Help, fluctuating A/C 120 Volt power

[pegmikef]

Suddenly, last night my 120 volt lamp dimmed, then brightened, then off for a second, then back on. Same thing with the tv, fan and other things trailer wide. In a couple of instances it has been long enough for the frig to switch to gas and for the satellite receiver to lose its locational data.

It always is the same, a slight dip in power first, and then no power for a second or two, and then power restored and it seems to affect all circuits.

My first thought was the pedestal power. I have a progressive external EMS and it shows everything as normal and it seems like it is returning power too quickly if there is a drop or spike.

I have checked all breakers. I shut everything down, checked the plugs on the EMS to the pedestal and rig to EMS, and reset the pedestal circuit breaker. Turned things back on and after a few minutes it happened again.

I don't know if it might be related, but when we arrived at our site yesterday, we had no 12 volt power to anything in the rig until we hooked to shore power. Checked the batteries and they were at 12.7 volts so the converter wasn't charging them. Found and reset the tiny circuit break switch on one of the breakers and converter started charging at 13.5. The 120 volt problem didn't start until several hours later.

I think I may have lost the microwave in this deal.

Has anybody ever seen something like this or have any ideas what could be causing it?\

Thanks.

 

[Roller4tan]

Is your EMS at the pedestal or hardwired near the distribution center? If a portable unit at the pedestal, I would check all your connections after the unit toward the trailer. Since the EMS is not shutting down, there is a problem after it. If the EMS is hardwired, I'd check the connection to the distribution panel. Look for burnt spots.

 

[avvidclif]

The slight dip in power and then none tells me your EMS is working correctly. It sees a low voltage (lights dim) and then shuts down. Once corrected it powers back up. Is anything kicking in (AC) when it dims? Think about it, an increased load causes a voltage drop because of a bad connection, once the load is removed the voltage goes back up and the EMS resets. Since it's at the pedestal start by looking at the plug on the EMS going to the pedestal. Is the breaker hot? Any voltage drop after the EMS will not be seen, it takes a drop on the input. Any discoloration or signs of overheating? If not then it could be park power sagging. If hot outside too many AC's kicking on at the same time?

 

[wdk450]

Any chance you can plug into an adjacent power pedestal with a 30 or 50 amp extension cord to see if the problem is in the pedestal? Does your EMS device store/display power error codes?

I very much doubt this AC problem is related to the initial 12 volt DC problem.

 

[rxbristol]

Plug in a voltage monitor like the AECM20020. It has saved me three times and it allows easier troubleshooting than a surge protection device. We had a problem with the distribution box circuit breaker arching causing wild voltage fluctuations at my pedestal. It was easy to find because our RV was next to the distribution box and I could hear the arching--put two and two together with the voltage flux and the RV park replaced the CB immediately.

 

[pegmikef]

The slight dip in power and then none tells me your EMS is working correctly. It sees a low voltage (lights dim) and then shuts down. Once corrected it powers back up. Is anything kicking in (AC) when it dims? Think about it, an increased load causes a voltage drop because of a bad connection, once the load is removed the voltage goes back up and the EMS resets. Since it's at the pedestal start by looking at the plug on the EMS going to the pedestal. Is the breaker hot? Any voltage drop after the EMS will not be seen, it takes a drop on the input. Any discoloration or signs of overheating? If not then it could be park power sagging. If hot outside too many AC's kicking on at the same time?

We are in cool weather in Colorado, so no a/c's kicking in. In fact when it started occurring last night it was and still is a very light load (lamp, TV, receiver, computer, fan) . . . 7 amps on L-1 and 0 amps on L-2. It did it all night off and on (I could tell by the fan). I am now leaning towards the pedestal, because it has now been a couple of hours since it happened and before it was sometimes a matter of minutes. Thanks and I am keeping my fingers crossed.

 

[TravelTiger]

I would pull the plug and ask for a different site. Power fluctuations are not something to play with-- from what I read, undersized wires in the pedestal under load can cause damaging fluctuations.

But it's odd your Surge protector is not catching it? Or is that what is killing the power? If so you should see some codes E-0 is good, other numbers not.



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[danemayer]

Mike,

Do you have gen prep which includes a transfer switch?

