# mounting conduit on existing flat roof



## bhe (Feb 3, 2007)

Can any one recommend a product or method to run conduit on an existing flat roof? First time for everything! Thanks in advance for your input.


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## curranelectric (Sep 25, 2007)

Here is a web site and Picture that has what I hope you are looking for.


http://www.pipepier.com/


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## bhe (Feb 3, 2007)

That was fast! thank you.


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## 220/221 (Sep 29, 2007)

One hole straps on short pieces of PVC.


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## mdshunk (Mar 13, 2005)

I usually use one hole straps on chunks of 4x4 pressure treated lumber.


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## 480sparky (Feb 1, 2009)

mdshunk said:


> I usually use one hole straps on chunks of 4x4 pressure treated lumber.


 
Same here. 

If it's a rubber-membrane roof, I also collect scraps to place between the 4x4 and the roof. Let the roofing crew know you'd like the scraps, and they'll most likely save some for you.


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## bhe (Feb 3, 2007)

Thanks for the input everyone, I think I am going to try the first product recommended. The cost is pretty low and I think it will look nice. I need to run 2" rigid (engineer's specs) for the air handlers on a private school, should be a money maker.


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## mdshunk (Mar 13, 2005)

bhe said:


> Thanks for the input everyone, I think I am going to try the first product recommended. The cost is pretty low...


I don't know. The last time I looked in to those heavy rubber chunk things with the Kindorf groove buit-in, they were something like 8 bucks a piece. Not really what I'd call cheap, but maybe you don't need very many.


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## bhe (Feb 3, 2007)

According to the website the "classic" is $2.70 each and the "deluxe" is $11.00 each. I need about 20 of them and I bid the job at almost $25,000, so it really isnt all that much in the scheme of things. This is an upscale school in an upscale community, so nothing but the best will do. This whole job is going to cost the customer almost $100 k.


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## nEighter (Nov 24, 2008)

Isn't there going to have to be a temperature factor added to the calculation to keep the temp of the wire down? in the NEC 2008codebook table 310.15(B)(2)(c) provides temperature values that must be added to the expected ambient temperature.










Good luck though man!:thumbsup:


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## bhe (Feb 3, 2007)

nEighter said:


> Isn't there going to have to be a temperature factor added to the calculation to keep the temp of the wire down? in the NEC 2008codebook table 310.15(B)(2)(c) provides temperature values that must be added to the expected ambient temperature.
> 
> 
> 
> ...


Whoa dude.......are you sure your not an electrician? If not, you should consider it. But seriously, this has already taken into account and wire has been spec'd to be oversized by the engineer.


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## nEighter (Nov 24, 2008)

Will be someday soon! LOL glad you took that good, don't want to come across as a know it all, I am learning.. actually.. in school for electrical, we just went over that stuff the other day  :lol: :thumbsup:


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## bhe (Feb 3, 2007)

Good for you and best of luck. The people that take things the wrong way on these forums dont hang around very long. And by the way we all are learning, thats why we are here.


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## nEighter (Nov 24, 2008)

:thumbsup:


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## mahlere (Aug 6, 2006)

bhe said:


> According to the website the "classic" is $2.70 each and the "deluxe" is $11.00 each. I need about 20 of them and I bid the job at almost $25,000, so it really isnt all that much in the scheme of things. This is an upscale school in an upscale community, so nothing but the best will do. This whole job is going to cost the customer almost $100 k.


i gotta ask....how many man hours for your $25,000 portion of the project? tell me 100 man hours, and i'll buy you a drink and pick your brain


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## Magnettica (Dec 19, 2006)

nEighter said:


> Isn't there going to have to be a temperature factor added to the calculation to keep the temp of the wire down? in the NEC 2008codebook table 310.15(B)(2)(c) provides temperature values that must be added to the expected ambient temperature.
> 
> 
> 
> ...


I'm glad you pointed that out. That's a new table for the 2008 NEC and I hadn't noticed before. :thumbsup:


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## Archania (Jan 21, 2009)

I learned those temperature correction factors for my electrical classification test a few months ago... Didn't realize it was so new in the NEC.

Anyway, those special blocks are cool, and not that expensive. I just do the pressure treated blocks. But you have to think, who the heck is going to go on the roof and see them? Not saying you should "cheat" them, but if they never see them, it will be kind of pointless...


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## nEighter (Nov 24, 2008)

Magnettica said:


> I'm glad you pointed that out. That's a new table for the 2008 NEC and I hadn't noticed before. :thumbsup:


:thumbsup:


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## Magnettica (Dec 19, 2006)

Any time you see a thin black line to the left of a paragraph in the NEC it means that it's new or the wording has changed.

Although looking at it now the 2008 uses shaded sections for new or modified wording so the thin line might just be for new.


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## 480sparky (Feb 1, 2009)

Magnettica said:


> Any time you see a thin black line to the left of a paragraph in the NEC it means that it's new or the wording has changed.
> 
> Although looking at it now the 2008 uses shaded sections for new or modified wording so the thin line might just be for new.


Read the last paragraph on page 1. That explains the lines, bullets and grey shading.


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## bhe (Feb 3, 2007)

mahlere said:


> i gotta ask....how many man hours for your $25,000 portion of the project? tell me 100 man hours, and i'll buy you a drink and pick your brain


 
I am planning on about 160 to 200 hrs. But we may be able to come in less than that.... especially if I can find an easier way to run the conduit......we'll see......... also half that number is material costs.


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## Jm H (Dec 30, 2008)

As a roofer speaking 4 x 4 sleepers are sufficient. Just make sure that scrap pieces are used between block and membrane roof


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## 220/221 (Sep 29, 2007)

> I need to run 2" rigid (engineer's specs) for the air handlers on a private school, should be a money maker.


For securing *big* conduit we use unistrut. We don't get enough rain here for rust to be an issue.


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## mahlere (Aug 6, 2006)

bhe said:


> I am planning on about 160 to 200 hrs. But we may be able to come in less than that.... especially if I can find an easier way to run the conduit......we'll see......... also half that number is material costs.


sounded much better when it was $25k for 100 man hours and a few thousand in material...now it just sounds like a normal job:laughing:


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## bhe (Feb 3, 2007)

mahlere said:


> sounded much better when it was $25k for 100 man hours and a few thousand in material...now it just sounds like a normal job:laughing:


 
Lowest bidder probably...........but these days any job over a couple grand seems like the big time.


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