Melted 30a Dog Bone and Voltage Imbalances

[jm_bc_]

Hi all-

Been having some odd electrical issues as of late and am wondering if these are unrelated coincidences or a sign of a systemic issue & hoping you can help! We have a fairly elaborate system including dual Victron Multiplus 12/3000 inverter chargers. The system was wired, and inverters are programmed to run in split-phase. Everything has been working perfectly up until last month. My Victron setup has the ability to limit my incoming amperage, which ensures I don't pop a pedestal breaker. So I can tell it we're on a 50, 30, 20, or 15a connection and it will limit incoming shore power accordingly. Any additional power called for by my rig is simply made up from the inverters boosting from the battery bank.

We spent all of July at a park in a very harsh marine environment - only a few hundred feet from the ocean and lots of fog (every 2nd or 3rd day) - salt everywhere. 30a pedestal, and set Victron inverter system to 30a max incoming. Didn't notice any issues during our stay for the month, but when packing up to leave I pulled our 30a dog bone adapter out of the pedestal and saw both the hot and neutral terminals on the male end in rough shape (melted). On the 50a female end of the dog bone, the neutral terminal was melted. And on the male end of our surge protector, the neutral terminal was also slightly melted. No other visible issues further down the line (female end of surge protector, and male end of shore power cord had no visible signs of anything). Photos attached.





We are now on a 50a pedestal at the new park we've been at this week. With the previous melting I have been keeping a closer eye on things, and I am seeing large voltage differences between my hot legs, especially when under a decent load. Examples:

Voltage readings w/ no load @ pedestal L1/L2 @ 120/120

Voltage under load right now:
L1 - 112v @ 25.3a load
L2 - 128v @ 1.6a load

At one point yesterday I had voltage on L1 @ 106v and L2 @ 132v under a very imbalanced load (random set of circumstances - panel is generally well balanced between L1/L2).

I understand this difference can be caused by a neutral issue. What I am unsure of is whether the problem is internal (my rig) or external (the park). I am still using my surge protector (with some melting on the male neutral prong - yes, I know I need to replace it), but tried removing from the setup to see if it was the cause. No improvement/change to voltage imbalance when removed.

I am also seeing roughly equal voltage drop on both legs under balanced loads. Was pulling ~25-30a on both legs yesterday at one point and voltage dropped to 115/116 per leg (from no load 120).

Tried unplugging from shore and running off inverter system only (pulling from batteries) and voltage stays perfectly constant at 120v per leg even with a load imbalance on the two legs. This makes me think the issue is external, or at least upstream from my inverters/main breaker panel.

The park electrical system here is somewhat suspect - the 8/3 feed to my pedestal is standard interior, unprotected ROMEX wire running (partially) underground (see photo), so I suspect there are other issues at play here. I cannot see the distribution panel near my site, so have no idea how far this wire run is from the distribution to my pedestal.



These things make me think the issue here is voltage drop from undersized/long park wiring runs, since I am seeing voltage drop under balanced loads and the extreme voltage imbalance I am seeing under imbalanced loads is caused by the voltage drop on the neutral wire carrying the current difference between L1 & L2. Thoughts?

The outlier here is the melted 30a adapter at the previous park. Could that have simply been pulling close to the max 30a limit of the pedestal/dog bone for an extended period of time in a harsh environment where the connections at the terminals were less than perfect?

We're moving again tomorrow, so will be able to try some additional testing on a new pedestal. The joys of RVing!

Thanks in advance!

[jkwilson]

My two cents is you should ignore the overheated 30A adapter when it comes to troubleshooting. They are prone to overheating from loose connections and shouldn’t be trusted without regular inspection.

Your current problem looks like a neutral issue with park wiring. Maybe just a loose screw in the pedestal, but possibly more complex. You can test by monitoring the line voltages with the loads in your trailer off. If the imbalance goes away, the problem is likely local to your site.

