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. I'll add more to this "pre-introduction" as they become relevant. For now, here are three highlights that exist further on in the thread. (Perhaps someone can show me the code to use on this site to show the link as the title of the post instead of the title of the thread.):

How to Think Like an Electrician at this link. (Ignore the underscored link title. This will take you there): Rewiring a La Cimbali Microcimbali

Making Sure Circuits are Connected and Not Shorted. (Ignore the underscored link title. This will take you there): Rewiring a La Cimbali Microcimbali

Online References to Get You in the Ballpark. (Ignore the underscored link title. This will take you there): Rewiring a La Cimbali Microcimbali

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_wiring_in_North_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/Resettable-Thermal-Safety-Switch_p_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.

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.

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!

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