How to Terminate Mineral Insulated Copper Wiring Cable (MICC)

 

How to Terminate Mineral Insulated Copper Cable 

Unfortunately, it is quite unusual for an electrician to learn how to terminate an MI Cable. Below we have outlined a step by step guide on how to manage this process. 

What you need  

A complete termination consists of a shroud compression gland and seal, whilst a seal must always be used, the compression gland and shroud are optional.

For example, a compression gland would not be used with cable grip type terminal boxes.

Fitting

It is advisable to cut the cable with a hacksaw, since this will later facilitate stripping the copper sheath. If the cable is plastic covered, then a plastic gland shroud will normally be used.

This is best fitted by offering it up to the cable in reverse. It is then simple to determine the amount to cut off, thereby ensuring a tight fit over the cable.

The shroud can then be slid over the cable in the correct fashion.

The next stage is to remove the plastic covering mark, the covering to the correct tail length, plus an additional 70 millimeters to allow for the gland.

This additional length will vary depending upon the gland size.

From this point, remove the plastic covering with a knife.

Don't use the edge of the blade at right angles to the cable as this may damage the copper sheath.

Stripping Cable

After removing the plastic covering the copper sheath is stripped back.

It is advised to use the Joi Stripper.

In order to remove the correct amount of copper sheath, Mark off the tail length plus eleven millimetres, point. A.

This additional amount will again vary depending upon the SEALs size.

Add a second mark, point B, a further one tool's width along the cable.

Insert the cable into the joi stripper until the end just touches the cutting blade.

Beginning with forward pressure, rotate the tool clockwise. Forward pressure is not required once stripping has begun since the tool will pull itself along the cable.

Stop the tool at the required position A by gripping the cable with pliers at Position B.

Fitting Gland and Seal parts

The glands should now be slid onto the cable.

It consists of three parts, a back nut compression ring and gland body.

Once they are suitably fitted, a seal can now be fitted.

This comprises a brass pot, plastic stub cap, PVC insulating sleeping and gray ceiling compound.

The pot has a self cutting thread which enables it to be screwed onto the cable, using pliers, A pirate potter, or as in this case, a pirate wrench.

Insert the pot open and first into the pirate wrench recess.

Slide over the cable until the self cutting thread is in contact with the cable sheath.

Engage the ratchet wheel into the middle section of the pot.

Applying forward pressure and cranking action, screw the pot onto the cable.

This section through a seal illustrates the correct position of the pot, with the inside base level with the end of the cable

Incorrect positioning of the part will make it difficult to fill with compound.

If the pot has an earth wire, position it equidistant from two adjacent conductors.

After fitting, the brass pot examined the interior beware of eye damage from the exposed conductors and remove any loose insulant.   

Slide the step, cap over the conductors and into the mouth of the pot to preform the conductors, then partially withdraw it.

Ensure moisture stays out

The pot should now be filled with grey ceiling compound (TRMX)

It's essential that this compound covers the face of the cable, thus effectively sealing the end and hence preventing the insulation from absorbing moisture.

This can be achieved by overfilling the pot with compound from one side, only, to exclude air pockets.

Care should be taken to avoid contamination of the sealing compound. So use the plastic wrapping to keep it clean.

Reposition the Stub cap in the mouth of the pot.

Don't let it overlap the edge of the pot, since this will damage the thin brass lip during crimping.

Crimping

The pyro crimp is advised for crimping into place.

-Fully slacken the hollow drive screw by means of the handle,

-Slide the conductors through the hole in the crimping plate and through the centre of the drive screw

-Place the pot into the seating in the body of the tool.

-Tighten the screw by hand, which will drive the stub cap fully into the pot recess and secure it into position by means of the indent crimp

-Slacken and remove the tool.

-Cut the sleaving to the required length.

-Slide it over the conductor's and then push it onto the stub to anchor it in place

 

Finishing the Termination

You can now identify the conductors.

Connect the gland into the box, ensuring that the net is sufficiently tightened to grip the cable.

If the covering has been selected because the cable is being used in a corrosive environment, then any exposed copper sheath and brass gland must be covered with adhesive tape before positioning the gland shroud.

The termination is now complete.

 

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