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Low Voltage on One Leg - Thanks PI EMS-PT50C


Kevin H

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The past two nights my Progressive Industries EMS-PT50C has kicked off due to low voltage on leg 2 - 108 volts. It lasts only a few minutes - perhaps 10 or 15, then all is well. I don't know if anyone else in the CG is having a problem, but I have not noticed any indication of surge protectors either. Would a voltage drop to 108 on one leg be noticeable without a surge protector like the PI EMS-PT50C?


I switched to the 30 amp side with a 50 amp dog bone. The surge protector registered 108 on both legs.


I'll discuss it tomorrow with the CG owner, but wondered if anyone has any thoughts on what may be going on???

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There could be a number of things going on. Wiring inside the park a tad too small for the loads, the utility transformer may be undersized, too many pedestals on a circuit, the utility may be having voltage problems on the high voltage side of the transformer. If you are getting the same voltage on both hot legs, I would say the utility has a problem. If only one leg was low, then more likely the problem is inside the park. As a retired utility lineman, I have seen many more issues than what I mentioned, and I don't think any real damage was done at 108 volts, but you were protected, which is good.

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The Progressive Industries EMS will shut down power to your RV below 103 and above 132 volts. It shouldn't at 108 volts although that is a low voltage. It is quite probable that you have a constant low voltage of 108 that intermittently falls below 103 volts. The EMS should tell you it had PE4 (Previous Error, line 1 low voltage) or PE6 (Previous Error, line 2 low voltage) error. If the 30a (which has one power line) outlet is on the low voltage line of the 50a (which has two power lines) outlet you'll have the same troubles. If the 30a outlet is on a good voltage line of the 50a outlet you'll be OK running on 30a. When you talk with the CG they will probably say it's not their problem, no one else is complaining. That's because no one else has an EMS to tell them there's a power problem. You can try a different power pedestal as the problem is often (from my experience) the outlet or circuit breaker on the pedestal, or a poor connection. Greg

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The past two nights my Progressive Industries EMS-PT50C has kicked off due to low voltage on leg 2 - 108 volts. It lasts only a few minutes - perhaps 10 or 15, then all is well. ................................
I switched to the 30 amp side with a 50 amp dog bone. The surge protector registered 108 on both legs.

You don't say what it shows on the other leg? Have you checked each leg with a meter? What is the voltage before the problem takes place? The online documentation states that it interrupts power if voltage drops to 104V so it must fall below that point, or your EMS has some problem. At the same time, 108V is not an acceptable power supply for no load conditions. Modern power supplies should be at 120V, +/- 10% which means that 108V is at the minimum design voltage when unloaded. I do not stay in any RV park that can't supply a minimum of 110V before I connect to it.

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What some (none of you fine gents) may not understand when they make a blanket generalization about how low voltage is due to A LOOSE CONNECTION that may well be true HOWEVER FYI REMEMBER its ONLY after a load is applied and current flows through a loose resistive connection a voltage drop (V = IR) occurs so there's something less then the input voltage present. If an RV pedestal reads 120 volts with no load applied but then it reads say 108 volts when an RV is plugged up and an appliance or load is activated that draws current, THERE MUST BE A LOOSE RESISTIVE CONNECTION IN THE RV PEDESTAL OR ITS UPSTREAM SOURCE FEED (assuming normal current). Since the voltage is measured between the Ungrounded conductor and the Neutral Grounded Conductor, the voltage drop causing loose connection may be in EITHER. THERES NO VOLTAGE DROP ACROSS A LOOSE RESISTIVE CONNECTION UNTIL SUCH TIME CURRENT FLOWS THROUGH IT. If a load is applied to one leg L1 of a 120/240 volt transformer and there's no appreciable drop but the same load is applied to the other leg L2 and there is a significant drop, Id look for a loose L2 hot wire connection.

 

Of course, low RV park secondary distribution voltage can also be caused by the utilities low Primary transformer input voltage instead of a loose resistive connection in the park itself. If the HV utility primary coming into the park is supposed to be say 7200 or 9600 volts but is low, THE LV SECONDARY DISTRIBUTION VOLTAGE IN THE PARK will also be low. BUT THE UTILITY IS FAIRLY RELIABLE and I would bet low voltage is more likely due to the RV park then the Utility.

