First, this SBDU machine has some interesting differences from its brethren in terms of temperature management. For one thing, it has 4 thermostats. There is, of course, a brew thermostat which has the typically wide deadband that makes getting a consistent brew temperature profile challenging. The PID replaces this thermostat. In addition, there is an overtemperature thermostat that shuts down power to the machine if the boiler gets too hot.
Here’s where things get a little interesting: there are two (yes, two) steam thermostats. The first brings the boiler up to 115°C when the steam switch is thrown. But there’s a second 135°C thermostat which is needed because the Solis turns the heating element on when the steam switch is engaged and the steam valve is opened. This keeps the steam flowing strong. If the boiler tops 135 while steaming, this turns the heating element off.
What this steam management system means is that there’s nothing to gain from having a PID steam control as there is in the Silvia for instance. So you can use a very simple PID with one set point temperature.
On other SBDU machines that are often PIDed (such as some Silvias and Gaggias), there is a thermostat mounted in a threaded hole on the boiler; this thermostat is usually replaced with a threaded RTD sensor or a washer thermocouple is placed under the screwed-in thermostat. The Solis does have its steam thermostat screwed into the boiler, but that needs to remain in place, and it is tough to find a washer thermocouple that has good response characteristics. THis is one reason why Jim Galtt custom manufacturers washer thermocouples for his PID kits.
So what I decided to do was use a bare-bead thermocouple placed below the brew thermostat (which will be disconnected). This thermostat, as well as the overtemperature and high temp steam thermostat, sits in a recessed hole on the top of the boiler, and held in place by a clip. This clip is held down by the steam thermostat’s screw mounting.
The process for installing the PID and integrating it into the temperature management of the machine is very similar to the other SBDU units, so I will be somewhat brief here. Refer to any of the other very good guides to installing a PID the Silvia
Here are the parts I used: (1) Watlow 935A PID from eBay. If you order this unit, be sure to get one with AC power. To do so, look for 0 before the second hyphen in the model number. Some recommended model numbers are 935A-1CC0-00R (2 switched DC outputs with Watlow logo and red display) or -00G (green display). Getting one with -1CD0- in the model number is fine (electromechanical relay instead of the second switched DC output). (1) Bare-bead thermocouple probe, either type K seems to the the traditional choice, or T is fine. Insulation to exceed 150°C - fibreglass is fine. 30 gauge wire is the best for this application. (1) 25A SSR with input range accomodating the 6v output from the PID. (1) Heat sink for the SSR (1) Project box - minimum dimensions 5” long by 3” wide by 2” high.
Wire: — 18-20 AWG wire for the dc signal from the PID to the SSR - 2 colors (I used red & green to differentiate from the AC power wires). — 16-18 AWG wire (both white and black) for AC power to PID and from/to the SSR. Get wire rated for high heat - 150°C and above. Auto stores sell wire for use in engines that is rated at quite high temperatures. I used some Teflon insulated appliance wire purchased at Surplus Center.
Some thin insulating material to go above the TC bead, between it and the brew thermostat. I used some Buffalo Snow material I had left over. You want to keep the thermostat from acting as a heat sink for the thermocouple bead.
A short (4-6”) piece of black heat-shrink tubing, 3/16 or larger to accomodate 2 AC power wires, 2 DC signal wires, and thermocouple wire.
(2) male crimp quick-disconnects, .187” size, with AWG rating larger than AC power wires. You will need a larger barrel on the crimp because you’ll be inserting 2 wires into the barrel. If you can find it, I recommend a piggyback quick disconnect, but they are pretty much impossible to find in .187” size.
(1) female quick disconnect, .25” size, with AWG rating appropriate for the AC wire.
A roll of double-sided adhesive foam tape. I used some 3M tape purchased at Lowes. This will be used to mount the SSR heat sink and the PID project box to the machine.
A small tube of thermal grease for the thermocouple and the thermostats.
First, open up the machine. Use the excellent instructions given by Kristi in the CoffeeGeek thread: click here - remove the cup warming tray only. The other OPV-related disassembly is not required.
Remove the wires from the steam thermostat (the middle one in the row of 3), and using needle-nose pliers, grip the outer metal barrel of the thermostat and turn counterclockwise to remove it. Be careful as it can be broken.
