1963 Globe Trotter

[lbell]

Am refurbishing this unit. Not an electrician.

Noticed that the kitchen sink has a ground wire from a mouning screw to a screw on the interior shell.

All electrical outlets are 2 prong only. The box is a 15amp 110 service only.

Is this original? Where is the ground coming from? What are your recommendations?

[TomW]

Originally Posted by lbell

... Is this original? Where is the ground coming from? What are your recommendations?

I don't know if this is original, but I would leave it.

The interior shell is usually tied to the shore power ground. Grounding the sink in the way it is would help keep you from being electrocuted if you should accidentally bump the toaster, for example, into a sink full of water & reach in to get it.

If you are curious, you may want to get your ohmmeter out, and measure the resistance between your 15 amp service box shell, and your Airstream's skin. I will bet you will measure close to zero ohms resistance.

Tom

[Jim Jarzabek]

What you have are original ungrounded two prong outlets. Perfectly safe. New ones can be purchased to replace the old. Do not purchase or install grounding type with the third pin at the bottom. For extra safety, you could have the electrical panel changed and install g.f.c.i. (ground fault circuit interruptor) circuit breakers for extra safety. Only have this done by a qualified person.

Good luck!

[Jim Jarzabek]

The original poster discovered a "bond" wire and not a "ground" wire. The two serve different purposes. Two prong outlets were used during this period and new replacement two prong outlets are available for replacement purposes. The original poster did not mention any problems with stray voltage when touching the sink. An ohm meter is only as useful as the person using the instrument. Readings can vary depending on atmospheric conditions and the reference point to "ground". A 43 year old travel trailer will have some type of corrosion. Without getting technical and without other concerns being presented by the original poster, replacing the two prong outlets would suffice. Adding g.f.c.i. protection to the wiring at the circuit breakers would add extra protection. The poster should already be plugging into a g.f.c.i. 120 volt 15 or 20 amp circuit already, so this may be redundant.

[65CV]

I echo the GFCI recommendation -- it's cheap insurance, especially if you can't inspect all connections. The wiring in our '63 Globetrotter was updated, so I can't make a comparison. If you do have BX cable, you can consider the 3 prong replacement if the third leg is properly grounded through the shield on the BX.

On well-built boats, large metal objects are grounded for lightning protection. Is this what the original builders were up to?

63GT

[Jim Jarzabek]

Bond wires are used to maintain an equal potential return path in lieau of the normal return path; i.e. if the current returns on a path other than the intended neutral. This way, in theory, there is a balance and electrocution is minimized. Armored cable from this period was not intended to have the outer jacket utilized as a ground.

[lbell]

Thank you for the help. Like the GFCI breaker idea for safety.

[C Johnson]

On my install of the new electrical panel I put a central GFCI on the circuit that powers all of the outlets. It is mounted under the panel in its own electrical box. Here is a picture of what I did. I now have 4 separate circuits plus a separate main to shut everything down at once. I wired the ground exactly as it was in the old electrical box. Do not tie the white and bare ground wires together as you would in a house.

Chris

PS - Since I had the inner skins off I put all new grounded outlets in the trailer and replaced wiring as needed.

[TomW]

I missed this thread after making my last post to it. The traffic it has received warrants clarifying a few issues.

zero ohms between you and ground is extremely dangerous.

Yes it is. My original post suggested checking the resistance between the skin & the breaker box - Not between the user & anything else.

Originally Posted by 65GT

...In ESD safe environments there is always a 10K ohm resistor between whatever it is you are working on, your ground mat and true ground for your protection...

That resistor is, by design, fusible. It will blow to keep the person attached to the ground strap from being electrocuted. Most companies require wrist straps be verified on a separate device on a routine basis because the resistor gives up easily.

The original poster discovered a "bond" wire and not a "ground" wire.

Jim, you lost me somewhere. My take is that both bond & ground wires, in this application, would serve to protect the end user. Did I miss your point?

The poster should already be plugging into a g.f.c.i. 120 volt 15 or 20 amp circuit already, so this may be redundant.

Wishful thinking around here - Nothing like that in the bulk of campgrounds I have visited.

Ibell - Your safest course of action is to install GFCI breakers in your Airstream after ensuring that your shore power is properly wired for ground (three pins on your shore power plug).

Tom

[DavidsonOverlander]

Originally Posted by Jim Jarzabek

What you have are original ungrounded two prong outlets. Perfectly safe. New ones can be purchased to replace the old. Do not purchase or install grounding type with the third pin at the bottom.

Can you explain this, please? If I want to run something that has a 3 prong plug (like a microwave) should I cut off the third prong so it will fit? That doesn't seem like a good idea.

Couldn't new 3-prong outlets be installed and grounded to the trailer since the trailer is grounded through the 30 amp cord when you plug it in? I suspect from your post you're going to say no, but I'm not sure why.

Thanks,

[TomW]

Originally Posted by DavidsonOverlander

...Couldn't new 3-prong outlets be installed and grounded to the trailer since the trailer is grounded through the 30 amp cord when you plug it in? ...

Yes; while this implementation would not fit current code, it would serve to protect the user. It certainly meets the intent of the code.

I think I know what Jim is getting at, but it is not coming out clearly. Hopefully he will catch this thread & end the confusion.

Tom