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-   -   Solve this one (takes some thought). (http://www.diychatroom.com/f18/solve-one-takes-some-thought-67234/)

bernieb 03-20-2010 06:43 PM

Solve this one (takes some thought).
 
This is a campground in Florida (poor man's campground) and we have an electrical problem among five trailers. Right now everything works fine electrical speaking, but the start of the problem started with a knock on my door at daylight two days ago with five upset campers (I'm not the owner of the grounds) . Anyway at the service panel on the pole, the neutral wire ground buss bar had rusted at the base and was heavily arcing behind the buss. The main service was grounded to earth nearby. One camper lost an electric water heater,a new lcd thin tv,a computer,a microwave. The other four campers lost two tv's, a micro wave, an electric heator.The others lost single tv's only. As far as I know nothing was turned on. I know that ground wires can start a fire if loose and arcing, but what happened at the appliances to destroy them? What I want to do for one friend is run a heavy solid bare ground wire from his neutral white wire ground buss to a copper driving rod with a clamp.....any problems with this as repairs have been made at the pole service ? The pole ground is 50 feet away from proposed new ground. bernie

brric 03-20-2010 06:47 PM

My guess is the neutral was compromised and the appliances were zapped with 240 volts.

Billy_Bob 03-20-2010 07:03 PM

Yes, if you lose the neutral, you can get 240 volts on a 120 volt circuit.

AllanJ 03-20-2010 08:13 PM

Quote:

Originally Posted by bernieb (Post 417391)
What I want to do for one friend is run a heavy solid bare ground wire from his neutral white wire ground buss to a copper driving rod with a clamp.....any problems with this as repairs have been made at the pole service ? The pole ground is 50 feet away from proposed new ground. bernie

This proposed new ground will only protect the appliances and electronics in case of a recurrence of the broken neutral if but a small number of amperes, say less than five are being used. The earth is not all that great a conductor.

Meanwhile ground is not meant for that purpose, serving as a backup return path in a current carrying circuit. If each trailer hookup is a main panel, it probably should already have such a ground rod setup for lightning protection and protection from electric shock if a fault from a live conductor to ground should occur.

tpolk 03-20-2010 08:36 PM

if each trailer is a sub panel do they need isolated ground/neutral? and if at a later time they are then teir own main do they then need to rebond in the panel? could this have been part of the problem, not a sparky just curious

bernieb 03-20-2010 08:42 PM

Thanks brrick and Billy Bob for considering but.......
 
I'm under the opinion that 240v can only be had with one phase at 120v rms which is .707 of peak voltage and the second phase directly opposite from the zero neutral line. One being positive, the other being negative and the difference between the two is 240. With that said (if I'm right ) how can a neutral buss (arcing at that) become a live wire and become a 120v live wire? I'm thinking that the arcing buss is sending voltage spike pulses back through the neutral because of the quick on and off sequence ........maybe thats where your 240 comes in to play. And what do you think of the solid grounding wire for backup going from camper neutral buss to the copper grounding rod in the earth with a clamp?

kbsparky 03-20-2010 08:54 PM

Quote:

Originally Posted by bernieb (Post 417431)
...what do you think of the solid grounding wire for backup going from camper neutral buss to the copper grounding rod in the earth with a clamp?

Waste of time, and it won't work when the neutral connection goes bad. You will still have burned out electronics and appliances, etc.

Call an electrician and have him repair the neutral wires, and connections as necessary to ensure continuity of the entire assembly all the way back to the POCO transformer.

AllanJ 03-20-2010 09:02 PM

(copied from another post)

On the 120/240 volt service, all of the loads on the A side or leg collectively have a net resistance of so many ohms. All the loads on the B side collectively have a net resistance of so many ohms. Should the neutral be broken, the same number of amperes will flow through (and be divided up among) all the loads on the A side as will flow through (and be divided up among) all the loads on the B side.

