Author Topic: Intermittent Shedding by EMS  (Read 7437 times)

Ron Johnson

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Intermittent Shedding by EMS
« on: June 25, 2015, 07:22:18 PM »
The symptoms are that sometimes for no apparent reason the EMS 'sheds' the front AC, the water heater and the laundry power. For instance early this morning [5:00 am or so] this happened when only the back AC and the water heater were on [fridge on propane]. At other times we have run both ACs the WH and they continue fine. At other times the 'shed' event happens when the front AC comes on.

A little history - 2 years ago I stomped the 50 amp cable with the driver's side rear jack and had the crushed part cut out and had the plugs replaced on both the remaining RV cable [about 10 feet] and the remaining 15 foot 'extension'. Since then I've usually been attaching the 2 together to plug into the post and have had no issues. However recently I noticed the plug from the RV [male] was not clamping the cord and the insulated wires were exposed. I put this on my list to replace the plug when we finished out trip [2 weeks ago].

The 'shedding' issues began when we got home  so I bought a yellow male plug with a handle to replace the black one the RV shop had put on and started  on the job. When I got into the plug I noticed [a] the white [neutral] wire was loose when I peeled the black wire insulation back the strands were not bright copper but black. I replaced the male plug and the same 'shedding' issues happened so I replaced the female end on the extension and the 'shedding' continued. By the way, the black wire strands on the extension are also black and the old black plug was a little distorted obviously from heat.

It has been suggested that I cut the cable on both ends about a foot back to see if the blackness stops. I am also going to look in the transfer box to see if any blackening has happened in there. I am guessing if the blackened strands continues to the transfer switch I will have no choice but to replace the 50 amp cable right into the transfer switch ... an expensive fix.

Does anyone have any suggestions re troubleshooting this??  We're heading into a very hot week so I'm not going to take a chance of messing anything else up right away up so would welcome any suggestions. Could the EMS be weakening?? Or is it for sure the blackened black wire that is the culprit? Is the EMS behind the breaker panel or in the transfer switch box?

I would sure welcome any suggestions, etc about this.

Phil N Barb Rodriguez

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Re: Intermittent Shedding by EMS
« Reply #1 on: June 25, 2015, 09:49:34 PM »
Ron,

Could be a cable issue with the problems you stated, but just for giggles...is your input amperage on your inverter set to match your shore power output?

Ron Johnson

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Re: Intermittent Shedding by EMS
« Reply #2 on: June 26, 2015, 05:09:33 PM »
Thank you for responding Phil .. we are plugged into a 50 amp receptacle on the post and the shore power is set at 50 amps charging 80%. Haven't had a chance yet to check the transfer switch wires for burning.

Edward Buker

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Re: Intermittent Shedding by EMS
« Reply #3 on: June 26, 2015, 11:34:43 PM »
Ron,

I think you might start out with reading about your EMS and how it operates. What is unclear is if it is responding as it should. For instance, even though you had a light load on your coach shedding started, but the camp ground circuit you were on could have had a heavy load elsewhere and voltage on your pedestal might have been low at the time. When shedding occurs you need to measure and see if the EMS is acting according to spec for voltage and current or not. Start up current on air units can be significant and can cause momentary high currents which can cause issues.

As far as black copper, there should be no signs of excessive heat or any issues like that. If there is then I would change the wire out. Heat means voltage drop and possible fire hazard. If it was night time with no sun involvement and you placed as heavy a load on the circuit as you can (2 airs, water heater element, toaster, hair dryer, whatever it would take) and you measured the heating of the cable after from end to end with an IR gun you would have some idea how much heating is taking place and if the ends have absorbed moisture or blackened and the heating is primarily there or uniformly along the whole cable. The copper itself could have been contaminated and it is a uniform issue or perhaps just the ends. It may take a bit of time under load, given the rubber covering insulation, to sense the highest level of heating by IR gun. You may have to repeat a similar high load test on a friends coach to compare cable heating and interpret the results if it is not obvious. If you had heating end to end uniformly that issue would probably need a known good cable result to compare to.

Last but not least, the contacts on the plug should be bright and shiny and push into the outlet with some physical resistance. That location can heat significantly due to poor contacts. I watched a 37 ft fiberglass boat go up in flames due to heating of the plug due to resistance issues.

Later Ed

Fred Brooks

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Re: Intermittent Shedding by EMS
« Reply #4 on: June 27, 2015, 03:41:16 PM »
     Hi Ron,

  What kind of EMS system do you have? Can you post a pic of the display that is indicating what is being shed? Once I know that, I'll walk you thru the trouble shoot process and repairs. Regards Fred
Fred & Cindy Brooks
2000 Marquis, Jasper
C-12 Wild Cat (U of A)
2014 Honda CRV
Proverbs 3: 5 & 6

Ron Johnson

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Re: Intermittent Shedding by EMS
« Reply #5 on: June 29, 2015, 07:18:59 PM »
Ed - thank you for responding. ** No luck thus far finding a paper or online manual will keep searching ** the RV park upgraded wiring throughout to full 50  Amp 7 yrs ago ** I will recheck the prongs on the male plugs ** The 100F heatwave has abated now it is raining but still very warm so will hold off cutting the 50 amp cord [to see if the blackened black wire strands go back another foot] back till it is cooler.

