Rocket Appartamento Scorching Wire Connectors - Page 3

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
Nunas
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#21: Post by Nunas »

It was Molykote 111, if that changes anything. It's running fine as-is, so I'm a bit hesitant to pull the terminals and clean them off if I don't have to and stress them out in any way.
Molykote 111 is a silicone oil. If you only put on a thin film, I think you're good to just leave it. As for the connectors, leaving them alone, once installed, is the right call. Every time they are pulled apart/put back together, one risks degrading the integrity of the joint.
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DeuxInfuso
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#22: Post by DeuxInfuso »

I gently disagree with Maurice's concern about grease on electric junctions presenting a fire risk. Silicone paste grease such as Dow Molykote 111 or Triflow synthetic grease is safe inside electrical junctions. I've made thousands this way, and they never fail. I recommed using synthetic grease on all the metal contact surfaces of all electrical connections to prevent corrosion at the faying surface (the point of contact where electrons travel from one surface to the other). Grease is an insulator (dielectric), true, but it doesn't interfere with the connection, the electrons find a way!

The grease film is thin, and synthetic silicone grease does not easily burn, at least in my oxy-acetylene experiments trying to ignite it; it just turn into a puff of smoke and white powder at about 450/500 F. The application of synthetic grease to the metal contacts on power plugs & sockets, and to contactor surfaces such as relay contacts on pressure-stats, is WIDELY USED by experienced physicists, chemists, electrical engineers, submarine electronics techs, cell phone tower installers, ham radio operators, etc. And you should use it on your espresso machine connections. You solder all junctions you can, and you silicone grease all junctions you can't.

This technique is safe and is used in electronics in many hot, humid & salty environments including boats and submarines and automotive connections and radio antennas and electronic components going down water and oil wells, subject to water incursion, rain, humidity and salt water. The grease ENVELOPES THE METAL/METAL POINT OF CONTACT. The electric connection is guaranteed by the voltages involved, and if the connection is so loose it may spark and ignite something, then more care should be taken to ensure tight connections during instalation.

The grease excludes oxygen and moisture from the slightly warm spot where the current jumps across at the contact patch. This slight resistance causes local heating due to the electrically imperfect junction at the contact patch, which sometimes has a reduced surface area metal/metal junction compared to the conductor cross sectional area. By excluding oxygen & moisture with grease, the positive feedback loop between resistance heating and corrosion is stopped.

When exposed to a little heat, moisture and oxygen, the silver or tin electroplating on brass or copper electrical connectors oxidizes. Oxides are nonconductors. Over time the electrical junction quality degrades and more resistance heating develops. This promotes more oxidation. The positive feedback loop between heating and oxidation continues until the materials burn up or the insulation melts and it burns open, or you get a short to ground. This process causes burnt wires or insulation, such you see in the original photo, or it anneals the copper such that it loses its spring grip on the spade plug, and it opens the connection. In your espresso machine, it usually occurs first at the leads to the heating element, but any high current junction is susceptible.

Cheers!

-Deuxinfuso (former submarine electronics tech)

achosid (original poster)
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#23: Post by achosid (original poster) »

After a couple of nice weeks:



Another schorch. This is the sole wire in this area of the machine that I didn't replace, given the complexity. Is it worth totally replacing this wire, or should I assume I biffed the connector somehow and take another swing as-is?

Nunas
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#24: Post by Nunas »

Given the location of the scorching, it's a bad crimp, not a bad connection between the male and female connector. Cut the wire back to bright copper and install a new connector. Be sure to use a quality connector and attach it using a ratchet style crimper. Given the condition of the insulation on the wire, however, you may have to replace the wire, as cutting it back may result in the wire being too short.

achosid (original poster)
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#25: Post by achosid (original poster) »

That's good to hear. Getting a good crimp on these thinner wires is difficult. Any tips?

Nunas
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#26: Post by Nunas »

Sure, If the wire is too thin to fill the connector, you can cut back the insulation farther, double over the copper and then insert and crimp. It isn't exactly SOP, but it works. If you have to replace the wire, you can go up a size; bigger is always better. Given the heating and discoloration of that connector, I'd say that the wire is handling quite a bit of current. I don't know if it's still true, but on older machines, they used the same wire for the 220-volt version as they do for the 120-volt version, despite the fact that the current is twice as high when halving the voltage.

Pressino
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#27: Post by Pressino »

achosid wrote:That's good to hear. Getting a good crimp on these thinner wires is difficult. Any tips?
I notice that the burned turquiose colored wire does appear to be thinner than the other wires, which makes me wonder if besides a loose terminal crimp the conductor may be marginal for for current carried. If the wire is indeed smaller than the other (light blue) one, you might conider replacing it with the same gauge wire.

achosid (original poster)
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#28: Post by achosid (original poster) »

Pressino wrote:I notice that the burned turquiose colored wire does appear to be thinner than the other wires, which makes me wonder if besides a loose terminal crimp the conductor may be marginal for for current carried. If the wire is indeed smaller than the other (light blue) one, you might conider replacing it with the same gauge wire.
This thread has gone on for some time, so I don't expect folks to dig deep into the history, but back in post 14 I detailed how I replaced the other three wires in this area of the machine with thicker wiring. Re the last wire, per homeburrero in post 17:
homeburrero wrote:That's a DIN plug that powers your solenoid. The two blue wires both connect inside there and provide neutral to the coil and then on to the thermoswitch and element. The coil doesn't draw much current but those blue wires do carry the full neutral current from the element. I wouldn't worry about trying to beef those wires up, but if you really wanted to do that you may want to run a long heavy gauge wire that replaces both those two blue wires all the way to the thermoswitch, and tee off a branch from that wire (from anywhere convenient, and doesn't need to be heavy gauge) just to the solenoid.
Given the substantial rewiring required and the role of that wire, I'm hoping to avoid having to swap it out. If this current crimp doesn't fix it, though, I assume that's my endgame here.
Nunas wrote:Given the heating and discoloration of that connector, I'd say that the wire is handling quite a bit of current. I don't know if it's still true, but on older machines, they used the same wire for the 220-volt version as they do for the 120-volt version, despite the fact that the current is twice as high when halving the voltage.
I expect the 220/120 swap is the issue here, though this machine is only 6-7 years old.

Pressino
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#29: Post by Pressino »

As regards the idea that the thinner turquoise and thicker light blue wires are meant to carry different currents, the fact is they will carry the same current when the fused switch is closed. The 220/120 issue is real enough, and if that is the case it's another reason to increase the ampacity of that and other wires involved in carrying significant current.

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homeburrero
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#30: Post by homeburrero »

Pressino wrote:As regards the idea that the thinner turquoise and thicker light blue wires are meant to carry different currents, the fact is they will carry the same current when the fused switch is closed.
I don't think anyone is under the impression that they carry different currents. The thicker wire was easy to replace but the thinner wire, with the far end in that DIN plug was trickier so it remained with the factory wire.

The issue here is whether the factory wiring loom is adequate for 110 machines that carry twice as much amps as a 220V would. Rocket engineers clearly believe that it is. We do see a lot of melted connectors with these machines but I think they are all related to bad connections or crimps rather than inadequate wire ampacity.

P.S. The parts list indicates one wiring loom for all machines. They do have different power cords for different machines, but I don't know if the 100-120V cords use a larger gauge. For power cords the ampacity is more critical than chassis wiring because of the two current carrying wires together inside the cord.
Pat
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