How much is too low?

[AJMike]

We normally are boondocking or dry camping so this is not an issue, but yesterday we stepped at an actual RV park with hookups and so I connected the electric. The place was almost deserted so I did not bother to check the voltage when we first hooked up (yes, that was my mistake) but when I plugged my voltage monitor into an outlet I saw it varying between 104 and 106 volts. Of course I immediately disconnected and so we are now at the most expensive dry camping site we have ever used.

Because we so rarely actually use electric hookups I never went to the trouble to buy one of those automatic disconnects, and that is something that I will fix when we get back home, but I did want to know what voltage is so low its is dangerous to the appliances in an RV. At what low voltage should I make sure the electric is disconnected? As far as I can tell now everything is OK, but I don't want to take this kind of a chance again.

It would also help me to have some recommendations as to a good voltage monitor that would automatically disconnect at both high and low voltages so I can make sure I get one that will do what I need. Not having much experience with this I don't know which units are good and which are merely expensive. Even a quick check on Amazon this morning showed me that some units are only surge protectors and some are actual voltage monitors. I assume I can do a search of the threads on this forum for that, but the technology changes so quickly that anything I see from 2 for 3 years ago may now be outdated.

Thanks for any help.

[powercat_ras]

Plus or minus 10 percent from 120 volts is OK for everything, or 108 - 132 volts.

I'd avoid using Air Conditioning Unit and Microwave in particular outside that range.

The current generation of converter chargers like you have in your 2018 unit is rated to operate down to 105 volts.

So far as protection, anything that costs less than $ 200 is just a surge protector with fault indications and will not automatically disconnect if outlet not wired correct or voltage is outside the 108 - 132 range. Personally I use a Southwire 30 amp hardwired unit, they also make a unit that plugs between the pedestal and the end of your shore cable.

[Ozarkryder]

Progressive, Hughes and Southwire seem to be the biggest names in EMS (Electrical Management System) both for hard wired and portable. We never have had a Hughes. We have a Southwire 30 amp unit for our current rig and inn our last rig we had a Progressive 50 amp version. They are both good, we chose mostly based on availability when shopping. Plug it in and it does a diagnostic on the park electric. If something isn't right it lets you know and won't turn on to let power through. If something happens after it's plugged in it will shut down or blow and keep the electrics in the rig safe.

[Bones2003]

Originally Posted by AJMike

........The place was almost deserted so I did not bother to check the voltage when we first hooked up (yes, that was my mistake) but when I plugged my voltage monitor into an outlet I saw it varying between 104 and 106 volts.......

AJMike, just out of curiosity did you plug your voltage monitor into an outlet in your RV and then plug it into an outlet on the campground power post to compare the readings? I'm wondering if there was some type of loss in the path from the shore power pole through your RV to the internal outlet.

[AJMike]

Originally Posted by Bones2003

AJMike, just out of curiosity did you plug your voltage monitor into an outlet in your RV and then plug it into an outlet on the campground power post to compare the readings? I'm wondering if there was some type of loss in the path from the shore power pole through your RV to the internal outlet.

The monitor I have is the simple 2 prong plug and it only plugs into normal 110 outlets, so I used it inside the RV. But when I saw the low voltage I immediately disconnected, took my voltmeter and measured the voltage at the pedestal. In the RV it varied between 104 and 106 and at the pedestal it measured as 106 volts.

[AJMike]

Originally Posted by powercat_ras

Plus or minus 10 percent from 120 volts is OK for everything, or 108 - 132 volts.

I'd avoid using Air Conditioning Unit and Microwave in particular outside that range.

The current generation of converter chargers like you have in your 2018 unit is rated to operate down to 105 volts.

Thanks for the information. I noticed that the automatic disconnect voltage varies from product to product with some disconnecting as low as 102, and I assume that each product sets its cutoff at what it considers to be a seriously low voltage. Odd that they would vary so much, 102 - 108 volts.

In this case I had run the microwave (although only for about 4 minutes) and not seen any issue, but then as long as it worked I don't guess I would see anything. This being Arizona in March we were fortunate that the temperature was cool enough to not need the AC, and the only way I even knew there was an issue was when an incandescent bulb was flickering from low voltage.

