I handle large above NEMA motors, starters, and drives all the time. I carry #22 to 500 MCM lugs and tools stock on the truck. I carry terminations to 15 kV too. Customers that know this sometimes just call to buy lugs in emergencies.So long story short there are some 600 mcm feeders that due to settling are getting to the point of being to short. I talked with a contractor today about possibly splicing on a short piece to the end to save them. I'm just curious what would be the best option for wire this big. Big hydraulic crimp barrel? Polaris type lugs ? Old school eye barrels and tape? I don't have any knowledge of splicing this big of wire (hence bring in a contractor) but just want to learn what's out there.
Depends on you needs. Hands down Cadwelded terminations/splices are the most permanent. Next to that crimped termination nations are permanent but more or a cold rather than hot weld. Utilities use cadweld underground on ground grids in substations and crimped lugs everywhere else. Some even spec it for control wiring.
Whether to use a bolted pair or lugs or a barrel connector is a function choice: Barrel connectors are cheaper but you can never take them apart: Once you crimp it on removal means cutting off more cable. With lugs you have options. There might be a tiny bit more risk but bolt failures are either lack of proper sizing, not tightened or galled, or bad tape jobs.
Insultaps or Polaris taps work for a while. I have replaced many failed ones. Like any mechanical lug you have a huge working size range but higher failure risk. The crimp stuff is very idiot proof. On my crimper I hold the trigger until it finishes and retracts. On my manual you squeeze until the pressure relief trips. On an Allen head 85% of the torque goes into overcoming thread friction. How do you know how much tension you applies? You don’t. That’s on top of the tendency for aluminum and brass set screws to strip or gall or jam on a thread of wire. Lugs are so much easier.
There can be a Code issue. You aren’t supposed to have joints in the middle of raceways. Strict interpretation means pulling out the old cable. Cadweld really is not a joint. You can argue barrel connectors aren’t either. All others can be taken apart so it’s as legal as using wire nuts in a conduit body.
The splicing decisions are the SAME no matter the size. You just have fewer options at larger sizes. I’m sure Mike will be along any time now to talk about Wago Levernuts but I have not seen a 600 MCM Wago. I have seen that size cam locks and pin connectors but that’s another story.