Eric, could I have a TC at the head and another at the boiler and still have the ability to control the boiler with one PID (dual readout) at the tank and view the water temp at the head as well. Any clue how much of an difference of temp between the screw and the PF?

Yes, but that is a relatively expensive PID as it is a dual loop control wherein you are simply monitoring one of the loops. There are probably several manufacturers of these - one that I am aware of is the Love 32DZ. Applying a PID to a hx machine has been discussed on this forum. See the heat exchanger section here: http://www.home-barista.com/espre...vorites-t1541.html

Monitoring grouphead temperatures should be a separate issue. As far as temperature differentials are concerned, I do believe that these machines behave similar to the Rancilio Silvia and a good read on her temperatures is here: http://www.home-barista.com/espre...out-pid-t4691.html

erics wrote:Yes, but that is a relatively expensive PID as it is a dual loop control wherein you are simply monitoring one of the loops. There are probably several manufacturers of these - one that I am aware of is the Love 32DZ....

The Watlow 988 can optionally be configured (hardware-wise) with one input or two inputs.

I have a 2-input model on my home Silvia. The first input reads a type T thermocouple on the top of the boiler and is used to control the heater.

The second input reads a grouphead sensor, but is not used to control anything. I have to press a button to switch the displayed temperature from boiler sensor to grouphead sensor, but this is not a great inconvenience.

The 988 can also be optionally configured with a digital event input, which comes in handy for selecting a 2nd setpoint for steam mode on a single boiler machine. [Edit: the digital event input is standard on all 988's].

Configured as described above, this controller is priced well over $500, BUT can frequently be found on eBay for a fraction of that. IMO, plucking one of these from eBay is your best bet for a dual loop PID to be used as Jeff described. You just need to make sure it has the right hardware to support 2 inputs.

Jim

JimG wrote:Configured as described above, this controller is priced well over $500, BUT can frequently be found on eBay for a fraction of that. IMO, plucking one of these from eBay is your best bet for a dual loop PID to be used as Jeff described. You just need to make sure it has the right hardware to support 2 inputs.

Jim

Thanks Jim!

Would the software have to be the enhanced version (allowing dual PID set) or can that be changed somehow. I think I am looking for something like this:

988B(Software B (enhanced) instead of A (modbus)?)-11(Inputs 1 and 2 which greater are >0 )CD(output 1 and 2 >A)-JA(output 3-4)RR.

I a am also thinking that having the inputs 11 (thermocouple only) would be preferred but then it maybe a long wait to find one with the perfect set.

Any tips on the outputs?

I did find this on Ebay 988A-10CD-JARR but I think since it is a single input it would be useless other than a single controller (no TC at head) to bypass the PS.

Thx!

Jef

Lockman wrote:Would the software have to be the enhanced version (allowing dual PID set) or can that be changed somehow. I think I am looking for something like this:

988B(Software B (enhanced) instead of A (modbus)?)-11(Inputs 1 and 2 which greater are >0 )CD(output 1 and 2 >A)-JA(output 3-4)RR.

Offhand, I don't know for sure what you get with 988B vs 988A. But I can tell you that the 988A works for the application we're talking about. Unless you plan to use the second loop to control something, I think a single set of PID parameters is OK.

I believe you are correct about the rest of the model number. IOW, I think you want something like this:

988A-xxCy-yzzz, where
x = 1 or 2
C = DC voltage output (needed to drive a standard zero cross SSR)
y = don't care
z = R or G

Jim

Sorry guys, I had no Internet access for several days but now I'm back This thread developed so much since the last time I was here; now I lost track.

Any S26/7 specifics you'd still like me to comment on? Are you guys getting shots that are either sour, bitter or sour&bitter at the same time but not good ones? Have you yet noticed how headspace (i.e. dose & basket) and brew flow rate affect brew temp?

Why do I see PID talk here? I don't think PIDing this monster's boiler will improve its brew temp stability. But maybe if we PID its grouphead...

Hi Max,

I would PID the boiler just to get rid of the PS. Mine is really noisy! Click, clank. Click, clank. I think you are right though. Knowing the head temp is probably of more use than controlling the boiler in regards to the results in the cup. However, we wouldn't really be using the PID for anything other than a thermometer at the head. My thought is to do the TC at the head and use a dual use controller (really only need one controller and 2 displays) or 2 PIDs or a meter at the head and a PID to bypass the pressure stat.

Actually, I am getting good shots most of the time with the flushing routine. I pull a couple of blanks before the shot (a double at 14g). The screw just touches the puck on the DB basket. I do get some variance at the mouth but nothing bad. With my fresh roast it is up to 90-95 percent crema! The reason I am so interested in some control at the puck is I think a 2 degree difference might bring really cool flavor differences. I pulled on the other day with some SM Monkey I had roasted about 48 hrs before and got berries off the crema (disappeared quickly) and was floored. Never have duplicated it though...
I haven't monitored the head temp yet so that will be the first thing on my to do list. I remembered I have one of those point and shoot laser temp things that might be fun to play with. Sure do love those 58mm baskets!
I have a hell of a wicked chest cold though so I am moving a little slower. Back to tea again as well.