This is a case where an EMS is critical since it will shut things down if a line voltage gets unacceptably high.

[Ynot4me2]

^^^x2 what he said. However, I'm no electrician but have some knowledge of it due to my work. Please post back after you've changed sites.

[el Rojo]

It sounds like a pedestal issue but I would look at your connections (especially neutral) in your power converter. Make sure they are tight.

[SolarPoweredRV]

Hi all-

Been having some odd electrical issues as of late and am wondering if these are unrelated coincidences or a sign of a systemic issue & hoping you can help! We have a fairly elaborate system including dual Victron Multiplus 12/3000 inverter chargers. The system was wired, and inverters are programmed to run in split-phase. Everything has been working perfectly up until last month. My Victron setup has the ability to limit my incoming amperage, which ensures I don't pop a pedestal breaker. So I can tell it we're on a 50, 30, 20, or 15a connection and it will limit incoming shore power accordingly. Any additional power called for by my rig is simply made up from the inverters boosting from the battery bank.

We spent all of July at a park in a very harsh marine environment - only a few hundred feet from the ocean and lots of fog (every 2nd or 3rd day) - salt everywhere. 30a pedestal, and set Victron inverter system to 30a max incoming. Didn't notice any issues during our stay for the month, but when packing up to leave I pulled our 30a dog bone adapter out of the pedestal and saw both the hot and neutral terminals on the male end in rough shape (melted). On the 50a female end of the dog bone, the neutral terminal was melted. And on the male end of our surge protector, the neutral terminal was also slightly melted. No other visible issues further down the line (female end of surge protector, and male end of shore power cord had no visible signs of anything). Photos attached.





We are now on a 50a pedestal at the new park we've been at this week. With the previous melting I have been keeping a closer eye on things, and I am seeing large voltage differences between my hot legs, especially when under a decent load. Examples:

Voltage readings w/ no load @ pedestal L1/L2 @ 120/120

Voltage under load right now:
L1 - 112v @ 25.3a load
L2 - 128v @ 1.6a load

At one point yesterday I had voltage on L1 @ 106v and L2 @ 132v under a very imbalanced load (random set of circumstances - panel is generally well balanced between L1/L2).

I understand this difference can be caused by a neutral issue. What I am unsure of is whether the problem is internal (my rig) or external (the park). I am still using my surge protector (with some melting on the male neutral prong - yes, I know I need to replace it), but tried removing from the setup to see if it was the cause. No improvement/change to voltage imbalance when removed.

I am also seeing roughly equal voltage drop on both legs under balanced loads. Was pulling ~25-30a on both legs yesterday at one point and voltage dropped to 115/116 per leg (from no load 120).

Tried unplugging from shore and running off inverter system only (pulling from batteries) and voltage stays perfectly constant at 120v per leg even with a load imbalance on the two legs. This makes me think the issue is external, or at least upstream from my inverters/main breaker panel.

The park electrical system here is somewhat suspect - the 8/3 feed to my pedestal is standard interior, unprotected ROMEX wire running (partially) underground (see photo), so I suspect there are other issues at play here. I cannot see the distribution panel near my site, so have no idea how far this wire run is from the distribution to my pedestal.



These things make me think the issue here is voltage drop from undersized/long park wiring runs, since I am seeing voltage drop under balanced loads and the extreme voltage imbalance I am seeing under imbalanced loads is caused by the voltage drop on the neutral wire carrying the current difference between L1 & L2. Thoughts?

The outlier here is the melted 30a adapter at the previous park. Could that have simply been pulling close to the max 30a limit of the pedestal/dog bone for an extended period of time in a harsh environment where the connections at the terminals were less than perfect?

We're moving again tomorrow, so will be able to try some additional testing on a new pedestal. The joys of RVing!

Thanks in advance!

