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Open Roads Forum  >  Tech Issues

 > Low Voltage on One 50A Leg

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TechWriter

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Posted: 07/31/20 11:24am Link  |  Quote  |  Print  |  Notify Moderator

In several campgrounds I've noticed that my 50A legs were "unbalanced". For example, unloaded, L1 at 105V and L2 at 117V.

What's causing this?


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theoldwizard1

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Posted: 07/31/20 11:33am Link  |  Quote  |  Print  |  Notify Moderator

You need to confirm that this unbalance is at the power post and not something inside your RV.

The cause is likely imbalanced loads. To many 120VAC loads on one leg.

BB_TX

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Posted: 07/31/20 11:54am Link  |  Quote  |  Print  |  Notify Moderator

Measured “unloaded” I would guess the campground power was low on that leg. Resistance can cause the voltage to be lower. But that would only occur if there as a load (current flow) thru that resistance. Did you try measuring voltage at the park pedestal receptacle?

time2roll

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Posted: 07/31/20 12:10pm Link  |  Quote  |  Print  |  Notify Moderator

Poor connection or unbalanced load. If this is at the pedestal you will need the park to fix it or move or use your voltage booster.


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Posted: 07/31/20 02:10pm Link  |  Quote  |  Print  |  Notify Moderator

Since 2004 I've had one CG with low 50A voltage. It was a older CG, hot summer day, full sites and everyone running A/Cs.

"several campgrounds" may suggest it's your problem. When was the last time you inspected and tightened ALL AC connections in your 2001 MH? They do become loose as you vibrate and bounce down the road. This should be a periodic maintenace item.


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Posted: 07/31/20 02:50pm Link  |  Quote  |  Print  |  Notify Moderator

Have seen differences on the 2 legs of 2 or 3 volts depending upon which A/C is running at the time. Never have seen a 12 volt difference. As mentioned above, verify that the low voltage is not in your rig, then ask the CG if they can fix your pedestal. Some older CGs have wiring issues that can cause these imbalances and cannot be fixed without rewiring the whole CG.


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Posted: 07/31/20 03:00pm Link  |  Quote  |  Print  |  Notify Moderator

Such imbalances can also be caused by poor neutral connections; when the neutral has a higher resistance than it should, its voltage tends to float based on the relative loads on the two legs. (The extreme version of this is an open neutral, which generally causes lots of problems and lots of expense in a short period of time.)

If you're seeing such voltage variations pretty consistently, it would be advisable to verify that your RV's power inlet connections, transfer switch connections, etc. are in good shape and properly tightened down.





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Posted: 07/31/20 03:18pm Link  |  Quote  |  Print  |  Notify Moderator

DrewE wrote:

Such imbalances can also be caused by poor neutral connections; when the neutral has a higher resistance than it should, its voltage tends to float based on the relative loads on the two legs. (The extreme version of this is an open neutral, which generally causes lots of problems and lots of expense in a short period of time.)

If you're seeing such voltage variations pretty consistently, it would be advisable to verify that your RV's power inlet connections, transfer switch connections, etc. are in good shape and properly tightened down.


MEH.

A "poor Neutral" most likely going to cause more other collateral damage depending on just how much draw is on one or both "legs".

As long as both L1 and L2 amperage is equal, then the voltage on both legs will also be equal.

Draw more on L1 and now you get an imbalanced voltage.

I suspect what the OP is seeing is an issue in the campgrounds electrical system coming from MORE 30A 120V usage..

Most pedestals will by default have the 30A 120V outlet on the SAME "Line" and most likely that default IS L1, and more folks will be hooked up to the 30A outlets..

Hence the reason OP is seeing the voltage mismatch..

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Posted: 07/31/20 03:48pm Link  |  Quote  |  Print  |  Notify Moderator

Gdetrailer wrote:

DrewE wrote:

Such imbalances can also be caused by poor neutral connections; when the neutral has a higher resistance than it should, its voltage tends to float based on the relative loads on the two legs. (The extreme version of this is an open neutral, which generally causes lots of problems and lots of expense in a short period of time.)

If you're seeing such voltage variations pretty consistently, it would be advisable to verify that your RV's power inlet connections, transfer switch connections, etc. are in good shape and properly tightened down.


MEH.

A "poor Neutral" most likely going to cause more other collateral damage depending on just how much draw is on one or both "legs".

As long as both L1 and L2 amperage is equal, then the voltage on both legs will also be equal.

Draw more on L1 and now you get an imbalanced voltage.

I suspect what the OP is seeing is an issue in the campgrounds electrical system coming from MORE 30A 120V usage..

Most pedestals will by default have the 30A 120V outlet on the SAME "Line" and most likely that default IS L1, and more folks will be hooked up to the 30A outlets..

Hence the reason OP is seeing the voltage mismatch..


Bingo, you win.

camperdave

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Posted: 07/31/20 03:57pm Link  |  Quote  |  Print  |  Notify Moderator

so as a 30a RVer, sounds like it may be worth carrying two 50a - 30a adapters, one for each line. Pick the one with the higher voltage. Anyone do that instead of plugging into the 30a receptacle?


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