For anyone interested, this thread is a continuation of a discussion that started with repairing a broken terminal on the La Cimbali Microcimbali. That discussion started here: Newly acquired Microcimbali Liberty: had a few restore questions. I asked to make the actual rewiring of my machine, an older model of the Liberty with different wiring, a separate topic so it would be easier to find.

Pre-Introduction

This thread already has an introduction below. But as it unfolds, I'm developing it into a reference for others learning some of the basics of rewiring an espresso machine. For instance, you'll find a post further on laying out the most fundamental concepts needed to understand electric circuits. Here are three highlights that exist further on in the thread:

How to Think Like an Electrician

Making Sure Circuits are Connected and Not Shorted

Online References to Get You in the Ballpark

Figuring Out the Wiring

Before you read the thread that follows and look at the pictures, let me set up what I'm trying to do. That came clear after doing the exploration below, which revealed that I'm trying to connect a low and high power heating element to a separate switch for each. Those switches are wired in series, with the low power one closest to the power cord. The wiring also includes a thermal safety switch, and all of this is grounded. I'll be replacing an old wiring harness with a newer one in better shape that came out of a similar machine. The pictures below show you what I found and reveal that I disassembled things without taking adequate photos or making a circuit diagram. I'm a first-timer on this, so go easy on me, folks! What follows is the reasoning I did earlier to come up with this introductory paragraph. So here's where I'm asking for help. I'm new to circuit diagrams. How do I connect these parts together? And let me definitely say I take on this risk myself and hold anyone offering suggestions and the site itself harmless from any liability whatsoever!

So now to my detective tale. I'm also developing this thread to offer an information source for anyone trying to rewire a La Cimbali Microcimbali with the dual switches that preceded their Liberty model. I haven't found anything that shows how to do this on the web. Anyone reading this and using its information does so at their own risk.

To put Humpty Dumpty back together I'll start with the wiring photos taken during disassembly:









Starting with Wikipedia's page on U.S. wiring standards http://en.wikipedia.org/wiki/Electrical ... th_America, here's what I make of the color coding going from the power cord to the junction unit.

The yellow/green striped plastic wire in the middle is ground. As you'll see in a picture below of the wiring harness I removed, I believe the blue plastic insulated wire connects to the black woven one that supplies the heating element switches in series. The brown plastic wire connects to the silver woven one that goes to the temperature safety switch. The corresponding woven wires exiting the junction unit are neutral white/tan for ground, and for the two elements, black for blue and silver for brown. The neutral woven wire labeled "3" goes to the ground connection on the chassis, and I'm not sure where the loose woven wire may connect.

The connections to be made are to two separate on/off switches for the low and high power heating elements and connections to a white thermal safety switch that was mounted on the bottom here. Fortunately the photo shows the orientation of the switch terminals by revealing the writing on one side.



and removed here:



I'm guessing that the metal bridge must connect the ground sides of the heating elements. I'm assuming the white switch is a thermal safety switch because of its resemblance to that type of switch for a Microcimbali on the Orphan Espresso web site here http://www.orphanespresso.com/Resettabl ... _3328.html. My white switch is stamped with Elmwood 8 between the terminals. The black letters on the side read 2455RC98-969 L135C 99/40 .

Here's a closer look at the bottom of the boiler taken today so you can see the markings. You can clearly see the ground connections for the two different elements on the left and the hot connections on the right. The bottom right shows this machine was made to U.S. standards at 110 volts. To the left of where the safety switch mounts is a capital "E" and to the right a zero and a 79. Perhaps that last number indicates when this machine was made. The top right has what appears to be an electrical symbol, which is a T opposed by three increasingly small parallel lines. It's discolored so it looks like an "L" but it is clearly a T when closely inspected. This looks like a symbol for "ground" and probably applies to the stud connected to the chassis to its left. Those of you following my rebuild of one of the heating element terminals will see that a threaded stud is now inserted into the rebuilt epoxy and glyptal structure.



I left the old wiring harness mostly assembled. This should help reconstruct the connections. You can see that the prior owner, who knew enough about electricity to label it, did so with numbers and indicated which switch goes to which heating element. But he was going to re-use the old frayed wire ends. My take on the layout is that the switches are wired in series, with the 300 W switch upstream from the 1000 W switch and the red lead numbered "1" being the hot lead to the 1000 W element and the loose end on the bottom of the photo coming from the 300 W switch going to the hot side of the 300 W element. From the first picture in this series, silver wire 4 goes to one pole of the thermal safety switch, but I'm not sure which pole. Closer inspection shows me that each switch has only two tabs with the off setting to the left on each. Fortunately a wiser soul preceded my fumbling by scratching "on" to the other side of each switch. The black wire that goes to the "on" tab on the 300 W switch then goes to the "off" side of the 1000 W switch. The "off" side of the 300 W switch is a brown wire that twists together with another brown wire and seems to be a ground that connects (per the above picture) to one of the heating element terminals connected by a bar to the other. Another brown woven wire connects to the hot side of the 300 W heating element per one of the photos above, where the loose silver woven wire went to the grounding contact on the chassis.