Based on your description of the salty environment in your previous campground, I would guess that none of the terminals were very well connected to the power pedestal due to internal corrosion in the outlet. Your Dogbone probably got hot because of the poor connection within the receptacle. This might also be the cause of the overheating on the neutral on the other end of the dogbone.

You had a poor connection between the dogbone and the receptacle and poor connections generate heat which melted the terminals.

I would replace the Dogbone and monitor the situation.

[jm_bc_]

Hi all-

Thank you so much for all of your replies - I am always grateful for this community, it's knowledge, and willingness to share and help! We have moved and are now at a new location with only a 30a service (using a NEW 30a dog bone of course), so am unable to replicate the (possible park-related) neutral issues. Been having fluctuating voltage here in the new location as well though, likely due to the excessive heat. Yesterday felt like 109º w/ humidex when we arrived, and everyone had their AC's running full tilt. Voltage dropped as low as 106 and is now back up to 115 since the heat has broken and temps are down significantly overnight. Will continue to monitor, and post updates once I get back to another park with 50a service.

@jkwilson - appreciate your comment re: EMS for shutdown in hazardous electrical conditions. The two Victron Multiplus' in my system have settings to accept/reject shore power based on a number of criteria including input voltage, so I think I'm covered there, though I will revisit my settings to ensure I have them set correctly!

That said, this recent experience has made me think more about the overall protection of my electrical system. I am currently using a Hughes "Watchdog" portable surge protector that offers surge protection and basic diagnostics of the pedestal wiring. I have been thinking about possibly switching to the actual Hughes 50a Autoformer instead and hardwiring it into my rig, which would provide the voltage boost I need in low voltage situations, and also now includes 4800 Joules of built-in surge protection. Just wondering your thoughts on this, as well as whether there would be anything else needed to provide robust overall system protection? The one downside I can see off the top of my head is I would now no longer have a quick visual of the pedestal wiring to ensure it's correct - with my current portable surge protector (linked above) I can easily see everything is correct provided I get all "Green" lights on it. Am I missing anything else?

[el Rojo]

I have the Hughes AutoFormer and use it on occasion. I would like to have it hard wired and in the unit (out of sight), 1 because they are expensive and 2 (believe it or not) I have been to parks where they were prohibited. Yes prohibited LOL. This was an old park with low voltage and the mind set was you were sucking more electricity than your fair share, LOL. The AutoFormer boosts the power it receives and in no way does it consume more than what's at the pedestal.

[MoonShadow_1911]

I have the Hughes AutoFormer and use it on occasion. I would like to have it hard wired and in the unit (out of sight), 1 because they are expensive and 2 (believe it or not) I have been to parks where they were prohibited. Yes prohibited LOL. This was an old park with low voltage and the mind set was you were sucking more electricity than your fair share, LOL. The AutoFormer boosts the power it receives and in no way does it consume more than what's at the pedestal.

If you are going to hardwire the Autoformer, here is what I would recommend buying. Also, I have not done this myself, yet. It would go behind the basement wall, close to where the 50 amp power receptacle is.

Hughes Autoformers Mounting Bracket
Install Kit - 50 Amp

Of course, don't forget the AutoFormer

I got my ideas from RV Geeks.

[el Rojo]

If you are going to hardwire the Autoformer, here is what I would recommend buying. Also, I have not done this myself, yet. It would go behind the basement wall, close to where the 50 amp power receptacle is.

Hughes Autoformers Mounting Bracket
Install Kit - 50 Amp

Of course, don't forget the AutoFormer

I got my ideas from RV Geeks.

I like that bracket...Thanks Mark.

[jm_bc_]

If you are going to hardwire the Autoformer, here is what I would recommend buying. Also, I have not done this myself, yet. It would go behind the basement wall, close to where the 50 amp power receptacle is.

Hughes Autoformers Mounting Bracket
Install Kit - 50 Amp

Of course, don't forget the AutoFormer

I got my ideas from RV Geeks.

This is awesome - thanks Mark! Love that bracket as well.