Community Forums

Stakealot · 07-13-2010, 10:51 PM

I recently installed a 120/240v 4 wire/50 amp (14-50R)outlet in an enclosure right beside my garage to plug my '99 Allure (50 amp) into. I used 3-#4 aluminum U.S.E. conductors to run to the new pedestal and outlet, and an 8' copper clad ground rod and #6 bare copper wire at the pedestal for the 4th wire (ground), (I chose to not run the 4th wire). I used a double pole (240v) 50 amp breaker in the existing panel to supply the outlet, and the neutral tied directly to the neutral bus in the existing panel. This is what I need help with...when I test the new outlet, it is just as the book says it should be, 120v on the right (x) or left (y)vertical slots, to the center slot (w), or the tunnel looking ground slot (g), and 240 volts between the x and y. When I plug the rigs 50 amp cord into the new oulet...the circuits coming from the inverter (2000w 20D heartinterface) drop the voltage from 120 volts to 88 volts. All circuits running directly from the cord are fine @ 120 volts!!! And just to make it stranger...I took the multi-meter and put one probe in the ground (dirt), and the other on the frame of the rig, and got a reading of 27 volts AC... Now I am at an rv park with 50 amp service plugged in and EVERYTHING is normal...I just don't get it...what did I do wrong???

Thanks for listening

MonacoMama · 07-13-2010, 11:12 PM

You will find the info needed from the link on the left side of this page...
Good Luck!

DriVer · 07-14-2010, 05:00 AM

Quote:

Originally Posted by Stakealot

...I just don't get it...what did I do wrong??? Thanks for listening

I would have carried a "Bond" (Green wire) from the source to the remote panel, thereby bonding the RV enclosure to the main service. This is usually accomplished using a #8 solid cu wire.

I don't believe that a ground rod at the RV panel is required.

I believe that I would isolate the Bond (Green) from the Neutral (White) in the RV panel as well. Perhaps you have tied in the neutral to the same bar as the ground rod. I would have tied in the the bond (ground rod) on a separate lug directly attached to the enclosure. maybe this is the source of the problem, more than likely not, but I might investigate it.

This is what I see as anomalous however I am not sure this will resolve the leak to ground you are experiencing.

Absent in your description, I also might ask if you used the "antioxidant paste" on the conductors?

Route 66 · 07-14-2010, 05:07 AM

The link that MM mentions above explains it all and is the correct way to wire a RV receptacle.

94-Newmar · 07-14-2010, 06:22 AM

If wired properly you should see 240vac if you measure across L1 and L2. The only way you would see leakage across ground is if your neutrals are grounded. Wrong wrong wrong. If your other panel in the garage is wired this way it needs changed. Your neutrals must not be to ground. You may have wired the new box correctly, however if your neutrals are wrong on the box you stubbed from, then yours is incorrect as well.

HD4Mark · 07-14-2010, 06:46 AM

I am curious why you would drive a ground rod rather than carry the ground from your electric panel? Not sure if it would make any difference but wouldn't that make a difference in potential between the panel and your ped? I can see no problem with adding a ground rod though.

DriVer · 07-14-2010, 07:35 AM

Quote:

Originally Posted by 94-Newmar

If your other panel in the garage is wired this way it needs changed. Your neutrals must not be to ground. You may have wired the new box correctly, however if your neutrals are wrong on the box you stubbed from, then yours is incorrect as well.

94-Newmar, I was thinking along those lines however IF the main panel was finished and inspected one might want to investigate the destination panel more closely. I would also like to see how the sub panel was tied into the main, wouldn't you as well?

94-Newmar · 07-14-2010, 08:52 AM

Yea, would be neat to see a pic of the existing panel with the cover off. Almost sounds like the Neutral and grounds are reversed.. Even more interesting is the 88vac reading, which shouldn't be caused by the neutral or grounds being wrong/reversed.

Paul R. Haller · 07-14-2010, 10:09 AM

The only time a ground and neutral are bonded together is in the main panel. That's the only place they are bonded. In all other sub panels or electrical pedistles they are to be separate. The only place a ground stake is to be used is at the main panel and then it must often be bonded with the water and gas pipe using a continuous piece of copper bare wire # to be determined by the size of the main panel in amps. J weaver Jr clamps are used and acorn nuts on the ground stakes. If you are using more then one ground like a ground rod at the panel or 2 rods at the panel like in my juisdiction or even a ufer ground at a sub, those 2 grounds need to be bonded together so there is no potential between grounds. Your wiring job would be red tagged in any municipality as inappropriate. There is clearly a difference between grounds in your pedistal and house. The differences between grounds could explain the 27 volts seen at the trailer but I'm guessing that is just too large a drop. I bet your heart inverter has died. The use of aluminum conductors is upsized to carry the current load as you have done but Aluminum is required also to use antioxidant paste in the connectors to prevent corrosion. The use of a trick I have found when using aluminum is to tighten down the connectors and wrap the connector with the handle of a large screwdriver and check it again. You'll usually find it's loose and requires a further tightening again. Repeat until you no longrer find any loosness in the connector.

