NM-b to THHN Transition

[Wileel]

Looking for a little advice and see lots of info but nothing that exactly answered my situation.

I running new wire for my mini-split and plan to run NM out of the box, up into the attic and over to the sofit across the shop where the heat pump will be outside. From there I will change to THHN and run it through PVC down out of the soffit to the unit.
Here is the question, how do I transition from the romex to the THHN?...Do I need to make the connections inside a box that has adapts to the conduit?

Thanks

 

[American Locomotive]

You do it the same exact way if you were joining two pieces of NM-b together - inside a box.

 

[ard]

.Do I need to make the connections inside a box that has adapts to the conduit?

Thanks

Yup. And needs to be 'accessible', so in the attic will be fine, assuming a human can access that space.

 

[Norcal]

Plus needs to be dual rated THHN/THWN, as THHN is dry loctions only like NM cable.

 

[MJO]

Fitting

 

[alfredeneuman]

That's an NM to EMT connector.

"From there I will change to THHN and run it through PVC down out of the soffit to the unit."


NM can't be run outside, and if you used fittings like that it would require it.

 

[bmwpowere36m3]

NM can be run outside... however it cannot be in a WET location. In some locals you could run that NM-B all the way to the unit in the manner you desire (conduit out the soffit, down along the siding, to unit).

However transitioning within a junction box is likely the way to go.

 

[Norcal]

NM can be run outside... however it cannot be in a WET location. In some locals you could run that NM-B all the way to the unit in the manner you desire (conduit out the soffit, down along the siding, to unit).

However transitioning within a junction box is likely the way to go.

Any location outdoors is defined by the NEC as a wet location.

 

[Bert_]

I'd be the "hack" and just run the NM down the PVC. No water will ever accumulate in that vertical piece of pipe, the average bathroom is probably exposed to more moisture than this will ever see.

If you want a totally code compliant answer then run UF for the whole run. As a rule I avoid unnecessary junction boxes.

 

[wyliesdiesels]

Fitting

How would one do a splice from NM to THWN in that?

 

[Wileel]

Ok, so I just need to do the connection in any box? I was thinking the box would need a way to adapt to the conduit. This connection will be is a "dry" location (the attic) but once it leaves the sofit its is a "wet" location (along an outside wall) the way I read the code. Even thought this whole run isn't sealed from box to termination I was figuring they might have wanted the connection to happen inside a box that adapted to the pvc conduit

 

[grounded-b]

Ok, so I just need to do the connection in any box? I was thinking the box would need a way to adapt to the conduit. This connection will be is a "dry" location (the attic) but once it leaves the sofit its is a "wet" location (along an outside wall) the way I read the code. Even thought this whole run isn't sealed from box to termination I was figuring they might have wanted the connection to happen inside a box that adapted to the pvc conduit

Yes the splices need to be in a box (metallic or non-metallic). You will ALSO need connectors, to connect the wiring method to the box....

A connector for the NM could be a "snap-in" connector or a metallic 2-screw NM connector.

The connector for the PVC will be a PVC "male adapter" and a locknut.

The wiring method needs to be secured to the box AND supported within 12" of the box for NM and 36" of the box for PVC.

If you use a metallic box, then you MUST bond the box to the ground wire (green or bare)

 

[Wileel]

Thank you thats what I needed!

 

[rick carpenter]

NM can be run outside... however it cannot be in a WET location. In some locals you could run that NM-B all the way to the unit in the manner you desire (conduit out the soffit, down along the siding, to unit).

However transitioning within a junction box is likely the way to go.

Southwire makes UF-B wire suitable for direct burial in wet locations. It's similar in appearance to NM but it has a better plastic for the jacket and each wire is separately encased. Makes it less fun to strip.