 

If an RV pedestal reads say 108 volts with nothing plugged into it, I would for sure say the RV park has a problem instead of your RV DUHHHHHHHH.

 

Having been to a ton of RV parks and hearing the same old excuse ITS YOUR PROBLEM NO ONE ELSE COMPLAINED I am likewise skeptical...

 

John T Too long retired EE so no warranty but my best recollection

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That seems to be typical of park owners. Perhaps they get a lot of power complaints that really are operator error. Mystery to me.

I get power complaints all the time in the Park. VERY rarely is it anything to do with our equipment. It is almost always the guests equipment. But occasionally we will have a bad receptacle.....generally the customer also has a bad power cord. The combination of the two causes issues. I do check the receptacles every year and replace those that look bad. But sometimes one gets by or they degrade with use. It is amazing how many singed and ugly looking power cords I see in a season. Cleaning the ends is something everyone should do at least once a year. And if they are pitted much they need replacing.

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We have been in this spot for over two weeks with not problems until the past two nights. Now, that does not mean that the voltage did not drop. It may have just not dropped low enough for the EMS to pop.


Those two nights were some of the coldest we've had here in Asheville, NC - mid to upper 20s. If others are using electric heat like us, things could be being affected.


Normal voltage on both legs is 122 +/-. The error is PE06 - Leg 2 Low Voltage. During the error time Leg 1 = 122, Leg 2 = 108-109. Last night, the second night it happened, Leg 2 read 108 consistently during my observation. I did not observe anything lower than 108, but, that was after it had tripped. So, given the info above, one would assume it dropped to the 104 threshold at some point.


When I hooked to 30 amp, voltage read 108 on "both" legs.

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When I hooked to 30 amp, voltage read 108 on "both" legs.

There is a very simple reason for that. When you use that adapter to connect to a 30A outlet, that adapter ties both legs to the very same pin in the adapter, because a 30A RV plug has only one phase supplied to it. In other words, you now have only one leg that can supply no more than 30A but with you plug to the 50A outlet that outlet has 4 pins, one ground, one neutral and two hot legs, L1 and L2. Each of the two hot legs can supply you a maximum of 50A so the real world is that you could draw 100A, if each leg were to carry exactly the same 50A load, which in the real world doesn't happen but it is very common for one to be able to use a total of 80A or more while the 30A outlet is exactly that, 30A maximum by all combined loads in the RV. There is no way to be sure which of those two phases your 30A plug connects to.

 

The fact that one leg only is dropping off makes it sound like the 30A outlets in the park and not well distributed and one phase is over loading while the other is not. The fact that temperatures have fallen probably does mean more use of 120V heaters in the park as that is pretty normal when power is supplied with the rental fee. When temperatures fall, not only is there very likely more use of such heaters, but those in use are turned on more of the time so the number in use at any given moment will be higher and so the load on the total system is bound to increase. If the park were well balanced, the load increase should be seen fairly nearly uniformly on both phases of the power, but it seems to not be the case in the park where you are.

 

One thing that you may want to try is moving your heater to the other end of the RV, if you are using only one. Your 50A RV probably has two different circuits for outlets each one with a separate circuit breaker and usually the two are on different phases of power. If you use only one, try moving it to the other end of the RV, in the hope you get to the higher voltage phase leg. That probably won't solve the problem if it is a park issue, but it won't make it worse either.

 

While I do believe that if you were in the park that Jack takes care of you probably would have well maintained equipment and could expect supply problems there to be rare, I also know from experience that there are very few parks that have a "Jack" doing maintenance in them and that older parks especially tend to have poorly maintained electrical supplies and rarely have anyone on staff you really understands electricity and electrical problems. I have heard some really outlandish statements by RV park maintenance folks about electrical issues. :)

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Yo Kirk, Happy Thanksgiving and to all the rest. I will be crossing your great State (darn its a long way across) a couple times again next April on I 10.

 

You say "The fact that one leg only is dropping off makes it sound like the 30A outlets in the park and not well distributed and one phase is over loading while the other is not" FWIW I agree that's certainly one possibility.............

