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PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
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Discussions > Espresso > Machines > PID versus HX...  
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calblacksmith
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calblacksmith
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Posted Thu Jan 5, 2012, 1:55pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

HTDAVE Said:

PIDs and HX have been around for about 5 years.  but only as a mod.

but for a year or so, Izzo has pidded their HX model, the ALEX.  -- kind of validates the HX+'PID' methinks

Posted January 5, 2012 link

Not really but manufacturer will sell what they think the public wants and if a noob who does not know any better makes a decision on buying machine a or b based on a PID, they will put the pretty flashing lights on a HX machine weather or not it really makes much of a difference. We have to constantly educate people here about why a PID really is not a huge plus on a HX machine.

Statement: A PID will not hurt a HX machine in any way and if you want one, go ahead and buy a machine with one or add it to a machine yourself, I am not going to tell you what you like, that is a personal decision.

Points against and for a PID on a HX machine:

Positive points for a PID on a HX machine.

It looks nifty.
It does not have mechanical points to wear out and requires no connection to the steam/pressure system.
It makes the adjustment of static boiler pressure easier.
It more closely keeps the steam boiler temp to the set value.
It sells machines to people who are uncomfortable not having a PID.

Points against:
It adds cost with little added value to the way the machine works.
Once your boiler pressure is set, it is the very rare occasion that it will ever need to be adjusted again.
The way a HX system works, ultra accurate temp regulation in the steam boiler is not need.
It adds heat sensitive electronics into a moist and hot environment, adding a possible point of failure when mechanical points are not prone to failure in this environment though they will eventually wear out (though points are rated in millions of cycles)

Just because a manufacturer adds a device to a product, that device does not mean that it improves the product, rather it could be that the manufacturer thinks they will sell more products and that is reason enough to add something that really is not need.

 
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Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

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calblacksmith
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calblacksmith
Joined: 25 Nov 2007
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Location: Riverside, Ca, U.S.A.
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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 Thu Jan 5, 2012, 2:03pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

Randy, that is an accurate pictorial view of what the heat cycles would look like, no disagreement from me.

As you said, the example is totally made up, but remember for even the worst Pstats the difference in the swings from centerline of the graph are only about 3deg F (6 dF swing) and for commercial P stats the swing is likely only 1.5 d F (3 deg F swing) so the addition of scale helps a bit to see what you are saying.

 
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Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

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scanfield
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Posted Thu Jan 5, 2012, 3:10pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

An HX machine is going to pretty much give you the same temperature shot after shot, correct? How does one manage the temperature? If one coffee says it should be used at 196 degrees and another says 202 degrees, is this information at all useful for the owner of an HX machine?
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calblacksmith
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calblacksmith
Joined: 25 Nov 2007
Posts: 7,499
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 Thu Jan 5, 2012, 3:24pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

Yes, it is
This is where learning your machine comes into play and how you taste things.
If you want it warmer, just do not flush quite as much or wait a little longer between shots, This IS a little like temp surfing but it is not mandatory for operation of the machine, by waiting a little longer, I don't mean a long time. I tend to run about two minutes between shots. If I go a little slower like two and a half minutes that makes the difference but it is not something I use a watch with, it just comes with use of your particular machine. Some like to use the thermometer that mounts into the group head of an E61 machine. I was tempted for a while but I find I really do not need it and for me, most coffee works just fine at the "default" operating conditions. My boiler is set to 1.1 bar at idle and I pull at about 10 bar when connected to line water pressure and it pulls at about 9 bar when off line and on the built in water tank.

It all depends on how you want your machine set up. For the most part, I do not bother with warmer/cooler than normal, my normal brew temp is set for about 198 and my palet is not quite sensitive enough to taste  one or two deg. Some can, I can not. I get the different flavors from the coffee by dose/grind adjustments and I am getting the flavors that are advertised. YMMV

As with anything there are those who excel at tasting the differences and there are those who get most of it then there are those who have no clue, I fall in the middle, if the roastmaster describes the flavor, I can find them in the brew, on my own, I will come up with different flavors, either way, it's all good and light years ahead of green aprons.

 
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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davethebrewguy
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Posted Thu Jan 5, 2012, 5:27pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

HTDAVE Said:

Izzo has pidded their HX model, the ALEX.  -- kind of validates the HX+'PID' methinks

Posted January 5, 2012 link

Validation? Or just marketing gimmick?

calblacksmith Said:

Not really but manufacturer will sell what they think the public wants and if a noob who does not know any better makes a decision on buying machine a or b based on a PID, they will put the pretty flashing lights on a HX machine weather or not it really makes much of a difference.

