Or maybe the boiler is tilted. If the vacuum breaker and the steam wand outlet are at the same water level, supposedly mostly air and maybe a little bit of water would come out of the vacuum breaker...

Have not heard back from Chris' Coffee. I'll shoot them another email. Making phone calls during work hour is inconvenient for me...

OK, gotta run.

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