Where I work use of aluminum, like an SCR cable, is frowned apon and in my house I would never use it no matter how upsized it is. It tends to swell when current is drawn through it and it always has more resistance then copper does causing the connetions to be often unreliable after use and causing the installer to return again and again to tighten down the connectors to prevent heat caused from loose conections. All that said, it is legal.
-Paul R. Haller-

Stakealot · 07-14-2010, 10:11 AM

Thank You All for the possible solutions to this rather baffling problem. I will check to see if the grounds and neutrals are isolated in the existing panel. also add a bond wire from the existing panel ground bus to the new outlet / enclosure ground. I used inhibiter on all terminal connections, especially the aluminum to copper ones. I added a ground rod at the new pedestal just out of habit, I believe you can never have too many ground rods (retired power lineman). Thanks again, I knew I could count on you good folks to set me in the right direction! S.

TQ60 · 07-19-2010, 06:23 PM

The GREEN wire is safety ground, some folks call it a bond, but it is bonding the grounds together so any short to any item is safely shunted to ground and trips the breaker.

As others have stated, only at the MAIN ac load center will neutral and safety ground be bonded together.

It is here that the safety ground is connected to earth via water pipe or ground rod, some folks call this "meter ground".

If you are measuring a difference in voltage between the coac frame and earth ground then it is clear that the safety ground is not close to neutral.

This could be deadly if you are standing on the lawn and touch the coach while something is running, get it unplugged until the ground is correct.

There should be zero current flowing in the green wire so there should be zero voltage drop across it, but with a 27 volt drop there is current flowing someplace.

The ground rod may need to be removed depending on local code requirements, an additional connection needs to be made from the green safety ground buss in the main load center out to the new 50 amp outlet.

This wire needs to be large enough to insure any short does trip the breaker, it may be a smaller guage than the main lines, this depends on local code requirements.

The best bet would be to make a trip to the local building department, they can advise the correct wire sizes for the given lengths and help you install everythig as it should be.

A permit would be best as you rinsurance carrier may frown in the event of a fire, the permit is cheap.

Regarding the inverter, if the outlets in the coach are remaining the correct voltage whil ethe inverter has less then there may be other issues here, if the inverter is an aways on type that always supplies the power to the output side then the grounding problems may be confusing it as they often have leakage that is absorbed by the safety ground, they are "switching power supplies", these cause a lot of strange things is not properly grounded, this may be the source or your 27 volt reading.

ccook129 · 07-19-2010, 07:58 PM

I do hope that no one will put a ground from electrial,plumbing,ground rod and hook any of them to a GAS line.Gas lines should never be grounded to power ground,and I would not want to be around in a lighting storm and have a hit at your house.When the strike looks for a ground a gas line would be "oh poop",fire in the hole.

Paul R. Haller · 07-20-2010, 10:11 AM

[QUOTE=ccook129;672259]I do hope that no one will put a ground from electrial,plumbing,ground rod and hook any of them to a GAS line.Gas lines should never be grounded to power ground,and I would not want to be around in a lighting storm and have a hit at your house.When the strike looks for a ground a gas line would be "oh poop",fire in the hole.[/QUOTE

Uhh sorry, but in my municipality, it is required along with 2 ground rods, 8 feet apart from each other. Here where the soil is expansive the inspectors want 2 ground rods driven into the ground at least 8 feet from each other and then bonded to the ground buss using a # 8 or larger wire. The wire has to include in a single run unbroken, between both ground rods, the water pipe, and the ground buss in the panel. In another continuous run, another #8 or larger wire at the hot water heater, a single wire run between the cold water pipe and the gas line using j weaver Jr clamps. A upher ground is now required on all new construction but 2 ground rods 8 feet apart and bonded for remodel where the footprint of the house is not changed. A upher ground is simply 25 feet of rebar or # 8 copper wire completely enclosed in concrete radiating in two directions ( 25 feet in each direction) and bonded electrically to the main ground buss. They do not care if rebar used for the upher is structural. A upher ground is superior to ground stakes because the wire or rebar is surrounded by concrete preventing the corrosion build up around the ground by preventing 02 from coming contact with the ground stake. Additionally, the concrete is porous allowing the water in the soil to reach the upher ground ensuring a good contact between ground water and the conductors. I'm guessing, the gas line is included in the ground schemes because 1, ignorant workers will ground receptacles with no grounds in the wiring to the nearest threaded pipe assuming it's a water pipe. 2, because the gas pipes are often buried in the ground to the service and then onto an above ground meter with plastic isolators on the transition between below ground and above ground pipe construction rendering the gas line above ground as a floating ground. Also required is a plastic isolator between the water connections at the water heater to prevent corrosion of the sacrificial anode inside the water heater. However, where all pipes (cold and hot water and gas) are grounded to the same potential, no excessive corrosion should take place at the anode inside the water heater.

Additionally, Pacific Gas and Electric can and do refuse to work on the gas line if there is a potential difference between the pipe ground and the existing soil, sighting the possibility of fire and requiring the homeowner to get the gas line grounded by a licensed electrician along with an inspectors sign off before they will proceed with gas line work.
-Paul R. Haller-

wa8yxm · 07-20-2010, 10:56 AM

Ok, The problem here seems to be voltage loss under load... SOME voltage loss under load is 100% normal but 120 to 88 volts... That is a bit too much loss.

You said you used #6 Aluminum.. My question is this: HOW LONG IS THE RUN

There are voltage loss pages scattered about the internet,
Wire Size Calculator

Plug in the length of the run (1/2 the total circuit path = length of cable)
I used 25 amps and 100' and 120 volts... And got a minimum wire size of 4ga

In addition make sure you have the right connectors at each end, Connecting Aluminum wires to copper/brass screws is not as simple as connecting copper wire to them.

My Advice.. Upgrade to copper wire.