Voltage problem revisited

Topic: Voltage problem revisited (Read 2889 times) previous topic - next topic

Re: Voltage problem revisited

Reply #50 – December 21, 2019, 04:55:55 pm

Quote from: GleamB – December 21, 2019, 03:19:44 pm

Can someone decipher this info for me? Is the reel still suspect??

Howdy Glen,
IMHO your reel is definitely suspect and very likely the cause of your erratic voltage readings. As mentioned before, I would monitor your readouts and pull out (or retrieve) more cord and see if your readings change. Bad/worn brushes, burnt spots on the collector (brush) rings or both, will cause your symptoms. By moving the reel in/out you may find a "clean" spot, where the voltage is steady. I finally removed our Power Reel (for this very reason) and just manually coil/recoil the power cord. The Power Reel is very handy, but is possible failure point.
Good Luck, Dave A

Re: Voltage problem revisited

Reply #51 – December 21, 2019, 05:59:12 pm

Glenn
If your monitor always works correctly when on generator power and only reads incorrectly on shore power, then yes......... I would say with reasonable certainty that your problem is between your ATS and the shore cable plug. The cable reel is a likely suspect, bypass it if you can and then see if the problem still exists. Sure sounds like you have a poor neutral connection somewhere.........

Re: Voltage problem revisited

Reply #52 – December 21, 2019, 06:23:14 pm

Mine always reads way off down here and checking all outlets it is 123.4 on every plug and shows both legs at that too on the progressive monitor safety control. See picture of my readings
JohnH

Re: Voltage problem revisited

Reply #53 – December 22, 2019, 01:11:16 pm

Today monitor read 106 and 131.
Progressive Industries read 116 and 116
Tested outlets behind monitor
116 and 116
Wouldn't mind getting monitor repaired
Sent Jim a PM, but no response
John....you think it's just a Mexico issue?

Re: Voltage problem revisited

Reply #54 – December 22, 2019, 06:24:06 pm

Glenn,
There is a calibration screw on the back of the monitor. One for each line. Adjust the reading to match your reading at the plugs.
John M.

Re: Voltage problem revisited

Reply #55 – December 22, 2019, 06:30:30 pm

Quote from: John Morales – December 22, 2019, 06:24:06 pm

Glenn,
There is a calibration screw on the back of the monitor. One for each line. Adjust the reading to match your reading at the plugs.

If the voltage readings are fine at other camping locations, wouldn't adjusting the monitor be masking the symptoms rather than curing the problem? Not necessarily the best course of action if there is an electrical issue.

Re: Voltage problem revisited

Reply #56 – December 22, 2019, 07:42:35 pm

Michelle,
Reply 53 states that the voltage outside matches the voltage inside at the plugs behind the line monitor. So adjusting the monitor isn't going to mask anything. The monitor is not calibrated to the correct voltages.
John M

Re: Voltage problem revisited

Reply #57 – December 23, 2019, 01:40:22 am

OK. This discussion is becoming dangerous. As Michelle pointed out, don't adjust meters to mask an electrical problem and Glenn, don't ignore the problem just because you are in Mexico.

We are on vacation, now coachless, so I'm away from my normal media equipment and I need to try to talk from hand drawn pictures, instead of the more desirable schematics, but (keeping this as basic as possible) here goes anyway:

From the second picture, normal single phase power gets to your coach via Power lines that have (typically) 2400 or 4800 or 7200 VAC electrical potential.

This is stepped down to two lines of 120 Vac potential through a center tapped power transformer on the power pole. That single phase power is carried throughout your building/house or RV Park as single phase, 180 degrees opposed, Line 1, Line 2 (at 120 Vac potential) and a neutral wire (at ground potential).

Using Ohm's Law (I=E/R, Current in amps is equal to Voltage in volts divided by resistance in ohms) and a simple drawing (first picture), if your combined load on L1 is 10 Ohms of resistance (oversimplifying, but not unrealistic), then 12 amps of AC current will flow through that equivalent load and back to the power source (Transformer Power Lines at the street), with 12 amps AC flowing through the neutral wire.

Now, at the same time, if your combined load on L2 equals 30 Ohms of resistance (oversimplifying, but not unrealistic), then 4 amps of AC will flow through that equivalent load and back to the power source (Transformer Power Lines at the street), with 4 amps AC flowing through the neutral wire.

BUT that 4 amps AC will flow in the opposite direction, because the transformer on the power pole has a center tapped secondary winding (equal number of turns in the windings, but wound in the opposite direction, therefore equal and opposite voltages and current flows that are proportional to the line loads). Center tapped is the typical design for the highest percentage of buildings and 120 Vac commercial use in America.

Thus the TOTAL current in the neutral conductor will be 8 amps AC.

