Community Forums

digNbubbs · 07-02-2007, 07:59 PM

I seem to have two different voltages in my coach right now. The rear is running ~119V and the front 104-108V. I am plugged into 50A service at a state park right now. I am on my second service post, as I had to move sites today. Both sites gave the same results.

My coffee pot zonked out this morning, just as it was grinding a fresh batch of beans. Not a good way for me to start the day - no coffee

Not sure if it is related to the low voltage, but that is what made me meter the front.

I always have a meter stuck in a rear outlet always so I can monitor the voltage. I didn't figure I could have two "zones" of voltage. Any thoughts on why? I have not metered the post. Is it possible one leg is different than the other? Is there any reason I am seeing this?

Thanks -

--kev

digNbubbs · 07-02-2007, 07:59 PM

I seem to have two different voltages in my coach right now. The rear is running ~119V and the front 104-108V. I am plugged into 50A service at a state park right now. I am on my second service post, as I had to move sites today. Both sites gave the same results.

My coffee pot zonked out this morning, just as it was grinding a fresh batch of beans. Not a good way for me to start the day - no coffee

Not sure if it is related to the low voltage, but that is what made me meter the front.

I always have a meter stuck in a rear outlet always so I can monitor the voltage. I didn't figure I could have two "zones" of voltage. Any thoughts on why? I have not metered the post. Is it possible one leg is different than the other? Is there any reason I am seeing this?

Thanks -

--kev

RV Wizard · 07-02-2007, 11:31 PM

Kev, I bet that if you check the pedastal you will find the same thing. It sounds like one leg has high resistance and is causing the voltage differences. It could be the whole run from a bad connection, breaker, or transformer feeding it. Do you have & use a Surge Guard?

Route 66 · 07-03-2007, 05:03 AM

This could also be a bad neutral with the 50 amp service.

As Mike posted, check the pedestal, and see if others have the same problem.

digNbubbs · 07-03-2007, 07:11 AM

Thanks for the suggestions. I just metered each leg and got 111/112V (left and bottom, right and bottom), then across was ~237V (left to right). I do not have a surge guard.

I am going to start my generator a little later (after my neighbor leaves) to see if I am getting the same results inside the coach. I metered as many outlets as I could and found that the pattern seems to be that the outlets that are on the inverter circuit are the low voltage ones. Makes no difference if the inverter is on or off.

Thanks again for the help -

kev

Joe-K · 07-03-2007, 07:56 AM

The two poles of a 50 amp service feed can have different voltages depending on the loads applied to them. As different loads are applied to each leg, there will be differing voltages drops in the wiring connected to the pedestal as well as within your coach.

As the current requirements on a leg increase, the voltage will decrease. Voltage drop increases as the current increases through the wiring.

Mr George Ohm way back in the days before RV's came up with his famous Ohm's law formula E=IR where Voltage (E) equals the current (I) times resistance (R)

If you have a 1 ohm resistance in your wiring and are drawing 10 amps, you will develop a 10 volt drop across that resistance. Electrical designers try to avoid connection points with wiring because each connection can add fractional resistances. Depending on the tightness and quality of the connections in the RV and the distribution system, you will have resistance in your wiring. By tightening connections, you may be able to reduce the resistance.

I frequently see the leg that is supplying power to my Air conditioner be several volts less than the other leg but it's not that much of a concern unless the voltage begins dropping below 110.

Route 66 · 07-03-2007, 08:36 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">The two poles of a 50 amp service feed can have different voltages depending on the loads applied to them. As different loads are applied to each leg, there will be differing voltages drops in the wiring connected to the pedestal as well as within your coach. </div></BLOCKQUOTE>

I agree. However, if one leg gets down around 104 volts, the campground wiring may be under sized.

If one leg gets up around 130 volts, then there is a neutral problem.

digNbubbs · 07-03-2007, 09:23 AM

Thanks guys. Admittedly, I am not very well versed in the world of speeding electrons. If you could tell me some specific things I can test, I would appreciate it greatly.