 

That being said here's the problem as I see it at MANY RV Parks. If I had been the power distribution design engineer at an RV Park and was running power down a lane, I would have ran 4 wires (L1, L2, Neutral, Ground DUH) and fed EVERY OTHER 120 VAC 30 amp off opposite legs, L1 and next space L2 etc. etc. etc. If a string of 120 VAC 30 amp (3 wires, L1 only) was ran down a lane (or all was on one leg only), its easy to see how the farther down the lane you were the lower the voltage if others ahead of you were using power TYPICAL PREDICTABLE LINE VOLTAGE DROP. That's a place where the NEC's "Tap Rules" might come into play.

 

But in defense of the engineer or electrician who designed the power distribution, even if it were done as I proposed, it may turn out certain spots are more level or have more shade so all the 20/30 amps RV's ended up connected to mostly just one leg of 120. When given a project the layout is on a flat piece of paper and the designer might have no idea what sites were level or had shade or were more likely to be used!!!!!!!!!!!

 

HOWEVER a good designer should take such into account and provide BY OVERSIZING THE CONDUCTORS TO ACCOUNT FOR PREDICTABLE LINE VOLTAGE DROP. My design method was to apply a diversity duty cycle factor in order to calculate the max continuous current,,,,,,,,,,,size the feeders to have a minimum ampacity of 125% over that,,,,,,,,,,,size the overcurrent protection to protect the feeders,,,,,,,,,,,,,BUT ALSO CALCULATE VOLTAGE DROP and increase feeder ampacity accordingly. If the problem is line voltage drop due to unequal loads or inadequate wire size, there's not much any park caretaker (Jack or otherwise) can do, regardless how well he maintains it unless he were to upgrade the distribution system or make people park on certain sites to balance the loads.

 

In addition to voltage drop due to small wire size at MANY older parks, a TYPICAL problem Ive observed is simply worn out loose fitting or carboned and burned receptacles. They can pass a plug in checker for proper polarity etc., but if the terminals are loose and worn and carboned and burned that means PROBLEMS. Of course quality spec grade 20 amp T Slot NEMA 5-20R receptacles should be used for the small duplex outlets while the 30 and 50 amp need to be checked regularly for fit and tightness and integrity. Regardless, when Billy Bob or Bubba pull in with their worn frayed undersized often incorrect polarity worn out cords, theres not much the caretaker even a good one like Jack can do lol. Ive been to parks where the receptacles are so badly worn the plug will barely stay inside and see Billy Bob use a 50 or 100 foot 16 gauge cord YIKES talk about voltage drop when he turns on his AC!!!!!! then blame the park when his AC unit overheats and fails...

 

Nuff said

 

John T (Think I will run out and polish and shine the blades on all my RV extension cord ends which I often do even if my buddys make fun of me)

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John, it is typical to alternate the phases when running the feeders. I generally alternate the leg positions on each pedestal. I also NEVER use the NEC factors that are in the campground section of the code book. They are not going to give you enough voltage at the pedestals, IMO. Modern coaches tend to use a lot of power and the power factors specified don't cut it - again, in my opinion.

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You need to travel on I-20 as it is better road and you could stop by and visit us! :P

 

Wonders never cease as we are agreeing again! Having looked into the electrical design of some public parks we volunteered in, I'd bet that the design they had in older parks was often the same in commercial ones. I have found that frequently, the 4 wire cable is run down the ends of the rows of sites, with only a 3 wire supply to each row and the load balancing is done by alternating rows, rather than sites and thus saves some expensive 4 wire cable. But your issue of trees, as well as view and water access make some rows far more heavily used than others. Then you throw in the fact that use also causes splices, connections, and even outlets to age more quickly and those really popular rows usually have to poorest power stability. I highly suspect that this is also true of many older commercial RV parks. That is very common in parks that have no 50a sites. I have also seen parks where the main distribution panel has only a series of single, 120V single phase breakers, each feeding a 3 conductor cable to a row of section of 30A RV sites with no 4 wire feeders at all.

 

It is not at all uncommon for electrical maintenance & repair to be performed by some work-camper or ranger who thinks that he knows what he is doing, but some of us might disagree.

