Jump to content

What are some of the causes the AC Voltage Line Meter fluctuate?


Velos

Recommended Posts

The weather is warming up and yesterday both our A/C's were on and the AC Voltage Line Meter was in the red 106 to 112. We let the park office know and they check the pedestal and the power was good there.

 

Our rig is 12 years old 50 amps.

 

Could it be a bad AC Voltage Line Meter?

 

The power cord is as old as the rig doesn't feel hot. it is wore around the connector could that cause power fluctuations?

 

Thinking about having the connector replaced with a Ez Grip handle?

mbVXbJfg90IA7sUyogiA5_w.jpg

 

We have never used an AutoFormer

31d7DYglb4L._AA160_.jpg

 

but will be here for 3 mo's so thinking it may be good insurance to protect the rig?

 

Would appreciate your comments or suggestions.

Thank you.

Link to comment
Share on other sites

Weak circuits only sag when under load. They notmally test fine at rest or low load. When parks check the outlet at their pole, they are not checking the circuit under normal load. Changing things on your rig ...other than seriously reducing the power demand ...will not change the weak circuit.

Link to comment
Share on other sites

Saying this very tongue in cheek - if the wire connections are tight and the plug blades are clean.

 

GREATLY simplified - Voltage starts out at a generator somewhere. Probably at 15,000 volts. It goes through a large transformer closed transition tap changer that steps it up to 120 kv / 240 kv / 345 kv or so for long lines distribution. The tap charger tries to maintain the grid voltage, This is where power is part of the grid (tall towers with long insulators).

 

It may pass through various electrical 'yards' mixed with other power on the grid until it gets to a 'local' yard. There, it is brought down to a distribution voltage (another closed tap transition transformer) to 2300 to 15 kv. and from there to the park / house. This is where voltage regulation normally ends. This 'yard' could be next door or 20 miles away.

 

Once to leaves the yard - and regulation - another electrical law takes over. (It is there all the time but the regulators "modify" it with the taps.) This is P(ower) L(oss) = I (current) ^2(squared) *R(esistance) and basically - twice the power through the line, 4 times the loss - 10 times the power, 100 times the loss.

 

So dead of winter, no one in the park, voltage is high everyone is happy. Summer heat comes, your air is on, everyone else's air is on, as is the farmer down the road, wait, that is a dairy farm so he has big chillers to cool the milk, etc. and so on for the 20 miles back to the last regulator.

 

 

What the autoformer is doing is using more current to bring YOUR voltage back to it's nominal value. VA=VA -- VA(park side) = 100 volts x 12 amps = VA (your side) 120 volts x 10 amps. Your compressors are happy, the rest of the park, not so much. Your 12 amp load just added more 'problems' to the park service, but YOUR compressors are much happier.

 

Get it - wire it into the 'belly of the beast' and out of the eyesight of the park management. Some, take a dim view of them. Install this before the EMS.

 

Just make sure that the rest of your system is good first. (quick way to tell, measure at the box before your trailer and if the readings are the same as the internal of the trailer. Use the same meter for all readings to eliminate that as a variable.

Link to comment
Share on other sites

The only way you can tell if the problem is in your rig is to simultaneously monitor the voltage at the park's outlet, and again inside your rig. This requires two meters, one at the park's pedestal, the other inside your rig.

 

If the voltage is fluctuating at both places, the problem is in the wiring up to and including the pedestal outlet.

 

If it's only fluctuating in the trailer, you either have too much wire between the pedestal and the trailer, or a bad connection creating resistance.

 

Again, both meters have to be observed at the same time, under the same amount of load. You can't unplug your trailer and then test the park outlet because that changes the load and affects the observed voltage.

Link to comment
Share on other sites

Thank you for your input, I think you saved me the price of a autoformer.

 

My understanding of electricity is very limited. The "bad connection" comment got me to thinking about another comment that 50 amps has 2 legs.

 

I tried my volt line meter in several outlets in the RV and the power is great on the passenger side and low on the driver side. I believe I may have a bent connector in the power inlet causing the bad connection?

 

Will call a RV Mobile Service in the area and have them check it out.

Link to comment
Share on other sites

A weak leg and a strong leg could be a problem with a Floating Neutral, the Neutral leg is not well connected to Gound where is should be.

