sleeves for power conduits - purpose & best practices?

[malachi constant]

Hi all,

Consulting engineer here. A contractor is asking questions about sleeve language that is in our master spec. Doing some research I am having trouble determining the purpose and best practices related to conduit sleeves. Note this is NOT a question about sleeves for cables.

Our spec requires sleeves for conduits passing through floors, footings and exterior walls. It also calls for sleeves for conduits 1-1/4" and larger "passing through walls". Which has yielded the question "exterior walls, or ~all~ walls?". The way the spec is written it could be interpreted either way, I am less concerned about the spec interpretation and more interested in learning pros and cons, best practices etc.

So for what purposes would a conduit sleeve be installed? Only in exterior envelope and fire rated walls? Is it intended to protect conduits from expansion/contraction, building shifting, etc? All our project are in non-seismic areas so not worried about anything more than normal thermal expansion between summer and winter, normal building settlement over the decades. Do these ever get installed in interior walls, if so would that just be CMU or would it also be sheetrock? I could actually see sleeves for large conduits being a benefit in sheetrock walls, as the walls would be less likely to crack if a conduit is floating in a sleeve instead of secured direct to the sheetrock. I assume in all instances of sleeves we would want a harder grouting on the exterior of the sleeve and a softer caulking on the interior.

Any insight is appreciated!

 

[LarryFine]

1. It sounds like all penetrations for 1-1/4" and up, but not necessary for 1" and down for interior walls.

2. Maybe for movement, but I think more so for replacement without disturbing the construction.

 

[synchro]

1. It sounds like all penetrations for 1-1/4" and up, but not necessary for 1" and down for interior walls.

2. Maybe for movement, but I think more so for replacement without disturbing the construction.

Agree. Also a sleeve could have its thickness and material determined for structural reasons only, independent of electrical constraints.

 

[malachi constant]

I spoke with a mech engineer to get their take on sleeves (obviously gas and water pipes are different than electrical conduits, but some takeaways):
1. Movement due to thermal expansion is a big reason - which is less of a concern for electrical conduits than it is for their systems. But sleeving conduit penetrations through exterior walls makes sense.
2. He didn't say this, but I am guessing walls/penetrations are better protected from piping condensation when they are sleeved. Not really an issue for electrical conduits, except where passing between two dramatically different thermal environments (in which case the walls are presumably rated and in that case our spec requires them to be sleeved and sealed).
3. Replacement of piping is a concern - not wanting to damage walls when a system pipe gets installed or replaced. Less of a concern for electrical as we generally reuse conduits, only replacing conductors every 30-40 years or so (in my world at least). Mechanical codes *require* pipe sleeves in new walls, if I understand it correctly the reason is to protect the walls. It is not believed that code requires pipe sleeves in existing walls but our mech engineers require it because of the occasional rogue inspector.
4. Sleeves are required in floor penetrations, and the sleeves are required to stick up a certain amount. This is in case of a spill, the sleeve prevents the spill from leaking to the floor below.

So my take is in the environments I typically design in (schools, and government office-type environments) conduit sleeves should be installed at all exterior walls, at floor-to-floor penetrations, and in rated walls.

If anyone has any further comments/suggestions I'd love to hear them. Thanks all!