Plastic connectors vs junction boxes

[Tin Gill]

Is there any accepted wisdom about using plastic connectors instead of junction boxes? Are plastic connectors acceptable for extending a wire and are they acceptable insetad of a junction box?

I've extended a cable and used plastic connectors and then wrapped it up in insulated tape. Is this okay?

Thanks.

 

[alexnic]

Only if it's then enclosed in a plastic/metal junction box and preferably fixed to a surface