My compressor fridge seems OK, but it is DC only and I suppose wired to the battery power so perhaps the low AC would not be an issue. At least it seems to be OK now, as does everything in the RV. I reported the issue to the RV park office and they sent someone out to check, and I am now told they have to completely disassemble and rebuild the 30 amp outlet.

[Elkman]

The technology in terms of line conditioners for sag and boosters and surge protection has not changed at all in the past 40 years that I have been involved with electrical equipment and computer devices.

A true line conditioner will boost the voltage and these are far heavier and far more expensive than a surge suppressor of any type. The portagle plugin surge protectors while not being the best way to protect from surges they do have a simple LED display to show if there is a problem with the electrical supply at the pedestal so you know before attaching the power cord from the RV.

If I plugged in the tester and found any problems I would go to another campsite and see if the problem existed there as well. What I would never do is simply take it on the chin if I am being cheated by a park owner or operator.

The Hughes Autoformers are designed to boost voltage and protect equipment from surges. At $340 it is a good investment.

Sags or low voltage results in come equipment, like an air conditioner compressor, running hotter and failing sooner. With electronics the result can be a failure of the device to operate or to operate in an erratic manner (think of a TV remote with old batteries).

[slabman]

This is one of the mist mis-understood problems we RVers face...the dreaded loose neutral terminal situation. When you don't have a good, positive neutral connection, you get a return current flow through one of your hot legs and it'll spike the voltage up past the std. max of 132 volts. The other leg will swing to the lower side of 108 volts. So if you call the park's maintenance guy, he'll come out with his multi-meter and probe both legs, telling you both are fine...(and you must be some kind of an idiot and don't bother me with these errant claims). But because there is no load when using his probe, he won't find the problem!

When this happens, I tell them they must move me to another site (and I might suggest they get a REAL electrician to check that pedestal before they damage the next guy's equipment).

[NeilV]

Originally Posted by Elkman

The technology in terms of line conditioners for sag and boosters and surge protection has not changed at all in the past 40 years that I have been involved with electrical equipment and computer devices.

A true line conditioner will boost the voltage and these are far heavier and far more expensive than a surge suppressor of any type. The portagle plugin surge protectors while not being the best way to protect from surges they do have a simple LED display to show if there is a problem with the electrical supply at the pedestal so you know before attaching the power cord from the RV.

If I plugged in the tester and found any problems I would go to another campsite and see if the problem existed there as well. What I would never do is simply take it on the chin if I am being cheated by a park owner or operator.

The Hughes Autoformers are designed to boost voltage and protect equipment from surges. At $340 it is a good investment.

Sags or low voltage results in come equipment, like an air conditioner compressor, running hotter and failing sooner. With electronics the result can be a failure of the device to operate or to operate in an erratic manner (think of a TV remote with old batteries).

Ditto on the Hughes Autoforners. Better than a shut down device that only protects you from extreme voltage dips and not long term brownouts just above the point of shutdown. Low voltage damage can be accumulative as the lower the voltage the higher the amperage draw will be to maintain the required wattage to continue running which translates into extra waste heat building up in your devices (electronics, wiring, AC Compressors, etc, etc), Over the long haul the Hughes Autoformer has saved me many times its cost since failures of 120 volt electrical and electronic devices in my RV since it was installed 10 years ago have dropped to almost Zero.

[TravatoJohn]

Hopefully you told the RV park. Usually it’s their outdated system. They will also try and deny their is a problem. Travato John

[AJMike]

Originally Posted by TravatoJohn

Hopefully you told the RV park. Usually it’s their outdated system. They will also try and deny their is a problem. Travato John

Yes, I told them. I was worried that someone else might not have found the low voltage and it might end up damaging their RV.

They sent someone over to check the outlet and he told me that apparently there was some issue with the wiring in the outlet and they would get it fixed. He offered me a dog bone so I could use the 50 amp outlet but I told him that I had one of those but that we did not need power. We prefer dry camping except in the heat of the summer and were at the RV park for the mineral water baths, not for the power.

The place was largely empty and if the voltage was down to 104-106 volts when empty I think it must be even lower when the place is full.

