Securing EMT to a flat roof fixed or free to move?

[WHayward]

I have customer who called me for an unrelated project. While there I found that the contractor who built a “Tiny house” for an AirB&B ran a single 12/2 Romex in flexible nonmetallic 1/2 PVC conduit from the panel over the roof of the primary home down the back side, under ground and came up under the tiny house. Then out of the pvc “bare Romex for a single circuit to run the whole place.

The customer mentioned that guest trip the breaker often and the owner had to remove the provided hairdryer prevent tripping.

Going over the roof is still the most practical route to bring the new feeder over. The roof is flat tar and gravel. Planning to use 1” EMT.

I have not encountered this specific situation before. From what I have read, EMT conduit with rain tight fittings is acceptable, but the question is how to secure the 40 ft run. Do I need to secure the EMT to the roof every 10ft or secure the EMT to blocks that can move to allow for expansion?

Secondly, is a pressure treated 4x4 block of wood acceptable or should a listed support device be used?

 

[hillbilly1]

Usually it’s fastened to the pt blocks, or blocks made for pipe support. Doesn’t have to be listed. You will not be able to use Romex in it.

 

[ptonsparky]

I’ve used 4x4 and also the strut and composite combinations available. Most everything I’ve seen in the past floats.

 

[WHayward]

I am planning to run THHN to a new subpanel.

 

[ptonsparky]

I am planning to run THHN to a new subpanel.

…THHN/THWN…

Arrange to drain.

 

[marmathsen]

Are you saying they used 1/2" LFNC the entire way?! How the heck did they pull Romex through that? Must have needed 10 gallons of lube! Or maybe you just meant regular PVC.

I'm also curious to see responses from others about the supports as this is not a typical install for me.

Rob G
Seattle

 

[marmathsen]

…THHN/THWN…

Arrange to drain.

I've never seen one without the other. Can you get THHN only?

Rob G
Seattle

 

[ptonsparky]

How? Lay the LFNC out on the ground, push a fish tape thru, pull wire. Lay it on the roof and trim to fit.

 

[WHayward]

Are you saying they used 1/2" LFNC the entire way?! How the heck did they pull Romex through that? Must have needed 10 gallons of lube! Or maybe you just meant regular PVC.

I'm also curious to see responses from others about the supports as this is not a typical install for me.

Rob G
Seattle

I tried to post photos, but the file size is to large…
You would laugh or cry if you saw them.

 

[ptonsparky]

I've never seen one without the other. Can you get THHN only?

Rob G
Seattle

I hadn’t either, but I guess you can in larger sizes.

 

[WHayward]

How? Lay the LFNC out on the ground, push a fish tape thru, pull wire. Lay it on the roof and trim to fit.

Yes, I am sure that is what they did. I forgot to mention that they used sch 40 pvc and made a “custom heated and crimped” 45 under the house.

 

[Eddie702]

Pulling through LNMC is tough I did a 20' run at my bosse's house 3/4" with 3 #12s and 2 #14s and I was swearing the whole time. Seems to me it should slide right in but no way. Had maybe 3 bends in it that were not tight. I like the LNMC its pretty tough but the fittings are crap and tough to pull.

As far as the EMT it just floats on the supports you buy with the strut mounted on them. They cost $$ but 4 x 4s and mounting strut takes some time

 

[hillbilly1]

Fiberglass or nylon fish tapes push through Smurf and LNMC easier than steel.