Community Forums

YC1 · 01-05-2023, 08:19 PM

Yeah I tend to toss out the dielectric term a bit too loosley. I use a silicon grease as well. Just a thin film of anything to help keep the oxidation down. Tight connectors are important of course.

Old Scout · 01-05-2023, 09:39 PM

Hey Mark, YC1 provided a great explanation of the "Bubba" pedestal. In this case, Bubba was only part of the problem. The real "red flag" was using a 30-amp cord on a beautiful, big coach like yours which normally needs a 50-amp service. But not really your fault, it amazes me that the "industry" even permits adaptors that allow the integration of a 30-amp cord into a 50-amp circuit. The 50 to 30 adaptor eliminated the phasing issue as only one leg gets thru, but it was likely 50 amps if Bubba changed it. Then the 30 to 50 adaptor splits out the single 30-amp rated cord and fed both legs of your coach. Newer coaches with modern energy management systems might have caught this and shut down the circuit--or perhaps not?

markpj23 · 01-06-2023, 05:54 AM

Quote:

Originally Posted by Arch Hoagland

Mark...Do you turn off the breaker before plugging and unplugging from the pedestal?

Yes every time.

markpj23 · 01-06-2023, 05:58 AM

Quote:

Originally Posted by alank

I have a bit of a different take on all the Bubba connections made here.
The picture of the plug appears to be a 50A plug that has the neutral burned. Normally if the coach 50A plug was put in a properly wired socket, the neutral spade would only carry the current difference between L1 and L2.
Adding a 30/50 adapter takes power only from one slot of the 50A plug and conducts that current through the 30A extension cord. Using a 30A source of power requires you to be very careful about the number of things you try to run in a 100A coach.
The original plug was a 30A plug, which Bubba switched out to a 50A socket, so the original 30A wire was connected to both sides of the 50A socket and in phase. Also in Bubba fashion, he may have switched the original 30A circuit breaker to a 50A circuit to better match the 50A socket. Now you would have 50A of current available to draw through the 30A extension cord that was used. Could be a bit of an overload there.
Since the failure was the neutral prong in the 35/50 adapter, I would suspect the female part of the neutral connection was in very poor condition and provided a very poor electrical connection for the current path resulting in the heat that burned the connection.

The adapter was actually brand new, and the coach shore power plug prongs were in good shape.
My fault for using the 30a extension cord. I have a 50a extension on my shopping list. Next step is to check the pedestal connection to see if bubba has been there or not.
In the meantime, and also if we do have a 'bubba 50,' we set the EMS to 30a and live with one AC unit running.

bigb56 · 01-06-2023, 08:27 AM

Quote:

Originally Posted by alank

Just as a point of interest for discussion, read the label on the dielectric grease tube or look up the definition. Dielectric means "NO Electric", it's an insulator and resists the flow of electricity, so why would you ever put it on the prongs of an electric plug? There is conductive greases for that purpose.
The purpose of dielectric grease is to prevent corrosion and leakage of electrical connections after the clean, dry, electrical connection is made. Then apply dielectric grease to help prevent any voltage leakage to other conducting components and reduce corrosion at the joint.

I might note that the posts of a plug are what can be cleaned, it's the slots that can't be effectively cleaned.

There has been extensive discussion on this so I won't go into the details but will note that dielectric grease does not interfere with conductivity, that is a myth. When applied to a terminal before the connection is made it gets pushed aside and the areas that make contact when tightened are now protected against corrosion (oxygen, moisture etc). It does not prevent or inhibit contact, it merely protects it, making for a longer lasting connection. Further, the only difference between dielectric grease and conductive grease is that conductive grease contains metallic powders and in some cases can lead to corrosion thru galvanic action of dissimilar metals when the metal powder is not compatible with the base metals.
I've been using dielectric grease all my life with good results. I only use conductive grease for thermal conduction on certain electronic components. As far as the camp site connection, I don't do anything to it except make sure it's tight. If the 30 is loose and worn I use the 50, which is seldom, if ever worn badly.
The link below explains the mis-understanding of dielectric grease, there are more regarding conductive grease and it's dis-advantages when used with dissimilar metals which you can find by reading some of the case studies.

Not trying to tell anyone what to do, you should do your own research and reach your own conclusions which is exactly what I did and I am totally confident that I made the right decision, especially after all the years of successful connections I have behind me.

https://www.nyelubricants.com/myth-g...h-conductivity

THenne1713 · 01-06-2023, 03:33 PM

IF use of L1/L2 = balanced, then Neutral current=zero?, but if all loads on L1, then L1=N, and if Unbalanced 10+40, then Neutral can be 50a? (or something like that? :-) , but LOOSE screws/ bad solder joints/ frayed/broken strands in cord/plug = HEAT/MELT are the USUAL culprits.

oldenavy · 01-06-2023, 04:27 PM

The attachment YC1 provided is very helpful, but it has a glaring error. Their diagrams show the voltage values on the sine waves as peak values but the values we are tossing around are RMS (root mean square), not peak. For example, a typical 120 volt outlet is 120v RMS which is actually about 170v peak (120*sqrt(2)). The diagrams show the peak values to be 120 & 240v.

