Electric

I have a problem that I am trying to resolve for some friends of mine.

They have a mobile home that is receiving some strange voltages to the sub main panel located In their bedroom. One of the hot legs is getting like 47 volts and the other is getting 0. Could this be the result of a "loss" of neutral or a conductor? Is it possible that there is a loose connection in the meter base or going to the leads where they are hooked up at the weather head or transformer? What is your idea or suggestions?

Is the mobile home wired with copper or aluminum wire? What is the age of the unit? What type of meter are you using to check the voltage? Are things plugged in to that end of the unit not working correctly?

You mentioned the (sub) main panel. That is a little confusing but if I read you right one leg of the 240 entering the unit is 47 volts and the other zero. If that is the case the problem is outside the unit I would think as you mentioned and I would suggest contacting the power company and have them take a look as there is no way for you to access those connections to check them.

Pros will be along shortly with more advice.

Welcome to the forum.

The wire is aluminum throughout the whole trailer. The trailer looks pretty old, I would say early 80's. I said sub main, but it is or should be considered the sub panel since the riser, meter base, and panel with main breaker are located all on same utility pole not but 10' from the sub panel. I was using a multimeter volt meter which was used on 200 v to.check the conductors phase to ground. I switched to 600 volts when checking phase to phase to get 240 across both legs. None of the stuff inside is working.correctly. The outside receptacles are powering 2 extension cords to their bedroom. They are energized because those outlets are powered from the main panel box.

Aluminum wire as notorious for these problems in mobile homes and the problems could go back to that. If you can safely disconnect the sub panel from the main and kill all power to the mobile home so you can work on the connections that’s what I would do. Again I’m not a pro just a homeowner with some skills. I would look at cleaning and recoating the aluminum connections with a proper dielectric coating and then retightening.

My guess like yours is bad connections and or bad grounding.

Have you checked voltage at the main panel as you said the extension cords are working properly. So the issue sounds like it is between the main and the sub.

Once I got proper power restored I would do my best to check every outlet one at a time and make sure they are not also having problems. What you will find is those outlets are special made mobile home stuff that’s not the greatest of quality.

Hope this helps and again I hope others drop in to offer their advice for you.

If you are comfortable working behind the dead front panel in the main panel, and you have 240V on the leads, not the breaker screws, leaving the panel, there is likely a good connection there.

When you measure at the trailer panel, measure the leads then the screws and if there is a difference it is indicative of a bad connection, and easily corrected.

Thank you for your input I will go ahead and try the new ideas listed and keep you posted!

Thanks for your input! I will keep you posted.

I am still stumped. I got a better multimeter to use. I retested the conductors from the meter to the main breaker in the main panel. I get 120 both legs. 240 across both. I then tested the conductors leaving the main from the main panel. Again, I get good readings. Now, I go inside where sub panel is, I get 88 volts on one leg and 0 on the other. Together 88 volts. I pulled out each lead from where it terminates and cleaned off aluminum with wire brush and used No-Ox and retighten them all on each lug.....what could this be? I did notice the ground bond is broken and not attached to the ground rod. Connected but not attached to rod. Could this be a short in the feed fromain to sub? Is this a main breaker issue? How do.I determine if I should replace both feeders or what?

Also, the feeder that has a 0 reading. I took out of main in subpanel and tested. It still showed same reading. Does this outrule main breaker in subpanel and mean the wire has a short in the pipe? It is fed underground and has a 2" galvanized metal conduit.

You cleaned the lug connection. Did you turn something off before you did that.

chennault05 said:

I am still stumped. I got a better multimeter to use. I retested the conductors from the meter to the main breaker in the main panel. I get 120 both legs. 240 across both. I then tested the conductors leaving the main from the main panel. Again, I get good readings. Now, I go inside where sub panel is, I get 88 volts on one leg and 0 on the other. Together 88 volts. I pulled out each lead from where it terminates and cleaned off aluminum with wire brush and used No-Ox and retighten them all on each lug.....what could this be? I did notice the ground bond is broken and not attached to the ground rod. Connected but not attached to rod. Could this be a short in the feed fromain to sub? Is this a main breaker issue? How do.I determine if I should replace both feeders or what?

Click to expand...

If you have 240V at the leads of the main and you do not have 240V at the leads, either attached or detached from the breaker in the trailer, than you have a break in the line from the main breaker to the sub-panel.

The ground not being bonded is significant and should absolutely be
reestablished.

Have there been any lightning storms in close proximity to the occurrence of these difficulties?

Snoonyb said:

If you have 240V at the leads of the main and you do not have 240V at the leads, either attached or detached from the breaker in the trailer, than you have a break in the line from the main breaker to the sub-panel.

The ground not being bonded is significant and should absolutely be
reestablished.

Have there been any lightning storms in close proximity to the occurrence of these difficulties?

Click to expand...

There should be a fused link between the meter and the trailer breaker box too.

Testing at the main panel the test probes of the meter would be contacting the lugs most likely and not the conductor. If there was oxidation on that end (likely as it is outdoors) then cleaning, redressing and torque could be in order. If not it would have to be in the underground wire. That is unlikely if the right type of wire was run thru the conduit and no digging has taken place in the area. If the wrong type of wire was used and conduit has rotted out it is very likely.

I would first check and clean etc at the main end like you did the sub end, or at least make sure your meter readings were taken from the wires not the lugs.

By all means repair the ground also.

I’m sure by your description of what you are trying you are making sure power is off connected to any work you are doing. When you go behind the cover on the main panel be aware there will still be active power in that panel even when you kill the main to do your work. always check before you touch anything and be on alert to stay away from active points.

There might be some digging in your future.

bud16415 said:

Testing at the main panel the test probes of the meter would be contacting the lugs most likely and not the conductor.

Click to expand...

And if there were oxidation interrupting the contact between the lug and the conductor and the OP is reading 120V each leg from the conductors, but not the lug?

It's a process of elimination.

Snoonyb said:

And if there were oxidation interrupting the contact between the lug and the conductor and the OP is reading 120V each leg from the conductors, but not the lug?

It's a process of elimination.

Click to expand...

Well I read what he wrote and a lug is a conductor just as everything is that is not an insulator or a semi conductor. Some of this is semantics as lots of people most people in fact assume that the connector and the conductor are of the same potential at the point of contact. I was merely pointing out that connection could also be a point of high resistance. I don’t see a condition where the wire “conductor” would have normal voltage but the lug would show low voltage. That could be possible with a digital meter and surface oxidation I suppose. Many electricians for that reason use a solenoid voltage tester called a Wiggins tester or Wiggy. They draw a sizable amount of current from the source being tested and in doing such will burn thru slight areas of oxidation.

Before he grabs his shovel I was just suggesting he be 100% positive he has good connection at both ends. I suppose also that once he has both ends of the suspicious underground wire disconnected that would also provide him any number of additional tests he could do on those wires to determine if he has shorts or poor conductivity.

And if you eliminate a step in the process, you may have overlooked the cure.