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Kirk, I agree that older parks are often laid out that way. It makes it hard to improve anything without starting fresh. I used to have some pictures of "challenged" electrical implementations, but they disappeared in some upgrade. Some of the stuff you see is downright scary. Like the #14 Romex strung tree to tree with staples to feed the nonGFCI 15 amp outlets screwed to the trees. Now THAT was impressive.... :(

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Mornin Jack, you state................"They are not going to give you enough voltage at the pedestals, IMO. Modern coaches tend to use a lot of power and the power factors specified don't cut it - again, in my opinion"

 

I TOTALLY AGREE as a past power distribution designer I consider the NEC as a set of MINIMUM requirements and in my career I was often guilty of OVER DESIGN AND OVER KILL. If we designed an RV park I bet there wouldn't be low voltage problems (caused by us at least) lol Of course, its different if say an office complex was the design criteria. One problem a designer may face is a tightwad penny pincher client grrrrrrrrrrrrrr. In such a case I might give him an NEC minimum and legal and inspector approved design (X dollars) and then my recommendations (more dollars).............. Of course its then his money and his call as to what to install even if it still meets NEC

 

That's where VOLTAGE DROP CALCULATIONS AND CONSIDERATIONS come into play and if the NEC were used (which many parks do NOT have) properly and completely coupled with common sense and experience, an NEC approved PLUS practical workable system that allowed for heavy RV use would result. When I was NEC savvy those darn diversity and duty cycle calculations were cumbersome, but still if the actual practical uses and loads were taken into consideration and being an experienced RVer who believed in over kill I BET I COULD DESING A GOOD SYSTEM THAT MOREEEEEEEEEEE THEN MEETS NEC MINIMUM REQUIREMENTS

 

AN EXAMPLE If I were the designer I might consider a 50 amp RV using 40 amps per leg and a 30 amp user 24 amps (for diversity and duty cycle purposes) BUT THEN FIGURE 100% CAPACITY AT THE PARK!!!!!!!!!!! THEN FIGURE NO MORE THEN A 5% VOLTAGE DROP,,,,,,,,,,,,,,,,Then if the wire runs were very long YOU MAY END UP (subject to amps and distance) HAVING TO RUN 500 MCM CABLE DOWN THE ROWS and that expensive and bordering on impractical WHATS A DESIGNER AND THE PERSON PAYING THE BILL TO DO LOL I can design with capacity to allow no more then a 5% voltage drop but if the park is full and each uses maximum current and the runs are long WILL THE PARK OWNER PAY FOR THAT DESIGN AND INSTALLATION??????????? That's my design but not my call grrrrrrrrrr

 

 

 

 

Kirk, my route across Texas is from the daughters in Austin to the son in San Diego, therefore I use I 10 but hey I may have to swing North to visit you.

 

"It is not at all uncommon for electrical maintenance & repair to be performed by some work-camper or ranger who thinks that he knows what he is doing, but some of us might disagree."

 

Count me in as far as might disagree lol But you and I usually agree, for whatever that's worth lol

 

I have been enjoying antique tractor forums and RV forums for yearsssssssssss and am glad to help. However here is an observation:

 

If say a mechanical or hydraulic or HVAC or any other question is posed, the responses are often from those experienced in those particular fields HOWEVER if an electrical or legal question is asked IT DRAWS MORE RESPONSE THEN ANY OTHER TOPIC BAR NONE Everyone and their brother in law crawls out of the woodwork and all are experts and know everything there is to know about electricity. You hear most from Billy Bob or Bubba who wired their barn or garage while downing a case of beer and BY GOLLY IT WORKS and they are now experts, if you dont believe it just ask them lol I have a friend who is an excellent mechanic and wired his shop but mixed n matched Neutrals and Grounds to no end, but when I (an EE) questioned him he gets mad and says I can show you in the panel where they (N & G) BOTH wire TO the SAME PLACE !!!!!!!!!!!!!! I just have to walk away as there's no explaining to that mindset

 

Oh well Im not griping, just stating an observation. Im thankful for all here and other sites and am glad to help what little I can. God bless all the fine gents who try to help their fellow man.

 

Happy Thanksgiving

 

John T

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Kirk, my route across Texas is from the daughters in Austin to the son in San Diego, therefore I use I 10 but hey I may have to swing North to visit you.