Sorry to be picky but I teach electric power systems. That company gets 7 points off their homework for not knowing the difference between peak and RMS.

YC1 · 01-06-2023, 04:30 PM

Brian, thanks for that link on the dielectric grease use.

I felt a bit sheepish when someone said I should not use it. This after more than fifty years of using it or some other forms of simple grease after cleaning contacts.

So I thought perhaps I was simply using the term a bit too loosely.

Your link gives me back the confidence to once again use my recommendation.

Even after more than fifty years it is fun to learn new things. And having articles to support those old habits as well.

YC1 · 01-06-2023, 04:32 PM

Thanks for the support on the use of dielectric grease. It caught me a bit off guard when someone challenged my recommendation of using it. Having used it or simple silicon grease for fifty years and never had an issue but I never want to give bad suggestions on this or any other forum. Suggest using WD 40 and some folks lose it. A thin layer for me has worked as well. Great article you referenced.

bigb56 · 01-06-2023, 05:01 PM

Quote:

Originally Posted by YC1

Thanks for the support on the use of dielectric grease. It caught me a bit off guard when someone challenged my recommendation of using it. Having used it or simple silicon grease for fifty years and never had an issue but I never want to give bad suggestions on this or any other forum. Suggest using WD 40 and some folks lose it. A thin layer for me has worked as well. Great article you referenced.

Yep, when I was young and we didn't even know about dielectric grease we would put wheel bearing grease on our battery terminals. Another trick is to tighten the battery terminals down then hit with spray paint

YC1 · 01-07-2023, 08:42 AM

I used vaseline for years on battery terminals. Anything to cut off the exposure to gasses.

alank · 01-07-2023, 09:55 AM

So much good discussion here, and the devil may be in the details. I never claimed that dielectric grease prevented an electrical current, just that the best connection was a clean dry connection, then add dielectric grease for corrosion prevention and leakage. This is much like everyone is saying as bigd56 said above, in bolting the battery clamps on tight, then put on the spray paint, not putting the spray paint on everything, then bolt the battery clamp on tight. I agree with the battery spray paint, which my coach has from the factory, bearing grease will help, I have WD40 in my battery bay for the terminals, and dielectric grease is good, all to be put on after the clean dry electrical connection is made.
To help prevent battery post acid corrosion, be sure that the little vent hole in the cap next to the post, is pointed away from the battery post to direct the off-gasses away from the post. I also run mineral oil in all the cells on top of the water to cut down on off-gassing.
Grease, by its very nature creates a very thin separation between metal parts allowing them to move more easily against each other. Some greases allow electrical currents to flow much more easily between the metal parts than other greases.
As for the video that bigd56 provided, I don't disagree with anything they presented. Here is where the devil is in the details. In my post #8 about dielectric grease being a bit of a non-conductor, I also mentioned that there are greases to enhance the conduction of electricity. If you paid attention to the narrative and the print on the video, they are demonstrating the performance of their "electrical conductive grease", they never describe their product as a dielectric grease.

If you like using dielectric grease on sliding connections such as the 50A plug prongs, go ahead and use it, you probably won't notice any difference in your coaches electrical performance, I just don't think it's the best product for the job.

Thanks everyone for your input.

Bigceasar · 01-07-2023, 10:21 AM

I’m confused as to your use of a 30amp extension cord. Did you plug in to the 50 amp receptacle on the pedestal with a 50 to 30 amp adapter, then connect the 30 amp extension cord, then adapt back up to the 50 amp cord on your RV? If you did something similsr to this you would not have a 30 amp breaker protecting that 30 amp extension cord effectively turning that cord into a big long fuse. Since the coach could draw 50 amps per leg and the pedestal provide 50amps per leg , that 30 amp cord could be overloaded by 60%.

alank · 01-07-2023, 11:49 AM

Quote:

Originally Posted by Bigceasar

I’m confused as to your use of a 30amp extension cord. Did you plug in to the 50 amp receptacle on the pedestal with a 50 to 30 amp adapter, then connect the 30 amp extension cord, then adapt back up to the 50 amp cord on your RV? If you did something similsr to this you would not have a 30 amp breaker protecting that 30 amp extension cord effectively turning that cord into a big long fuse. Since the coach could draw 50 amps per leg and the pedestal provide 50amps per leg , that 30 amp cord could be overloaded by 60%.

My take on your question is this, the shore power pole was 30A. The OP parked a 50A coach in the spot, and Bubba, being a good guy came and put s 50A socket on the pole for the coach plug. Both slots on the 50A plug would have most likely been on the same leg from the transformers, but we don't know for sure. If that's the case, the line would have been protected by the 30A circuit breaker, so the 30A extension cord should be fine. Question is, Bubba being such a good guy may have added a 50A breaker in place of the original 30A breaker, so it would match the 50A socket. Then we may start to have a problem with the overload. We don't know all the details of what happened.