I opened up my Le'lit PL041 for the first time do do some investigating and to satisfy my curiosity. It's fun to check out the innards! Even at the more humble level of home machines there's some pretty good craftsmanship inside. I was also investigating a tiny bit of steam leakage, but that's irrelevant to my primary question.

I was tracing the water path to see how it works exactly when I got confused. I don't understand how the 3-way solenoid functions within the system. If those of you who are more experienced would offer some help I would be very grateful.

My original understanding:
Solenoid valves release the pressure in the portafilter by allowing "dirty water" (pressurized excess brew water with coffee oils) to be expelled through the solenoid itself into the drip tray. This avoids "sneezing" and gives a drier puck - a general convenience factor. The dirty water does not enter the boiler, but rather is diverted along another path. Backflushing cleans the solenoid valve and this path.

My confusion:
My machine has the boiler mounted directly over the group head. It's not an offset design like some other single boilers. Therefore the solenoid is not placed in between the boiler and the group. In fact, the leads to the solenoids go up through the boiler and then back down to the drip tray. Does this mean that dirty water is coming into contact with boiler water? Are there just pipes that run through the boiler? How does the solenoid control the system (i.e. why do the hot water and brew switches do different things?

I'm going to try attach a lot of images so that I everyone can see what I'm talking about. I've color coded a few pipes and pointed out others. All pictures are from the same side (same orientation).


Here's the whole thing. Blue pipe is water intake. Yellow pipe is OPV drainage. Red pipe is unknown. Sorry the wires are everywhere, hopefully you can sort through it.


As we follow along the water path, the blue intake goes into the Ulka pump.


The other side of the pump is a thinner pipe, which I have indicated with my sky-blue paint brush.


Continuing along the water path, the same indicated pipe connects to the right side of the non-adjustable OPV.


This is the left side of the same OPV, where the top pipe is the yellow pipe leading back to the tank.


The bottom of the casing has another T-joint. Directly below this, just to the left of the joint, is where the steam wand exits the casing. Indicated is the control for the steam valve.


Attached to the right of the T-joint is the 3-way solenoid valve (indicated).


Indicated is the pipe leading to my drip tray. Dirty water decidedly travels through here.


I have no idea what this red pipe does, but it is obviously attached to the other side of the solenoid valve.

So, tell me exactly what happens when I brew a shot, please. The pump activates, pushing tank water into the boiler, which pushes water out of the boiler because the solenoid valve and steam valve create back pressure? Or does a tube travel through the boiler to the now opened solenoid valve by means of the red tube? What path and how does dirty water move when the pump turns off? Somehow dirty water has to go through the boiler, and I'm under the strong impression that it doesn't mix with clean boiler water. Does that mean that there are one way valves in the boiler / group head, then?

I will stop guessing and wait for some better explanations. Thank you for your time!

Try my article 3-Way Valve How and Why.
Also, How a Pressure Relief Valve Works
Those might fill in a few of the blanks for you.

I had read your article and it is very good. However, you handy diagram places the 3-way in between the boiler and the group. With a Silvia, this is exactly where it is. In my case, it appears that the 3-way is connected to the boiler... and then the boiler again. I'm wondering about any internal piping or mechanisms inside of the boiler besides a simple "hot pot" with ports.

The easy way to understand it is that you have a valve with two inputs and one output.

The output is fixed, and is your group head.

It can switch from the head to the drain, or from the head to the boiler.

Since there is a spring that holds the line open from the head to the drain you have to supply power to get the head to connect to the boiler.

That is the way a 3 way solenoid valve works.

-Cecil

I really appreciate the help guys. Especially so quickly.

I'm pretty tired. If I'm not being logical, and maybe I'm not, then I apologize. This is definitely my last post before bed.

However, it seems to me that there is one input and two outputs. Outputs = [to the drip tray] and [to the head (when energized)]. Input = from boiler to solenoid

Still, I can clearly understand the solenoid in Randy's diagram. What I can't understand is my specific situation. I don't know which pipe feeds water into my solenoid, red pipe or brass pipe, so I only know one output.

It seems to me, on a cursory investigation, that boiler water can travel straight to the portafilter without every going through the solenoid valve (though, I know this is NOT the case based on the way these machines work).

1. I see water entering the boiler through the OPV from the pump
2. The boiler is bolted directly on top of and onto the group head
3. The end?

The only explanation I can come up with is that there is internal piping that runs through the boiler, to the solenoid, then back to the boiler, then to the group. And even if this is the case, I want to know exactly how this works.

The three way valve doesn't need to be three way on a dedicated boiler machine. The entire system, puck, group, boiler, and line to the pump head is at shot pressure. Opening a valve anywhere along the line relieves the pressure. The pressure relief on the Gaggia machines works like this too, exhausting from the boiler.

Your PL041 is a bit different from those I just received, mainly due to repositioning the steam valve and knob off to the right hand side and eliminating the attached tamper to free up the internal space. However, the fundamental logic of the water flow hasn't changed.

Water flows from the tank to the pump to the boiler inlet/overpressure valve. Then it flows through the boiler direct to the steam/solenoid valve. At this point flow changes depending on switch configuration.

If the hot water switch is ON but the steam valve is closed, water flows back into the tank via the second (yellow band) hose from the overpresure valve.

If the hot water switch is ON and the steam valve is open, water flows from the steam wand.

If the brew switch is ON, the solenoid is activated and water flows through the solenoid valve, through the red banded pipe and down through the boiler via a central copper pipe to the water distributor and showerscreen.

The configuration is common to the Imat Mokita machines and the Nemox Opera, see http://www.coffeeco.com.au/articles/repair.html for a look inside the boiler.

When the brew switch is turned OFF after brewing the solenoid is also off and pressurized water from the top of the puck flows up through the pipe in the boiler, into the red banded pipe and out through the tube at the base of the solenoid valve.

All the action is easy to see if you play with the switches and backflush the group with the top of the machine off. I've attached a pic of the current PL041 layout for reference purposes.

Alan

Yay!

That makes sense to me now. Dirty water does go "into" the boiler. It just goes through it via a central copper pipe. This also explains why the Le'lit is prone to wet pucks. There is a thin pillar of water all the way up through the boiler, so even after the solenoid blows off some water, there still can be more. Thank you very much, Alan.

The tinkerer in me is also intrigued by the thermal stability and control. What is the red marked tube made of? Is it a good insulator?

edit: A quick look at the parts list determined that it was PTFE (Teflon).

Thanks for posting the pictures.
The plumbing on the Le'lit threw me; I was not aware the brew water path was like that. (from the top of the boiler, then running external to the boiler, then piped back through the boiler to the group.... ) I wonder how that works for brew temp stability....

The Gaggia and Isomac Venus have the 3-way plumbing drilled into the grouphead, the 3 way bolts to the back of the grouphead. Brew water enters through a standpipe straight down into the grouphead plumbing. It seems like a simpler and more temp stable approach.

The Red Marked tube, I would think, is to feed how water out of the steam arm... No?