Terminal strips

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  #1  
Old 08-05-04, 01:03 PM
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Terminal strips

I need some help from someone out there that is into theory and formulas. I need to find out what the expected heat would be travelling through a terminal strip. I know there is such a formula out there and I have even used it in the past problem being that was a few years ago and I know longer remember it. This need for the formula comes from an occassion when someone ignored manufacturers instructions on wiring a device and instead of providing a seperate dedicated neutral for each phase in the box cut corners by running one neutral and connecting it through terminal strips to each of the other neutrals, this in itself might not of been a problem but the neutral was connected to daisy chain each of the terminal blocks thus causing more heat to build up in each block then the manufacture had intended it to have. the result fire. Unfortunately this has now been done on three different occassions and in each case the same result I need the calculations to prove this is the cause of the damage and it can be corrected with proper wiring or with an alternate method of connection. Any one out there with any ideas where I could find the formulas or any information I might use to back this up?
 
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Old 08-05-04, 06:31 PM
Zel
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Your question is way over my head. But it's an interesting one, and when you find the answer, please share it.....
I tried doing a few searches, (even though I really don't know what to search for)..... maybe this will help:

http://www.okonite.com/engineering/index.html

http://www.controlledpwr.com/product...k/ukharma2.htm

Like I said, it's over my head....... but if ya find what ya need, post us a link or the info.

-Zel
 
  #3  
Old 08-05-04, 06:45 PM
johnnyelec
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what was done would have been OK if the neutral conductor was sized properly.
You need to add up the load on the outgoing neutral conductors.
 
  #4  
Old 08-07-04, 06:24 PM
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If the neutral was sized large enough to handle the heat under normal circumstances but electricians note the diameter of the wire to disapate the heat and in this case didn't take the length into consideration. Number 10 wire 6 inches long will not heat up in the same way a piece one inch in diameter. The biggest problem is the terminal strips (according to the manufacturer) rated to handle a 30 Amp long will break down only after 100 to 130 degrees C which is great but the screws that tighten the wires in the strip are made of different metals and constant heat and cooling will loosen their grip, which in turn may cause the wire to come loose and then the fun starts. The heating and cooling is the result of have some incadcent lights on one of the circuits in question this I remember from school but for the life of me I can't remember how much of a load it would have to be or why it actually is more of a factor then any other load. The biggest problem on this is at what point does a number 10 copper wire create the heat neccessary to cause this set of problems to arise. As I said in the origional post there are a great deal of different formulas to get these answers but frankly I don't remember them and could sure use help if anyone knows of any that might help, not looking for the answer to the problem only in sources to help find it.
 
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