Rooftop conduit

[hhsting]

What is the best conduit for running service drop conductors from weater head on rooftop till it drops outside wall to service disconnect other side of weather head?

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[LarryFine]

1. What? :blink:

2. Why not EMT?

3. Pic or drawing?

 

[rlundsrud]

I've always used RMC or at least IMC. If you did use EMT, you would have to use compression fittings.

 

[hhsting]

Is their anywhere in code their is Article which says specifically conduit for use on rooftop?

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[infinity]

Is their anywhere in code their is Article which says specifically conduit for use on rooftop?

No you could use PVC, if subject to physical damage then SCH80. You will need to be concerned about expansion fittings with PVC. We only use Aluminum RMC or PVC coated Galvanized RMC on the roof

 

[hhsting]

Would not PVC conduit schdile 40 or schedule 80 melt under high tempersture on roof or under extreme cold get brittle?

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[kwired]

Would not PVC conduit schdile 40 or schedule 80 melt under high tempersture on roof or under extreme cold get brittle?

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There is no general prohibition of using PVC on rooftops, but those extremes are design considerations regardless of whether it is service conductors or feeder/branch circuit conductors.

 

[cowboyjwc]

You might what to check with the local utility.

 

[tom baker]

Washington restricts the wiring method for 'unfused service entrance conductors' to 8 methods, while many of the wiring methods in chapter 3 are allowed by the NEC. For exmaple SE cable and EMT are not allowed. Your POCO may require sch 80 PVC.
Keep in mind service heads need to be vertical, in a rooftop applicaiton the service head could be horizontal.
PVC exposed outside, especially on a rooftop, needs to well supported or it can sag. If allowed in you area, EMT with raintight fittings or as suggested, Rigid AL conduit.

 

[tom baker]

Is their anywhere in code their is Article which says specifically conduit for use on rooftop?

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Check the uses permitted and uses not permitted at the beginning of each wiring method article in Chapter 3

 

[sameguy]

Around here it's up to the poco. That would be galvrig.

 

[kwired]

Washington restricts the wiring method for 'unfused service entrance conductors' to 8 methods, while many of the wiring methods in chapter 3 are allowed by the NEC. For exmaple SE cable and EMT are not allowed. Your POCO may require sch 80 PVC.
Keep in mind service heads need to be vertical, in a rooftop applicaiton the service head could be horizontal.
PVC exposed outside, especially on a rooftop, needs to well supported or it can sag. If allowed in you area, EMT with raintight fittings or as suggested, Rigid AL conduit.

SE I can understand, some, why not EMT?

 

[tom baker]

Restriction on EMT dates back to 1965. May be due to EMT and high levels of fault current conduit will melt.

 

[kwired]

Restriction on EMT dates back to 1965. May be due to EMT and high levels of fault current conduit will melt.

One extreme case seen by the right person and now all similar installations are dangerous - right?

Fittings are going to be the weak point. Small service with single raceway of say 2 inch or less - may not even be enough fault current available to do that. Large service with high fault current and parallel conduits - just having them in parallel lowers resistance, especially if mechanically bonded to each other periodically by something like unistrut racking.