Electrical Issue

rjlong38Q · 08-14-2021, 03:45 PM

2015 Adventurer 38Q. Left for the day and came home to no AC. When we left we had the front AC on. Turned on the rear AC and it came on with no issues but the front will not start. Checked the Powerline EMS and LI shows 0 volts and L2 shows 240 +/-. Disconnected the 50 amp service and started the generator. After 30 seconds the transfer switch tried to latch but would not latch. Turned off generator, reconnected 50 amp service. Transfer switch latch and accepted power. Check the L1 and L2 line out from the switch and had 110 on each line and 240 v between L1 and L2. Checked Powerline EMS and it is still showing L1 0v and L2 240. Thinking it may be a transfer switch problem? Fridge, MW and other AC systems seem to work properly. Thoughts?

Doorguy88 · 08-15-2021, 09:08 AM

So today we unhooked from shore power to move camp sites and hooked back up. Now we are having issue power to our TVs. The power will jump from 120 to 0 then turn inverter on every thing works as it should. Also have adequate power at breaker box

eyecando · 08-15-2021, 01:30 PM

When you say LI shows 0 volts and L2 shows 240 volts, what is the reference? I would assume it is the neutral or ground, but there is way you should have 240 volts referenced to neutral unless the service you are plugging into has an open neutral.

I suspect there is something wrong with your EMS display and the actual voltages are not what you are seeing.

jerichorick · 08-29-2021, 05:50 PM

Quote:

Originally Posted by rjlong38Q

2015 Adventurer 38Q. Left for the day and came home to no AC. When we left we had the front AC on. Turned on the rear AC and it came on with no issues but the front will not start. Checked the Powerline EMS and LI shows 0 volts and L2 shows 240 +/-. Disconnected the 50 amp service and started the generator. After 30 seconds the transfer switch tried to latch but would not latch. Turned off generator, reconnected 50 amp service. Transfer switch latch and accepted power. Check the L1 and L2 line out from the switch and had 110 on each line and 240 v between L1 and L2. Checked Powerline EMS and it is still showing L1 0v and L2 240. Thinking it may be a transfer switch problem? Fridge, MW and other AC systems seem to work properly. Thoughts?

I have a lot of experience with RV power and the many problems that come with it. What you are describing is very troublesome to me. Please be more specific as to where you are taking the voltage readings. This almost sounds like a power transformer issue.
At the pedestal, measure the voltage across the left and right receptacle ports (L1 to L2). This should be 240VAC or there abouts.
Measure the voltage from each of these ports to the bottom port (neutral). Each should read 120V.

Do the same for the top port. (ground) Should see about the same readings.
If these are correct leave the cord unplugged.
Remove the cover of the ATS and look for discolored wires, especially the white (neutral). In any case tighten ALL of the connections in the ATS.
If a wire is damaged because of overheating you must cut the burned section off and reconnect the wire. The terminal should be okay. This repair is not always easy. You may have to loosen the cord at the box connector and strip back a bit of the jacket to get enough wire to make a good connection. The end of the stripped wire needs to feed deep into the connection but leave very little bare wire out of the terminal to the insulation. After tightening a repaired terminal go back and tighten it again. Repeat till it is firmly tight but not over tight. The wire relaxes after the initial tightening.
Hope this helps you find your problem.
If you see 240VAC on L1 or L2 to neutral, advise the park owner and your neighbors. You should all be having problems.

Rick

eyecando · 12-16-2021, 06:27 AM

I agree. It's almost certainly an open neutral.

Open neutrals can cause things like this to happen since most of your 120 volt appliances may be connected between L1 to neutral. With an open neutral the voltage between L1 to neutral would be very low and could appear to be zero volts. With no or few 120 volt appliances connected between L2 to netural, the L2 to neutral voltage would approach 240 volts. The L1 to L2 voltages would be normal for an open neutral.

Problem could be in your wiring or the pedestal.

I agree, check the pedestal voltages first. If it is correct, check the wiring in your RV.

I would ensure the pedestal plug is disconnected from the RV to the pedestal and the generator is off. Turn off all AC circuit breakers. Measure from the neutral resistance between the RV plug to neutral in the RV. Expect less than 1 ohm. If the resistance is very high, continue to check part of the circuit until you discover the problem. The cord you plug into the pedestal is a likely problem. Be aware that the connection could be intermittent and affected by manipulating the plug end of the cord.

rjlong38Q · 12-16-2021, 07:12 AM

You are dead on with your trouble shooting. The problem was in fact the plug at the end of the 50 amp cord. Line voltage had crossed over to the neutral leg and I actually ha a small amount of voltage on the neutral. Changing the plug at the end of the cord fixed the problem. Also had to change the control board on the front AC since it got smoked with the voltage back feed. Everything works fine now.

jerichorick · 12-17-2021, 07:19 AM

Quote:

Originally Posted by eyecando

I agree. It's almost certainly an open neutral.

Open neutrals can cause things like this to happen since most of your 120 volt appliances may be connected between L1 to neutral. With an open neutral the voltage between L1 to neutral would be very low and could appear to be zero volts. With no or few 120 volt appliances connected between L2 to netural, the L2 to neutral voltage would approach 240 volts. The L1 to L2 voltages would be normal for an open neutral.

Problem could be in your wiring or the pedestal.

I agree, check the pedestal voltages first. If it is correct, check the wiring in your RV.

I would ensure the pedestal plug is disconnected from the RV to the pedestal and the generator is off. Turn off all AC circuit breakers. Measure from the neutral resistance between the RV plug to neutral in the RV. Expect less than 1 ohm. If the resistance is very high, continue to check part of the circuit until you discover the problem. The cord you plug into the pedestal is a likely problem. Be aware that the connection could be intermittent and affected by manipulating the plug end of the cord.

In the RED highlight I have a question. If the Neutral is open how can the coach see 240V on L2 to Neutral? As I recall from my years in electrical work, if you loose the neutral you are applying 240VAC to the load and not 2 120VAC feeds.
When I lost the neutral from a pedestal I was under the load of my A/C units. All kinds of things happened. My generator started and we could hear arcing from the A/C unit overhead and smell wires burning.

I have replaced the burnt wires and relays in the A/C controllers, but.... I have been left with damage to the controllers. Now, when on shore power, if I have the generator in Auto Start and the A/C units come on the generator starts. I have not had the time or the weather to address this issue.
I like keeping my generator in Auto Start when plugged in. We are often in areas that have the reputation of loosing power of going into brownouts. I like the safety of the generator in case we are out and the power fails. Don't want the coach to be too hot or cold when we get back.

eyecando · 05-28-2022, 10:18 PM

If 240 volts is applied between L1 and L2 and the neutral is open between the system neutral and your coach Neutral, your voltage is divided between L1-N and L2-N where N is your coach neutral. It's like applying the voltages across 2 series resistances. In other words, it's a simple voltage divider.

If most of the 120v loads are applied between L1-N, then the voltage between L1-N will be much less than is what is across L2-N and the voltage across L2-N will be equal to 240 - (Voltage between L1-N).

Another way to look at this is to consider the two resistances R'L1' and R'L2' and an infinite resistance connected between the N terminal and the system neutral. The first resistance is the resistance between L1 to Neutral. The 2nd resistance is the resistance between L2 to Neutral.

The voltage across L1 = 240*R'L1' / (R'l1'+ R'L2').
The voltage across L2 = 240*R'L2' / (R'l1'+ R'L2').