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pid vs antivac valve
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mauricem
Senior Member


Joined: 16 Sep 2003
Posts: 57
Location: Sunshine Coast QLD
Expertise: I love coffee

Espresso: La Cimbali Junior
Grinder: La Cimbali Cadet
Roaster: Heat gun
Posted Tue Nov 12, 2013, 6:21pm
Subject: pid vs antivac valve
 

My daughter has just bought a new Bezzera BZ13 De PID and its not getting up to temp. No steam, no movement on pressure gauge and water from the brew head comes out at about 45/50 C even if left on for hours. PID temp has been upped from 90 to 95 and still no difference. Note this model has a heated group head not controlled by the pid AFAIK which is probably whats luke warming the water.

Whilst we're waiting to see how the supplier will respond (it was from an importer) I thought Id see if it could be something simple as opposed to dead electronics which I concede is more probable.

Now i have some experience with a sticky vacuum breaker valve on my La Cimbali which relies on the pressure stat to cycle the boiler and when its sticks in the closed position going from cold to hot the machine will not get up to temp and barely move the pressure gauge. However Im assuming the pid cycles the boiler based on temo not pressure so even of the vac valve was stuck it would still keep heating till it hit the set temp ie 90c at group head would be 100+ at boiler.

Is this how the PID works? Any other suggestions?
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nobbi4711
Senior Member
nobbi4711
Joined: 20 Apr 2005
Posts: 334
Location: Germany
Expertise: Professional

Espresso: Dallacorte Mini EX4
Grinder: Casadio Instantaneous
Vac Pot: none
Drip: French Press
Roaster: Mini-500/800N drum roaster;...
Posted Fri Nov 15, 2013, 4:16am
Subject: Re: pid vs antivac valve
 

mauricem Said:

My daughter has just bought a new Bezzera BZ13 De PID and its not getting up to temp. No steam, no movement on pressure gauge and water from the brew head comes out at about 45/50 C even if left on for hours. PID temp has been upped from 90 to 95 and still no difference. Note this model has a heated group head not controlled by the pid AFAIK which is probably whats luke warming the water.

Whilst we're waiting to see how the supplier will respond (it was from an importer) I thought Id see if it could be something simple as opposed to dead electronics which I concede is more probable.

Now i have some experience with a sticky vacuum breaker valve on my La Cimbali which relies on the pressure stat to cycle the boiler and when its sticks in the closed position going from cold to hot the machine will not get up to temp and barely move the pressure gauge. However Im assuming the pid cycles the boiler based on temo not pressure so even of the vac valve was stuck it would still keep heating till it hit the set temp ie 90c at group head would be 100+ at boiler.

Is this how the PID works? Any other suggestions?

Posted November 12, 2013 link

Even with a hanging vac breaker, pressure should build up first (and break down again when opening the steam valve), so the gauge should show movement. The problem seems to be another issue. Does the pump work when pressing the knob for coffee? Is the tank set in correctly?

Greetings \\//

Marcus
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calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 7,666
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Fri Nov 15, 2013, 4:46am
Subject: Re: pid vs antivac valve
 

If the temp is controlled by a PID, the vacuum breaker has nothing to do with anything.

The machine is brand new? Return it, it has more problems than a sticky vacuum breaker.

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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nobbi4711
Senior Member
nobbi4711
Joined: 20 Apr 2005
Posts: 334
Location: Germany
Expertise: Professional

Espresso: Dallacorte Mini EX4
Grinder: Casadio Instantaneous
Vac Pot: none
Drip: French Press
Roaster: Mini-500/800N drum roaster;...
Posted Fri Nov 15, 2013, 11:42am
Subject: Re: pid vs antivac valve
 

calblacksmith Said:

If the temp is controlled by a PID, the vacuum breaker has nothing to do with anything.

Posted November 15, 2013 link

If the PID controls the Steam Boiler (which seems to be so at the BZ13), the machine will just act as any other HX machine.

Greetings \\//

Marcus
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uscfroadie
Senior Member
uscfroadie
Joined: 2 Aug 2008
Posts: 394
Location: San Antonio
Expertise: I live coffee

Espresso: GS/3 Strada MP, BDB; owned...
Grinder: Forte, Zass and PeDe hand...
Vac Pot: Nope
Drip: Nope
Roaster: owned Behmor
Posted Fri Nov 15, 2013, 1:28pm
Subject: Re: pid vs antivac valve
 

nobbi4711 Said:

If the PID controls the Steam Boiler (which seems to be so at the BZ13), the machine will just act as any other HX machine.