 

If this is the problem, it will only show under load as the leg with the load will cause the leg voltage to drop and the other leg voltage to rise. That is one condition to look for, does the good leg voltage equal the bad leg voltage without a load.

 

A floating Neutral can be in your power cord but usually it is a problem from the Power Post back to the Park Breaker Panel. This is a job for the Park's electrician.

Link to comment
Share on other sites

In some parks the neutral wire gauge used is the same as the legs which will not seem much of an issue if the 50amp rigs were true 220. BUT most of the rigs 30 & 50 amp are just 120 volt units with the 50 amp rigs splitting the loads between the L1 & L2 with neutral the common return. This causes the neutral to pass current for both legs essentially doubling its load. If properly configured ½ the pedestals on each park ciriuit would have their 30 amp outlets fed from L1 & the other ½ from L2 but even then depending on site utilisation there may be a disproportionment. On top of that most/all manufactured 50 > 30 DogBones use L1 as the source for Hot.

 

Our rig is 30 amp and in an Army Travelcamp in Columbia SC we were experiencing low voltage at our site during the day such that the EMS was interrupting service. I tried moving the cord to the 50 amp outlet, synptoms remained, made up my own DogBone tapping L2, synptoms remained. I then discussed the issue with park management they sent out an electrican which found the pedestal in order. Further discussion with the electrican revealed there was a contract in the works to upgrade the park feed and wiring to address the low voltage issues. He acknowledged the neutral was weak and needed to be doubled.

 

RV parks are uncommon beasts regarding power distribution because of the way the legs are used. I suspect most Distribution Engeneers could miss the heavy neutral current requirement unless the park expressly specified that reality. Noting the phase assignment for each site would also allow park reservations to assist in maintaining a better phase balance if trained to use the information.

 

I am not a lineman nor an electrician, just a 20 year Navy Submarine Veteran Electronics Tech. I DID NOT sleep @ a Holiday Inn Express last night either I'm afraid.

Link to comment
Share on other sites

I agree with the answers, especially those of Bill & Lou, but must address a part of your post not answered up to now.

Could it be a bad AC Voltage Line Meter?

The meter in your link is of very poor quality. There is a reason that they are so cheap; they are very cheaply made and most are not accurate at all. Before you get too far you need to spend $30 or so on a good quality, digital meter. I have tested my meter of the type in your link against my Fluke 77 and found it to be very lacking. With the one that I have it is reasonably close in the center of the range, near the 120V reading but goes farther and farther off as you move out of that area in either direction. Using a variable power supply and both meters I found that as the analog meter went up it was reading 130V when my Fluke read 126V and when the Fluke reached 130V the analog was reading nearly 140V. Going lower produced very similar results. If I lowered the voltage to 110V measured with my Fluke meter the analog fell to 102V, and continued to get less and less accurate as voltages dropped. That is pretty typical for a cheap analog meter movement as even the very best ones are most accurate in the center of the meter's range. I suggest that your plug-in meter is better than nothing, but not much.

 

Thinking about having the connector replaced with a Ez Grip handle?

This is also a good idea in my opinion, but it is easy to do so you may want to do so yourself. There is another thread currently that discusses this job. I have done that and really like the new plug. It is a vast improvement over the OEM plug that came with the RV and you can get a tight fit on the power outlet and still have little difficulty in disconnecting it.

Link to comment
Share on other sites

If your power cord goes through a hole, make sure the EZ Grip will go through that hole. I know someone who made that mistake.

Me too! But the guy I'm thinking of then made the hole bigger and used a different access cover. :P

Link to comment
Share on other sites

Me too! But the guy I'm thinking of then made the hole bigger and used a different access cover. :P

The last person I knew who made the mistake was not a guy, it was a woman who lost her husband and had trouble pulling the connection apart. Now she uses a Plug Dog, http://www.coilnwrap.com/products/PLUG-DOGS-50-Amp-4-prong.html, from Coil n'Wrap.

Link to comment
Share on other sites

UPDATE: Was going to replace the ends of my cord but went into the local RV Supply and the parts were almost $60 and a new cord with the ez-pull handle was $199.00 so I bought a new cord. It seems to have solve the voltage problem but now the bedroom A/C is freezing up so the damage may have already been done. The rig is 12 years old so is bound to hiccup.

 

Thanks again for all you input much appreciated.

