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Bezzera BZ07 w PID - does it limit the steam?
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jeffu
Senior Member


Joined: 22 Jan 2003
Posts: 7
Location: Houston
Expertise: Beginner

Posted Mon Mar 11, 2013, 5:55am
Subject: Bezzera BZ07 w PID - does it limit the steam?
 

I'm just about to pull the trigger on a BZ07 - moving up from a Gaggia Classic.  I mostly make lattes - and really love the idea of having steam without the wait!

Anyhow - I really don't understand the whole PID thing and the only machine currently available has a PID - which I may want to play with, I hear some say it's worthless on a HX machine and others say it's ok.  Not to open that whole debate, I'm just wondering, if I get the BZ07 with the PID, will the steam be more limited than if I get one without the PID?  If the temp is set via the PID screen, does that keep the temp lower and thus generate less steam?

Can I turn off or just not use the PID?

Sorry for the newbie questions - but we all have to start somewhere.

Thanks!
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calblacksmith
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calblacksmith
Joined: 25 Nov 2007
Posts: 7,734
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 Mon Mar 11, 2013, 6:13am
Subject: Re: Bezzera BZ07 w PID - does it limit the steam?
 

I answered the base question in another thread. Your question comes from not understanding how a HX machine works, perhaps this will help


Short answer, no, one maker is not much different than another for stability.

There are several great articles about how HX machines work etc. I will try to just make it pretty simple here.

HX machines are the back bone of industry. They are dependable, work well and abundant.

They work by thermal mass, they have a lot of metal and large boilers. The Pstat (pressure stat) keeps the temp in the boiler to within 2 to 5 deg F, on the low side for a new machine and on the higher side for a well used machine due to mechanical wear but at any rate well within easy operating range.

The HX (Heat eXchange) system works by keeping the boiler at steam temp of about 235 to 240F or even higher depending on how you want  your machine to work. The temp is indicated in Bar thus you have a gauge that reads from about .8 bar to about 2.5 bar or so, with an operating range from 1.1 bar to about 1.4 bar. This is nothing more than just a thermometer with a scale that reads in bar, you can look up the temps if you like they are widely available online.

The temp of the boiler stays constant by the use of a Pstat. This device is sensitive to pressure (bar is a measure of pressure) and the Pstat keeps the boiler at the set temp within it's range of operation accuracy or the 2 to 5 deg f. (if set for 240 f this would give you a range of say 237.5 to 242.5 or Plus or minus 2.5 deg f for a pstat that swings 5 deg.

When someone uses a PID on a HX machine, it replaces the Pstat which is operating well within need accuracy so a PID really does not add anything to the system but if you like digital readout of numbers, it does not hurt either but it does NOTHING to improve the machine.

The HX system, think of it as simply a tube that passes through the boiler but does NOT connect to the water in the boiler. As water passes through the HX tube, it is heated by the water in the boiler. The tube is designed to a size and distance so that in constant operation, say pulling a shot every minute or minute and a half, the water will be heated to the proper brew temp of 195 to 205. If you continue to work at the same speed, the water temp will be the same shot to shot and all is well with the world.

The problem comes when you stop pulling shots. Now the water in the HX system is sitting inside the boiler longer than it was intended to and it becomes the same temp as the water in the boiler. This is not a big deal as you simply FLUSH this over heated water out of the system and return the system to normal brew temp. If you do not flush a lot of water, you can make the shot temp rise a little or if you pull a couple shots quicker than the system is designed for, you can get a cooler shot, but unless you are all thumbs, you will be in the proper brew zone of 195 to 205 and this is the way a HX machine will allow you to make one shot warmer or a little cooler, depending on what you want for the shot. If you work at the machines design rate, the temp will be the same within a deg or so time after time.

Now, adding to the way the system works, you will have a lot (LOT) of metal in the brew group, in the case of the E61, this is 8 pounds of brass that is also being temp regulated through a balance of exposure to air and active heating of water from the boiler flowing through water passages in the brew group. This is eight POUNDS of mass that is at temp. Your shot of water is (for a double shot) two OUNCES of weight or mass, the affect of the heat stored in the group head acts on the temp of the water that is flowing through it, either warming or cooling the water passing through it, depending on if the water is hotter or colder than the brew group temp.

