in-floor power?

[Factory48]

hey all. We are in the process of laying out conduit for electrical runs under the "soon to be poured" concrete floor. I will be installing a 2 post lift. The lift won't be close to a wall and I don't really want electrical hanging from my ceiling. I was thinking we could run some conduit so we could tie straight into the power right at the floor. I wonder though:

1.) would having conduit close to the baseplate of the column make the area more prone to cracking, or even worse, failure?

2.) are there other considerations I'm missing?

any help would be greatly appreciated! Sorry if there is a thread about this already here somewhere. I couldn't find one.

Thanks!
Lee

 

[Radix2]

Run the conduit under the floor not in the floor.

 

[Firebrick43]

Any opening cast into the floor is prone to cracking there. It's a stress riser. Many will saw cut a square around the opening and then the pattern from the corners to let the slab crack where they want. Remembers all concrete cracks, some are just small enough you can't see. It may not crack there. You never know?

Are you just coming straight out of the floor with conduit? Or are you placing a junction box?

The conduit itself shouldn't cause any cracking(following the pipe horizontally) if either completely below the slab or held up off the ground in the center of the slab. If left laying on the ground it makes the slab there and 1-1.25" thinner and prone to cracking. Some will actually purposely do that and place their saw cuts directly above.

If the slab sub base is proper, concrete has the correct slump, and is cured correctly I would not worry about about failure.

 

[Factory48]

Run the conduit under the floor not in the floor.

sorry! I meant underfloor. The conduit we've put down so far is about 2" below the underside of the floor.

 

[Factory48]

Are you just coming straight out of the floor with conduit? Or are you placing a junction box?

not sure on that yet. A junction box could be good because maybe I could have a plug for a welder there also?

 

[Radix2]

I think it will be fine, you can use a round junction box for extra protection against creating a stress riser from corners if you are concerned.

I have bunch of square floor drains with no issues.

 

[Thumper68]

I have 3 conduit runs under my floor, 1 for the vise one for the jib crane location and one for the table saw and jointer, the table saw run has a 4 square box set level with the floor.

 

[ard]

Personally I would NOT have any 'devices' or boxes IN the floor or at the surface. Too much debris, sawdust, water, etc to have that on the same plane.

Id for sure run conduit up through the pour, then into a box or boxes, outlets, etc.

I would probably use a double conduit- ie sleeve the conduit that will carry the wire with a larger size conduit. Can cut them both later, but this way the inner conduit will not be bound in the concrete. Could trim it flush later, caulk or cover the slight opening- or leave it a few inches long for added impact protection

 

[rlitman]

I don't see a problem with the conduit being trapped by the slab, but if that's a concern, just wrap it with pipe insulation where it will be buried in concrete.

 

[grantw]

I don't see a problem with the conduit being trapped by the slab, but if that's a concern, just wrap it with pipe insulation where it will be buried in concrete.

My driveway contractor did this for a NG line.

He wrapped a thick foam pipe insulation around the NG line and poured the driveway / walkway. No cracks to be seen near this pipe, and it's a few years old.

 

[NebrTd]

I ran 2 conduits under my floor for an eventual lift. One for the power to the lift and one for a 220v plug to be set on or near the lift. This will give me a welder outlet in the center of my shop and it will be "protected" by the post of the lift. Hopefully it works out as planned.

 

[sberry]

If you have the location p[erfect there is nothing wrong with floor wire but,,, once the hoist is ion place coming from the top wont be noticed. While its all bare the view is different. Once you get it sitting there it wont look the same. Depending on the lift motor the same circuit may be used for a welder. I have an outlet on mine for it.

 

[mm08822]

Only drawback I see to that is if you don't know the touch-points locations of the lift (including bearing plate sizes) your stub up location could be wrong.
Same goes for if you change your original location after the building is up b/c you better realize the internal space and decide to move it a few feet.

A ceiling drops eliminates these issues.

 

[rlitman]

Only drawback I see to that is if you don't know the touch-points locations of the lift (including bearing plate sizes) your stub up location could be wrong.
Same goes for if you change your original location after the building is up b/c you better realize the internal space and decide to move it a few feet.

A ceiling drops eliminates these issues.