 

[Jesstruckn/Jesstalkn]

I believe if the EMS is at the pedestal and it is not showing any problems then it between that and the transfer switch or the main breaker panel. That's not good.. It could be loose connection in your transfer switch or at your main breaker panel. You have a weak connection somewhere and as you draw power from it it's heating up causing the week power feed. If you have a electric power reel, I have seen 1 guy on here were his power reel swivel connection burned up.
If not then check your transfer switch and see if you can smell any burning wires there or at the breaker panel. Smell around there. It is all bad and could cause a fire if not found asap.
Just my 2 cents but you need to find it before you burn something up.

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[jmgratz]

The first thing I would check would be the transfer switch. First be sure all AC power is OFF. Then remove the transfer switch cover. Check all of the screws for tightness where the wires are attached. A loose one can cause your problem. One other thing to check would be the screws for tightness in the circuit breaker box in the RV. Again before checking be sure AC power is OFF.

 

[murry135]

Sounds like there might be a loose neutral vibrating. Check all neutral connections with power disconnected from pedestal. I have seen them loose several times at the transfer switch and also at the back of the breaker panel in your coach.

 

[Gaffer]

As a 43 year member of the IBEW and retired Supervising (Master) Electrician, my first thought is a neutral problem. Check all you connections in the electrical panel (and transfer switch if you have one).

 

[pegmikef]

As a 43 year member of the IBEW and retired Supervising (Master) Electrician, my first thought is a neutral problem. Check all you connections in the electrical panel (and transfer switch if you have one).

Thanks everybody! Several of you nailed it as you can see in the picture. On the upside we eliminated the pedestal and the EMS as the problem so I started digging and found this. We have had this rig 2 years plus and 20K miles and this damage doesn't look like it happened over night, but has been building and finally reached the point where it surfaced and started showing symptoms. Does that sound right?

Now my question for the knowledgeable folks. I have filed and cleaned all the burnt wires and plan to use shrink tubing to replace the little bit of burned insulation. The bus bar itself doesn't appear to be burned or damaged so will I be safe in reinserting the cleaned wires and making sure that they are all super tight?

As an added note, we have never had any burning smell even when it started acting up earlier this week. Is that normal?

 

[Jesstruckn/Jesstalkn]

I am not a professional, but I do think if you have enough extra wire there I would try to cut it back beyond the burnt section. To get to a cleaner wire for better Conections.
Glad you found it....

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[avvidclif]

I would try and get rid of all the burned pieces. If the copper gets that hot most likely it has crystallized and will be brittle and easier to break from vibration.

 

[pegmikef]

I would try and get rid of all the burned pieces. If the copper gets that hot most likely it has crystallized and will be brittle and easier to break from vibration.

Unfortunately it will be a major undertaking to even get two inches of wire. Fortunately, the ash was mostly the residue from the insulation and the wire itself looks new (but could probably be weakened). Since we are on the move I am forced to try it and will monitor it and do more extensive repair when we get to our next long term destination. If it looks like there is a problem, then I go to plan 2 . . . battery charger and 110 through the window. I am on plan 2 right now.

Thanks everyone for your advice.

 

[JohnDar]

Might need to add an annual inspection of the breaker panel connections to the list of things to check at the start of the season. With no power, that is.

 

[Jesstruckn/Jesstalkn]

I would replace those buss bars also.. You may be able to move them to a closer location to get back to good wire.
You'll find the bad section of wire won't bend and the good wire will bend, so you'll know how far back you need to go to get to the good part of the wire.

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[pegmikef]

Might need to add an annual inspection of the breaker panel connections to the list of things to check at the start of the season. With no power, that is.

I certainly agree John! It would have saved me a couple of days of grief and I would have probably caught it early on instead of it surfacing here in Creede, CO at 8,800 feet where everything is a chore when you haven't adapted to the altitude and there are really no support facilities in the area. Would have been much easier at home.

- - - Updated - - -

I would replace those buss bars also.. You may be able to move them to a closer location to get back to good wire.
You'll find the bad section of wire won't bend and the good wire will bend, so you'll know how far back you need to go to get to the good part of the wire.

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Bus bars look good and show no signs of charring. There are almost no retail facilites. From the condition of the wire, I think I caught this pretty early as it started Tuesday evening then no problem for two days and then started up yesterday afternoon and continued to deteriorate so I went to the plan 2 I described below. I am getting ready to test it so I'll post the results.

 

[Jesstruckn/Jesstalkn]

Ok good luck

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