Reply
 
Thread Tools Search this Thread Display Modes
 
Old 07-10-2008, 06:10 PM   #1
Rivet Master
 
guy99's Avatar
 
1984 31' Airstream310
Dunsmuir , California
Join Date: May 2004
Posts: 1,336
Images: 16
I know these shouldn't look like this.

Click image for larger version

Name:	burnedPlug1 (Small).jpg
Views:	115
Size:	60.4 KB
ID:	63479 This is the female plug on the 30 amp extension I use to connect to power.

Click image for larger version

Name:	burnedPlug2 (Small).jpg
Views:	122
Size:	65.1 KB
ID:	63480 The is the male end of the 30 amp cord from the MH.

Click image for larger version

Name:	burnedPlug3 (Small).jpg
Views:	114
Size:	61.2 KB
ID:	63481 This is the inside of the male plug. If you look carefully you can see a bulge of insulation on the black wire and some discoloration on the white wire.

What I can't figure out is why this is happening. I have been plugged into a 50 amp connection via a 'dog bone' but since the main breaker in the MH is 30 amp, I don't see how I could be drawing more than 30 amps long enough to do this.

I's been hot and the AC has been running almost constantly.
__________________

__________________
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion - The Dalai Lama

1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border
guy99 is offline   Reply With Quote
Old 07-10-2008, 06:50 PM   #2
Rivet Master
Airstream Dealer
 
Inland RV Center, In's Avatar
 
Corona , California
Join Date: Feb 2002
Posts: 16,499
Images: 1
Quote:
Originally Posted by guy99 View Post
Attachment 63479 This is the female plug on the 30 amp extension I use to connect to power.

Attachment 63480 The is the male end of the 30 amp cord from the MH.

Attachment 63481 This is the inside of the male plug. If you look carefully you can see a bulge of insulation on the black wire and some discoloration on the white wire.

What I can't figure out is why this is happening. I have been plugged into a 50 amp connection via a 'dog bone' but since the main breaker in the MH is 30 amp, I don't see how I could be drawing more than 30 amps long enough to do this.

I's been hot and the AC has been running almost constantly.
The problem is the "dog bone."

Look at it's rating and you will see why it burned what it did.

Dog bones are usually rated at 15 amps, and then only if there is a few inches of wire between the plug and socket.

The dog bones that do not have those few inches of wire, will burn up every time you use your AC.


If you want to run the AC, you must plug the trailer directly into an outlet, without any type of dog bone.

Andy
__________________

__________________
Inland RV Center, In is offline   Reply With Quote
Old 07-10-2008, 06:50 PM   #3
Rivet Master
 
TomW's Avatar
 
1967 26' Overlander
Huntsville , Alabama
Join Date: Dec 2003
Posts: 2,918
Images: 2
Wire is not the only heavy-duty element

Contacts are rated for a particular load just like wire size.

My first thought is that inferior contacts were used in the female connector.

A good contact for high current loads needs to have plenty of surface area to transfer power.

If you get bored, purchase a 33 cent, 15 amp, household outlet, and a $3.79 certified 20 amp household outlet from the your local home improvement store. Then smash each with a heavy hammer.

You will find that the 15 amp outlet has knife-like connectors instead of the 20 amp outlet's sleeve-like connectors.

More surface area means better contact.

Tom
TomW is offline   Reply With Quote
Old 07-10-2008, 09:03 PM   #4
Retired Moderator
 
john hd's Avatar
 
1992 29' Excella
madison , Wisconsin
Join Date: Aug 2002
Posts: 4,644
Images: 40
oxidation on the blades and internal parts can cause heating. were the connectors green before use?

another culprit could be low voltage at the source. the load does not change, the voltage drops and the current goes up!

watts = volts x amps if you decrease the voltage the current rises to meet the demand.

john
__________________
you call them ferrets, i call them weasels.
john hd is offline   Reply With Quote
Old 07-10-2008, 09:10 PM   #5
Rivet Master
 
guy99's Avatar
 
1984 31' Airstream310
Dunsmuir , California
Join Date: May 2004
Posts: 1,336
Images: 16
Quote:
Originally Posted by Inland RV Center, In View Post
The problem is the "dog bone."

Look at it's rating and you will see why it burned what it did.

Dog bones are usually rated at 15 amps, and then only if there is a few inches of wire between the plug and socket.