Now open (fault) the neutral conductor, as shown in the first picture, second drawing . 240 Vac will be felt across the very same total of 40 Ohms of load. When this happens, by Ohm's Law, the current in the 240 Vac circuit will be 6 amps AC, the heavily loaded line (10 Ohm equivalent load) will (by Ohms Law) have only 60 Vac shown across it when you look at the coach's power meter - or any other meter. And if that load was all in lighting, those lights would suddenly become much dimmer.

At the same time, with an open (faulted) neutral conductor, the lightly loaded line (30 Ohm equivalent load) will (by Ohms Law) have 180 Vac shown across it when you look at the coach's power meter - or any other meter. And if that load was all in lighting, those lights would suddenly become very, very bright, just before they blew out.

Now it is easy to understand that if the loads are perfectly balanced (between L1 and L2) there will be 0 amps of AC current flowing in the neutral. So it's also easy to see that if you fault (open) the neutral in this condition, nothing changes (equivalent resistances and voltage drops all stay the same until you create some imbalance between the two sets of loads).

BUT, if your meter (built in or handheld high impedance [resistance] Volt-Ohmeter) shows a difference in voltages [L1 to L2]), you need to correct the neutral conductor problem, not ignore it or adjust readout instrumentation.

So how do you find the open or high resistance Neutral connection?

Well, the FT Xantrex Readout Panels are notorious for failed components and/or board foil on the neutral sensing circuit. Based upon percentages, that is a logical place to look first. It is near the end of the power circuits because it is downstream of both ABT's, power distribution panels and all incoming wiring. If you cannot reliably duplicate the problem at the readout panels, then split the train of incoming power on one leg and look for it there. Keep halving the power path until you capture the fault between two points and that point is the problem. Because the neutral path is shared and may get commoned-up in certain (unknown) places, you have to do L1 and then L2 loads and trains of power.

Keep in mind that if the fault is not at the Xantrex readout, each and every wire/contact/power reel brush/manual power plug/ABT or PI terminal connection/etc/etc., in the entire power path has nearly equal probability of being the problem, all the way from the center tap on the power pole transformer, to the park utility pole to your 50 amp plug and receptical, to the ABT's to the machine screws to the circuit breakers in your coach power panel to the outlet screws in the split duplex outlet at the readout meters. Going after this (Easter-egging it) in a random fashion will be very frustrating and usually non-productive.

But the neutral problem must be found and resolved. What Glenn is experiencing IS a neutral conductor power problem. Saying it only happens in Mexico is dangerous because if one of your power lines L1 or L2 in the coach has no load, then all of the loads on the other line (including you, if you happen to touch the wrong thing) are likely to have 240 volts applied to them. If you start opening up circuit breaker panel breakers, you could easily end up applying 240 Vac to your TV or Computer or other unforgiving recievers.

I have found this open neutral (or, more commonly, high resistance neutral conductor) condition to occur more frequently in Mexico and Canada than in the US. That has to do with different regulatory emphasis and different electrician mindsets.

AND, bear in mind that if the open neutral is in the park wiring, absent any load on the 50(or any) amp receptacle, the capacitive coupling in the power leads to your power pole may cause your high quality (high impedance) VOM to read L1 = 120 Vac, L2 = 120 Vac at the power pole. That is because when you use a high impedance meter, the meter does not draw enough current (doesn't have enough load) to drain the built up capacitance line voltage (charge) in the power leads.

Sorry for the long dissertation, but this was getting to be dangerous. Find the problem and fix it. Don't ignore or mask it. Too dangerous and it may well kill you or burn your house down.

HTH,
Neal

Re: Voltage problem revisited

Reply #58 – December 23, 2019, 08:35:00 am

Very good explanation Neal, and as you stated, the "loose neutral" problem is not normally a "broken" neutral but a high impedance one that won't show up if there is a "no load" condition and with only a VOM (meter) connected while troubleshooting that is what you would have.

My question was...... and I don't believe was answered.
Does this condition only show up on shore power and never while running on the generator?

Knowing this WOULD narrow down the search significantly...............

Justin

Re: Voltage problem revisited

Reply #59 – December 23, 2019, 09:11:39 am

Quote from: FourTravelers – December 23, 2019, 08:35:00 am

My question was...... and I don't believe was answered.
Does this condition only show up on shore power and never while running on the generator?

See Reply #48 - yes, voltages are good when running the generator, and the condition apparently only shows up on shore power.

Here are the 2 other topics on this issue (I would merge them in, but it would create a huge topic)

Voltage Problem

Power Cord Reel

Re: Voltage problem revisited

Reply #60 – December 23, 2019, 09:15:24 am

Yup, if voltages read correctly when on generator, but not on shore power, it is NOT the gauge at fault!

