I keep burning out 30A plugs...

[SLJKansas]

I was having a problem melting the male end on my power cord in a spot I was using all summer, Also had a AC lights flickering (DC was ok). I pulled the cover off the pedastal and found that the hot lead on the 30amp plug had had a crimp on round eyelet under the screw, the eyelet was so burnt that only about 3/8 " was left holding the wire to the screw.  I took the wire loose, cut it back to clean/bright copper, and refastened the wire. Problem was solved.

I would have the maintance man pull the cover and check the connections. Older parks don't always check there pedistals like they should.

 

[Ned]

Turning the temperature down on the refrigerator will just make it cycle less often.  When it's cooling, it will use just as much power.  Try it on propane for awhile and see if it makes a difference.

 

[Jammer]

So you can absolutely guarantee that the breakers work perfectly?

I've seen failure to trip before but it is extremely rare and with two breakers in series I don't believe that's a likely explanation.

 

[Jammer]

Just so everybody is clear on this...when I replace the plug I always strip the wire back to clean, shiny wire.  The wires are twisted good and tight, and the screw clamps are clamped down HARD!

Good for you.  Have you tried some contact grease?

 

[Jammer]

I didn't address the comment to you Steve, it was addressed to Jammer, who seems to think everyone else's advice is folklore. I think his reply was folklore.

Tom

Next time you're in the Minneapolis area, stop by my place, and we'll pick up some receptacles and plugs and cords of different sizes at Menards and set up a lab out back and run a bunch of power through them, and measure temperatures and stuff, and see at what point things start to melt.  We can make a youtube video or something.

Bring some friends.  I have room for 4 rigs in my driveway, 50a, water.

 

[seilerbird]

Sounds like a plan. I will be in Minnesota in May of 2012. Hopefully that will be before the mosquito season.

 

[Ned]

Time for the MythBusters?

Jammer, where in the MPS area are you?  Email reply is OK if you prefer.  We get through there twice a year most years and will be in Apple Valley at the end of Aug. for 2 weeks.

 

[Jammer]

Well we will just have to keep this thread going for another two years then

 

[Luca1369]

Well we will just have to keep this thread going for another two years then

That's gonna cost me a fortune in plugs...

 

[Gary RV_Wizard]

I think Jammer gave a pretty good tech overview on what goes on in our power systems on 30A.

Since I have a 50A rig and a power hog to boot, I typically run 28-29 amps when hooked to a 30A source (as I am this week). During this really hot weather, it stays at that level all afternoon and into early evening until the a'cs (two) stop running 80-100% of the time.  My energy management system (EMS) keeps the total demand just under 30 amps, and it if stays at that level too long, it will back it off to 24 amps by shedding additional load for awhile.  The hot wire pin on my 50/30 adapter shows signs of heat,  a bit of discoloration around the pin, but it isn't melting down. Yet.  I'm pushing it hard just to keep the coach cool. Water heater is off and the fridge is on propane until evening when it cools down a bit. Then I can shut one a/c off and turn the water heater back on and fridge back onto 120vac for the night.

I've replaced plugs and outlets on my 30A extension and even on my 50A shore cord, all due to overheating on one or more pins.  And I've had to disassemble and re-tighten them a few times as well.  Wear and tear, vibration, whatever, they loosen up.  And I'm not impressed with the quality of the 30A replacement plugs on the general RV market either, but there doesn't seem to be much choice since it is not a NEMA standard configuration.

 

[Alfa38User]

How about the receptacle in the RV?? from the descriptions above , it may have been over-heated a number of times as is likely suffering from metal fatigue too, just as the cord end was..... But then again, maybe not.... YMMV

 

[Johncmr]

Lots of very good info on this thread.  My note is regarding how most AC circuit breakers work.  They are a combination of heat sensing loops and the magnetic properties of that loop.  SO - a quick rise in current, like my screwdriver shorting something out, will trip the breaker quicker than a slowly added load, such as what might be expected during a stay at the campsite.

With this in mind, some breakers may well be more susceptible to not tripping with low voltage situations, I mean, not a pulse of magnetic energy, but higher temperatures (watts) as calculated using the formula in one of the posts above.

Also I agree with the no-ox paste as a good way to assure the best connections within the plug, as well as on the pedestal.  Those following you to that pedestal will probably not thank you, but they'll benefit from your no-ox!

Good luck

johncmr

 

[Jammer]

Lots of very good info on this thread.  My note is regarding how most AC circuit breakers work.  They are a combination of heat sensing loops and the magnetic properties of that loop.  SO - a quick rise in current, like my screwdriver shorting something out, will trip the breaker quicker than a slowly added load, such as what might be expected during a stay at the campsite.

With this in mind, some breakers may well be more susceptible to not tripping with low voltage situations, I mean, not a pulse of magnetic energy, but higher temperatures (watts) as calculated using the formula in one of the posts above.

Here are the trip curves for the widely used Square-D QO series breakers:

http://ecatalog.squared.com/pubs/Circuit%20Protection/Miniature%20Circuit%20Breakers/QO-QOB%20Circuit%20Breakers/0730CT9801R108.pdf

The 30 amp breaker trip curve is on page 24.