The dog bones that do not have those few inches of wire, will burn up every time you use your AC.


If you want to run the AC, you must plug the trailer directly into an outlet, without any type of dog bone.

Andy
The dog bone is a 50 amp to 30 amp device. The 30 amp extension then plugs into the dog bone, then the MH plugs into the 30 amp extension.

The pictures I posted are of the female end of the extension (male end is plugged into the dog bone) and the male end of the MH power cord.

There is no sign of over heating where the extension plugs into the dog bone or where the dog bone plugs into the 50 amp outlet.
__________________
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion - The Dalai Lama

1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border
guy99 is offline   Reply With Quote
Old 07-10-2008, 09:16 PM   #6
Rivet Master
 
guy99's Avatar
 
1984 31' Airstream310
Dunsmuir , California
Join Date: May 2004
Posts: 1,336
Images: 16
Quote:
Originally Posted by john hd View Post
oxidation on the blades and internal parts can cause heating. were the connectors green before use?

another culprit could be low voltage at the source. the load does not change, the voltage drops and the current goes up!

watts = volts x amps if you decrease the voltage the current rises to meet the demand.

john
The connectors were not green, they were not shiny either, pretty much a tarnished brass.

Unless the utility power had low voltage (could happen) I don't think there was low voltage at this outlet. I have had friends with big motorhomes with fancy power management systems report that it supplies good voltage even at heavy load.

I do have an autoformer in the motorhome. Is it possible for it to draw more than 30 amps even though it is supplying 30 amps or less?
__________________
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion - The Dalai Lama

1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border
guy99 is offline   Reply With Quote
Old 07-10-2008, 09:22 PM   #7
My Grandparents Airstream
 
Andrew Selking's Avatar
 
2007 28' Safari SE
Hillsboro , Texas
Join Date: Dec 2002
Posts: 171
Images: 15
Send a message via AIM to Andrew Selking
John hd Give us some more good advice is the dog bone the problem or is as you suggested a problem with the cord or the ends of the cord?
__________________
Andrew Selking
WBCCI #6062
International 3rd Vice President

"Airstream the Best trailer ever built."
Andrew Selking is offline   Reply With Quote
Old 07-10-2008, 09:37 PM   #8
Rivet Master
 
Tom Nugler's Avatar

 
1972 25' Tradewind
Currently Looking...
McHenry County , Illinois
Join Date: Jul 2003
Posts: 1,129
Images: 5
How tight were the screw clamps in the housing? Like John said, resistance = heat. The more current, the more heat. Heating causes the contacts to weaken, loose tension and cause more resistance. Resistance creates a voltage drop and the cycle repeats.
I had to hit a customer yesterday for over $400 for a new starter and cable. Reason? Loose nut on the cable terminal.

Tom.
__________________
AirForums # 2806
WBCCI / VAC # 6411
TAC IL-11

Not All Who Wander Are Lost.

Avid supporter of trailing edge technology.
Tom Nugler is offline   Reply With Quote
Old 07-10-2008, 10:00 PM   #9
Rivet Master
 
guy99's Avatar
 
1984 31' Airstream310
Dunsmuir , California
Join Date: May 2004
Posts: 1,336
Images: 16
Quote:
Originally Posted by Tom Nugler View Post
How tight were the screw clamps in the housing? Like John said, resistance = heat. The more current, the more heat. Heating causes the contacts to weaken, loose tension and cause more resistance. Resistance creates a voltage drop and the cycle repeats.
I had to hit a customer yesterday for over $400 for a new starter and cable. Reason? Loose nut on the cable terminal.

Tom.
The screw clamps were very tight (I had to use a socket to loosen them).

Most of the heat seemed to be around the 'blades'.
__________________
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion - The Dalai Lama

1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border
guy99 is offline   Reply With Quote
Old 07-10-2008, 10:38 PM   #10
Rivet Master
 
bkahler's Avatar

 
1974 20' Argosy 20
Richmond , Kentucky
Join Date: Jan 2003
Posts: 6,350
Guy,

I had to replace the male connector on our motorhome this past weekend as well. It did the EXACT same thing yours did although the melting wasn't quite as bad. I ended up buying a plug from Lowe's although while installing it I realized the quality was very poor so I'm going to shop around for a good quality replacement and put that on in its place.

