Connectors don't fail on airplanes because then the fall out of the sky and people die. No one make sure the connectors in an espresso machine are suitable for the job. Most of the traditional European machine I've worked on use 1/4" brass Faston terminals connected to what often seem to be tin plated connectors on the mating parts. If they really wanted to solve the problem they'd use silver plated connectors on all the high current applications.

An espresso machine is a hostile environment and at least for home machines there does not seem to be much thought put into the wiring, or at least not into it's ability to survive a long life.

And while a 1/4" Faston is rated for 15 amps and espresso machines don't pull 15 amps, I'm guessing that rating is not in a 100C humid environment.

The work fine 99.9% or more of the time, they are not generally hazardous when they fail, they are easy to come by and inexpensive so they are still used.

When I rewired my first car after the loom caught fire one evening, I use bigger wire for everything that carried current, used better connectors wherever I could, put heat shrink over all the crimps to help keep them clean and dry and weirdly when I was done all the problematic Lucas electrics were not problematic any more.

You also need to ask, what equipment is used to build the harnesses and how consistent are the crimps. The OEM crimps I've seen look like they are don't properly, but how often do the check crimp height and all the other things that matter. The crimper I use in my company is $5000 and every different pin requires a $2000 applicator, the CNC wire stripper was $9000, but I know that the product we ship is consistent. Then again our crimps only carry 10ma so not much of a worry about perfection.

Making them live longer on average would not be that hard, but it would require the whole industry to change and it would be expensive to fix something that rarely breaks.

Conceptually if the crimp is done properly, there will be no room for the solder to flow. It's pretty commonly not recommended to solder crimps. I've personally never seen a problem with it, but if the solder wicks past the strain relief and the wire is subjected to vibration or movement it will tend to fail where the solder stopped flowing.

Yeah - again that's kinda my lack of faith in my own crimps. I've usually just added a drop of solder to the bare wire ends stick out toward the spade side...not sure if tinning ahead of time is going to help all that much given how it'll probably hamper the initial crimp. Anyway I'm pretty sure this doesn't wick past the second crimp around the insulation, so for heating element or high limit connectors (where I've been having a problem with overcooked plastic covers), I don't see vibration being a problem.

Since the screw terminals were mentioned, I am thinking of replacing the original mains power connection (screws on the cord side, spades leading to the main toggle switches) with a terminal block, mostly to get it away from the solenoid fill valve in my cramped machine. I've wondered about the connection quality on those; If I use a ring connector and the screw heads are ridged, does that do a surface wipe (similar to spades) when you torque the screw down, or are these relying on the high clamping force of the screw to deform the connectors? Are those ring terminals doing anything other than convenience of not wrangling bare wire strands?

Conceptually bare wire makes the best contact. If I wanted to do that in an espresso machine, I might slip a piece of heat shrink over the wire, strip about 3/4 or 1 inch, twist tightly, wrap it around the screw, then wrap the end around the wire so it doesn't pull out and then heat shrink the wire. Likely not very vibration resistant, but the best possible connection as the wire will flatten out a bit and make an excellent connection. But a good crimp to a high quality ring terminal will likely do as well and be a lot easier to work with.

I finished the re-wire this weekend - getting a good pic in that tight environment was too elusive.

The connector package specifies the crimp or solder method to be used in order to meet their published specification. It is against code to use solder if crimping is specified or vice versa.

The reason the hot connectors melted was because the heating element dissipates energy into the heating element. The wiring diagram I published for the Club was proven to be dead accurate, (uh, bad term) - was proven correct. With the diagram, tracing the hot wire from the socket to the heating element showed the wire temp was just high enough to cook all of the plastic connectors. After the heating element all wire connectors were below the heat specification.

Never buy anything electrical for an espresso machine at Home Depot. Silicone may or may not be up to the heat spec; the silicone wire I posted literally flaked apart to expose bare copper. Amazon or McMaster Carr has the temperature rated materials that should be used.

My electrician consultant, who teaches at the trade school, said he'd go with stranded 12AWG wire in a 1350watt machine. He said bare stranded wire gives greater surface area contact. His view is this is a harsh environment for materials.

I am thinking about editing my prior posts to highlight where they are ill advised.

Jake_G wrote:I was thinking the likely spot for poor contact is between the connector and the device, not the crimp to the wire.

