Marretts or Wire nuts on 600V VFD feed wires

D

Thread Starter

Dave van Rhijn

Dear List,

Simple opinion of course or if there are legislative rules regarding this matter I would greatly appreciate those references. A VFD lead wire is to be spliced. Why because it is cheaper, and yes a point of failure. Now to marrett and tape or splice in a junction panel? To locate the splice some where in a wire trough at the ceiling or on a terminal block in a panel is the choice. My reasoning for the panel is so in time when it does loosen or need to be checked, access and location is defined, not some where between here and there. I invite experience comments and those interpretting rules of reference someone may have.

Dave van Rhijn
 
Hi!

The National Electrical Code, Section 300-15, requires electrical splices to be made in a junction "box."

This provides accessibility (as well as protection) for the purpose that you just mentioned.

Hope this helps.

Gary
 
C

Crucius, Wesley

Screw Clamp Terminal Block, period.
Bad/Loose splices can actually cause harmonic signal reflection, destroying the drive's power electronics circuitry.
 
M

Michael Griffin

I don't know what section in the Canadian Electrical Code may address this, but I've never looked very hard for one since I wouldn't want
to do this (put a splice in a wire trough) anyway. I can however inflict my opinions on you.
I would be surprised if any potential wiring cost savings could equal the cost of even one problem with this splice. Using marretts to
splice a wire in the middle of a trough sounds neither reliable nor safe. You evidently feel the same way, or you wouldn't be asking this question.


**********************
Michael Griffin
London, Ont. Canada
[email protected]
**********************
 
J

James Bouchard

We have spliced wires in a lay in duct ( 6 x 6 hundreds of control wires and another with quite a few power wires including DC drives but no inverters ) but we used the crimp on insulated sleeves. The wiring was all stranded wire so they worked quite well. The Canadian Electrical Code requires that splices be accessible and a junction box or a lay in duct is allowed. I do
not know about tray. I would not use marretts in a tray or duct only in a motor connection box or other junction box. They take up a lot of space and work especially if you have to tape them.

James Bouchard
 
M

Michael Griffin

I have usually heard the "crimp on sleeves" referred to as "butt connectors". They do work quite well, provided they are crimped properly, with the correct tool. In fact, they are often used in automotive wiring and seem to survive in that environment (which must be one of the toughest around).
They can be a problem if not correctly performed. If they are too loose, the wire can either pull loose, or they can over heat. If they are too tight, the plastic insulation can crack and come off. Another problem can be using the wrong size connector for the gauge of wire. I must admit that while I have seen more than a few problems with marretts, butt connectors seem to be fairly reliable (if done properly).
I believe the original writer was referring to marretts, which are not very mechanically strong. They seem to be easily pulled apart, which may be a problem in a cable tray.
I believe that your suggestion is a good one, and that if a permenent splice is required, butt connectors could be a better solution
than marretts.


**********************
Michael Griffin
London, Ont. Canada
mgrif[email protected]
**********************
 
J

James Bouchard

When we do these types of splices we are careful to see that the correct splice and tools are used. And as a final test we require a pull
test where two techs pull on each splice to make sure it is good ( we don't want to have to go back into a duct to find a bad one ) The same thing works quite well for power cable ( like 500 MCM ) but you need the hydraulic compression unit and generally have to use a separate heat shrink tube to insulate the joint. They are a lot better than the ones done with a split bolt connector covered with putty and yards of tape.

James Bouchard

Montreal
 
Top