Link to comment
Share on other sites

FOR INFORMATION to some of those who aren't familiar with typical residential 120/240 volt single phase three wire electrical service. This is NOT to disrespect or criticize anyone or a posting, but ONLY to help people who try to learn when visiting this forum.

 

 

(A) Mark and Dale

 

You stated "A weak leg and a strong leg could be a problem with a Floating Neutral, the Neutral leg is not well connected to Gound where is should be"

 

Here's the deal: Its indeed true if there's a loose Neutral connection, just like a loose Hot connection, in a branch circuit voltage drop occurs (V = I x R) and you could encounter less then 120 VAC out at a connected load (say 5 volts across bad resistive connection and 115 at load).

HOWEVER if at the main distribution panel where the Neutral is bonded to a "Grounding Electrode Conductor" (No 4 bare copper wire) which leads to a "Grounding Electrode" (copper rod driven into earth ground) IF THERES NO CONNECTION OF THE NEUTRAL TO EARTH GROUND the Neutral is indeed "FLOATING" and NOT tied to earth, but that condition would NOT cause the voltage of one leg with respect to Neutral to be higher then the other leg with respect to Neutral. The Neutral is center tapped in the transformers LV Secondary winding such that its only 1/2 of the voltage from Line to Neutral (120) as it is Line to Line (240) THAT'S THE SAME REGARDLESS IF NEUTRAL IS CONNECTED TO GROUND OR NOT. Having Neutral connected to earth ground or not connected to earth ground (floating) DOES NOT CHANGE THE VOLTAGE OF EITHER LEG WITH RESPECT TO NEUTRAL. In the main distribution panel the Equipment Ground Buss is connected to the Neutral Buss and the Neutral (at main panel or riser or in meter base) is connected to mother earth 'Grounding Electrode" via a "Grounding Electrode Conductor" In the event the Neutral Buss has a poor or even no connection to Ground, that doesn't alter L1 or L2 voltage with respect to Neutral. Its if there's a poor connection of any branch circuit to Neutral (some call Loose Neutral) that's when voltage drop occurs.

 

I have seen a loose or resistive connection inside a panelboard where the big incoming Utility Neutral conductor bonds to the Neutral Buss (aka Loose Neutral) and that's when things and voltages can go to pot, BUT THATS NOT THE SAME AS "the Neutral is not well connected to ground" as in your post, as if its connected to ground or not makes no difference in the utility transformers Line to Neutral voltage.

 

In my opinion to help some understand all this, the more correct statement would be a faulty/resistive Neutral connection, just like a faulty/resistive Hot connection causes voltage drop, such that out at a connected load voltage could be less the nominal 120 VAC BUT THATS TRUE IF THE NEUTRAL IS CONNECTED TO GROUND (Bonded) OR FLOATED AND NOT CONNECTED TO GROUND.

 

 

 

( B) SC Clock Dr,

 

You stated "In some parks the neutral wire gauge used is the same as the legs which will not seem much of an issue if the 50amp rigs were true 220."

 

Actually, a 50 amp RV service IS "TRUE 240" same as at your home. The 4 prong 50 amp NEMA 14-50 Plug and Receptacle has two Hots (L1 & L2) Neutral and Equipment Ground. Its 240 Line to Line or 120 either Line to Neutral same as in your home. Some 120 VAC RV loads are fed from L1, the other from L2 same as in your home. AND IF THE LOADS ARE BALANCED THE NEUTRAL CURRENT BACK TO THE SOURCE WOULD BE ZERO !!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

You stated "BUT most of the rigs 30 & 50 amp are just 120 volt units with the 50 amp rigs splitting the loads between the L1 & L2 with neutral the common return.

 

Actually, 30 amp rigs are 120 ONLY, while 50 amp rigs are 120/240 (even though no 240 loads). Its true 50 amp rigs split the loads between L1 & L2, and again if they were the same, Neutral current to source would be zero NOT DOUBLED.

 

You stated " This causes the neutral to pass current for both legs essentially doubling its load"

 

Actually, the Neutral DOES NOT HAVE ITS LOAD DOUBLED. The worst case is if there were say 30 amps on L1 but 0 amps on L2, Neutral current would be the full max 30 amps. HOWEVER if L1 has 30 amps and L2 has 30 amps, NEUTRAL CURRENT IS NOTTTTTTTTTT DOUBLED TO 60 AMPS BUT REDUCED TO ZERO

 

L1 is 180 out of phase with L2, that's why if the same they cancel out.