You can see that there are a lot of design factors taken into account in a HX machine to regulate the temp of your brew water. Yes, you can affect the temp of the water you brew with but it will not be wild swings of temp, just a little warmer or cooler depending on your actions. As long as you flush long enough for the water to stop flashing to steam (an easy thing to tell when you listen to the flow of the water and watch the flow of the water) you will be darn close to brew temp. If you flush just a couple of oz past this point, you will be in the zone, if you flush a little more, you will be on the cool side, a little less and you are on the warm side. It really is as simple as that. No drastic failure of the brew either way, just the ability, through your actions, to alter the  temp of the shot a little warmer or cooler.

DB machines also have a great deal of thermal mass in the brew system. The do not have a single boiler (hence the name Double boiler) They use a PID to (the new ones anyway) maintain the temp of the brew water to a set temp. This water then flows through the group head where it's temp has an affect on the brew water. In MOST instances, the brew group will be COLDER than it should be due to sitting, exposed to the air, bleeding heat to the air. The first shot through the group will then WARM the brew group to it's operating temp but the result is that the first shot or so of water through the system will be too cool to properly brew your espresso, thus you need to flush the system to WARM the brew group so the machine pulls shots at the desired temp. Either way, you are flushing the system.

There are double boiler machines with actively heated and thermostat regulated temp (brew group) but they are not part of this discussion nor are they in the price range of what we are discussing. So for this discussion, they are a moot point.

One is not "better" than the other, it really comes down to how your brain works, what floats your boat and how you like to work. While it is true, you can just change the temp of a shot on a PID controlled DB (or sbdu for that matter) machine with a touch of a button as some are fond of saying, you need to wait for the whole machine to change it's operating temp and normalize at the NEW operating temp. This can take about 15 minutes or so. Not a big deal but not as rapid as watching the number change on the digital readout either.

I hope this helps to clear things up a bit.

 
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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calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 7,734
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 Mon Mar 11, 2013, 6:18am
Subject: Re: Bezzera BZ07 w PID - does it limit the steam?
 

The short answer is NO, a pid will not affect steaming one way or the other but no you can not turn it off if the machine is equipped with one.

If you use the PID to set the temp to brew temp on a HX machine, you will lower the temp of THE WHOLE BOILER to brew temp and you will not have ANY STEAM at all as brew temp for espresso is lower than the boiling point of water.

A PID is of value on a SBDU machine such as yours or on a DB machine with an indepenendent brew boiler but on a HX machine is just a pretty display of number that have no direct affect on the brewing of espresso. Then again, if you like pretty lights on a digital display, it will not hurt anything either but there will not be any gain in quality because it is equipped with a pid.

You WILL need a good grinder with a move to this class of machine so I hope you are planning on upgrading the grinder at the same time.

 
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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jeffu
Senior Member


Joined: 22 Jan 2003
Posts: 7
Location: Houston
Expertise: Beginner

Posted Mon Mar 11, 2013, 7:07am
Subject: Re: Bezzera BZ07 w PID - does it limit the steam?
 

Thanks guys for the info!  Sounds like I can get the BZ07 with PID and it won't impact my steam ability :)

Also - thanks for the tip on the grinder - I found that out with the Gaggia, I was getting horrible results until I broke down and bought a Rancillio Rocky - made all the difference in the world.  I think it will work fine with the BZ07.
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dyqik
Senior Member


Joined: 7 Oct 2011
Posts: 383
Location: Cambridge, MA
Expertise: I love coffee

Espresso: Bezzera BZ07 PM
Grinder: Baratza Virtuoso Preciso...
Vac Pot: Cona D
Drip: Bona-Vita, CCD, Aeropress.
Roaster: Gene Cafe, Modded Poppers
Posted Mon Mar 11, 2013, 7:47am
Subject: Re: Bezzera BZ07 w PID - does it limit the steam?
 

All the PID will do is control the temperature of the (steam) boiler directly, rather than via the steam pressure.  If you set it to the temperature that produces a particular pressure on the gauge (if fitted), then it will steam exactly the same as a pressurestat set to that pressure.  The size and thermal mass of the boiler plus water in equilibrium with steam is high enough that a PID controller will not produce a significantly more stable brew temperature, which is more controlled by the dead band in the group head cartridge heater and by the flushing of the HX.

Unless the machine you are looking at is cheaper than the equivalent BZ07 without PID, there's no point in going for it.  You'd be much better served with a simpler machine with less to go wrong.  What would be of value on a BZ07 is some kind of brew temperature readout built into the group head, or tighter control of the temperature of the electrically heated group head.  Since it's not an E61 group, aftermarket options for either are limited to DIY.
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