Conduit on Side of Building with Snow and Ice Falling from Roof

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maintee

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Electrical Engineer
We have the need to replace 13.8 kV switchgear (8 feeder circuits) with new gear. A steel plant in western New York with heavy snow and ice load on gable roof. We cannot interrupt power to any of the operations during construction, so project activities need to occur during normal plant operations. We desire to run new 4' or 6" conduits on the outside wall of building so no interference to production operation occurs. We will take a one-week outage to tie in the new circuits. My question is how durable will the conduits running the sides of the building be with snow and ice falling from roof? Thanks, Pat
 
Type of conduit? RMC? PVC?
Could you install temporary snow melting and deicing equipment and gutters to eliminate the problem altogether?
 
This would be rigid metallic conduit. I hope to not be dependent on needed power to keep things thawed. We currently use underground bus ducts but they are flooded from lack of maintenance on sump pump systems. Thank you for the idea!
 
Question is not how durable the conduit is, but how securely are they fastened to the building?
Can a 200# man stand on top of the conduit and bounce up and down?
Would a 'snow shed' above the conduit (a roof to deflect the ice & snow around the conduit) be a simple preventative?
 
We currently have a small overhang on the sloped side of the building but it's not enough to cover the conduit. If we expand the overhang then it needs to be stronger than a piece of sheeting extended out. I wonder how firmly the conduit can be anchored to the side of the building, we will investigate that. It has been suggested we install the ice breakers along the side of the building so no large chunks fall. Thanks for your replies!!
 
Not sure how durable heavy wall steel conduit would hold up with ice falling on it but would go with two things. Install the conduit directly to wall using either heavy duty anchors and a shield with maybe a 45 degree slope extending an inch past the conduit diameter from at least 10 guage steel to intercept falling ice. Would stay away from using unistrut or mineralac clamps due to falling ice will act liking a speeding wedge and get between conduit mounted on strut or mineralac clamps. At the large hospital that I retired from they had two problems
with falling ice. Before they installed a snow melt on Tenth floor helicopter landing they would use a snow blower to blow snow off that area to a side street they would close off. A piece of ice that snow blower blew off roof got hit with a strong wind and broke a patient window.They built a fancy 3/4 billion dollar 12 story ambutory care building where every 3rd or 4 th floor roof would curve out over lower floors. They installed 277 volt heat trace lines along those roof and down a foot into roof drains. Every time it snowed more then an inch or so they would have falling ice and would have to close off sidewalk. Brilliant designer expected a single run of heat trace to melt snow & ice on 5 to 7' wide areas.
 
In my experience, ice never falls directly down the side of a building, it usually piles up about 1 foot away. This effect is more pronounced with steeper roofs. Your existing overhang may be sufficient it it covers more than half of the conduit and is pitched around 45°.
 
Again, thank you for the different perspectives! We take electric service at 115 kV via a 20 MVA transformer and then drop to 13.8 kV. The 13.8 kV gear is very old hydraulic actuated circuit breakers. This old 13.8 kV gear needs to come out.

We have considered locating the conduit high on the wall (just under small overhang) for more protection. We may add some extra protection too. Jim Dungar your perspective has some value.
 
maintee said:
This would be rigid metallic conduit. I hope to not be dependent on needed power to keep things thawed. We currently use underground bus ducts but they are flooded from lack of maintenance on sump pump systems. Thank you for the idea!
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Perhaps you can convince the client to extend the roof overhang.
 
maintee said:
We take electric service at 115 kV via a 20 MVA transformer and then drop to 13.8 kV.
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Steal smelting plant requires 115 KV transmission lines to 20 MVA substation, with 13.8 KV secondary distribution.
electrofelon said:
So should the OP follow the advice from some random person on the internet suggesting to speak to a structural engineer?🤔😉
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Seen underground distribution raceways, but not attacked to buildings.

Is 13.8kv within NEC scope of 2kv wiring methods, much less for new construction without plans, permits, or engineering?
 
ramsy said:
Steal smelting plant requires 115 KV transmission lines to 20 MVA substation, with 13.8 KV secondary distribution.

Seen underground distribution raceways, but not attacked to buildings.

Is 13.8kv within NEC scope of 2kv wiring methods, much less for new construction without plans, permits, or engineering?
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While the NEC does not do a good job with rules for high voltages systems, everything on the load side of the service point is within the scope of the NEC, no matter what the voltage may be.
 
electrofelon said:
So should the OP follow the advice from some random person on the internet suggesting to speak to a structural engineer?🤔😉
Click to expand...
Last time a few of us electricians questioned a structural engineer in thinking he did not have the iron workers install enough steel for what the inspector said was the largest junction box that he ever came across. We called it the 80 way because it had 80 4" conduits at each end. Was 20' long and had expansion slotted holes on it. Before halve of the 4" conduits where filled with 500 MCM copper wire the steel U channel started to bend. Run had 8 rows of 10 side by side 4" EMT conduits. At my first job I was labeled a trouble maker because I told the boss that it was not legal to use a romex connector thru the cover of a 1900 box to ever support ceiling cord drop. Only brought that up once. A few years later OSHA told them the same thing.
 
How about a "shroud" (sections), of galvanized heavy duty sheet metal, to cover the run of conduit on the wall. The ice is less likely to attach to the smooth surface. Run a couple of lengths of ice-melting cable to get rid of snow. There may be some other measure to prevent corrosion, e.g. zinc coat over the entire shroud.
 
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