I mounted our 30 amp PI EMS adjacent to our panel. What I noticed at first was that the way the terminal/lug is designed in the contactor, if using solid wire, there is flat surface on two sides of a round wire making contact - screw on one side, flat surface on opposite side. IMO, this does not provide a good contact (see photo), may loosen and could lead to overheating.
What I did is use short lengths of stranded wire and spliced it to the incoming solid conductors inside the EMS unit. (can't seem to find a photo I thought I took). If done this way, you won't have to remove any jacket material from the existing incoming 30 or 50 amp wire and can easily be redirected back into the panel in the future. I used stranded cabtire cable from the EMS into the panel as it was readily available. Doing it this way would be easier and cheaper than plugs & connectors.
If your shore power cord goes directly to the panel (ie., isn't the detachable type), then not a problem because the cord has stranded wire.
For splices, I used vibration proof marrette connectors for splicing solid to stranded wire as it makes for a better connection.
Another thing I'll mention while on the subject, is that IIRC, the instructions (on the 30 amp unit at least) say to connect the incoming & outgoing ground wires via ring terminals to a stud inside the box. Instead I spliced the incoming & outgoing wires directly together then with a 3 piece of wire over to the stud. You want a really good connection with the incoming & outgoing grounds for safety and under short circuit conditions.
A plug and connector is a good idea but you'll need two sets to make it work. You shouldn't really be using romex with them and should be using flexible cable or power cord which would mean a junction box to convert romex to cable. As well, if using two sets of plugs and connectors, you'll have a lot more connection/contact points (wire to plug/connector & connector to plug, times two) - 6 per conductor as opposed to 1 splice. Fewer connections is always better. Nobody will ever see what you do or inspect it tho. so it's up to you... Can't see any reason why you'd need a twistlock connector/plug and straight blade will be fine.
I have read of a few cases of these things having a meltdown and I suspect it could have been due to poor connections.