Find and correct the problem. And, if resistance/poor connection on the neutral, the more unbalanced the load between L1 and L2 the further out of spec will be voltage. This will "let the smoke out" of appliances if too far out.

Re: Voltage problem revisited

Reply #61 – December 23, 2019, 09:27:26 am

Quote from: Michelle – December 23, 2019, 09:11:39 am

See Reply #48 - yes, voltages are good when running the generator, and the condition apparently only shows up on shore power.

Here are the 2 other topics on this issue (I would merge them in, but it would create a huge topic)

Voltage Problem

Power Cord Reel

Well that bit of information narrows the search to starting at the neutral connection on the power pole to the shore power contacts on the automatic transfer switch. Easy Peasey.

Re: Voltage problem revisited

Reply #62 – December 23, 2019, 09:31:43 am

Quote from: Old Toolmaker – December 23, 2019, 09:27:26 am

Well that bit of information narrows the search to starting at the neutral connection on the power pole to the shore power contacts on the automatic transfer switch. Easy Peasey.

Yup, and if shore power cord reel, add that (toward the top) of the suspect list.

So:
Male end of shore power cord (assuming this has occurred at more than one pedestal so are ruling out bad power to pedestal).

Female end of shore power cord if no reel. Male receptacle on coach that shore power cord plugs into. OR reel and its contacts.

Shore power "IN" side of ATS.

Lastly and least likely, a wiring issue between these points. Most common if rodent damage.

Re: Voltage problem revisited

Reply #63 – December 23, 2019, 10:12:24 am

Quote from: wolfe10 – December 23, 2019, 09:31:43 am

So:
Male end of shore power cord (assuming this has occurred at more than one pedestal so are ruling out bad power to pedestal).

Gleaned from first topic - discovered during first report of the issue that the original male end had a prong break off, male end was replaced (Reply #10 of this topic shows wiring and there is some discussion of that which follows that reply)

Re: Voltage problem revisited

Reply #64 – December 23, 2019, 10:47:39 am

Quote from: Michelle – December 23, 2019, 10:12:24 am

Gleaned from first topic - discovered during first report of the issue that the original male end had a prong break off, male end was replaced (Reply #10 of this topic shows wiring and there is some discussion of that which follows that reply)

And reply #25, Voltage problem revisited points to a problem with using modern high impedance digital volt ohm meters. The input impedance of these meters is in the millions of ohms range. So no load on the circuit under test.

Now the second trap of the ubiquitous (translate that as cheap) VOM is that most don't measure true RMS voltage. Now I freely admit I don't have the same level of education Mr. PIllsbury, but I have been living with an electronics engineer for 30 years. Now before I met Lynn I had learned to read RMS as Root Mean Square, FWIW here's the formula i cribbed from Wikipaedia, I should have it memorized but I don't:

"Peak values can be calculated from RMS values from the above formula, which implies VP = VRMS × √2, assuming the source is a pure sine wave. Thus the peak value of the mains voltage in the USA is about 120 × √2, or about 170 volts. The peak-to-peak voltage, being double this, is about 340 volts."

And herein lies the rub (again, that writer of bawdy stories) once you lose the neutral connection you can no longer assume that you have a pure sine wave. There are true RMS voltmeters but you won't find them at Harbor Freight.

Here is a nice lesson on voltage measurement:

Dual Impedance Digital Multimeters | Fluke

Finally, just as the man who wears three wrist watches never knows what time it is, pick one volt meter and stick with it. Don't go around recalibrating other volt meters until you measure the true voltage at the meter.

As Mr. Pillsbury said in post #57, Voltage problem revisited

"Sorry for the long dissertation, but this was getting to be dangerous. Find the problem and fix it. Don't ignore or mask it. Too dangerous and it may well kill you or burn your house down." Neal Pillsbury

And if Glenn and Amy Beinfest want to come this way, Marshall has some empty spaces in the trailer park* for $100/month and I'm willing to push Lynn out the door and say "don't come back until it's fixed." If you're willing to ask questions when your eyes glaze over, Lynn will teach you what you need to know.

*The nuclear plant team arrives in January.

Re: Voltage problem revisited

Reply #65 – December 23, 2019, 10:55:20 am

How about leaving the shore power reel out of the loop and just borrow a normal cable to install and then check voltages?

Pierce

Re: Voltage problem revisited

Reply #66 – December 23, 2019, 11:19:18 am

If your monitor always works correctly when on generator power and only reads incorrectly on shore power, then yes......... I would say with reasonable certainty that your problem is between your ATS and the shore cable plug. The cable reel is a likely suspect, bypass it if you can and then see if the problem still exists. Sure sounds like you have a poor neutral connection somewhere.........