Greetings \\//

Marcus

Posted November 15, 2013 link

Which is exactly why Wayne implied the vacuum breaker has nothing to do with the water being lukewarm at the grouphead.
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calblacksmith
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calblacksmith
Joined: 25 Nov 2007
Posts: 7,666
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Fri Nov 15, 2013, 2:44pm
Subject: Re: pid vs antivac valve
 

uscfroadie Said:

Which is exactly why Wayne implied the vacuum breaker has nothing to do with the water being lukewarm at the grouphead.

Posted November 15, 2013 link

DING DING  
DING DING  
DING DING
DING DING
Exactly right, two points for you!

The PID is what is regulating the temp in the boiler. It uses a sensor probe to detect what the temp is. On a regular HX machine, the Pressure stat controls the pressure in the boiler which indirectly controls the temp. If the vacuum breaker is stuck on a regular HX machine, the pressure stat will see a false pressure and stop adding heat to the boiler. The PID does not use pressure but actual temp so it would add heat anytime the actual temp is below what the PID is set for, the pressure in the boiler is a moot point and the PID could not care less!

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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boar_d_laze
Senior Member


Joined: 21 Nov 2006
Posts: 1,066
Location: Monrovia, CA
Expertise: I live coffee

Espresso: La Cimbali M21 DT/1 Junior...
Grinder: Ceado E92; "Bunnzilla"
Vac Pot: Royal Coffee Maker
Drip: Chemex + Kone; Espro Press
Roaster: USRC Sample Roaster
Posted Sat Nov 16, 2013, 10:42am
Subject: Re: pid vs antivac valve
 

calblacksmith Said:

DING DING ... DING DING. Exactly right, two points for you!

The PID is what is regulating the temp in the boiler...  The PID does not use pressure but actual temp so it would add heat anytime the actual temp is below what the PID is set for, the pressure in the boiler is a moot point and the PID could not care less!

Posted November 15, 2013 link

Sounds right if you say it fast, but -- sorry -- no.  

The breaker valve is mounted directly on the boiler.  It is meant to open when the machine cools down in order to vent the boiler to the surrounding environment, preventing the formation of negative pressure.  Thus, if the valve is stuck open, the boiler cannot achieve higher than environmental atmospheric pressure.  But in order to generate the necessary temperatures, an HX boiler must operate at a pressure higher than atmospheric -- otherwise the boiler water escapes when it turns to steam at the environmental boiling temp.  

In short, if the vac breaker is stuck open on an HX, p-stat or PID, she's a no gonna work.  You'll get hot (boiling temp) water, and no pressure.

Contrapositively, if it's stuck closed the boiler will over-pressurize when it reaches temp and will require venting to get pressure and temperature right.  Remember that pressure and temperature are inter-dependent.  

PV = nRT.  If air is stuck in the boiler and can't vent as the water is heated, than they will combine and give a "false" pressure, until vented.  Temperature can't increase beyond what pressure allows, and vice versa.

With a valve jammed closed on a p-stat machine you'll get a high but "false" pressure reading, and warm water.  On a PID machine, you'd begin to see WAY too much pressure as the water heated up.  How high you could push the water temp depends on a lot of things, but I doubt you'd get it hot enough to steam.

Responding to the OP and more generally:
If it's the breaker valve, you should get no steam but warm (at least) water to the head.  Since you're not getting any heating without the group heater, it's probably not the valve.  

Sometimes things jar loose during shipping.  The first thing I'd do is open the machine up and make sure that no wires are dangling.  

As you already know, the real tension isn't between vac breaker and PID, but between p-stat and PID. So...
  • Q:  Why a PID on an HX?
  • A: A PID should be better overall than a p-stat for its greater longevity and resistance to wear.  The user shouldn't see much difference in operation.

Finally, if it's any consolation I just replaced the vac breaker on my La Cimbali M21 for the second time in three years.  The first died jammed closed, and the second jammed open.  Presumably both died because hard water screwed up their internal o-rings following filter failures in my water line. I put in a Pasquini G3 breaker which is brass on brass (no o-ring), and we'll see how that works.