Fred -thank you for responding as well **a Magnetek 100 I believe [this is the label on the breaker and fuse panel] ** This system does not have a display however we know the front AC, water heater and washer\dryer plug are being shed.

Currently [no pun intended], during the recent heat wave for the last 3 days we have had both ACs, the water heater, battery charger and other smaller loads [TVs, chargers, internet,TV,phone componenets,printer, VCR] on with NO shedding events. The fridge has been on propane and at various times we have used the microwave, coffee maker and toaster while the ACs are running with no events. Today we will run the laundry and see what happens.

I do not profess to know how these things work but if both ACs are on and running at the same time along with the water heater wouldn't one think that both hot legs of the 50 amp are being used?? [I am referring back to the blackened copper stands in the black [hot] wire]

Thanks again for any advice .. Ron

Edward Buker

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Re: Intermittent Shedding by EMS
« Reply #6 on: June 29, 2015, 09:49:55 PM »
Ron,

Shedding takes pace when some aspect of the power being supplied is insufficient, usually driven by low voltage being supplied while heavy current load is being drawn, by you or by you and others on the grid. There are other measurements like frequency or over voltage that can cause shedding but they do not usually come into play.  Both legs are being used if both air units are on.

The fact that you can now handle multiple high current loads with your coach (water heater, 2 air units, etc) leads one to believe that the problem could have been, at least partially, an issue with power grid in the campground or beyond. You should have readouts in your coach for AC voltage and current on each leg. You should record some of those values when shedding is happening and when it is not so that you are able to see if the shedding makes any sense vs typical unit specs.

As Fred mentioned the EMS unit needs to be found and described at some point in order to understand this issue. Maybe the main bay near the transfer switch or where the main power cord comes into the coach.

The black copper wire is a problem if heating and abnormal voltage drop occurs but it is not a given that blackness of the copper, just by appearance, always needs to be replaced. It can be considered a blemish and cosmetic or it could be a source of extra resistance and heating which would be considered a defect that requires replacement.

Because you have a non molded plug on now cutting back a foot and seeing if the black copper disappears and then remounting the plug seems like a good plan anyway. If the black persists then resistance measurements would need to be taken. How many of the 4 wires have the black copper? If just one of the two heavy gauge hot wires (usually black and red insulation) has the black copper then using an ohm meter to compare the resistance of those two wires would help answer the question if this is a blemish or a defect needing to be replaced.

Later Ed 
« Last Edit: June 30, 2015, 02:56:24 AM by Edward Buker »

Fred Brooks

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Re: Intermittent Shedding by EMS
« Reply #7 on: June 30, 2015, 02:14:19 AM »
     Hi Ron,
 
   Here is how the EMS system works, It was originally engineered to come into play when 50amp services are stepped down to 30amps via 50amp to 30amp adaptor. It knows you have used the adaptor because it now sees that both legs of 120volts are on the same phase inside the coach. Once it determines that, it monitors the amperage being used via a shunt coil that the neutral wire is going thru. If it determines you have excedded the 30amps available, It starts shedding loads that have an alternative energy source until the load goes below 30amps. It was designed for coach owners who did not monitor their loads and or were never advised that when you use the 50 to 30 adaptor you give up 70amps of available power.
     I agree with Ed about your problem being a park issue. Here is what I advise my customers that are in a park and experiance ANY kind of electrical issue (especially thunder storms). If you loose power to your coach the very first thing you do is go outside and unplug your coach. Then inquire if your neighbors are having a similar condition. Just imagine if you are in a park and 200 coaches loose power all at once in the middle of July and it is 95 degrees outside. Most people don't do anything and patiently wait for the power to come back on. Well here is the problem with older parks. When the power is restored it creates a momentary "surge" and it is not good to be on the recieving end of that. Once power is restored and stabalized, turn off your airs and then go outside and plug your coach back in.
           Hope this helps, Fred   
Fred & Cindy Brooks
2000 Marquis, Jasper
C-12 Wild Cat (U of A)
2014 Honda CRV
Proverbs 3: 5 & 6

Ron Johnson

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Re: Intermittent Shedding by EMS
« Reply #8 on: June 30, 2015, 07:27:53 PM »
Thanks Ed and Fred ... we ran 2 loads through the washer\dryer, the airs came on and off and there were no shedding events. We'll put the fridge on AC later today.

 The only thing we can think of that changed recently was when the power provider [Fortis] came and checked the power at our meter [Thursday or Friday] which is about a lob wedge from our site. They found no anomalies but I assume they 'rebooted' the power to our meter. The Park is responsible for the power from the meter to our post but we did not call them. We have had no 'events' since the, we don't think.

In the meantime we'll test things with the fridge on, look for burnt black wire at the transfer switch, and test for heat at the outside connections. Thanks again for all your help.
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Ron Johnson

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Re: Intermittent Shedding by EMS
« Reply #9 on: July 03, 2015, 06:51:53 PM »
Hopefully, this is a wrap-up report ... after 2 days with the fridge and everything else on AC, the washer\dryer running and the A/Cs running we have had NO shedding events. We definitely had some events after I had replaced both ends but have not had one since the electrical provider checked the meter.

I am of 2 minds now about cutting the power cord back a foot to see if the blackened black wire persists ... I think I will do it but maybe a little later when it is cooler. Thank you everyone for the advice and the education!! ... Ron
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