All the loads on the A side will get so many volts and all the loads on the B side will get so many volts where the latter voltage is 240 minus the former voltage. The share of the 240 volts each group receives is proportional to the net resistance presented by the loads (, which are connected in parallel,) in that group. For example if at one moment all the loads on the A side present a net 2 ohm load and all the loads on the B side present a net 4 ohm load, then the A side loads all get 80 volts and the B side loads all get get 160 volts at that moment. Turn on more stuff on one side and the net resistance on that side goes down and the proportion of resistance and also voltage on that side gets smaller. It is quite rare that loads on one side will be subjected to close to the full 240 volts.

Ohms Law states that, at all times in any circuit, the voltage across any two points is equal to the current flowing through times the resistance between those points. The two points chosen can be the ends of the same straight piece of wire which has some resistance, thus there is some voltage drop in that wire. If an arc is occurring, that means current is flowing (across a gap) but there is considerable resistance so if you measured at two points, one on each side of the arc, there would be a considerable voltage difference. In the example given, the arc was happening at the neutral bus, so it was the neutral current trying to get back to the pole transformer that was causing the arc. There is now a voltage difference between the neutral bus bar and the pole transformer neutral and therefore we cannot have 120 volts from neutral bus to side A and 120 volts from neutral bus to side B.

frenchelectrican 03-21-2010 03:52 AM

The safest way is call the electrician to come out and do the proper repair on the system and you allready have bad netural connection that is the key issue there.

While the electrician is there doing the repair it will be a good time have electrician to check out the pedstals { a post where you hook up your power source } to see if any other issue do come up on netural connection and ground connections.

I have my fair share to see burnted connections on campground pedestails.

So., Basically this is not a DIY project to tackle due there are couple codes it will be arised due this situation is on the campground and there are couple codes it will show up on it.

Merci,Marc

beenthere 03-21-2010 04:27 AM

Since this is the electrical service for multiple units. You want an electrician to come out and at least verify what needs to be done.

Running another ground to act as a neutral isn't the answer.

bernieb 03-21-2010 08:51 AM

Thanks to all the wisdom that has come here, but have to add this if only to help others in the learning process. This service main panel sets just outside a pump house that pumps underground water to campers .What the inside of the panel consist of is an aluminum stranded wire pulled apart and put in the small openings in the buss bar, dividing equally to other buss bar on other side. There are no bare copper equipment ground bare wires in box. The neutral wires coming from campers going to ground buss appear to be a solid 8 wire and the hot wires going to individual breakers are also a solid 8. The campers are 5th wheels mostly and around 30 footers ,so they are consuming lots of amps. This service panel is a 200 amp box and also I'm thinking that because of the number 8 supply hot wire that it's getting very hot and loosening the ground screws in buss bar. God knows how the stranded aluim. wire is divided underground going to the individual sites (all breakers are full in box. ) Felling pain for unsuspecting campers. But I will have a talk with owner in private who probably done all this mess to begin with........thanks to all

brric 03-21-2010 09:03 AM

You are correct the aluminum neutral should not be divided among several buss openings. A proper lug should be installed on the buss to accomodate the larger wire.

AllanJ 03-21-2010 09:19 AM

Had anyone noticed unusual brightening or abnormal dimming of lights before the big arcing in the panel box was finally discovered? This would (should) arouse suspicion of voltage problems including those resulting from neutral problems, and electronic equipment of all kinds should be unplugged until the problem is fixed.

Big Bob 03-21-2010 09:42 AM

Excellent advise provided by responders... Get an electrician to check it all out.

I have seen the damage you describe to appliances many times sourced to: lose nuetral...either utility side or past the meter.

In the humid south it is advised to flip your breakers once a year to help keep the contacts clean. I don't believe it is prudent for a HO, even a seasoned proud DIY, to remove panel covers and tighten down the connections as routine service.

I applaud your empathy and desire to help your neighbors...

This situation maybe just one of the things that happens to all things that
depend on mechanical connections.

Things can be replaced or fixed much easier than people.. All should be glad nobody was hurt... stay safe

bernieb 03-23-2010 09:41 AM

Yes ,Allenj there was dimming of individual campers lights prior to melt down so to speak. I wish now when I heard first complaint of dimming lights the day before that I would've warned the owner of the campground, but I'm finding out this isn't the first time it's happened.


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