 

 

I HOPE THIS HELPS ALL HERE, post back any questions

 

With all due respect in an attempt to help and educate and NOT to criticize. I've been wrong before and may well be again grrrrrrrrrrrrrrrrrr lol

 

John T Long retired AC Power Distribution Electrical Design Engineer and rusty on all this so no warranty, this may be right or wrong, take it at your own risk

Link to comment
Share on other sites

  • 2 weeks later...

UPDATE: We had a RV Service check out our rig and so far it turns out while the rig was in storage (on a dairy farm) this past winter a bird built a nest in both our A/C's around the compressors. Fortunately they didn't damage the units but did cause them to get hot. He checked our cord and said that the two legs of the 50 amp should be pretty evenly wired but one side could have a little more and if it got hot over a long period of use the prong could get soft but it was not a problem with our cord.

 

The recommendation was to run the a/c fans on high when outside temps are forecast to be in the 90's so as to prevent ice build up and keep the compressors cool. We had thought that was only an issue in humid climates. Turns out bird nest had blocked the drain in the bedroom a/c thus dripping into one of the ducts.

 

I asked if moth balls would help if I put a box in the ducts** but he said they only way to prevent birds from getting in in storage is to cover them. Since DH is not able to climb on the roof we will have our mobile RV service at our home base check it out before we leave for next summers travels.

 

**Since we went part time I have put moth balls in the storage compartments and cupboards to prevent critters from coming in from the ground and though the odor is strong when we first start our travels it is gone after a day or so of fresh air and knock on wood we have had no problems with mice or squirrels and such.

 

Thanks again for all the suggestions, much appreciated

 

PS I do check the water heater for nests and wasps as that is at ground level but now will make sure the a/c's are on my check list for travel.

Link to comment
Share on other sites

 

Actually, the Neutral DOES NOT HAVE ITS LOAD DOUBLED. The worst case is if there were say 30 amps on L1 but 0 amps on L2, Neutral current would be the full max 30 amps. HOWEVER if L1 has 30 amps and L2 has 30 amps, NEUTRAL CURRENT IS NOTTTTTTTTTT DOUBLED TO 60 AMPS BUT REDUCED TO ZERO

 

L1 is 180 out of phase with L2, that's why if the same they cancel out.

 

 

 

 

John:

 

I totally agree with what you have said. The only caution I would add is that I have heard of parks where incorrect wiring has resulted in L1 and L2 being in phase instead of 180 out of phase. Although I've never experienced it myself I've read multiple reports of it. In such a case it would be possible for the current in the neutral to significantly exceed its design maximum.

 

Joel

Link to comment
Share on other sites

 

AC Voltage Line Meter was in the red 106 to 112.

If you have 2 AC units running, there is nothing wrong with running them at 106-112V.

That won't hurt anything. If that bothers you. Turn the refrig to LP & water heater to LP only.

 

I see that a lot in some campgrounds when everyone have AC's on. Even at times with my autoformer on boost.

Link to comment
Share on other sites

If you have 2 AC units running, there is nothing wrong with running them at 106-112V.

That won't hurt anything. If that bothers you. Turn the refrig to LP & water heater to LP only.

 

I see that a lot in some campgrounds when everyone have AC's on. Even at times with my autoformer on boost.

 

At the CG on Prince Edward Island where we are for the summer the power is so erratic (the grid itself, not just the CG) I just broke down and ordered an autotformer. Our Surgeguard will shut down at 102V but I don't like watching my digital voltmeter running in the 102-104V range a lot of the time.

Link to comment
Share on other sites

Joel, I'd say that you made a good decision. Most ac motors will run at a higher than normal temperature once voltage falls below 108V and how much below and for how long determine the effect it has. Heat is not the friend of electrical equipment and I have read more than one study that shows that such over temp use does shorten the life of a motor, rather like smoking has a negative effect on lifespan of a person. In either case the amount of effect can't be accurately predicted since no two motors or people are exactly the same but it isn't good and will probably effect you some day.

 

By the way, I envy you a bit at PEI as we liked it the best of any of the Canadian Provinces we have spent time in. :D

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

Guest
This topic is now closed to further replies.
×
×
  • Create New...