Busway

[brian john]

Over the years I have seen numerous problems made with busway, I am surprised by the number of contractors and end users that do not take the basic steps to insure a problem free installation.

In the last week I have been involved in two busway incidents, the first was water and the busway was de-energized and bypasses, in the second incident the 4000 amp busway was dripped on for a period of time and finally vaporized. While busway is an excellent way for distribution there are some draw backs and water is the number one enemy of busway.

In all the time I have been involved with electrical testing faulted busway ranks way above faulty cable as the number one feeder fault.

1. Busway when installed should be damned at all floors to prevent the intrusion of water.
2. Horizontal runs of busway should be shielded where water pipes, ducts that might condensate and expansion joints cross paths.

I have been involved in several instances of new installations where the contractor did not follow a few basic rules and the project took a monetary hit.

1. Upon the receipt busway should be numbered and meggered as it comes off the truck.
2. Stored in a dry location on 4x4 and COVERED.
3. Installed only after the building is sealed.
4. Each piece should be meggered as it goes up.
5. After installation of a new piece the entire length should be meggered.
6. Care should be taken to run the busway as straight and/or level as possible as angle bends at joints put undo pressure on the couplings and the plastic separators/insulators.
7. Upon completion the busway should be meggered and documented, all parties involved should be notified the busway is acceptable for use.
8. Prior to energizing for the first time the busway should be meggered and the original report should be checked for comparison of readings.
9. Should there be any water issues on the job megger the busway immediately and notify all parties of any issues.
10. During construction the GFP should be left set at 100 Instantaneous or minimum delay.
11. After construction as the GFP should be set to pick-up and delay as determined by the coordination study.

 

[augie47]

excellent suggestions, Brian.
It would probably fall on deaf ears, but you should forward them to the bussway manfacturers.

 

[infinity]

Over the years I've seen some horrible busway installations. IMO most of the problems are from the installer not reading the directions.

 

[EBFD6]

The worst electrical disaster I have ever seen was a busway fault.

16 story apt. building w/ 2000 amp buss running up the center core of the building for distribution.

Roof had a leak and water got into busduct. Buss exploded from 16th floor and didn't stop until the 10th. All 6 floors there was nothing left except a shell of the busduct and a pile of molten copper on the floor.

We ended up being able to disconnect the buss on the 8th floor and from 8 down megged clean, we replaced the buss on the top 8 floors and, obviously made them fix the roof.

The stupid part of the story is that the maint. people from the apt. complex knew about the leak for months, and instead of fixing it they covered the busduct with a tarp and called it a day.:roll:

Lesson learned - keep busduct dry!

 

[det_wireman]

water and electricity do not mix

water and electricity do not mix

I work in a large industrial facility and over the past 25 years I know of two or three failures in our plant. All were caused by water getting into the bus duct. The latest happened a month ago. A leaking pipe directly over the bus was the culprit. The damaged section of the bus had to be replaced. As I remember the others were caused by leaks in our ageing facility?s roof.

One positive story was a few years ago a loose connection between sections of bus was discovered by a tradesman doing thermal imaging. We were able to shut bus down and repair it on weekend before any disaster happened.

 

[infinity]

Yes, water is one of the biggest problems for not only busy duct but for most electrical equipment. I once witnessed a pipe that was leaking into a 480 transfer switch that we were trying to protect. Before we could get a tarp over it the door was blown off.

 

[don_resqcapt19]

I'll add one comment...make sure you tighten the connections. A friend of mine was appointed maintenance manager for a large manufacturing facility and on his second day they had a catastrophic bus duct failure....the production losses were well over a million dollars and the cause was that the original installer had never tightened some of the connections. The duct had been is service for about 6 months before the failure.
About 30 years ago I was involved in the evacuation of a hospital that was the result of the main service duct getting wet and failing. The electrical equipment room was underground, with dirt and grass over the roof...there was a leak and the aluminum bus duct failed.

 

[infinity]

Don brings up a good point. Most bus duct couplings have bolt heads that shear off when tightened to the proper torque. A quick visual inspection of every joint before it's energized will likely tell if every coupling has been properly tightened. As you can see from his post failure to do so can be very costly.

 

[mayanees]

...nice

...nice

Thanks Brian for the real-world, experience-based commentary on busway, which is readily specified in the world of data centers.
And also tx for the suggestions on how to improve.
... always looking for the perfect install.

JM


... and one quick edit Brian, as I read back over your post.... , do you suggest that we megger anything???