Metal Enclosed Bus Duct Systems

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D.V.L.SAB said:
I'm a student of an electrical technologies program and am working on a presentation to the class on Metal enclosed bus duct systems. I would like to include a list of disadvantages to them. If anyone could help it would be much appreciated. Thank you.
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Loose connections because of the poor mechanical skills of some electricians.

This can be due to,poor training,or just plain laziness and carelessness.


Welcome to the forum..:thumbsup:
 
There are no disadvantages. It is a very viable method for certain situations and has been successfully implemented on many projects. As is with any type of electrical installation, there is a degree of expertise that is needed. Without proper training and knowledge, what seems to be a simple task could cause the loss of property, or worse life.

I would not consider improper training a fault/disadvantage of the equipment, but of the installer, for which would apply to about anything including plunging a toilet; it's not the plungers fault the drain won't unclog perhaps the user does not have proper technique or patience. :blink:
 
kingpb said:
There are no disadvantages. It is a very viable method for certain situations and has been successfully implemented on many projects. As is with any type of electrical installation, there is a degree of expertise that is needed. Without proper training and knowledge, what seems to be a simple task could cause the loss of property, or worse life.

I would not consider improper training a fault/disadvantage of the equipment, but of the installer, for which would apply to about anything including plunging a toilet; it's not the plungers fault the drain won't unclog perhaps the user does not have proper technique or patience. :blink:
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In a perfect world I would have to agree with you. The most common problem we see with outdoor installations that are over 20 yrs old are blowups caused by water leaks. And the damage can be nasty. It is amazing how much current that can flow before the OCPD trips. Ground Fault systems help to reduce this damage but are not always part of the design plan, especially on older installations.
There was a case with a 4000A bus duct at a nearby hospital. Great efforts were made in sealing the joints to keep it dry including having a sheet metal cover fabricated over the entire run until it blew up the 3rd time and was finally replaced with cable.
The second common problem we see is overheating due to loose connections as a result of lack of proper maintenance.
Once the copper becomes annealed, the section has to be replaced and worst case, the whole run. In the case of aluminum bus duct, well that's another story. :thumbsdown:
 
ATSman said:
In a perfect world I would have to agree with you. The most common problem we see with outdoor installations that are over 20 yrs old are blowups caused by water leaks. And the damage can be nasty. It is amazing how much current that can flow before the OCPD trips. Ground Fault systems help to reduce this damage but are not always part of the design plan, especially on older installations.
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The bus duct is often on the secondary side of a lager transformer and on the load side of the secondary OCPD. It takes a lot of secondary current to trip the transformer primary OCPD.
There was a case with a 4000A bus duct at a nearby hospital. Great efforts were made in sealing the joints to keep it dry including having a sheet metal cover fabricated over the entire run until it blew up the 3rd time and was finally replaced with cable.
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The plant I often work is working on the replacement of their outside bus duct runs with cable bus as a result of a couple of failures related to water ingress.
 
don_resqcapt19 said:
The bus duct is often on the secondary side of a lager transformer and on the load side of the secondary OCPD. It takes a lot of secondary current to trip the transformer primary OCPD.
The plant I often work is working on the replacement of their outside bus duct runs with cable bus as a result of a couple of failures related to water ingress.
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i've installed both, and it's pretty hard to beat a cable with a swaged lug on the end of it.
if all you are doing is moving a bucketload of power without needing to tap it along the way,
it's pretty unbeatable.

largest bus duct install i've worked on was hughes electro optical, in el segundo, calif.
a long while ago.... they had a large amount of problems with the system, i'd say
2/3 labor, but 1/3 was moisture.

stuff got wet. they tried a lot of solutions including putting 1,000 amps at 12 volts thru
a 3,000 amp bus duct to warm it up and dry it out. they tried blowers, heaters, etc.

so, moisture is the nemesis. i never did understand why on earth they didn't megger each
piece before putting it into the system, and megger the entire bus after each torquing.
must have had something to do with 400 electricians working with the tools, on 7-12's. :huh:
 
LEO2854 said:
Loose connections because of the poor mechanical skills of some electricians.

This can be due to,poor training,or just plain laziness and carelessness.


Welcome to the forum..:thumbsup:
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and a classic is the one where theres signs of overheating on stranded conductor connections...caus they thought they had acheaved a good termination rather than use a bit of sense which was to tighten down terminations on stranded conductors...then `rattle` the cable near the termination....mark my words that termination screw will go another 1 1/2 turns at least as the strands bed down...

there....no more overheated terminations = no more callbacks...
 
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