Once this is removed, the clip that it holds down can be lifted up, and the three other thermostats can be removed. I took this opportunity to refresh the thermal paste underneath the over temperature thermostat and the steam high temp thermostat. I used some fine steel wool to clean off the old grease in the boiler thermowell and the thermostat. Then I reapplied a new thin layer of thermal grease to each one before reassembling.
The brew thermostat will remain in place, but you’ll take the thermocouple bare bead and place it in the thermowell with the insulator on top of it and the brew thermostat on the top of both. I cleaned out the thermowell and used a small amount of thermal grease on the bare bead before assembling it.
Put all three thermostats back in place, along with the hold-down clip, and screw the steam thermostat back into the boiler. Tighten enough to make sure the thermostats are tightly secured and not turning/wobbling in the thermowell.
Now we will start running wires. Cut two lengths of wire about 18” long from the black AC wire; one will go to power the PID and the other will go to the SSR. Strip one end of both wires and carefully insert the two wires into the barrel of one of the male quick disconnects. Crimp. We will use a male quick disconnect to plug into the female quick disconnect on the wire coming from the power switch to the brew thermostat (it is brown). Unplug the quick disconnect from the thermostat, and plug the double-wire connector into the brown wire’s connector. You may need to use needle-nose pliers to make the female connector’s pins tighter, as the width of the brew thermostat’s plugs are wider than most quick disconnects. Make sure it’s securely connected.
Cut another 18” piece of the same black wire and crimp a male quick disconnect on it. This will plug into the yellow wired connector that you will remove from the other side of the brew thermostat. This wire will also run to the SSR.
The SSR needs to be mounted on its heat sink. Use a *thin* layer of thermal grease on the SSR’s bottom plate and the top (smaller) heat sink surface. Too much thermal grease will impair heat transfer. Screw the SSR tightly and evenly to the heat sink. If you see lots of thermal grease ooze out from under the heat sink, you probably applied too much.
Screw the two black wires (one from the double-wire connector conencted to the brown wire, and one connected to the yellow wire) into the AC side of the SSR. Polarity is irrelevant on the AC side. Cut two 18” pieces of the 18-20 AWG wire, one of each color, and connect one color to the positive and one to the negative DC side of the SSR. Remember which is which because you’ll need to match the polarity on the PID.
The heat sink with the SSR on it can be mounted to the right side panel, above the pump. I used two pieces of the double-sided tape to adhere the heat sink footing to the right side panel. Thread the SSR wires up toward the top of the case, and toward the left rear.
Cut a piece of the white wire about 12” long, and crimp a female .25” quick disconnect onto one end. Plug this onto the power terminal block on the side where the white power wire is connected. This wire will be the neutral wire for the PID.
Now assemble the project box. I used a Dremel to cut out the opening for the PID. Download one of the manuals on the web, and in the installation section it will give you dimensions for the panel cutout. I also cut some ventilation holes in the bottom and the exposed left side. These turned out to be pretty ugly looking but will do the job. I installed a switch on mine, but it turned out to be superfluous because I decided to run the wire from the power switch instead of the main power block. Drill a hole in the back of the project box large enough to accomodate the wire bundle.
Now thread all 5 wires (line AC, neutral AC, SSR DC +, SSR DC -, thermocouple) out of the SL-70 by placing them in the slot between the top left side of the case and the back of the case. They will fit if you stack them vertically in the slot. This avoids having to drill a hole in the case. You could alternatively drill a hole in the case and in the project box, and thread the wires directly into the project box.
Now thread all the wires through the heat shrink tubing, which will keep them neat when exiting the machine and running to the project box. They can then be threaded into the project box. I used a rubber grommet to make the project box entry tighter and neater. Trim all the wires to the correct length, leaving a bit of slack. I did not trim the thermocouple wire.
The wires can now be connected to the PID. Be sure to get the polarity correct on the thermocouple wires and the SSR wires. Close the top of the project box and attach it to the left side panel, near the top. I used the double-sided foam tape.
Close the SL-70 case, pray a little, plug it in, and switch it on. If all is well, the PID will start up, the light near the power button will be illuminated. You need to immediately set the set point temperature (see the PID’s instructions) before the boiler heats up too much.
Setting the PID parameters is an art unto itself and is better left to other people’s instructions. You will probably want to start out autotuning the PID but will then need to detune it to perform adequately. The PID needs to be set to approach the set point slowly without overshooting. This will take some trial and error. Same with setting the appropriate set point temperature to result in the desired temperature at the brew head. On mine, the set point was about 6°F above the brew temperature.
