A narrow splice box that can replace this 4" LB?

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Jon456

Jon456

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Colorado
We have a 4" EMT conduit that turns the corner of a building via an LB. The conduit carries (3) 500 MCM copper conductors to a 250 kW solar inverter.

IMAG0734-Annotated.jpg


We know that one of these wires is bad: the upstream OCPD has tripped 4 times since it's been in operation, and a megger test shows a lower reading on one feeder. I suspect that the fault is in the conduit between the LB and the inverter (pictured in the bottom left of the photo). The reason I believe that the fault is in that section is because the installation contractor installed the LB the wrong way for the direction of their wire pull (red arrows). So instead of pulling out the side inlet of the LB and then into the back outlet of the LB, they pulled out the back and then into the side.

I observed them during the pull and they had a hell of time getting those 500 MCM wires through the LB. The difficulty of the geometry was compounded by the fact that they didn't bother to use any wire-pulling lube, which was typical for their pulling practices on this job. (The wire was not SimPull or any other pre-lubricated product.) As they got to the final few feet of wire going through the LB, the wire loop really jammed up hard on the inside corner of the conduit body. They were using a Bobcat front loader to pull the wire through the final 90 deg sweep into the side of the inverter, and they snapped their pull rope. (No tuggers or tension calcs on this job!) After the rope broke, the crew finally heeded my advice and slathered some wire lube on the problem area. Finally, they were able to get the wires pulled in, but I'm sure the insulation got damaged during that fiasco.

So now we plan to disassemble the conduit from the inverter pad to the LB and inspect the wires. If we find the damaged area and the rest of the wire tests good, then we'd like to install a splice box in place of the LB (or just before the LB). But I don't know if there's a narrow, rectangular, weather-proof splice box that will fit inline with that 4" conduit. Unfortunately, they ran EMT conduit for the solar DC feeders both above and below the 4" AC feeder conduit, so that prevents us using a standard square box.

Any recommendations? Here is another view of the conduit run:

IMAG1472.jpg
 
After all these different threads of failed conductors, is this contractor still in business? It doesn't seem like a company would last long if there were this many problems at just ONE site.
 
Cow said:
After all these different threads of failed conductors, is this contractor still in business? It doesn't seem like a company would last long if there were this many problems at just ONE site.
Click to expand...


Over the years problems show up and no one knows who did it.
 
iwire said:
Another vote for wireway, I would use a 48" long section, it only makes it easier to close up.
Click to expand...

yep. +1 twice on that.

as it seems you are going to have to cut the conductors, i'd
just saw thru the entire thing behind the LB about 6", take
it apart, use a GRC coupling to extend the short side of the
conduit run to the edge of the building, slide off emt back
to the coupling, megger all of it while it's apart. if it's just
damaged insulation at the corner as you suspect, reassemble
it with the gutter, hypress it back together, and use three
pieces of panduit 600v heavy wall direct burial heat shrink
to give it a UL approved coating.

stuff comes in 4' lengths, and is about $50 a chunk, from
mayday grounding. i've not seen it anywhere else off the
top of my head. they ship nationwide overnite.
 
Cow said:
After all these different threads of failed conductors, is this contractor still in business? It doesn't seem like a company would last long if there were this many problems at just ONE site.
Click to expand...
Yes, the contractor is still in business and working other large commercial installations. We hope he stays in business too because we are only 1.5 years into his 10 year warranty on this project!

There were many more problems than just the ones I've posted so far. Not all were related to wire pulling. :(

LEO2854 said:
Over the years problems show up and no one knows who did it.
Click to expand...
Many of the problems I witnessed myself as the job was being performed. I raised these issues with the crew doing the work, with their boss (the installation contractor), and with the facility manager. Some issues were addressed; many were not. But it got to the point where the installation contractor was actively trying to keep me away from where his crews were working so I couldn't observe what they were (or were not) doing. I thoroughly documented the problems with the early wire pulls because, as the facility manager's on-site representative, I was watching the entire operation. But I can't provide many details on the later pulls because the installation contractor started running interference on me.

In any case, the first serious problem manifested itself within 6 months after commissioning: the OCPD to one of the four 250kW central inverters tripped offline about 4-5 times. The feeders to that inverter are the subject of this thread. When the breaker tripped, I immediately suspected insulation damage to the feeders based on the problems I observed during the pull. But the the installation contractor argued at the time that there was nothing wrong with his work, even though he could not offer any other explanation. We replaced the breaker with another and the new one tripped also. The inverter was checked and tested, but no faults were found. The installation contractor borrowed an old vintage analog megger (his company did not own a megger at that time) to test the conductors, but the results were inconclusive. Eventually the fault cleared itself so no further action was taken. My conclusion was that the feeders were expanding/contracting within the EMT conduit and, as they moved slightly, the damaged wire was able to short out to the conduit wall. During each short, the exposed wire was burned back a little until the air gap was sufficient to prevent further shorts.

Last month is when half the service feeders that power our facility shorted out (eighteen months after commissioning). That is when we called in an independent testing company to test all the AC conductors, both for our service and for our solar installation. Out of 43 feeders, 16 had faults.

We know who did it.
 
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