Calling all electricians!!!!

[Terryl]

OK Guys and Gals I have a bit of a mystery on my hands.

Here is the story, I have a shop where I do some wood working, in the past it had a 100 amp electrical service to it, but the service run down to the shop was to be underground, so I ran conductors for a 200 amp service so if I planned to expand I could.

Well that time came around last year, I added a main vacuum system, and a pop up cutoff saw, the cutoff saw was 3 phase (all I could get) so I installed a rotatory phase converter, this alone took 80 amps to run the 35 amp 3 phase motor on the pop up saw.

So I upgrade to a 400 amp service to the house and split the load (with a new electrical panel) with 200 amps going down to the shop and 200 for the house, all this has worked fine for about the last 10 months.

Now for the mystery problem.

One day I go to turn on the vacuum system (40 amps) and it did not come on, investigating I found the the 40 amp breaker at the shop panel was popped, I reset it and it was fine, and has been working fine since then, yesterday I was doing some layout drawings for the houseboat radio mast welding, I was listening to the stereo and POP out goes the power.

Now the main power service goes out around here a lot, so I thought mummm power failure time to eat lunch, I get tot he house and the power is back on, OK good, eat lunch and go back to the shop and the powers out down there, I check all the breakers down there and all are fine, I go back up to the house and check the mains there and WHAT the heck!! the main breaker down to the shop had popped, mummmm now what could pop a 200 amp breaker when nothing heavy was running...????...???

A big mystery....

If it does it again I'm calling the Ghost busters.

Any help on this one would take a load off my mind as if my shop is haunted.

[dl76]

Have the power company check your meter, could be cut in the underground wire running to shop.

[hutch]

yep... a damaged/crossed main arcing somewhere between the house & the shop would be my guess... but since you have 400 split at the house I'd check to see that it isnt 400 going to the shop now also

[The Cobra]

Been doing any gardening with a roto tiller or anything of the like because you shouldn`t be popping that circuit unless you are shorting out somewhere enough to cause an arc that would give you the intermittent power outages....just a tick in the wires would be enough at times even if you broke some conduit underground and you`re getting water in the line somewhere. Sounds a lot like you`re arcing out somewhere......check meter, wiring to panel or get the hydro co. out to test your underground lines for full power first aka easiest accessible....if that fails get a shovel and start digging....

[jtpl]

You could trip the main breaker in the shop. Then put an amp clamp on the feed from the house to the shop. The meter should read zero. Anything other than zero and you have a short to ground....

[steveOtoo]

Would be nice to know your conductor sizes,also was the service wire run in pipe. Have you measured voltages from each leg to neutral also between phases.

[Terryl]

Well lets see the wire is #4.0 aluminum in a 3 inch conduit, it's about a 175 foot run, all voltages at the shop are normal as of today, 124 volts on one side 124.1 volts on the other, as asked I threw the breakers at the shop and the main then measured for a short, all reading at over ten meg-ohms between conductors, I even used a megger to check conductor insulation to ground, everything is in the 200 meg-ohms region....


So whats up?????


All normal today, you would think if I started up something big (phase converter at 80 amps) I would have a problem???

[The Cobra]

Well lets see the wire is #4.0 aluminum in a 3 inch conduit, it's about a 175 foot run, all voltages at the shop are normal as of today, 124 volts on one side 124.1 volts on the other, as asked I threw the breakers at the shop and the main then measured for a short, all reading at over ten meg-ohms between conductors, I even used a megger to check conductor insulation to ground, everything is in the 200 meg-ohms region....


So whats up?????


All normal today, you would think if I started up something big (phase converter at 80 amps) I would have a problem???