[orangeminnie]

Originally Posted by AJMike

We normally are boondocking or dry camping so this is not an issue, but yesterday we stepped at an actual RV park with hookups and so I connected the electric. The place was almost deserted so I did not bother to check the voltage when we first hooked up (yes, that was my mistake) but when I plugged my voltage monitor into an outlet I saw it varying between 104 and 106 volts. Of course I immediately disconnected and so we are now at the most expensive dry camping site we have ever used.

Because we so rarely actually use electric hookups I never went to the trouble to buy one of those automatic disconnects, and that is something that I will fix when we get back home, but I did want to know what voltage is so low its is dangerous to the appliances in an RV. At what low voltage should I make sure the electric is disconnected? As far as I can tell now everything is OK, but I don't want to take this kind of a chance again.

It would also help me to have some recommendations as to a good voltage monitor that would automatically disconnect at both high and low voltages so I can make sure I get one that will do what I need. Not having much experience with this I don't know which units are good and which are merely expensive. Even a quick check on Amazon this morning showed me that some units are only surge protectors and some are actual voltage monitors. I assume I can do a search of the threads on this forum for that, but the technology changes so quickly that anything I see from 2 for 3 years ago may now be outdated.

Thanks for any help.

Most modern electronic devices won't care. The better quality inverter/chargers will actually operate OK down to about 90 volts. The TV and computer won't care. But I completely agree that air conditioner compressors and possibly residential fridges might struggle with voltages below about 108. What did the park manager have to say? Did you measure at the pedestal? Did you look at both legs of their 50A outlet? Were you putting a big load on the feed at the time you measured?

[AJMike]

Originally Posted by orangeminnie

What did the park manager have to say? Did you measure at the pedestal? Did you look at both legs of their 50A outlet? Were you putting a big load on the feed at the time you measured?

The manager sent one of the workers to check on the 30 amp outlet and he confirmed that the output was down to around 106 volts. I had already checked the 50 amp outlet and it seemed OK to me, and he confirmed that as well. And yes, I had checked both legs of the 50 amp outlet.

We were putting little load on the line at the time as only our compressor refrigerator was operating. The one thing I don't know is how the fridge draws its power when connected to shore power.

The refrigerator itself is a DC only compressor refrigerator, and is hooked into the DC lines from the batteries, not the inverter, but I don't know what happens when hooked into shore power. I assume, perhaps incorrectly, that the batteries continue to supply power to the refrigerator and that shore power is only used to recharge those batteries.

Of course all of the AC appliances would draw power from the shore power line, but how a DConly refrigerator operates when connected to shore power is a bit of a mystery to me.

[orangeminnie]

Sometimes this is a utility problem, not necessarily the fault of the park wiring. If they're seeing less than about 117V at their main panel, the utility should be compelled to move a tap on the pole transformer.

[SmilingSimon]

Remember any heating element does not really care about voltage it is all about current.


but ALL or nearly all electronics DO care about power - but not as much as you would think - again all electronics are DC voltage powered, so it depends on the 120v to DC voltage conversion - look on any transformer for a device - input voltage can be huge.


but i would not want to trust my desktop pc to lower than say 105vac, laptop does not matter the battery intervenes in that.


if the low voltage is CLEAN, no spurious noise, then it can be 'ok' but if rapidly going up/down then it should be corrected or something may pop.


it is NOT constant low, but generally either large voltage spikes lasting hundreds of milliseconds, OR low dips of voltage - voltage deviation can kill MANY things in mh, anything not made robust, microwave on low voltage is NOT good, portable heater likely does not care.


but change sites to get better voltage !!!!

[reeman]

One method that may be a good way to ascertain if there is a possibility of damage occurring to the ac-dc unit in an RV might be some form of thermal sensor to indicate any sign of the unit putting out too much heat in the converter. Like any device that converts ac to dc it needs adequate heat sync capacity and either cooling fan(s) or good air circulation.
If a 120 to 12v dc converter has too much draw because of low incoming voltage it can also cook if it gets too hot. The main cause of failure of cheap battery chargers encapsulated without adequate air circulation and cooling. I have cooked battery chargers in the past by not checking to see if they were getting too hot under heavy load in a hot environment.

They are not the same as welding units but are still subject to I/R=E and all the key equations unless the RV industry has repealed the laws.