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Question Voltage detected in extension cord

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Hey Mike,

I have enjoyed your J.A.M. articles over the past couple of years and found them to be very informative and helpful.  I was quite interested in your 'hot skin' video, purchased a Fluke voltage detector and tested my Lance 2465 travel trailer.

Fortunately, there was no evidence of a 'hot skin' condition on any metal in the RV or stairs, but to my surprise the extension cords and adapters detected voltage! 

The extensions are connected as follows:  50amp outlet to a Watchdog surge protector to a 50 - 30amp adapter to a 30amp 50' cord to a 30 - 50amp adapter to the RV 50amp cord.

Voltage was detected on the 30amp extension cord, both adapters, RV 50 amp cord and screw at the point of connection to the RV.

Is this condition caused by dropping from 50 to 30 and back to 50amp?  Is this a condition to be concerned about?

Thank you,

Charlie Kissling

 20221208 102952

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Posts: 121


Actually, that’s exactly how all Non-Contact Voltage Tester are supposed to work. Yes, they will detect a voltage when pointed at an extension cord as you describe. I’m the guy who figured out you could use a NCVT to discover a hot-skin voltage, but the outlet and extension cord testing is what they were designed to do. Here’s a video of me demonstrating a dual-range Southwire NCVT which I really like.

Danger, Will Robinson

However, if I’m reading your connection description properly, by inserting a 30-amp extension cord in the middle between a 50-amp outlet on the pedestal and the 50-amp inlet on your RV, you’ve created a very dangerous fire hazard. There’s nothing to stop you from exceeding 30-amps of total current draw in your RV, and the pedestal will happily supply more than 30 amps without tripping the 50-amp circuit breaker. So you could easily start a fire in that extension cords or one of the 30/50 or 50/30-amp adapters.

I’ve had a few readers who stepped a 50-amp pedestal outlet down to a 15-amp extension cord, then stepped it back up to a 50-amp RV inlet. That’s WAY more dangerous since a 15-amp extension cord with even 30-amps of current can easily reach the boiling point of water in 5 minutes. Here’s a video I made a while ago demonstration this.

If you did have a fire the inspector (and insurance company) would look at the connection very closely and could refuse to honor a claim. Please let me know if I’m misreading your description, but if not then I recommend you plug into a 30-amp pedestal outlet or use a 50-amp extension cord (yes, I know they’re heavy).

Let’s play safe out there - Mike

This post was modified 2 months ago by Mike Sokol

 Charlie Kissling
(@Charlie Kissling)
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Joined: 2 months ago
Posts: 1

Thank you for the response Mike.  Yes, I have a 30amp extension between 50amp shore hook-up and 50amp RV plug.  However, I am aware of the heat risk (resistance) if more than 30amps are pulled.  In this case, the RV is parked unoccupied.  Power is used for lights, tending the battery and one AC unit set to control humidity.  Obviously, this jig rig is not worth the risk and it is time to invest in a 50amp extension!

 20221208 102822


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