I have tested at the post with the coach unplugged and breaker on (results in post above). When I turn off all draws - A/C, water heater, fridge - the "low" outlets go to 111.4V, while the "other" outlets are at 115V. Turn the rear A/C on and the voltage goes to 104V in the "low" outlets, and 118V in the "other" outlets.

With the voltage going that low when the A/C is on, is the issue just with the supply (shore power), could this one working A/C possibly be drawing too much and is dragging down the voltage? My front A/C is not working, so I can not turn it on to see what happens to the other outlets.

Sorry for the elementary questions. I don't think I have ever paid this close attention to electricity

Thanks again -

kev

Hitchhiker · 07-03-2007, 10:03 AM

Unplug the coach from shore power, make sure the generator is off, disable the inverter if you have one, then remove the cover from your coach's entrance panel. Tighten all the lugs that contain a wire, particularly the two that goes to each side of the double 50 amp breaker and the two on the bus bars. They all should be good and tight. Tighten the grounds and the white commons too, they'll be along the sides.

If you find a loose one, take a real close look at the wire, its insulation, and the lug for signs of being overheated.

You're dropping voltage someplace in the coach and the breaker box is the most logical. When voltage is dropped, heat is usually generated someplace where it doesn't belong.

If you're uncomfortable with any of this or feel you lack the necessary knowledge to do this, call a licensed electrician to check it out for you.

digNbubbs · 07-03-2007, 04:03 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Hitchhiker:
Unplug the coach from shore power, make sure the generator is off, disable the inverter if you have one, then remove the cover from your coach's entrance panel. Tighten all the lugs that contain a wire, particularly the two that goes to each side of the double 50 amp breaker and the two on the bus bars. They all should be good and tight. Tighten the grounds and the white commons too, they'll be along the sides.

If you find a loose one, take a real close look at the wire, its insulation, and the lug for signs of being overheated.

You're dropping voltage someplace in the coach and the breaker box is the most logical. When voltage is dropped, heat is usually generated someplace where it doesn't belong.

If you're uncomfortable with any of this or feel you lack the necessary knowledge to do this, call a licensed electrician to check it out for you. </div></BLOCKQUOTE>

Thanks much for the advice. I did as suggested, and looked at the connections in the transfer switch box, the inverter, then up to the main breaker panel. This is what I found in the breaker panel -

Good call!

I cut off the burnt crust and reconnected the wire. Saw much better results right off, although I don't think I am out of the woods yet. With the A/C on, the voltage drops to 109.5-110V now. However, when I turn the microwave on while the A/C is going, it will again drop to ~105V.

So, for now, I will run the fridge and water heater on propane, and not use the micro while the A/C is running. Hopefully I can find someone soon to take a look at the front A/C and this voltage issue.

Thanks again for all of the help.

--kev

MonacoMama · 07-03-2007, 07:22 PM

This stuff is why I

coming to this site!! Great catch, Hitch!!!

Hitchhiker · 07-04-2007, 03:27 AM

digNdubbs,

Glad you found the problem, check all the other connections while you're in there too. If you're really industrious, back off all the lugs, wiggle the wires, then re-tighten them firmly.

Doing this will provide a new contact spot between the lugs and the wires and may preclude a developing, future high resistance connection.

"007" · 07-04-2007, 07:59 AM

Some thing else to check is the load center devided up evenly not all heavy drawing units on same buse. Some people have found this to be the case with heavy load on one side of load center.

digNbubbs · 07-04-2007, 10:10 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by "007":
Some thing else to check is the load center devided up evenly not all heavy drawing units on same buse. Some people have found this to be the case with heavy load on one side of load center.

</div></BLOCKQUOTE>

Mine appears to be on a single bus. Just a single row of breakers on a single bar. Is this what you are referring to?

Today I was having more pretty extreme drops. It seemed the A/C would drop it to 109.5-110V. If I turned anything else on, it would drop to 107-108. When I see that, I shut things down. Tonight I tried it as well and there was much less of a drop, and with the A/C on, it was showing 112V.

I have only lost a coffee pot, but was able to upgrade, so it worked out

Thanks again for the suggestions.

kev