Guess it will require a trip via the scenic route, since we are east of you as well as north.. :P We are roughly 150 miles due north of Livingston.

 

Of course, none of this helps Kevin much! :(

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Guess it will require a trip via the scenic route, since we are east of you as well as north.. :P We are roughly 150 miles due north of Livingston.

 

Of course, none of this helps Kevin much! :(

Having retired out of Austin, it's fun to hear of others in Texas. Kirk - we must be somewhat kindred - Both spent lots of time in Cheyenne and then Texas, plus we are full-timers too boot!

 

Happy Thanksgiving to all!

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The last time we were at this park we had a "premium" electric site - 50A service. When I went to plug in I noticed that the 50A outlet was in really poor shape. Actually, part of it was missing. I could still plug in and had a decent connection, but it was dangerous for anyone who wasn't paying attention or didn't know better (think small children). I promptly reported it, and within a very few minutes someone was there to fix it. On the way back from the office to our coach I looked at some of the neighboring vacant sites, and almost all of them had new 50A outlets. I asked about that, and the maintenance man said that he was replacing those outlets as he could. I didn't say anything to him, but I thought that since most of the sites were empty that then would have been a good time to switch any that hadn't been changed. I may walk around one of these days and see how many of those sites have been taken care of. Not in the next couple of days, though, as I don't like poking at electrical things in the rain.

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I experienced that a few years ago. I informed park office, who sent a maintenance man to my site. He said it was my MH, I took him inside, showed him the digital readout, and requested he use his VOM to double-check my EMS equipment by measuring voltage at the pedistal. Lo and behold, he promptly said the low voltage was at park wiring. I was told to move to a different site. I walked over and checked voltage with my Beckman VOM, and low voltage there too.

He said no-one else complained, but the park obviously had a power problem. I was assigned a 3rd site(on a different branch circuit) which checked within limits.

Persistence and patience does pay_sometimes.

FWIW, if the 50A plug is pulled out enough to insert VOM probes, voltage may be measured under load. Of course you old sparkies know that.

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Roger, for some reason when park management tries to blame my RV and/or equipment, I take it as a challenge to prove otherwise.

I stayed in a CG out West a long time ago where the wiring was incorrect and sending 90VAC through the skin of my old Allegro MH. I wound up threatening to call the local fire dept. if they did not call an electrician and park owner to the site. Within 10 minutes the owner appeared with an electrician in tow, who soon confirmed my test results showing park wiring was wrong. Owner waived my site rent and moved me next to another site after confirming power was up to code.

Oh, it was my daughter stepping out of the MH barefoot who "discovered" the hot skin.

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Yo Neighbor Ray in Indiana,

 

INDEED hot coach skin is an extremely hazardous condition, especially if a small barefoot child (or anyone) steps out onto wet ground while in contact with the coach !!!!!!

 

That's where proper polarity of the parks Pedestal receptacles and coach wiring all comes into play. In the event the coach had its Neutral re bonded to the Equipment Grounding Conductor and RV frame and chassis, if you are in contact with the earth and RV at the same time, your body becomes a parallel current path with the current carrying Grounded Neutral OUCH and it only takes something like 30 to 50 milliamps to cause fibrillation in the old ticker and you could wake up dead. Any competent trained professional electrician or electrical engineer understands correct wiring procedures, but if Billy Bob or Bubba or the non sparky park owner or his know it all brother in law installed the wiring or maintenance (park or the RV) it can be wrong but still "work" but still get you killed......

 

Be safe yall

 

John T

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INDEED hot coach skin is an extremely hazardous condition, especially if a small barefoot child (or anyone) steps out onto wet ground while in contact with the coach !!!!!!

I can become a very difficult customer when I discover safety issues in any RV park. Back quite a few years ago, we were told to leave an RV park over such and issue and I did move to a different park, but then visited the local code enforcement office where I filed a complaint. The park owner let me know that the code folks did take action, by later writing me a nasty letter about having caused him grief, as well as attempting to charge some $300 it cost him for repairs against my credit card that was used to pay for our site. When the fee was rejected, he wrote the letter demanding that I pay for the cost.

 

That was more than 10 years ago so I wonder if he still remembers me? :rolleyes:

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