Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-08-2006, 01:02 PM   #15
Rivet Master
 
RoadKingMoe's Avatar
 
2001 34' Limited
The State of , Ohio
Join Date: Sep 2002
Posts: 1,605
Images: 23
The output of a small inverter-type generator is like the 240/120VAC split single-phase power coming into your house. Instead of neutral being bonded to ground and being 0 volts, neutral is at 60VAC with respect to ground and hot is at 60VAC with respect to ground. Just as the two legs of residential power have 240VAC between them, the generator hot and neutral have 120 volts between them. The difference is that the center tap of the 240/120VAC split single-phase is neutral to get 120VAC off of each of the two legs, while on the generator, the center tap is just chassis ground.

If either the hot or neutral wire in the trailer touch the trailer chassis, or if either the hot or neutral in an appliance or tool touches a grounded case, and the trailer chassis is connected to the generator chassis, as it should be through the power cable ground wire, current in that side of the generator will increase, causing an imbalance in the GFCI output, activating its protection. Note that neither the trailer nor the generator has to be earth-grounded for this to happen.
__________________

__________________
Maurice
RoadKingMoe is offline   Reply With Quote
Old 05-08-2006, 01:31 PM   #16
Rivet Master
 
1984 31' Excella
Norfolk , Virginia
Join Date: Jan 2005
Posts: 667
Images: 11
Proper Grounding of 120V input

No wonder theplug in cable is reffered to as "Shore Power". The Generator is hooked up like the NAVYships that I am familiar with(split 120VAC).
__________________

__________________
Beginner is offline   Reply With Quote
Old 05-08-2006, 06:19 PM   #17
3 Rivet Member
 
Currently Looking...
2005 22' Interstate
Afton , Virginia
Join Date: Sep 2005
Posts: 226
Let me see if I got this straight. Looking at the 120 VAC plug, there is a round hole and two rectanglar slots. The left slot is connected to the white wire and is longer than the right one which is hooked to the black wire. The round hole is green-wire (safety) ground, the long left-hand slot is neutral, and the short right-hand slot is hot.
OK, so I plug my light bulb into the left hand slot and the right hand slot, and it lights. If there is a GFI protecting this connector, and I plug my light bulb into the right-hand slot and the round hole, would the GFI sense an imbalance and shut down? What if I had plugged the light bulb into the right-hand slot and the round hole first?
__________________
herrgirdner is offline   Reply With Quote
Old 05-08-2006, 10:40 PM   #18
Rivet Master
 
Over59's Avatar
 
1959 26' Overlander
Putnam , Connecticut
Join Date: Sep 2003
Posts: 3,064
Images: 37
Quote:
Originally Posted by Beginner
House wiring (as it applies to our 120 volt trailers) goes like this:

GREEN WIRE: Connects to the Ground Buss in the Circuit Breaker Box. This Ground Buss MUST be connected to the Frame/Skin of the trailer, if not, it is possible (probable), in the event of a short(black wire comes in contact with the skin or an appliance shorts out) that the skin of the trailer could have 120 V on it. In short (no pun intended) if you touch the trailer barefoot, you will get shocked.
So I should run a separate ground from my shell to the internal system ground, ie the marine panel ground or an outlet's ground? Wait a minute. I do think my Marinco power recepticle has this covered, have to check.
__________________
Over59 is offline   Reply With Quote
Old 05-08-2006, 10:43 PM   #19
Rivet Master
 
RoadKingMoe's Avatar
 
2001 34' Limited
The State of , Ohio
Join Date: Sep 2002
Posts: 1,605
Images: 23
Quote:
Originally Posted by herrgirdner
Let me see if I got this straight. Looking at the 120 VAC plug, there is a round hole and two rectanglar slots. The left slot is connected to the white wire and is longer than the right one which is hooked to the black wire. The round hole is green-wire (safety) ground, the long left-hand slot is neutral, and the short right-hand slot is hot.
OK, so I plug my light bulb into the left hand slot and the right hand slot, and it lights. If there is a GFI protecting this connector, and I plug my light bulb into the right-hand slot and the round hole, would the GFI sense an imbalance and shut down? What if I had plugged the light bulb into the right-hand slot and the round hole first?
The answer is, "it depends." I have a neon 90-300V test light that doesn't draw enough current to trip a GFCI. With one of these, you should see light between hot (right) and neutral (left), and hot and ground (round), but NOT between neutral and ground.

But yes, if you put a typical incandescent light between hot and ground, it should trip the GFCI regardless of when you do it.
__________________
Maurice
RoadKingMoe is offline   Reply With Quote
Old 05-09-2006, 08:09 AM   #20
3 Rivet Member
 
Currently Looking...
2005 22' Interstate
Afton , Virginia
Join Date: Sep 2005
Posts: 226
Got it.
So, I am going to Lowes and get one of those little plug-in gizmos that tell if the 120 outlet is wired up correctly.

But that brings up another thought, how do you make sure that 30 amp outlet is wired correctly? Is it good enough to use the tester in your camper once you have connected to shore power, or is there something better to do before making that connection?
I wonder if they sell one of those gadgets that tests the 30 amp outlet, or do you have to use a voltmeter?
regards
__________________
herrgirdner is offline   Reply With Quote
Old 05-09-2006, 09:22 AM   #21
Rivet Master
 
1975 29' Ambassador
Reno , Nevada
Join Date: May 2003
Posts: 1,351
Caveats and caution. There is some information in this thread I'd be very careful about. Here's a recap of what I think is the good stuff.

Generally, hot and neutral are completely isolated from equipment grounds in all equipment.