Posted January 5, 2012 link

+1, pure marketing gimmick. Those with little understanding of how a HX works will think they see a benefit and will buy a machine that offers to solve a problem that doesn't exist.
The biggest problem with pressurestats is the lifespan of their electrical contacts, a large load (like a heating element) causes arcing as the contacts open and close, this will eventually causes those contacts to fail. A PID does not directly control the element, it controls a SSR which, in turn, controls the element. The SSR will usually have a much longer lifespan than a pressurestat. There is no reason that a SSR can not be installed between a pressurestat and the element, this reduction in load at the contacts in the pressurestat will eliminate the arcing and significantly increase the service life of the pressurestat. There are a few machines that have a SSR set up in this manner and pressurestat failures are very rare on these machines. My own machine has this type of equipment and has been happily running 24/7 for 8 years now on it's original pressurestat.

Edited to add:
One thing nobody has mentioned is that a pressurestat measures pressure in the boiler , pressure is a direct and instantaneous measure of water temperature. A PID usually (is there any machine with a thermocouple installed in a thermowell?) measures the temperature of the outside of the boiler, the measurement of the boiler's outer surface may respond less quickly to a temperature change in the boiler than the response you would have from a measurement taken inside the boiler.
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frcn
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Posted Thu Jan 5, 2012, 6:13pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

I agree that if one was to "update" a HX machine by replacing the pressurestat with a PID, a probe in the water would be best, or possibly replacing the water level probe with a sensor for the PID and use it for double-duty (it would need to be an ungrounded probe and that would lengthen its response time. Most accurate way would be a pressure transponder, but by that point, unless you find the parts which fell off the back of the truck, the cost to benefit ration would make it a silly venture.

I think, all theories aside (which most of this thread has been), the only real answer would be to compare machines so equipped within the OP's price range. At that point, I think the list for HX/PID machines is going to be quite short. Billy Barty vs. Kareem Abdul Jabbar short

 
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JGG
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Posted Thu Jan 5, 2012, 8:28pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

davethebrewguy Said:

Edited to add:
One thing nobody has mentioned is that a pressurestat measures pressure in the boiler , pressure is a direct and instantaneous measure of water temperature. A PID usually (is there any machine with a thermocouple installed in a thermowell?) measures the temperature of the outside of the boiler, the measurement of the boiler's outer surface may respond less quickly to a temperature change in the boiler than the response you would have from a measurement taken inside the boiler.

Posted January 5, 2012 link

Pressure is an instantaneous indirect measure of water temperature.  More accurately, it is an indirect measure of steam temperature.

To correlate pressure to temperature, the steam must be saturated.  So a pressurestat is easily fooled by "false pressure" when the machine is in its warm up phase and the gas in the boiler is trying to expand, but is not yet saturated.

There are several SBDU machines that use thermowells.  And all of the PID'd steam boilers I know of use an internal temperature probe.

Despite my picky-ass comments, I am in complete agreement that putting a PID on a steam boiler shouldn't be thought of as a path to consistent HX brew temperatures.  That's the main reason I don't make PID conversion kits for HX machines.

Jim
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JGG
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Posted Thu Jan 5, 2012, 8:31pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

frcn Said:

I agree that if one was to "update" a HX machine by replacing the pressurestat with a PID, a probe in the water would be best ...

Posted January 5, 2012 link

I welcome correction on this, but I think you actually want the temperature probe in the steam.  The heat transfer characteristics of steam are superior to liquid water, so the probe reacts more quickly to changes when it is "embedded" in the steam.

Jim
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frcn
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Posted Thu Jan 5, 2012, 11:27pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

You very well may be correct Jim, but it does make me wonder... The water is first heated, then the heat transfers to the steam. Being that the water is more dense this art major would guess that the water would be a good place for the sensor, but that was just a guess, and which is best is probably another matter.

And it was also brought to my attention that another reason for some owners to ditch the pressurestat for a solidstate solution would be to get rid of the loud click clack of the pressurestat where, in some situations, it could be an annoyance. For reference why, see this YouTube clip of the Catherine Tate character to see that some people are bothered by the slightest thing.

 
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Posted Thu Jan 5, 2012, 11:55pm
Subject: Re: PID versus HX Machine Temp Management- Shouldn't End Result Be The Same?
 

HTDAVE Said:

PIDs and HX have been around for about 5 years.  but only as a mod.

but for a year or so, Izzo has pidded their HX model, the ALEX.  -- kind of validates the HX+'PID' methinks

Posted January 5, 2012 link

No, it doesn't. That's just marketing. They might as well put a hygrometer on their machine. ;-)

 
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