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Discussions > Espresso > Machines > HX/E-61...  
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marrone
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Posted Tue Feb 15, 2005, 8:01pm
Subject: Re: HX/E-61 Temperature Control
 

Dan,

Thanks for the PID info. I've looked at specs and instructions for a couple of Fuji controllers the have timers, dual setpoints and a digital input (on-off).  The inscrutable instructions left me wondering if the component features all played together or not, since my knowledge of PIDs has mostly been gained on this forum.

Like Loring and Cubastreet, a hidden PID or at least a discreet one is preferred. If nothing else, heh, heh, one could get the Isomac knockbox drawer and have the drawer shortened so the electronics would fit in the back of that housing.

The double boiler is intriguing - this could be a tiny one shot pot attached between the grouphead and the HX. A 50W heat rope, cooling fan and a Heating/Cooling PID would do half the trick.

The clever part would be putting the little tank on a 3 way solenoid valve to get it out of the thermosiphon path.

Ted
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djmcmath
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Posted Tue Feb 15, 2005, 8:53pm
Subject: Re: HX/E-61 Temperature Control
 

You've gotta wonder exactly how easy it is to configure a self-timing dual setpoint auto-cycling whiz-bang PID controller using the 4 unlabeled front panel buttons and the single 4 digit display.  Not to say it can't be done, but I'd just about betcha dollars to donuts it'd be easier (and cheaper -- a $20 PID will do whatcha-need) to come up with some external circuit that did the job.  (shrug)  But that's just me.

50W heat rope might do the job.  It might also get in the way of the cooling.  I've been slowly mulling this problem all day long.  The big problem is that the space inside the box is so tiny.  The "boiler" almost has to be pancake-shaped to fit.  That means welding up some kind of custom shape, then adding heaters (probably from some other boiler?).  

Why does the mini-boiler have to be out of the thermosiphon path?  Isn't it just as good in the line?  Seems like you could get a pretty controllable GH temp that way, too.  The trick, rather, is mounting the boiler so that it doesn't disrupt the thermosiphon natural circulation flow.  (wink)  :)


Dan
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marrone
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Posted Tue Feb 15, 2005, 11:43pm
Subject: Re: HX/E-61 Temperature Control
 

time delay relay + pid  - one more component, sounds simpler than I first thought. Thanks.

Pancake boiler could be as simple as a 2 row concentric coil of tubing with the heat rope in the middle. Lots of thermal mass, lots of surface area. No welding.

One of the two legs is restricted by the 'gicleur' orfice, I'm assuming the little boiler would go on the other.

If the little boiler is on the cold leg of the thermosiphon, all might be well. On the hot leg, the incoming water will essentially be at steam temperature, which wouldn't be good.

Ted
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doubleristretto
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Posted Wed Feb 16, 2005, 1:12pm
Subject: Re: HX/E-61 Temperature Control
 

JeremyR Said:

Not done yet. I have a 2 group HEX machine I'm going to add brew boilers to for work, and a Silvia I'm going to add a steam boiler for at home. In the HEX machine I've added a modified central heating thermostat to the thermosyphon which seems to work OK, but it still needed a good mixer for the brew water. I decided that in the long term a brew boiler would be more reliable and probably more accurate.

j

Posted February 13, 2005 link

I realize I'm going back to Sunday on this thread...but this by cubastreet caught my attention.  In it appears you describe adding active heating to a thermosyphon.  This is something I want to do on my Brewtus (e61).  Can you describe in as much detail as you have time, what exactly you did?

TIA,

Eric
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djmcmath
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Posted Wed Feb 16, 2005, 5:50pm
Subject: Re: HX/E-61 Temperature Control
 

Marrone, the "coiled tubing with heat tape" idea seems good, but as I think about it more, I struggle with precision temperature control.  Where do you measure temperature?  

1 - Take temps towards the beginning.  The response to a temperature change happens before the problem really exists.  As cold water starts to enter the beginning of the pipes (or hot water, for the first shot), the PID will start correcting -- but it will correct the temperature throughout the system, producing shots that are over-corrected, per se.  The first shot will come out cold, subsequent shots will come out hot -- reverse of the problem we have now, sort of.

2 - Take temps towards the end of the piping.  Same problem, except backwards.  In this case, cold water (or hot water, for the first shot) will flood the system long before the heaters (or coolers) even begin to respond.  If you had 2 full ounces (56ml) of piping, it might not matter -- the PID wouldn't start correcting temperature until the shot was nearly done being pulled, at which point it's ok to start corrections (though it would be a bit late, perhaps?).  The system couldn't pull shots back to back, but the 30 second delay between shots is required to grind 'n' tamp anyway, no?


Hmmm ... if the pipe was fat enough, there would be some mixing during flow (emphasis on "some").  If the temperature was taken close to the end of the sequence, but not all the way to the end, correction could probably start just before the first shot finished, giving adequate results.  Spiraled tubing has lots of surface area for cooling, so fans on either side would be pretty darned effective.  I'm still not sure I'm following the heaters -- if there's heaters in contact with the piping, that will inhibit the cooling, won't it?  I'm trying to imagine the appropriate heating element, and I'm totally failing.


Good progress, but still .... ?????
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marrone
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Posted Wed Feb 16, 2005, 9:16pm
Subject: Re: HX/E-61 Temperature Control
 

Lots to ponder indeed.