Neutral is only connected to equipment grounds at the service entrance, which is where the meter is if on grid or where the genset is if using a somewhat permanent genset installation. This is also where the earth ground connection is established.

A portable genset won't usually have any connection between neutral and equipment ground. The hot and neutral are isolated. This means that the only voltage of any note (that will produce current) is in a path between neutral and hot. That would require two failures to obtain accidentally or improperly.

If you are using one of those three indicator light gadgets, you get two lights when on grid or permanent genset: hot to neutral and hot to ground. This is the way you can check any 110v grid power plug, including the 30 Amp RV plug.

On a portable genset, you should get only one indicator light between hot and neutral. This is unless your portable is wired as a permanent installation which would then have hot to ground indicator light, too (and an earth ground). You generally don't want portable gensets to have neutral and ground bonded together as that reduces the number of failure requirements to create potentially hazardous situation.

On a 50 Amp RV service, you'd have double the indicators of a 110v service plus the added double voltage between the two hots.

You don't normally want multiple earth grounds as that can create voltage differentials and unintended current damage in lightning strike situations.

As far as trailer grounding through jacks and such, forget it. That usually doesn't have a low enough impedance to be of any use other than maybe some static bleed-off

If in doubt, check the code. There is a chapter on RV wiring and another on gensets.
__________________
bryanl is offline   Reply With Quote
Old 05-09-2006, 05:57 PM   #22
2 Rivet Member
 
1965 26' Overlander
Acworth , Georgia
Join Date: Dec 2005
Posts: 43
More questions

Quote:
Originally Posted by steelbird312
Phil, Are you saying your shore power cord does not have the ground wire grounded to the trailer anywhere, and that the trailer wiring is not connected to the trailer either?
If it were mine, it would be tomorrow! Since that is the way new ones are wired aas well as houses, etc I would want mine the safest it could be!
Some will reason that the jack as well as the stabilizers will effectively ground your unit but I'm skeptical about that.
The "shore power cord" is not grounded....the green wire is cut and capped.

There is a bank of 110V green grounds from each trailer outlet, wired to a wire block, and that is connected to the trailer body. Since the trailer body is the ground for 12V, I assume I have to reconnect the ground to this block, and not the trailer body.

Correct?

Phil
__________________
PhilMateo is offline   Reply With Quote
Old 05-09-2006, 06:03 PM   #23
2 Rivet Member
 
1965 26' Overlander
Acworth , Georgia
Join Date: Dec 2005
Posts: 43
Quote:
Originally Posted by Over59
Three wires come from the cameground hookup, hot, neutral, ground. They need to stay separate in the trailer. Disconnect the AC and look inside your AC fuse panel. Are the neutral and ground connections common, that is are they connected electrically? Is there a third wire in the outlets. If not, prehaps someone modified a two wire system by adding grounded receptacles and grounding directly to the trailer. If so and your trailer is not connected to the service ground when plugged in at the campground I would fix it before using it again, the trailer could become hot and you become the ground when you touch it. The additional problems is how the fuse panel is mounted. Is the neutral electically connected to the trailer shell via the mounting. The neutral and ground "float" in a trailer and only come together out in the service panel at the campground, not in the trailer.
AC fuse panel? Do I have one? I saw a wiring box, but no fuses. I have an Armstrong Bay Breeze.

All the outlets have 3 wire.

I think I need to rewire box and look for AC fuses.
__________________
PhilMateo is offline   Reply With Quote
Old 05-09-2006, 06:10 PM   #24
2 Rivet Member
 
1965 26' Overlander
Acworth , Georgia
Join Date: Dec 2005
Posts: 43
Quote:
Originally Posted by Beginner
Our Trailers:

GREEN WIRE: Connects to the Ground Buss in the Circuit Breaker Box. This Ground Buss MUST be connected to the Frame/Skin of the trailer, if not, it is possible (probable), in the event of a short(black wire comes in contact with the skin or an appliance shorts out) that the skin of the trailer could have 120 V on it. In short (no pun intended) if you touch the trailer barefoot, you will get shocked.
So this means that the main power cable from shore or generators should have ground wire attached to the ground buss, where all the 110V appliances and outlets are also grounded? Should this ground buss be attached (grounded) to the trailer shell as well (like the 12V lines)?
__________________
PhilMateo is offline   Reply With Quote
Old 05-11-2006, 08:07 PM   #25
Rivet Master
 
1984 31' Excella
Norfolk , Virginia
Join Date: Jan 2005
Posts: 667
Images: 11
Yes it get confusing.
The Green Wire should be connected to the frame/shell of the trailer.
This Green Wire in the Campground Circuit Breaker box should be sonnected to the campground's Grounding System.
Most campground shore power boxes I've seen have standard 120V recptacles. Plug your tester into that and read the results in accordance with the legend on the device itself. That is a whole lot better than nothing. I very strongly advise getting an adapter that you can plug into the 30 or 50 amp recptacle and plug your tester into. The 50 amp adapter should have more than one place to plug into so that you can check both sides of the 120V. That is a whole lot safer.
__________________

__________________
Beginner is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Saggy Bottom ( rear end ) smily Repairing/Replacing Floor &/or Frame 127 10-01-2006 09:28 PM
proper rivet gun for AS oldvws Ribs, Skins & Rivets 12 11-23-2002 10:04 PM
Photos on the Portal Page. WE NEED YOUR INPUT! Vote please! Andy R Our Community 6 10-25-2002 09:55 AM
Best way to reground airstreamcaravel Electrical - Systems, Generators, Batteries & Solar 3 03-08-2002 08:20 PM


Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 07:17 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.

Airstream is a registered trademark of Airstream Inc. All rights reserved. Airstream trademark used under license to Social Knowledge LLC.