(Click for larger image)
Dana Leighton - Espresso hack and CoffeeGeek moderator
Kristi Senior Member Joined: 6 Oct 2005 Posts: 2,281 Location: Boston Expertise: I love coffee
Espresso: Gaggia Evo w silvia wand Grinder: Macap M4 mod to d&s-less Roaster: (Jeff at Redbirdcoffee)
Posted Sun May 9, 2010, 7:54pm Subject: Re: Solis SL-70 PID installation
I want one!
Nice!!! :o)
#--> I recommend Eric Svendson's adapter and thermometer for E61s (also Silvia) : easy surfing! # My photo albums have moved to http://picasaweb.google.com/krislema2
Kristi Senior Member Joined: 6 Oct 2005 Posts: 2,281 Location: Boston Expertise: I love coffee
Espresso: Gaggia Evo w silvia wand Grinder: Macap M4 mod to d&s-less Roaster: (Jeff at Redbirdcoffee)
Posted Sun May 9, 2010, 8:21pm Subject: Re: Solis SL-70 PID installation
Nay - no master of Solis here!!!
What do you set the PID point at and how's the brew?
#--> I recommend Eric Svendson's adapter and thermometer for E61s (also Silvia) : easy surfing! # My photo albums have moved to http://picasaweb.google.com/krislema2
PID set point was 206, which gave 200 at the brew head. The espresso was very good. I pulled only a few shots before I shipped it off to storage, but I would say the quality of the espresso was not very different than from my Isomac. I also had done the OPV adjustment, which likely helps too.
Dana Leighton - Espresso hack and CoffeeGeek moderator
Kristi Senior Member Joined: 6 Oct 2005 Posts: 2,281 Location: Boston Expertise: I love coffee
Espresso: Gaggia Evo w silvia wand Grinder: Macap M4 mod to d&s-less Roaster: (Jeff at Redbirdcoffee)
Posted Sun May 9, 2010, 8:30pm Subject: Re: Solis SL-70 PID installation
Nice! Yep, a great machine, and a nice mod!!! Thanks for daring! and sharing!!!
#--> I recommend Eric Svendson's adapter and thermometer for E61s (also Silvia) : easy surfing! # My photo albums have moved to http://picasaweb.google.com/krislema2
MonkeyK Senior Member Joined: 12 Dec 2008 Posts: 214 Location: Twin Cities, MN Expertise: I like coffee
Espresso: Vivaldi II Grinder: Baratza Vario Drip: Aeropress, Bunn Phase Brew Roaster: Behmor
Posted Wed May 12, 2010, 7:37am Subject: Re: Solis SL-70 PID installation
Awesome mod Dana! With the Solis Group built into the boiler, this has got to result in some rock solid temps.
Love my Euro2000, but sometimes I wonder how much of my improvements have been from the upgrade vs improved technique. If I find myself looking back at the Solis, I'll definitely be digging this thread back up.
Posted Sat Sep 25, 2010, 5:51pm Subject: Re: Solis SL-70 PID installation
I made some temperature measurements tonight. I am not too happy with the temperature stability, but it may be a product of my P, I, & D values. I have them set so they do not overshoot the set point when the boiler is warming up. The downside of that is that the recovery speed is quite slow, such that the temperature creeps up slowly as it gets within 15° F of the setpoint. So, when the shot is pulled the temperature drops off pretty steeply before the heater gets aggressive. I may play with the settings to try to get the temperature stabilization more aggressive. I can get more stability by manually activating the steam switch while pulling the shot. Here's an idea of what the temps look like over time.
This first graph is without activating the steam switch:
(Click for larger image)
Dana Leighton - Espresso hack and CoffeeGeek moderator
Posted Sat Sep 25, 2010, 6:07pm Subject: Re: Solis SL-70 PID installation
Overall looking at the graphs, I think this is just the product of the pump pouring cool water into the boiler so I am not sure making the PID more aggressive is going to deal with that initial drop from 199 to 194-195 over the first 15 seconds of the shot. The only solution I can think of is to have the inlet water preheated, but the Ulka pumps are not designed to pump heated water.
Anyway, the shots didn't taste too bad even when brewed without activating the steam switch, brewing at 192-194° F at the end of the shot... Not sure what that means. The experiment continues. :)
Dana Leighton - Espresso hack and CoffeeGeek moderator
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