Proper high current motor connections.

I hate to be the forum dummy but I have to ask this question for safety reasons.

I recently purchased a Marathon 3-phase 10HP motor, the motor wires inside the junction box are terminated by crimp connections, ring type, with a 5/16 hole. How do I "properly" connect my 240V wires to these crimp connectors? (I mean physically, I am OK with the actual wiring).

In the past when I have seen these connectors in old motors they were wired by simply clamping them together with the supply feed wires by using a short 5/16 bolt and nut protected by a million wraps of electrical tape. Seeing how fastidious NEMA specs. can be I would be a bit surprised that this is the approved procedure because it seems as though it could be a bit risky if poorly done.

What is the proper way to make these connections?

Thanks, Brian

While bolted (with a spring washer to maintain clamping force) and taped will work, if there is room to mount it and the wires are long enough a heavy duty terminal block would be IMO better. Most of the type I'm suggesting either have short studs or screws and an insulating cover that goes on after connections are made.

Right way?

Here is my way

Do your bolting

Cover with the stretchy RUBBER LIKE thick tape made for such things - this stuff is self bonding and sort of makes a blob of rubber

Cover this with electrical tape

Since this always comes off, TIE IT with thin insulated wire as found in a telephone cable - so it DOES NOT come off

Make the knot a SQUARE KNOT using TWO pairs of pliers to snug it up

Cut the pig tails short

As john said rubber splicing tape, then regular vinyl or cloth friction type, I would add it is wise to put some wraps of vinyl adhesive side out around the connections before the rubber tape so the splice can latter be easily opened, also somewhat prevents any sharp points from cutting through the rubber. This method using either bolted terminals or split bolts is actaully still common and preferred by many as the most reliable.

Before entombing the connections in tape of whatever flavor, be sure the crimps on the motor leads are
absolutely solid.

Not NEMA-approved -> my final go-to on this is remove crimp lugs, strip the conductors, solder securely, and
then insulate with correct temperature-rated heat shrink tubing.

But if the crimps are good then bolt-up is OK. Be sure the ring lugs you put on your incoming leads are solid
as well.

For a 10HP 230V motor, wire nuts can be a perfectly acceptable connection, when made up properly. Wires trained to prevent mechanical and vibrational stresses on the conductors, no tape required and proper sized wire nuts.

Bolted ring terminals are often specified on machine connections to facilitate frequent change-outs without needing to shorten the conductors each time a motor is reconnected for replacement or maintenance. No re-stripping and re-terminating required. 5/16" ring terminals are pretty large for a #10AWG conductor, normally one would use a #10 or 1/4" for those size wires.

To keep the bundle size as compact as possible, arrange the terminal barrels in a back to back fashion to reduce the terminal barrels from causing you to splay them out side by side (wider bundle).

As to taping there are many types to choose from depending on the conditions of use. Quality 3M 33+ Vinyl tape is rated to 600v with just one layer, but provides little in the way of mechanical abrasion protection from the normal vibrations. Rubber or friction tape is normally used for the physical vibration protection.

I dislike rubber for normal conditions, its good and also expensive. It vulcanizes around the connection and is very secure. Provides water and oil as well as vibration protection. I don't like it when its applied directly to the ring terminals, because it can vulcanize itself to them and make it a pain to remove for re-connection.

My preferred method under normal conditions is to bolt up the terminals, apply a few layers of 33+ vinyl, then several layers of friction tap for abrasion protection, then one more wrap of vinyl to ensure that the friction tape stays wrapped tight. This method is easy to undo and reconnect, leaves little adhesive residue to foul the re-connection surfaces and friction tape is inexpensive.

Some like to reverse tape the first layer of vinyl to prevent adhesive from fouling the terminals or use friction tape first. With quality tape this is seldom a problem unless the connection has been severely overheated.

SAF Ω

Thank you all for your useful and informative suggestions. I never would have thought that NEMA would have allowed electrical tape for insulation around such a complicated shape as a bundle of crimp connectors!

Still, clearly that is the way it is done so I will press ahead with your ideas making as thorough a job of it as is possible.

Brian

An electrician who has been doing it forever wraps a couple of layers of newspaper between the first tape and the outer layer. Many of these plastic tapes will cold flow if a point has continuous pressure against something. Paper will not. It sounds like a hillbilly solution but it works.

Bill

I have used a base of cambric tape on the bottom (expensive and harder to get now) if going over split bolts followed by scotch 33 or 88 vinyl tape. A rubber splice tape adds water protection if needed. This gives some mechanical protection for rubbing through and allows easy removal. Small motors just get marretts ( use high temperature rated ones). Now we use a 3M motor connection boot tywraped over the connection. They are quick and easy but seem to degrade with the motor heat after about 5 years. Crimped lugs are what we use on most of our larger motors bolted together with bolts and lock washers.

If anyone's curious here's a video by scotch on the procedure
https://m.youtube.com/watch?v=aW61nupfoB8

Camshawn said:

I have used a base of cambric tape on the bottom (expensive and harder to get now) if going over split bolts followed by scotch 33 or 88 vinyl tape. A rubber splice tape adds water protection if needed. This gives some mechanical protection for rubbing through and allows easy removal. Small motors just get marretts ( use high temperature rated ones). Now we use a 3M motor connection boot tywraped over the connection. They are quick and easy but seem to degrade with the motor heat after about 5 years. Crimped lugs are what we use on most of our larger motors bolted together with bolts and lock washers.

Click to expand...

Bingo. As trained at the Steel Mill in my apprentice days:
1) On all motor connections up to 10ga wire, you crimp on ring tonque terminals.
2) Bolted connection using stove bolts (coarse thread), locking washers and square nuts, not hex, because the ears don't strip off and the nut can be safely held by lineman's pliers (aka Kleins) for tightening.
3) 3 wraps of varnished cambric tape, because 10 years from now when you have to undo the connection, the varnished cambric tape will not be sticking to the bolts and terminals.
4) 6 wraps of Scotch 130 rubber tape. That will protect the connection from rubbing through when vibrating against other connections or the side walls of the peckerhead. But the rubber tape eventually fuses and will stick to everything.
5) 3 wraps of Scotch 33+ vinyl tape to protect the rubber tape from sticking to everything and coming unraveled.

Wires over 10ga, the same except substitute split bolts (Kearneys) for crimp on rings and stove bolts.

Marrets / wire nuts on any motor connected with 14ga or larger was cause for dismissal.

Now days the guys at that same plant are allowed to use Polaris connectors instead of split bolts on the larger connections, but 10ga and below are still the same.

Jraef said:

Now days the guys at that same plant are allowed to use Polaris connectors instead of split bolts on the larger connections, but 10ga and below are still the same.

Click to expand...

Polaris connectors are lovely, but I've never had a motor-mounted junction box large enough to fit more than one of the smallest P-cons inside. :-( Crimped rings bolted up, with glass or cambric tape, rubber tape and vinyl tape, while a bit bulky, is still more compact than any P-con I can get from the local electric supply house.