By pulling 2 blanks you're partially warming the cold, hanging, GH; which is better than no warming. @ 1 bar, the GH idle temp would be something like 180F (depending on room temp, PF on or not, etc), after two blanks it goes up by 5-7F. Then you flush a bit which gets the GH warmer by 1-2 more F. So, now your GH is @ 190 or so and your HX water is @ 210 or so. Your brew temp will start at ~210, bottom down to as far as 195(warming th GH), then shoot to very high F (212 or even more) depending on your brew flow rate and boiler pressure. That's a brew temp variance of ~15F

I'll quote myself again

coffee.me wrote:To create a not-so-bad brew temp line, you'll need to develop a routine that gets the GH hot enough and the HX temp cool enough at the same time.

Today, my brew temp variance is down to about 2-4F after using all the Abra Kadabra I could come up with. Not impressive, I know, but the coffee is good and I'm out of magic! I'd gladly go over how I manage this monster; but I have a feeling that by stepping back and telling you what I know about the machine (rather than what I do about it), you (or someone else) could come up with better ways than mine. No?

Ahh, maybe I need the temp monitor so we can all compare.

I have a couple of updates for this discussion.

The first good news is that I am getting the best shots ever after working a bit with Eric's adapter and a good probe.

The second bit of good news is that the setup process is rather easy, and managing the water dance once you dial the machine in is dead simple.

In short my goal was to hit and maintain 206 degF at the probe point above the shower head. This leaves me in the 7-9 degF drop to the puck face (not actually measured yet as of this time) so I figure a puck at around 198 is in the ballpark. I have found that the temp you stabilize at has three major points of adjustment.

The flow rate has to be at or near your 30 sec 2oz goal to even begin setting the stable temp point. So get out your pressure gauge with the needle valve you keep for setting up your pump pressure and get that needle adjusted to the target flow rate.

Next you have to unlock the portafilter with the flow restriction and purge the HX. This is the surprising part that is counter to any ideas you have from reading about an E61 head. You only need to flush about 1/2 a second at most, even from a long idle. You will see your temp reading spike, mine jumps to 218 then drops quickly, I try and stop it about 114-112.

I then lock in the portafilter with the needle valve and start a temp test run with out any delay. My first run was stable but at 209 degF at the probe. I fiddled two turns down on the Sirri pressure stat and waited 10 minutes for it to get stable. Second run with same flush/test cycle was stable, but at 205 degF. I overshot, but I know now that 1/2 turn on the pressure stat will shift my shot temp by 1 degF.

Final setting 9bar with 30sec 2oz flow with probe temp stable at 206 degF with a boiler pressure that cuts off just over 1 bar and cuts on at about .9 bar.

The part that just messes with my head is that I can turn the machine on and 20 minutes later pull a shot with that little 1/2 second flush, but it can stand for hours and the same 1/2 second flush nails the same temp. I always knew the E61 thermosiphon and the Rancilio direct thermal transfer heads would behave differently as HX machines, I just never guessed how far different they were.

Without the probe at the head itself I most likely would have kept on over flushing the HX on this machine and would have kept on getting low brew temps.

Words for the wise: Common knowledge is not applicable in uncommon situations.

-Cecil

Well not tired of playing arround I decided to get my FloJet pump working off the bottled water system.

I hooked it up and found that it added a +10psi pressure variable at the puck to my system. Even worse it was a pulsing variable. I didn't wait to see what that would do to my puck, I was sure it would not be good.

So it was time to add an accumelator to the set up. For those of you that do not know, all that does is store water under pressure with an air bladder to even out pressure differences over time. Think of it as a water pressure capacator. It will resist the change in water pressure if you are draining water from it, or adding water to it.

I checked both Home Depot and Lowes and all they have is a 'hot water' expansion tank bladder regulator. They dont have anything with John Guest fittings allready on it. But for 35 for the tank at Home Depot I could make it work.

You need to add a T fitting, a couple of reducing fittings, and a John Guest fitting for both the inlet and outlet sides, and with a liberal dose of teflon tape you will be ok.

Dont skimp on the teflon tape though. Be sure to add lots of tape on the metal to plastic fittings, or you will get a leak. I had to depressurise and add more tape. This is also true where you get stright english threads to standerd threads.

The tank came with the air side pre-charged at 40psi, that is to high for what we want to do, so let some air out of the bladder until the flojet just kicks in, then you will hold pressure for about 10 shots without the pump kicking in.

Also note that since you have added positive pressure on the procon pump inlet you will need to readjust your pump setting to get 9bar at the head.

-Cecil

PS Remember if you change you plumming to check it once an hour for the next day or so. No leaks are the best bet by a long shot, but better to check and know.