Dangerous electrical concern...

[JoeKnight]

This is a firsttime post from a longtime reader. We have a very serious electrical concern for which I have exhausted every logical recourse. On 2 separate occasions we have had 220 in our fifth wheel. Both times we were home and able to shutoff the main breakers. To date we are only $1k down in damages and feel quite fortunate for that to be all.

This happened at our home base where we have been for the majority of the last 2+ years, although it has only occurred in the last month. I have had the local service checked by a certified electrician as well as the electric provider side and an RV specific repair shop. Of course, everything checked out perfect in all locations. Believing it to be a random surge, I plugged back in.

After a 2nd similar event 4 days later I inserted the 30 amp adapter to remove the risk of 220 entirely. Since then, our power has simply shutoff twice. The first time, I replaced the shore power cable with a spare and restored power. On further examination, I discovered our original cable had a bad ground (although it read fine at the breaker box). Last night it shut off again with a repaired shore cable. No breakers thrown, no weather, no surge, no owner outage... Then it came back on after a few seconds.

I am at a loss, quite uneasy and unwilling to hook up to 50 amp without a solution. Anyone ever heard of such a situation? Shore power? Trailer problem? Something else? Multiple factors? Unrelated events? Sure could use some help.

 

[danemayer]

Hi JoeKnight,

I'm assuming you determined that the interior of the coach is getting 220V by using a meter to measure.

You may have a problem with an intermittent loss of the neutral connection. This could be at the outlet your shore power cord is plugged into, or even earlier in the electrical system. Since the problem has only happened intermittently with this one location, the home electrical system is suspect, even though checked by an electrician. It may have been working ok when he checked it.

When the neutral connection is open or partially open, voltage on one power leg can go up to 220V.

If the home electrical is ok, you basically have to check from the pedestal to the circuit breaker panel and all points in between. That would include the shore power connector on the outside of the trailer, the automatic transfer switch (if you have generator prep), and the back of the circuit breaker panel.

With shore power disconnected, examine the connections at the trailer power cord connector. If that looks ok, again with power disconnected, pull the main circuit breaker panel and look at the connections. The two hot legs and the neutral are all #6 AWG which is a thicker wire than anything else going to the panel. Look for heat damage or loose connections.

If you have generator prep, again with power disconnected, open the box and check the neutral connections. There's a wiring diagram on the inside of the cover. The switch is usually located behind the rear wall of the pass through storage. If the connections are tight, it could still be a problem with the contactors inside the switch.

If you'd like to understand how a lost neutral connection can cause this problem, here's a link to a folder with a Lost Neutral presentation.

 

[JoeKnight]

Thank you! Following the link now.

 

[AAdams]

After you check everything I would strongly suggest you get a surge protector/EMS like this one. We installed one of these in our rig right behind the fuse box and it has saved us twice since May at different parks. GL finding the problem. Intermittent ones are the hardest to find sometimes.

 

[Sniper]

After you check everything I would strongly suggest you get a surge protector/EMS like this one. We installed one of these in our rig right behind the fuse box and it has saved us twice since May at different parks. GL finding the problem. Intermittent ones are the hardest to find sometimes.

X2 on the surge protection we have this one http://www.dyersonline.com/progressive-industries-50-amp-portable-electrical-management-system.html saved us more than once.

 

[Gaffer]

Sounds like an open neutral. Check your neutral connections at the panel, receptacle, both ends of the cord, the cord reel if you have one and at the panel in the trailer. If you are pre-wired for a generator, check the transfer switch connections. Get that Progressive surge protector it will shut down due to loss of ground, loss of neutral, over voltage, under voltage etc.

 

[pegmikef]

I had similar symptoms and after eliminating the pedestal as the problem, suspecting the 50 Amp breaker in the trailers breaker box, I removed the cover (disconnect from shore power first) to access the breakers and immediately saw the burned neutral line on the neutral bus bar. It was loose enough so I could easily move it with my fingers. Fixed that and everything has been ok since. I have the progressive EMS, but sadly it would not have found this problem because it is located before the line ties into the breaker box.

 

[JoeKnight]

Thanks so much for your reply!

- - - Updated - - -

THanks... ordered one 30 minutes ago. I really appreciate all the help.

 

[rxbristol]

Those neutral connections have to be really tight, otherwise when it warms up, through electrical load, it will be loose and cause an open condition and that's when you get the 220.

 

[mslater]

i suspect a neutral problem too. might be all the way back to the transformer of the service