To remedy the condition of the old wiring harness, I ordered a replacement from Orphan Espresso's junk yard, and here's what that looks like.



And all of this is going to reinsert into a newly powder coated base.

Hm, it seems to me that the 300W switch is a single-pole double throw switch; the center pole is wired to the power source, and the switch selects between the 300W element or the 1000W switch. In this way, when the 300W switch is on, the 1000W is off; when the 300W switch is off, then the 1000W element is on if the 1000W switch is on, or off if the 1000W switch is off.

Is it desirable to have 300/1000 settings, or do you want 1300W ?

Here's a conceptual schematic I whipped up before I noticed that you had the switches connected in that funny fashion...

The switch with the squggle is the thermally activated switch (the L135 in the part number means it opens at 135 degrees C)

The boxes are the heating elements.

I'm taking the approach that the hot wire should be interrupted by the switches such that when the switches are off, the hot wire is disconnected. It should be okay to interrupt the circuit with the thermal switch by breaking the neutral wire, however I do not know if this is to code. I am not an electrician, and as noted, any heed you pay this is entirely at your own risk.

NOTE that this does not appear to be how your unit was originally wired; this schematic describes a way to have each switch independently control each element. That gives you 300/1000/1300W settings depending on if one, the other, or both switches are closed.

Interesting, and thanks for that, Allon. I'll post close-up pictures of the switches and other elements in the circuit later in the week in case that helps. Later add: What software did you use to make that nice illustration?

How would you diagram the way the machine was wired, and how could that make controlling it different?

BTW, I've written to the earlier owner to see if he remembers his numbering scheme, and I may be able to look at another one still wired in Christopher Cara's shop, although I don't believe that machine is a functioning one.

Okay. Now I get it. You do describe how to connect the switches as I discovered them and what that would do. Perhaps their connection in series is a temperature regulation scheme, one that keeps the machine from overheating as easily if the most power available is 1000 W. I lean toward connecting it as designed, especially if that's the case. This makes me want to take a walk over to Cara's so I can look at that machine.

drgary wrote:Interesting, and thanks for that, Allon. I'll post close-up pictures of the switches and other elements in the circuit later in the week in case that helps. Later add: What software did you use to make that nice illustration?

How would you diagram the way the machine was wired, and how could that make controlling it different?

The program is OmniGraffle: http://www.omnigroup.com/products/omnigraffle/

Here's how I think it was originally wired:



There are two switches and four possible states. I'll call the lower (300W) switch "sw1" and the upper (1000W) switch "sw2"; bold upper case is on, lower case is off:

sw1 sw2 - off
SW1 sw2 - 300W
sw1 SW2 - 1000W
SW1 SW2 - 300W


In my previous schematic diagram, the states would be almost identical, with the exception that the last state (both on) would be 1300W.

I just redid the electrical and switches on a Faemina which uses a single hi-low switch to much the same effect with a 200w and 800w elements. The 200w is always on (once the power is flipped on), and the hi switch engages both elements. The wiring diagram can be seen at the bottom of: http://www.orphanespresso.com/Faema-Fae ... 00-1.html.

The center post on the hi-low switch is wired to the power source, the 800w element to either one of the other posts. The third post is empty, which results in just the 200w receiving power. The elements themselves are wired the same as depicted in your pictures with the negative on both terminals bridged.

Not identical, but same idea.

Thanks Allon and Mike,

This gives me much more to go on. I walked over to Cara's to check out his machine and unfortunately it's not a useful reference point. When he consigns his machines to antique, display status, he takes out the wiring for safety reasons.

Later add: Is there a way to test the circuits before powering up? When I eventually do power it on, I'll have it on a ground fault, the machine filled with water, and will wear rubber gloves while standing on a dry floor. I promise!

Ha! You just described the scene in my house last Sunday when I powered on for the first time. I used a multimeter to test out the circuits and resistance. I still worried about the pop, the whiff of ozone and the death of my poor little lever.

It's not a difficult wiring job once you get your head around what the design is doing.

If you have a multimeter, measure resistance between the blades of the plug --

Check ground pin on plug to case -- should be 0 ohms
For each of the four power switch states, measure each blade to ground - should be open circuit no matter what.
For each of the four power states measure blade to blade.

Should be:
Open circuit with both switches off
About 2.5 ohms with 300W switch on (1000w switch either way)
About 8.7 ohms with 300W switch off and 1000W switch on.

If you're really ambitious, use a heat gun and thermocouple to gently raise the thermal cutoff switch to 145-150 degrees C or until it opens the circuit, should be around 135 degrees C. If it doesn't open, then replace it.

note: you'd have to be very gentle with the heatgun; I'd consider running it with a variac, and raising the temp slowly; this is only necessary if you don't trust the thermal cutoff and want assurance that it works.

Great help! I'll report back when I've got this going.