Yep. If you're absolutely positive about the location (and that it will never change), go ahead and pipe it under the floor. But a box on the ceiling with a kellem grip and an SO cord hanging from it won't look all that bad once the lift is in place.

 

[sberry]

I have done lines in the floor. As was mentioned, good if you know exact and so much easier than lots of overhead especially with pipe, hangers etc. But also done some in places it didn't work out and would have been just as easy to go wall mainly.

 

[matt_i]

Lay that out with utmost precision as there is no going back...

 

[prostreetamx]

I would not recommend using PVC pipe in a location that is subject to damage. You can just switch to a short piece of rigid conduit or even a prefabbed 90 at the stub up location to protect it from breaking if you hit it with your floor jack or welder. Wrap the pipe where it will contact concrete with 10 mill PVC tape. They used PVC stubs where I work for 100a power stubs and over the years many have been broken by fork lifts. They are in the process of fixing them now.

 

[Norcal]

I would not recommend using PVC pipe in a location that is subject to damage. You can just switch to a short piece of rigid conduit or even a prefabbed 90 at the stub up location to protect it from breaking if you hit it with your floor jack or welder. Wrap the pipe where it will contact concrete with 10 mill PVC tape. They used PVC stubs where I work for 100a power stubs and over the years many have been broken by fork lifts. They are in the process of fixing them now.

This! The point where PVC comes through concrete is a weak point that is easily damaged.

 

[ard]

Question, you would then need to run that conduit to the first box (at least), so it is grounded, correct?

How about an outer sleeve of metal conduit to protect the inner PVC? So you arent switching materials.

 

[prostreetamx]

In commercial applications you would normally continue the rigid stub up from the slab with EMT so it would be all metal above ground, solving the grounding issue. I would just switch to EMT to the control box as PVC can break pretty easy if hit with a heavy object. At work they switched to EMT but the part coming out of the slab was PVC and breaks a lot. They are cutting them off below the top of the slab after chipping out some of the concrete. They are refilling the hole with epoxy after reconnecting the emt to the pvc. The splice is now below the finished floor level. They are also adding 3/8" thick angle to protect the emt.

 

[mm08822]

I Would run galvanized rigid up through the floor, nothing less. If you cant bend, cut and thread, use straight length(s) of conduit and buy two 90 sweeps. Vector the run to the wall to make it fit and pick it up from there with whatever wiring method.

 

[sberry]

Been there done this. There would have to be significant well thought out reason to do this especially if overhead was convenient and not that much out of the way. Under floor has its place especially in big buildings where there is a lot of stuff, over big doors, across long floor runs. It is a lot faster to install, work in the ceiling is slow. In this case the same pipe may carry some for lights or other equipment that needs to be up there and is only one more pipe.

 

[metlmunchr]

I've done the HVAC in a couple tech school garages and a few car dealerships. In every case, the electrical contractor could run PVC under the slab but the turn up thru the slab and any exposed run within so many feet of the floor all had to be rigid. Can't remember the exact distance, but I'm thinking it's 4 or 5 feet. Unless you plow into it with a forklift or something similar, rigid is near indestructible while PVC will shear off at nothing and EMT isn't much better when used in an area subject to any sort of impact.

 

[the gypsy]

How hard is it to wire a shop with this system.
https://www.cableorganizer.com/cable-trays/
I would think it is much easier than running under slab, and if changes need to be made, it would also be easier. Mind you I did not price it so I don't know how it compares, but I personally would consider this.

 

[Firebrick43]

We use a lot of cable tray at work. Usually from the main electrical cabinet to the machine(large cnc). It's insanely expensive. Also it doesn't eliminate conduit, as you have to switch to it as you get out closer to the sensors and switches.

 

[cj7jeep81]

I thought about doing this with my lift, but ultimately changed my mind. I would run it by your lift manufacturer, to make sure its ok. This was in my install guide (and what changed my mind).

"There can be no cracks in the slab within 36 in. of the base plate location, and no seams in the foundation within 6 in. of its’ location!"

Not sure if they would consider the conduit coming up as a seam, and I didn't want it 7" away from the column, as that could be a trip hazard/one more thing to hit.

 

[prostreetamx]

I didn't want a floor stub for my future lift since it could be a few month or even a year out. Even with 14' ceilings I went with an overhead drop. I already have the wire in the ceiling and will probably switch to SO cord when I install my lift.