[betelgeuse]

I can remove the plastic box and install a metal box but how do I connect a metal box to plastic conduit?

With one of these and a locknut.

Cantex .75 in. PVC Male Terminal Adapter Conduit Fitting for Cantex PVC Conduits R5140104 - The Home Depot

Find the Cantex Inc. 3/4 in. Male Terminal Adapter R5140104, adapter transition from plain end PVC conduit to conduit with a threaded metal end or PVC female bell end from The Home Depot

www.homedepot.com

 

[betelgeuse]

What wiring method is in the plastic conduit?

He says Rigid PVC with B,W,G

 

[betelgeuse]

Ya only got to bond 1 end of the jacket?

If you're talking about the armor of the MC, it will be bonded at both ends if both boxes are metal.

 

[betelgeuse]

Bonding is any location past the point where the service is grounded. (Usually the main breaker).
Both metal boxes need to bonded with a screw (there's already a threaded 10-32 hole in the back of metal boxes) All grounding wires must be spliced together and bonded to the boxes with a pigtail

 

[betelgeuse]

So what if we simply bond the extension box,,, the first is plastic the new is metal, do we +++++++++++++need to bond both ends of the cable?

Yes. Since there is no threaded hole in an extension box you need to use one (or couple) of these:

Commercial Electric 14-12 AWG Steel Ground Clips, Green (10-Pack) GOEC CLIP - The Home Depot

The Steel Grounding Clips are designed for bonding pigtails to grounded metal junction boxes. Dual rated for copper and aluminum conductors. The suitable wire for copper ranges from #14 Sol/Str to #12

www.homedepot.com

The wire goes through the clip and is the clip is clipped over the sheet metal sides.

 

[betelgeuse]

[QUOTE="hornetd, post: 7166434, member]
In general a threaded male adapter is the worst of the available ways to connect a non metallic conduit to a box.
[/QUOTE]
How so?

 

[betelgeuse]

The one that would meet that concern the most readily would be to use a female thread adapter and a chase nipple in place of a box adapter into the box.

A female adapter has tapered threads and the chase nipple has straight threads though.