I bought Leviton “black and white professional” 20 amp 125V nylon connector(#5369 NEMA 5-20R) and plug(#5366 NEMA 5-20P)for my dishwasher. Both the dishwasher powerline from the panel box and the dishwasher line have solid 12 AWG wire (20 amp). But the instructions to both the connector and the plug both emphatically say “DO NOT use with solid wire”. Why is this? Is it dangerous?
Because that type of plug is specifically made to be used with cordage, which is electrical cable made to be a flexible cord. "Cordage" and "solid-core wire" are a contradiction of terms.
The cable you are trying to use is Romex, which is made only for permanent installation inside the walls of buildings. It's cheap per foot, since it has none of the wire protections of cordage, and this cheapness is why it's so widely misused as cordage.
You have two choices.
- The wiring provided with the dishwasher is intended to be hardwired into the building. Use a proper cable clamp where it enters the junction box, and you're all set.
- Or, pull the dishwasher out, visit your local electrical supply house (big-box stores will only mislead you on something this specialty) and obtain proper cordage sized for the dishwasher, with or without pre-molded plug. I like to buy my cordage with pre-molded plug attached, either from an electrical supply, McMaster-Carr or simply by hacking down an extension cord (provided the cable itself has the correct ratings on it.)
If all this malarkey is because someone told you that you need a GFCI on the dishwasher, there are other ways to solve the GFCI problem that don't involve putting a receptacle there. Ask.
Solid Romex style electrical cable is not designed for use as portable extensions or cords. The main reason for this is that the solid wires are not flexible and will eventually crack if flexed too much. The cable jacket is also not designed for it can be moved around, stepped on or driven over.
So with the understanding that the cable has to be flexible stranded wire it is also a requirement that the plug ends attached to the cable have to be designed for stranded wire as well.