I understand the critical look at heat ratings of electrical devices trapped in a poorly vented box with a heat source, but I still don't understand why the phase lead would be subject to higher temperatures than the neutral.

Any further thoughts on this?

When I bought my first Club all of the parts were still available to buy and I did some stockpiling. When I restored this machine I was able to use all NOS components.

I emphatically agree with ira's point:

ira wrote:Connectors don't fail on airplanes because then the fall out of the sky and people die. No one make sure the connectors in an espresso machine are suitable for the job.

We're crimping the stew out of the wire, only to affix it with wimpy spade connectors. The HomeDepot low temp/voltage connectors slide right on. The McMaster Carr connectors are made of different metal, are stiff and have very tiny gaps - they were extremely difficult to connect. I broke the micro-switch on the pstat trying to make a connection. That made for a perfect sizing tool for the new connectors, which I had to sort through to find those that weren't too tight. The new connections affixed so tightly it won't be fun to revisit them.

My other Club is untouched from the day it was made until I started using it. To ira's point, Olympia didn't do the best job to ensure the proper connectors were spec'd. I had a wire on the hot side literally fail at the connection due to heat and corrosion just before I restored this Club.

To answer your electrical question, there is greater heat on the hot side because of the resistance of the heating element. It's something like water flowing toward a dam, the reservoir is resistance and that elevates the temp.

The other point I'd like to raise is silicone insulation does not mean it has the correct temperature rating.
Note the blue wire leaving the pstat on its way to the power switch:


This is the same blue wire after 90 days:


The portion of the wire inside the red box is that same blue wire. The especially toasted portion of wire is what you see in the before picture as a nice blue wire. There used to be insulation all the way to the spade connector and that blue connector looks like the way my buddy liked his marshmallows at the campfire. The heat baked off the insulation, leaving bare wire.

The wire I used, which ira mentioned, is temperature rated to 200C, shown below. I added fiberglass sleeve with the same temp spec instead of silicone to reduce amount of exposed connector/wiring. Due to the amperage involved, if wires or metal is too close electricity will jump.

First off, great stuff regarding cheap spade connectors vs higher quality ones. Couldn't agree more. It is unclear to me whether any of the high quality connectors failed. Did they?

jwCrema wrote:To answer your electrical question, there is greater heat on the hot side because of the resistance of the heating element. It's something like water flowing toward a dam, the reservoir is resistance and that elevates the temp.

Couple arguments against this:
First, that simply isn't how heat is generated in electrical devices. Heating elements get hot because of the resistance across/in them. They are constructed out of a resistive element that is inside the protective casing. There is no heat generated outside of the resistance element on account of it being in the circuit.

Second, even if there was some sort of "reservoir and dam" effect that causes elevated temperatures on the "inlet" side of a resistive heating element (which there isn't) , we are talking about an AC circuit. This means the current is alternating and flowing equally in both directions, thus any such "preheating" effect that the line side might see would be equally present on the neutral.

I think cheap connectors are to blame, but I welcome more discussion on alternatives.

Cheers!

- Jake

Jake_G wrote: I think cheap connectors are to blame, but I welcome more discussion on alternatives.

Cheers!

Here is the crux of the mystery: In the few pictures I posted, every single hot side connector is burnt and insulation toasted. Not one of the connectors on the neutral side show any signs of heat. The same wire, connectors and crimping tool were used throughout all of the wiring. I really wanted to get holistic picture of this, because it was a stunning contrast.

While I hear what you're saying, I have "burnt" v "everything was clearly within temperature specifications". The evidence eliminates the connector/wire as the culprit. The only change I made last week was to replace the hot side wire and connectors; the neutral side all looks like the day I installed them 90 days ago, so I did not replace any of them.

Sometime in June, (+90 days from now), I'll open the machine up and see how the higher spec connectors and wire fared and I'll bet you a shot of Doma Chronic the neutral side cheap connectors/wire will look just like they do today. I'll drink it if I win.

I sent a PM to OldNuc, who used to weigh in on electrical issues, but I noticed he hasn't posted since 2019. I found his observations on electrical issues to be similar to Dr. Pavlis on the topic of in-organic chemistry and espresso.

Some day I might do a complete wiring rebuild with the same materials, but I'm more interested in understanding what is happening.

So sad to hear about OldNuc. I guess my sense of him being a smart dude wasn't far off the mark? A nuclear engineer! RIP Rich