If there were two flat coils of tubing that touched, water flow spiraling in on one, out in the other,  would make a classic counterflow heat exchanger- tending to average the incoming and outgoing temps. Intuition suggests the sensor be in the middle of the loop. The rope heater could be twirled in between the coils, leaving the outer surfaces free to be fanned.

Ted

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jason_casale
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Posted Thu Feb 17, 2005, 12:15pm
Subject: Re: HX/E-61 Temperature Control
 

I think this could be simpler. I think mosfet all ready got the temp to equalize with the 6 million dollar expobar by insulating the boiler the copper pipes from the boiler  to the group and wrapping copper tubing around the boiler then going into the heat exchanger. Then he pided the boiler This equalized the water temp. In other words the water coming out of the group is the same temp as the boiler water. And matched the pid temp it was set to.  The problem is steam would be hindered by this at lower temps there is less steam or no steam. So what I was going to do is do all these thing set the boil to 256 degrees 1.3 bar or so. The water would be that temp coming out the group good steam but to hot. I was going to put in a manual 3 way mixing valve in the top pipe of the group head and connect it to the main water line before it goes to the pump. Then adjust the valvs to regulate the amount of incoming cold water going to the group head instant cooling stable yes because the temp was all ready stable before the cold water mixing valve it just needs to be cooled Manual valves with a screw adjustment would work find and provide constent cold water flow to mix with the hot water regulating the temp. Tell me what you guys think I am planning to implement this on my current machine.

 
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djmcmath
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Posted Thu Feb 17, 2005, 1:19pm
Subject: Re: HX/E-61 Temperature Control
 

marrone Said:

If there were two flat coils of tubing that touched, water flow spiraling in on one, out in the other,  would make a classic counterflow heat exchanger- tending to average the incoming and outgoing temps. Intuition suggests the sensor be in the middle of the loop. The rope heater could be twirled in between the coils, leaving the outer surfaces free to be fanned.

Posted February 16, 2005 link

Some quick math shows that, for 1/8" copper tubing, 24.5ft would be required to produce a 56ml internal volume.  Some more quick math estimations tells me that two tight spirals, about 5 inches across, back to back, would do the job.  24ft of heat rope at, say, 4W/ft only gives me 100W, which may or may not be sufficient... Let me see what I can find in heat rope...

Dan
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Rick
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Rick
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Posted Thu Feb 17, 2005, 1:40pm
Subject: Re: HX/E-61 Temperature Control
 

jason_casale Said:

So what I was going to do is do all these thing set the boil to 256 degrees 1.3 bar or so. The water would be that temp coming out the group good steam but to hot. I was going to put in a manual 3 way mixing valve in the top pipe of the group head and connect it to the main water line before it goes to the pump. Then adjust the valvs to regulate the amount of incoming cold water going to the group head instant cooling stable yes because the temp was all ready stable before the cold water mixing valve it just needs to be cooled Manual valves with a screw adjustment would work find and provide constent cold water flow to mix with the hot water regulating the temp. Tell me what you guys think I am planning to implement this on my current machine.

Posted February 17, 2005 link

I wonder if it will work?  I'm not sure I understand it all correctly, but here are a few thoughts.

Assuming you are able to stabilize the temperature of the water coming from the HX (using the coil idea), you have part of the problem solved.  If the water from the HX is always the same temperature, a mixing valve fed partly from the HX and partly from a parallel bypass directly from the pump may do the job.  This is an interesting possibility.  If true, why not just draw the water for the shot directly from the boiler?  That way, you don't even need a heat exchanger.  

Assuming you still want to use a HX, will the water temperature from the HX really be constant enough to use a fixed mix setting, or must you use a mixing valve that adjusts cold water flow based on varying HX water temperature?  I think an adjustment of some kind would be desirable because you may want to vary brew water temperature to get the best results from various blends and roasts.

Second, the amount of cold water mixed into the HX stream would also have to change as shot volume changes.  A double that draws 2 oz in 30 seconds would need a different amount of cold water than a single that draws 1 oz in 30 seconds.  Would the pressure in the parallel feed lines (one from the boiler, one directly from the pump) take care of this?

I think the mixing valve needs to be connected to a thermoprobe so it varies the amount of cold water mixed into the stream to achieve a temperature that the operator can easily change based on what's best for the blend or roast you're using.

Overall, I think the mixing valve solution could work.  Draw water for the shot from a PID'd boiler that stays within a narrow temperature range.  No HX needed.  Have a parallel cold water supply line coming directly from the pump.  Use a mixing valve that varies the mix of cold and hot water to get the brew water temperature you set.  

I have no idea if the technology for this exists or is economical.

Rick
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djmcmath
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Posted Thu Feb 17, 2005, 1:52pm
Subject: Re: HX/E-61 Temperature Control
 

Jason -- the mixing valve would have to be continually and rapidly adjusting to get consistent temps.  You'd need some variant of a servo-controlled valve to do it right.  The problem is that, while the boiler temp is constant (roughly), the water coming through the HX piping temp is a function of how long it's been there.  It wouldn't need to move a lot, but the valve would be constantly changing to get that mix just right.  If moving parts are ok with you, then the mixing valve is a pretty good idea.

Mosfet's sol'n is good, but I really would like to have steam, too.  :)

Dan
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