BDL
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uscfroadie
Senior Member
uscfroadie
Joined: 2 Aug 2008
Posts: 394
Location: San Antonio
Expertise: I live coffee

Espresso: GS/3 Strada MP, BDB; owned...
Grinder: Forte, Zass and PeDe hand...
Vac Pot: Nope
Drip: Nope
Roaster: owned Behmor
Posted Sat Nov 16, 2013, 11:35am
Subject: Re: pid vs antivac valve
 

boar_d_laze Said:

Finally, if it's any consolation I just replaced the vac breaker on my La Cimbali M21 for the second time in three years.  The first died jammed closed, and the second jammed open.  Presumably both died because hard water screwed up their internal o-rings following filter failures in my water line. I put in a Pasquini G3 breaker which is brass on brass (no o-ring), and we'll see how that works.

BDL

Posted November 16, 2013 link

Rich,

Why replace the whole thing?  I just replaced the O-ring in mine for about $.20.  The rubber just became hard and would not seal completely, letting a little steam out, which was visible on the inner left-side panel and the top cover.

On a side note, why don't manufacturers use silicone rings there instead?  Seems like they'd last much longer, and their soft properties would mean a great seal, unlike Teflon which requires more pressure.

Sorry for thread drift.
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calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 7,666
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Sat Nov 16, 2013, 4:56pm
Subject: Re: pid vs antivac valve
 

Sorry BDL,the temp never goes over 45 to 50 c, only slightly hotter than room temp! If the water was heating up, it would be 100c, if the vac breaker was stuck open, it would be spewing steam and if it were stuck closed, there would be no problem and even if there was an overpressure reading on the gauge, it matters not as the pressure is not related to the actual temp as the PID uses a thermocouple to read the boiler temp, the actual temp of the water is independent of the pressure or the reading on the gauge.

As to not being hot enough to boil, whenever the temp of water (at sea level) is over 212f 100c and the pressure is released (granting that the water was heated in a pressure vessel, the water will flash to steam. As a thermocouple and PID is in charge of maintain temp, not a pressure stat the water will be above boiling temp in the boiler.


Iam quite aware of how a HX works and his problem in no way points to a vac valve when a PID is in charge of temp.

And yes, an o ring for a few pennies will repair the faulty leaking o ring in a vac breaker. That is how I repaired the leaking one in the M32 and the two group commercial machine.

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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boar_d_laze
Senior Member


Joined: 21 Nov 2006
Posts: 1,066
Location: Monrovia, CA
Expertise: I live coffee

Espresso: La Cimbali M21 DT/1 Junior...
Grinder: Ceado E92; "Bunnzilla"
Vac Pot: Royal Coffee Maker
Drip: Chemex + Kone; Espro Press
Roaster: USRC Sample Roaster
Posted Sat Nov 16, 2013, 6:03pm
Subject: Re: pid vs antivac valve
 

cal,

If you're trying to tell me that you never thought the problem was the vac breaker, I understood you.  I responded to:

The PID does not use pressure but actual temp so it would add heat anytime the actual temp is below what the PID is set for, the pressure in the boiler is a moot point and the PID could not care less!

 

Perhaps I was mistaken, but I understood that to mean you believed a PID equipped machine would reach brew temperature, even with a sticking valve.  My point was that even PID machines will not achieve functional steam pressure or brew temp with a stuck valve, and the nature of the dysfunction will let you know whether and which way the valve is stuck.

Here, I think the fact that the machine produces warm water might be a little confusing, because p-stat machines do something similar when the vac breaker is stuck closed.  The water definitely does not reach brew temperature, and 50C -- a bit hotter than a hot tub -- is -- in my experience -- pretty close.  But I'd expect a PID machine to exhibit some rather obvious symptoms if it tried to heat a boiler without some sort of pressure relief.

There's no point in continually rehashing this as we both agree that it's unlikely the problem was caused by a sticking vac valve.  I know you've rebuilt a few machines, and respect that.  

I replaced instead of repairing the sticking vac valves in my M21 because Chris Coffee sent me the first replacement under warranty, and because I decided to try something which would work without an o-ring after the second failure.  Besides, it's fun to go to Pasquini to BS with the old man, and drink his grappa; well worth the $25 for the ridiculously overpriced part.  But that's Pasquini.  

Another factor I considered in driving out there from Monrovia, is how a small purchase from Pasquini factors into the larger economics of the journey.  It's very close to a couple of restaurants my wife really likes. As it happens, I spent $40 at Guelaguetza on Mescal and gusanos before lunch -- almost twice the cost of the breaker.  Including lunch and gas,  it was well worth the money for a happy wife and an easy fix.  

So it goes,
BDL
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