Working on a project and got into discussions regarding the geotech report. One subject brought up was penetrations through walls into soil, and whether or not flexible connections are provided to accommodate soil movements. The building owner is now asking a design for 12? of movement. Currently I have shown PVC conduits penetrating wall but I don't think PVC will accommodate 12 of movement. Have you ever run into this? Can I use liquidtight Flexible Metal Conduits (LFMC) for this purpose?
Wall Penetration into Soil - Flexible conduit?
- Thread starter elec_eng
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ptonsparky
Tom
- Occupation
- EC - retired
12" in all directions?
renosteinke
Senior Member
- Location
- NE Arkansas
He wants to allow for that sort of movement, you're looking at a coil of sealtite at the penetration.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Is this some type of high rise? 12" of movement has got to be some type of unique design. I would think you would need to have a conduit tunnel exiting the building to allow for so much movement. Regarding LFMC, my instict would be don't do it. You have to be concerned about 360 degrees of bends and pulling after installation. You could use listed MC, but I think the whole issue of 12" should be assessed. It sounds arbitrary. Where are you going to get 12" of movement? Sheer at the slab level, Entire foundation shift? vertical shift?
Mainly vertical movement
Are you talking about LFMC?
Yes..It is a high rise and understand this is a very unusual requirement. The geotech report doesn?t really state that there will be too much differential movement, but the owner has experienced a significant heave around the existing buildings at the same site. Our engineer estimates about 4 inches for the worst case scenario but the owner is directing us to design for 12 inches.
Strathead
Senior Member
- Location
- Ocala, Florida, USA
- Occupation
- Electrician/Estimator/Project Manager/Superintendent
Totally amateur thinking here, but what about just providing a detail for all slab penetrations being sleeved with an expansion seal to prevent moisture and vermin infestation. The sealer can be inspected as part of the maintenance schedule and any movement would crack the expansion seal, but not the conduit? Howeve, IMO, a large building moving vertically would probably include ground movement and any conduits would move right with it.
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