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Topic: Pedestal: Open neutral on one leg (Read 560 times) previous topic - next topic

Pedestal: Open neutral on one leg

My surge protector alerted me to an open neutral on one leg when I plugged into 50 amp tonight. How is that possible, don't they share the same neutral? Testing with a volt meter, it read 120 and 120 on each leg at the plug. Possibly just a bad contact on one legs blade? The surge protector worked fine on a different pedestal this morning and at a different one here in the campground.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: Pedestal: Open neutral on one leg

Reply #1 –
I had that at a dilapidated rv park in north Texas.  Wires wrong at pedestal.  Disconnected and ran off battery and generator.  Don't risk it.
2001 4010 U320 build #5865 "Bluto-d-Bus" since 09/18
2006 Honda Element ESP Toad
Full timing since 2016 in Western MT
Copilot: Sitka
1975 GMC 260 Avion: sold

Re: Pedestal: Open neutral on one leg

Reply #2 –
Elliot,

I had a similar problem several years ago. Turned out the plug itself had an internal bad connection that was the cause. I replaced it and it fixed the problem (after driving me crazy for a while). The problem was intermittent and depended on the position of the wire entering the plug.

Best of luck.

Len
Len and Deb Speiser
1999 U270 36'
2017 Jeep Wrangler Unlimited
You're either on the bus, or you're off the bus!--Ken Kesey
If you're lucky enough to live in a bus, you're lucky enough!

Re: Pedestal: Open neutral on one leg

Reply #3 –
An open or poorly connected neutral will affect voltage on BOTH hots.  One will be above 120 VAC, the other below since there is no "reference" point.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Pedestal: Open neutral on one leg

Reply #4 –
Thanks guys. The owner was trying to tell me it'll be fine but I'm not risking it. They're sending over a maintenance guy this morning. I'm using the 30amp for now. Thankfully my inverter powers one AC so I can still run both off of 30 amps
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: Pedestal: Open neutral on one leg

Reply #5 –
Quote from: Elliott –
My surge protector alerted me to an open neutral on one leg when I plugged into 50 amp tonight. How is that possible, don't they share the same neutral? Testing with a volt meter, it read 120 and 120 on each leg at the plug. Possibly just a bad contact on one legs blade? The surge protector worked fine on a different pedestal this morning and at a different one here in the campground.

Elliott, let's think this one through.  Your 50A plug teminates a 4-wire power cord. Earth ground, neutral, 120V and 120V.

I'd be checking the terminations on my power cable.  Or cables.  Especially if I had a molded termination.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Pedestal: Open neutral on one leg

Reply #6 –
Yes, the open/poor neutral could be either shore outlet back to CG breaker box, your cord or connections to your coach surge protector/ATS/main breaker box.

If just a poor connection vs open, it may read just fine under no/light load, but not be able to work under heavy load.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Pedestal: Open neutral on one leg

Reply #7 –
Yes both legs use the same neutral.  If it is open for one side it should be open for the other.

What did you use to test when you got 120 on each leg? Were you plugged in when you tested (under load)?  When you use a simple VOM meter to test power that uses very little current it can miss high resistance neutrals.  Best to use what an electrician calls a wiggy. It is a meter that puts a small load on the circuit when it tests for voltage.

What surge protector told you that?  When you have an open neutral in a 120/240V circuit, if the load is inbalanced  (one leg drawing more current then the other)  you will have one leg with high voltage and the other will have low voltage.  Your surge protector may be seeing the low side and they just uses that message.  Need to see type of device and what all of it's message are.



2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Pedestal: Open neutral on one leg

Reply #8 –
Elliot. Since this is the first time it has accrued I would suspect panel first. Isolating neutral issues will hide and be Elusive to find. Most prevalent under a load. You only have one neutral going into your coach so makes me curious if the ground is also playing a part in this and may of just stayed well hidden till now? I would also power down and pick a new position on your power reel just to see if anything changes. May have a brush/slip ring issue in reel? Panel power first.
Scott

Re: Pedestal: Open neutral on one leg

Reply #9 –
I had some intermittant issues with power.  Inverter coming on during the night and ACs still running.  Both legs full power at pedestal. Sometimes loss of one leg at transfer switch. etc.  Finally tracked it down to the power cord reel.  Started early on in this trip.  Cut the reel out of the circuit, wired power cord to junction after reel.  Put the reel in my trunk to examine later.  Maybe repairable, the motor still works fine.  Will need to drill rivets out of junction box on reel to examine what went wrong.  Cost me microwave, coffee maker and a fan in reefer.  Consider myself lucky.  Find your issue before it goes too far.
Herb and Willie
Escapees 90802
2014 IH-45 Build 6581
2002 U320 40' AGDS Build 6021 Sold
1999 U320 36' No Slides Sold
2007 Monaco Dynasty Diamond IV Sold
2005 Discovery 39 Sold
1986 20' Wilderness TT,  Died a natural death after floods, etc.
Walldog's Journeys
And Willie Said

Re: Pedestal: Open neutral on one leg

Reply #10 –

I'm using this surge protector: Amazon.com: Progressive Industries 50 Amp Portable RV Smart Surge Protector...

I don't think it's my rig. If I unplug my rig from the surge protector and plug ONLY the SP into the pedestal I get the same results; open neutral. If I then carry it over to another pedestal and again only plug in the surge protector, the open neutral warning goes away.

After reading your guys' responses, I suspect the SP is applying a small load to the outlet and that's the reason both our simple VOM meters didn't detect an issue.

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1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: Pedestal: Open neutral on one leg

Reply #11 –
Quote from: Elliott –
My surge protector alerted me to an open neutral on one leg when I plugged into 50 amp tonight.

So you own the one in the link that has id10T lights?  Does this unit have 3 lights on the right and left side?  When it reported a problem you had all 3 lights on one side and the other side you had green and blue only on?  If this is the case you might ask your question to the manufacture, since it would show up on both sides but it might only report a low voltage and call that on open where the high voltage since they think is ok.  This one don't look like this unit will report or stop high or low voltage if both legs are reporting the same.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago