Electrical question

[Pat]

Daryl, "YOUR" movie was nicer to you that the "B-" movie "Pat" was to folks named Pat.

Glad to be in a position to have the opportunity to try to help.

Pat

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Pat, you might be interested to know that at one time in days past, a good-sized town in Eastern Oregon had an electrical system that used the earth for the third leg of the three-phase. The water pipes lasted, ..... well, ..... maybe three weeks. [img]/forums/images/icons/crazy.gif[/img]

[Pat]

Dave, buddy, 3 weeks? Musta been a long long time ago when each household used only a little current or three weeks would be longer than I'da guessed. These days of heightened environmental concern you wouldn't get away with passing the current through the ground as it woiud upset the worms and such.

Maybe and maybe not directly on topic but RV parks and marinas seem to be the worst when it comes to bad wiring. Hot neutral reversal, neutral ground reversal, open ground on 3 hole sockets... you name it, I've come across it. It can be costly via electrolysis damage to metal struts, shafts, and props as well as metal through hull fittings. Eat off a seacock with electrolysis and glug glug glug, howdy Mr. Jones! Prop damage can be expensive/extensive and it doesn't take long with the right goofs.

Pat

[Bird]

</font><blockquote><font class="small">In reply to:</font><hr />
RV parks and marinas seem to be the worst when it comes to bad wiring

[/ QUOTE ]

I know nothing about marinas, but you're right about RV parks, and I wonder why. During our years of full time RVing, I learned to always check at least the polarity and voltage before hooking up utilities to the RV. I found reversed polarity in one RV park in Arizona and one in Oregon, and in each case the park managers had no idea what I was talking about, so I showed them how to fix it. I found pretty low voltage in one park in Indiana, and in Pennsylvania, the park owner told me they had 30 amp service; turned out to be a 30 amp receptacle and a 20 amp breaker. [img]/forums/images/icons/tongue.gif[/img]

[Pat]

Bird, With a common ground and neutral connection at the breaker box and then wire the receptacle backwards, the lights and electrical appliances in the RV work when you plug in but if the metal skin of the RV is grounded in the RV electrical system you then have 120VAC on the metal skin. No problem with nice insulating rubber tires but if someone standing on the ground touches the RV they get 120VAC from their hand to their feet. NOT GOOD!

Not experienced with electrical problems at marinas?

Just imagine all the ways to mess up at an RV park and then add water and people who may know even less than a RV owner.

Pat

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] My x-FIL had a Chris Craft Connie which had an aluminum prop on it that the PO had installed after blamo'ing the original bronze wheel. The FIL plugged into some shore power in a marina which then proceeded to sacrifice that prop on the altar of electrolysis. At the time I was unaware of just how vicious a bad system could be, but that was a good lesson. When he hauled out for the winter and looked at the wheel, he could hardly believe his eyes. [img]/forums/images/icons/tongue.gif[/img] In my days as a water supply engineer, I saw countless numbers of stainless steel pump shafts eaten away by stray current from poorly installed electrical systems on motor driven pumps. [img]/forums/images/icons/tongue.gif[/img]

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] Leroy and Blanche decide to open a Ah-Vee Pahk. They git Balanche's brother's next-door-neighbor's cousin to put in some wirin'. Why put in a four-wire service; it's jest extra money? Who needs that little u-ground anyways? [img]/forums/images/icons/tongue.gif[/img] That liddle -old green whar don't do nuthin' fer yuh. [img]/forums/images/icons/crazy.gif[/img]

[Pat]

Dave, I previously commented in a post on TBN about how electrolysis from mis wired shore power could eat bronze props in an amazingly short time. This was in conjunction with a story of a new stink pot owner with twins. The guy hooked up to the erroneously configured shore power and had no active or passive anti-electrolysis system. Subsequently when he applied a massive burst of power in reverse to leave the slip in a grand fashion and wow his guests and onlookers, he hardly moved at all. Virtually all of both props except for the hubs was gone.

My guess is that the electrolysis left behind the characteristic spongy matrix in the shape of a bronze prop but severely weakened and the thrust pulled the weakened blades off.

Our little Dutch boy Renze pulled his finger out of the dike long enough to type a post claiming it to be an urban myth. In the interest of international relations (and I like the guy) I didn't hammer him. Youth, and lack of experience can give one a distorted picture of reality.

I once hung out for a few weeks at a nonferrous foundry doing product development and had to get seriously up close and personal with aluminum casting with sand molds and such. One of the mainstays of the guy's business was casting replacement props, struts, and rudders (out of bronze) which were typically damaged by one of two things: 1. electrolysis and 2. contact with something substantial enough to reshape the part beyond the elastic limit (things like Zuniga jetty, a long pile of submerged rocks defining the east margin of the entry to San Diego harbor. Monkey see monkey do, some guy with a short shaft outdrive putputs across the jetty at high tide and Mr. Bonzo tries it with his inboard drawing 3-5 times the draft hours later at a lower stage of the tide and SHAZAM more business for the foundry.

Of interest to denizens lurking here is the fact that frost free "bury" hydrants should be electrically isolated from ferrous metal such as a T-post or whatever often driven into the ground to attach to said hydrant to give it strength. A good way to protect the hydrant is to slip a piece of PVC pipe over the T-post or metal pipe or whatever "stake" is used. Then you can tie the hydrant tightly to the post with no worries mate. If you let the bare metal of the hydrant body touch the steel post or whatever there will be electrolysis/dissimilar metal corrosion at the point of contact which is NOT A GOOD THING. If you should actually read the instructions provided your hydrant came with instructions or you got them and didn't toss them out they warn you about the metal to metal contact.

Pat

[DUMBDOG]

Pat, this brings up an interesting question for me, not an engineer or electrician. A couple of years ago I had to replace a frost free hydrant that was connected to the shop plumbing via copper piping, was this the cause?

It is now connected by a braided line, will this cause a problem in the future?

[CJDave]

[img]/forums/images/icons/tongue.gif[/img] When I wuz first outa college I worked for a company that had a foundary. That was my first look at the business and lucky for me, the guys in the foundary were friendly enough to not kick me out when I asked too many questions. I would draw up an item and then they would tell me why it could or could not be cast. They poured mainly aluminum and bronze. As a testament to the skill of some of the molders, I witnessed a "lunch hour feat" of extreme difficulty. While eating his sandwich, Ivan, the chief molder was being pestered by a huge green blowfly. He smacked it with a swatter and the blow left it stunned and completely intact. Ivan took the fly, placed it in green sand in the smallest flask they had and rammed it up. Then using a tooth pick, he probed for the fly and estalished a gate and a riser. He poured it with 356 aluminum, and you would be amazed at how well it picked up the detail of the fly's body and even part of the wings. Of course that was the ultimate in one-off cores. [img]/forums/images/icons/crazy.gif[/img] Speaking of one-off.... have you ever done the "lost wax" thing? That's where the arteest makes the shape in wax, then it is poured in plaster and the wax melted out, and then the plaster is the mold for the metal, and then you break the plaster off. You can make re-entrant shapes that way that would be unmoldable if you had to pull a mold. [img]/forums/images/icons/tongue.gif[/img]