OOOPS....Terry did I see aluminum wiring???? That sends up a red flag to me. In my experience I`ve had many problems with it in the past to the point of recommending it be stripped in several renos I`ve done. Problem lies with wherever the aluminum and copper join, be it switches, plugs, breakers etc etc......Copper and aluminum heat and cool at different rates and becomes "loose" at the connection causing arcing after using it for a short while. When the wires cool(are off) they will work again until the heat builds expanding the wires at different rates causing the arcing. The cycle will continue indefinitely and drive you nuts. That is a big part of the reason they don`t use aluminum wiring in houses anymore(at least in Ontario). It`s not the wiring but the copper/aluminum joining together that MAY be your problem. I`d bet on it.
Even (as silly as it sounds) a slightly overturned marrett can squash aluminum wiring enough to the point of fracture causing an arc when heated and when the wire cools it works fine....till it heats up again. I wouldn`t believe it but I`ve seen it happen more than once.

[steveOtoo]

Looks like no shorting going on between conductors, just wondering what the cross phase voltage is, usually around 247 volts. A possibility might be in how many of your neighbors share the same transformer. I have seen as many as 7 households on one transformer. Sometimes they go bad.

[Terryl]

Well 4.0 aluminum was a ton cheaper then 2.0 copper, at 175 foot plus the connections at the boxes it was way cheaper then copper (at that time) stripping it out is not an option, not when it's buried 4 feet under ground, we had a tractor to help in the pulling.

One spool and lots of pulling lube.

And I on a regular bases pull the main connections and no-ox lube them then re-tighten them, I know about the possible problems with aluminum wire.

[steveOtoo]

OOOPS....Terry did I see aluminum wiring???? That sends up a red flag to me. In my experience I`ve had many problems with it in the past to the point of recommending it be stripped in several renos I`ve done. Problem lies with wherever the aluminum and copper join, be it switches, plugs, breakers etc etc......Copper and aluminum heat and cool at different rates and becomes "loose" at the connection causing arcing after using it for a short while. When the wires cool(are off) they will work again until the heat builds expanding the wires at different rates causing the arcing. The cycle will continue indefinitely and drive you nuts. That is a big part of the reason they don`t use aluminum wiring in houses anymore(at least in Ontario). It`s not the wiring but the copper/aluminum joining together that MAY be your problem. I`d bet on it.
Even (as silly as it sounds) a slightly overturned marrett can squash aluminum wiring enough to the point of fracture causing an arc when heated and when the wire cools it works fine....till it heats up again. I wouldn`t believe it but I`ve seen it happen more than once.Aluminum service conductors are still accepted almost everywhere. All meter cans are approved with al/cu lugs and the conductors should be coated with an antioxidant. Joining cu with al should be done with a proper split bolt connector. Usually problems with aluminum occur with wire under #6 gauge. The Cobra could have a point, maybe a loose lug or connector.

[steveOtoo]

On your cut/off saw is it starting normally or have you noticed a difference. In a rotary phase converter there is usually a bank of 6 or more 40u/f caps in series that make up the artificial leg. I have seen these caps go bad many times

[hutch]

I am not a fan of aluminum either... hopefully all splices are above ground & you can find the loose connection quickly

[The Cobra]

I ran your problem by our site guy this aft....and after his swearing tirade about aluminum wiring he muttered something about you melting down all of it and making beer cans with it.
OK seriously he also thinks you probably have a short that`s arcing when hot and the wires expand....nothing much to test unless you`re running a test exactly when it happens and then run the test again when it starts working...a lot of time and trouble and could get expensive depending on who is doing the tests etc.
His suggestion was to manually inspect and test where possible any GFIs, connections, breakers, caps etc etc...he also believes it`s a short from your post but finding it can be a pain.
Let us know what it ends up being.

[Terryl]

On your cut/off saw is it starting normally or have you noticed a difference. In a rotary phase converter there is usually a bank of 6 or more 40u/f caps in series that make up the artificial leg. I have seen these caps go bad many times

Well everything has been running fine for the last few days, ran all the equipment that takes a big load, and nothing happened, all breakers are normal.

I cycled the phase converter on and off several times (about 5 min between cycles) with the main dust collector on line for a total load of around 120 amps and all is well...If it happens again I will call in the reinforcements, the electricians that installed the new 400 amp service to take a look.