We see from the curve that the magnetic trip point is at approximately 1200 amps (40x nominal).  At that point the breaker will trip in 1/60 of a second.  At lower currents the thermal trip mechanism is used.  The breaker will carry between 200-300 amps for 1 second without tripping (allowing for manufacturing variation), between 60-105 amps for 10 seconds without tripping, and will carry somewhere between 30 and 42 amps indefinitely without tripping, at 40* C., in free air.

It is my experience that most breakers will, when new, trip at a point close to the low end of the specification curve, and will tend to trip sooner (that is, at lower currents) as they get older.  I believe that this is because of increased contact resistance, but the ones I've disassembled to try to understand why they trip early haven't shown conclusive signs of wear or corrosion in the contact area.  So, it may be metal fatigue in the trip element or something.

Low voltage does not cause breakers to trip.  The spec sheet I linked to makes it clear that the voltage ratings are maximums.  You could use these breakers for 12 volts DC if you wanted to.  They're even officially rated for it.

Other manufacturer's breakers behave similarly to the QO breakers in the spec sheet.

 

[Johncmr]

Good information Jammer.  The curves seldom include the "rate of rise" phenomenon which will magnetically trip one quite a bit before the 1,200 amps noted.

Lots of theory, I was just pointing out that there are numerous factors, some of which can keep a breaker in when it should have tripped, and some which trip it too soon.

johncmr

 

[Luca1369]

Thanks everybody for your help.  I'm making a conscious effort to lower my electrical usage, especially during the hottest part of the day, but I probably won't run the fridge on propane for two reasons.  It's costly (the electricity is included in rent here so for all practical purposes is "free"), and when the fridge is on propane the ice cream doesn't stay hard.

 

[DearMissMermaid]

I think you forgot a few things when mentioning your load like the battery charger and the little things like the microwave clock and so on. Did you know that most chargers continue to use power even when not charging?  Always unplug cell phone and other chargers when not in use.

Try turning your computer off when you aren't using it and unplugging everything you aren't using. A laptop computer draws a lot less than a desktop computer and you have the option of running it for hours, unplugged, on its own batteries. Many laptops can be outfitted with 12 volt plugs. Keep your printer and other peripherals unplugged when not in use.

I agree, you should run your fridge on propane if you need the super Air Conditioning running all the time.

On the other hand, wouldn't it just be cheaper to move to a cooler place?  I have been traveling around looking for places where I can live with all the windows open and no air conditioining. Very often, I am plugged into a standard household outlet with an adapter, so I have to be super careful not to trip my host's breaker which is often only 15-20 amps. So I leave the windows open, run the fridge on propane and make SURE I unplug everything I am not using. Even your TV draws current when not in use. Unplug it when it's off.

I don't leave anything plugged in that I am not using at the moment except the microwave and that's cause I can't get to the hidden plug behind the built in cabinet.

I think your main battery charger eats up 4-5 amps when running, something to consider in your math.

Maybe you need to upgrade to 50amp service, sounds like you're living a 50amp life on a 30amp plug. If I were you, I would doublecheck your insurance policy to make sure you've covered for fire.  Just in case.

 

[Jammer]

The upgrade to 50 amp service is possible though ordinarily not straightforward.  In many cases the old breaker panel isn't capable of supporting 50 amp service and there isn't room for a larger panel in the same spot with the same wires, so you end up with two panels, and then you need a new shore power cord.  I am a big fan of the Marinco inlets that allow the use of a detachable shore power cord but that adds $200 to an already expensive upgrade.

An interesting historical fact to consider is that 30A 120V service was standard for average size houses built before 1930 or so.  I have seen a few in recent years that were never upgraded.  As with an RV if there is no air conditioning and all the appliances are gas you don't need all those amps.

 

[wrenchhead30]

has anyone considered that the campground wiring may be to small (10-12-14ga?)all size wire is only good at a max. of 200' some less from the source of power and you will have lots of Resistance and lower the amprage where you plug in! its like running you rv on a long extention cord!

 

[ZuniJayne]

I had a problem once at a park with fluctuating voltage levels.  Before I parked, I tested the voltage at the pedestal and it was 120. However, during peak times of day, so many people had on air conditioning and other loads that the voltage dropped down to almost 100 for a couple of hours each night.

I knew this because I got one of those analog voltage meters from Radio Shack for about $17.  I keep it plugged in all the time, even when I'm running off the inverter and not connected to shore power.  It is in an outlet at eye level and easy to monitor. 

I also have a plug-in circuit tester.  To check a site's electricity, I plug the analog meter and the circuit tester into a 15amp female to 30 amp male plug adapter.  That way I know the power is OK for at least the time I'm testing.  ;D

I am not an electrician, but if the voltage to your RV lowers a lot and your load is the same, the increased resistance in the system can heat up your plug.

Just a thought.

 

[seilerbird]

I am not an electrician, but if the voltage to your RV lowers a lot and your load is the same, the increased resistance in the system can heat up your plug.

There is no increased resistance in an AC circuit when the voltage drops. There is an change in the impedance.