Yep........... see reply #51, maybe the OP has tried that already?

If they were only closer to me I would (as most on the forum) be happy to find this problem for them.

I actually enjoy troubleshooting electrical problems, I've made a good living doing it the last 35 years......

Re: Voltage problem revisited

Reply #67 – December 23, 2019, 11:57:01 am

Wish I could take advantage of the offers to help. I know I would learn a lot in the process. I guess I will try and bypass the reel ( which I have gotten REALLY fond of ), to see if that is the weak link. If it isn't, I'm not sure how to proceed.

Re: Voltage problem revisited

Reply #68 – December 23, 2019, 12:19:39 pm

Glenn
If it is the power reel, it could be just a case of dirty slip rings, poor contact connection. Possible easy fix no matter where it is..........just finding the problem is sometimes the difficult part. No need to not still have / use a power reel.
Good luck!

Re: Voltage problem revisited

Reply #69 – December 23, 2019, 01:36:10 pm

Quote from: GleamB – December 23, 2019, 11:57:01 am

Wish I could take advantage of the offers to help. I know I would learn a lot in the process. I guess I will try and bypass the reel ( which I have gotten REALLY fond of ), to see if that is the weak link. If it isn't, I'm not sure how to proceed.

Oh goody! I love spending other people's money.

Next step, hit the electrical supply store, Home Depot or Lowes and purchase "enough" 4-wire cable sized for 50A, a plug and whatever you need to connect it to your coach. Disconnect the reel, and wire in the new cable. Then go around with your VOM and check voltages both unloaded and under load the in input connection.

https://www.homedepot.com/p/Southwire-By-the-Foot-8-4-600-Volt-CU-Black-Flexible-Portable-Power-SOOW-Cord-55809399/204725138

https://www.homedepot.com/p/Go-Green-Power-50-Amp-RV-Replacement-Male-Plug-GGRV-ED507P/311642135

Re: Voltage problem revisited

Reply #70 – December 24, 2019, 12:28:28 am

I was kinda hoping to avoid buying wire/plug as mentioned. I thought that when I opened the junction box ( riveted ) that I could use the existing cord to join the line going into the transfer box with wire nuts. Am I dreaming ?

Re: Voltage problem revisited

Reply #71 – December 24, 2019, 01:28:59 am

That would be the same as making another cord up. As long as disconnecting the cord from the reel isn't too difficult.

Re: Voltage problem revisited

Reply #72 – December 24, 2019, 02:48:24 am

Quote from: GleamB – December 24, 2019, 12:28:28 am

................I thought that when I opened the junction box ( riveted ) that I could use the existing cord to join the line going into the transfer box with wire nuts. Am I dreaming ?

Glenn,
What riveted junction box are you talking about?

What evidence have you come up with that convinces you that the problem is in the power reel?

I would agree with taking the power reel junction box apart (is it the end bell that you are talking about?), but only if you can reliably repeat the problem symptoms of good voltages at the utility pole female receptacle while at the same time, the 120 Vac voltages at the ABT shore power/gen set inlet relay (your first ABT in line with shore power) shows bad readings. If you can do that , then the problem is in between those two points, which points strongly to the power reel.

Only then would I go to all of the trouble of dismounting and taking the power reel apart to look for anomalies. The power reel connections, inside the end bell, in any power reel that I have ever worked on, are very tightly packed and have little forgiveness regarding lengths and positioning. Also, unless you are very confident in what you are doing, you should not power up the power reel while it is partially disassembled, which would be required if visual inspection does not yield any apparent or real evidence of a problem. I've attached some photos of the inside of my 1998 U270 Power Reel.

The female receptacle on the utility pole and the ABT relay terminations, on the other hand, are (usually) much easier to access than the power reel innards are. I'm assuming that your ABT is under the foot of your bed and that you only have one ABT while your second ABT (shore power/inverter ABT) is contained within your Inverter/Charger

HTH
Neal

Re: Voltage problem revisited

Reply #73 – December 24, 2019, 08:48:47 am

COOL photos of the inside guts of the power cord reel!

Re: Voltage problem revisited

Reply #74 – December 24, 2019, 10:19:28 am

Quote from: GleamB – December 24, 2019, 12:28:28 am

I was kinda hoping to avoid buying wire/plug as mentioned. I thought that when I opened the junction box ( riveted ) that I could use the existing cord to join the line going into the transfer box with wire nuts. Am I dreaming ?

No, but now that you're past that brain cramp you have your choice of three places to measure the voltage while your system is under load.
At the plug into your power pole.
At the automatic transfer switch.
And if the voltage is off coming into your ATS, the connections on your cord reel.

Amazing how the thought of parting with money spurs the thought process along.

Art BTDT.

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