I also like you don't understand why the breakers aren't tripping.

Brad
__________________
Air forums # 1674
1974 20' Argosy Motor Home
1974 31' Excella trailer (parting out, as of 4/1/2015 I have wheels, brake drums, windows & holding tanks left to sell)
bkahler is offline   Reply With Quote
Old 07-10-2008, 11:05 PM   #11
Rivet Master
 
2002 19' Bambi
Lafayette , California
Join Date: May 2005
Posts: 707
I looked at the photos and read what Andy said and I think he is on the right track. Most of the melting seems to be around the female plug of the extension with the heat transmitted by the male prongs into the male plug. In other words, the female plug of the extension appears to have generated the heat.

Whether or not the rating of the extension was adequate, it looks like it was the part of the connection which began to heat up while trying to carry the constant load of your AC. As it heated up, its resistance increased which reduced its effective load-carrying ability. The breaker did not blow because you were within its 30-amp rating, but the female plug of your extension could not carry the 30 amps for an extended period of time.
__________________
Tim A. is offline   Reply With Quote
Old 07-10-2008, 11:09 PM   #12
Rivet Master
 
guy99's Avatar
 
1984 31' Airstream310
Dunsmuir , California
Join Date: May 2004
Posts: 1,336
Images: 16
Quote:
Originally Posted by bkahler View Post
Guy,

I had to replace the male connector on our motorhome this past weekend as well. It did the EXACT same thing yours did although the melting wasn't quite as bad. I ended up buying a plug from Lowe's although while installing it I realized the quality was very poor so I'm going to shop around for a good quality replacement and put that on in its place.

I also like you don't understand why the breakers aren't tripping.

Brad
Brad,
I don't get it either. I guess that since the heat is being caused by high resistance, the current flow never gets high enough to trip the breaker.

In my situation, the breaker for the receptacle is 50 amp so I would expect the 30 amp breaker in the MH to trip if the current got too high.

The male plug that failed is a replacement. I searched and found the highest quality I could. One concern was that it wasn't water proof. So I just replaced the male end of my power cord by splicing a molded 30 amp plug onto the power cord. I then replaced the extension with a brand new one. I noticed that when I plugged the MH in to the extension, it went in very easily. Doesn't seem like a nice tight fit. I would if this is part of the problem?
__________________
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion - The Dalai Lama

1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border
guy99 is offline   Reply With Quote
Old 07-10-2008, 11:15 PM   #13
Rivet Master
 
guy99's Avatar
 
1984 31' Airstream310
Dunsmuir , California
Join Date: May 2004
Posts: 1,336
Images: 16
Quote:
Originally Posted by Tim A. View Post
I looked at the photos and read what Andy said and I think he is on the right track. Most of the melting seems to be around the female plug of the extension with the heat transmitted by the male prongs into the male plug. In other words, the female plug of the extension appears to have generated the heat.

Whether or not the rating of the extension was adequate, it looks like it was the part of the connection which began to heat up while trying to carry the constant load of your AC. As it heated up, its resistance increased which reduced its effective load-carrying ability. The breaker did not blow because you were within its 30-amp rating, but the female plug of your extension could not carry the 30 amps for an extended period of time.
Just to clarify, Andy was pointing to the "dog bone". It shows no heat effects. I think you are correct however, high resistance between the male plug from the MH and the female plug of the extension cord caused the failure. I now realize that it isn't clear in the pictures but the damage was actually worse on the male plug.
__________________
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion - The Dalai Lama

1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border
guy99 is offline   Reply With Quote
Old 07-10-2008, 11:49 PM   #14
_
 
. , .
Join Date: Dec 2004
Posts: 8,812
hi guy'

have u checked the voltage?

have u checked the voltage while using the a/c?

while the bone may be rated for 30 amps and u might expect the breaker inside to trip...

they often don't before the cord/contact is toasted.

i too had a 30 amp male cord end melt during one brief session of a/c and low voltage...

the lineman has given you the good advice in post 4.

cheers
2air'
__________________

__________________
all of the true things that i am about to tell you are shameless lies. l.b.j.

we are here on earth to fart around. don't let anybody tell you any different. k.v.
2airishuman 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



Virginia Campgrounds

Reviews provided by




Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 01:54 AM.


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.