Community Forums

dirko · 03-30-2009, 11:03 AM

Hi Ho: Right on, good catch. However, if the voltage drop is one volt or two it is still small if the source is correct. Now if we were working with high-frequency signals there is also the skin effect which should also be included. As a young engineer I was surprised that this can be significant even at 50 KHz.

I still claim that the contact resistance where the plug(s) meet the cable(s) is probably as significant as the actual cable loss for short cables. I don't know what the average power loss is, but I have seen lots of very hot connectors.

Have a good day, Dirk

RVDude · 03-30-2009, 11:13 AM

Quote:

Originally Posted by Dirk Ostermiller

I still claim that the contact resistance where the plug(s) meet the cable(s) is probably as significant as the actual cable loss for short cables. I don't know what the average power loss is, but I have seen lots of very hot connectors.

You and me both! Corroded contacts would seem to be a far more prevalent loss problem (as evidenced by so many fried pedestals) than an extra extension cord!

Clay L · 03-30-2009, 01:07 PM

Skin effect sure can be important at 60 Hz but since we are dealing with relatively large diameter wires it shouldn't be a problem in this case.
The skin depth is about .333 inches at 60 Hz according to this site http://en.wikipedia.org/wiki/Skin_effect and since 01 gauge wire has a diameter of about .328 inches, the wire in question would have to be larger than 01 gauge before it would begin to have an effect.

Route 66 · 03-30-2009, 02:35 PM

What's the concensus on dielectric grease for power cord connections?

I think it's a good thing.

RVDude · 03-30-2009, 02:41 PM

dielectric - I'd say good thing when the parts are new/clean, but once they are corroded ain't nuttin gonna help! I dielectric all connections on-board that I take apart for whatever reason - sometimes I deliberately take apart just to get it in there. Have not done it on the shore plug though - no particular reason.

Roadking · 04-02-2009, 12:09 PM

RVDude ---- I'm still laughing at this: (Quote) Oh, I get it now, that CG wired by those DIYers is really multi-tasking - they are in a snowy area and they use the wire heat to melt the drieveway snow right? (End Quote) Maybe they are smarter than most, eah??? (That's Minnesotan)

Small gauge aluminum wire = Big fuses that also work as heaters. And most likely they didn't use the proper anti-corrision connectors at the end so after a few years the corrosion at the aluminum/brass end connections will make things really interesting!!!!

Ray,IN · 04-03-2009, 05:16 AM

Since dielectric grease is an electrical insulator, it must be applied over a new, clean, tight connection. When applied to a sliding connection such as a plug, the thin film remaining creates higher resistance than a dry one. There are several options better than dielectric grease for plug connections. Electric companies use a waterproof grease containing graphite to lubricate cutouts and fuse-blades because it is a highly efficient conductor, yet permits the sliding blade connection to move when manually pulled by a lineman.

What happens to a CG pedestal is time/use heat damage. This heat weakens the spring temper of the receptacle, creating a weak, loose connection =high resistance. This in turn causes motorized equipment to draw higher current, which slowly damages your A/C for example, eventually causing failure. If your RV plug is easy to insert/remove, the receptacle is worn-out.

Clay L · 04-03-2009, 08:12 AM

Yeah I used to hear to hear it called "skinning Grease". Thick and black and didn't flow - stayed put.

hamguy · 04-03-2009, 01:01 PM

Quote:

Originally Posted by RVDude

Don't you just love that type of DIYer? A double whammy eh? 1) that they did it and 2) nothing could convince him of the utter error/saftey hazard!!!!

So, the NEC rates #10 AL in 3wire configuration at 25amp at 25degrees C. They further rate it as fusing at 247amp. So either these guys are basically running a 300ft fuse for your protection (how nice of them LOL) or you are getting a line loss at 240v at ONLY 25amps of nearly 30V so each 120v leg is delivering only (240-30=210/2) or 105v at 25a/leg!!! And they are thinking that 2 * 50amp power hogs will plug into the same #10 line? Run Toto, run!!!

Oh, I get it now, that CG wired by those DIYers is really multi-tasking - they are in a snowy area and they use the wire heat to melt the drievway snow right?

When I initially plugged in, I was only running the converter and a couple lights. The current meter on the panel showed, IIRC 6A. The supply voltage was down to 110. When I kicked the one AC compressor on, it dipped to 90V or less. He claimed it was my metering. I read it with each of the 3 meters I carry and they read w/i 1 volt of each other.

I wonder if he has been sued for damages yet. Or if it is the same owner. He bought the park as a sideline to his fulltime Cop job.