How do you keep bugs/dust out of electrical conduit which terminates in the open?

Question

Though it isn't specifically stated in the code, I try to protect cable that is installed less than 8 feet from the ground with conduit. This tends to be accepted by inspectors as "protection from physical damage."

If I am going straight up from the electrical panel, into garage rafters, I would like to use a conduit sleeve up to the 8ft mark and then continue on with bare cable. This means the conduit would create a path for critters/dust to enter the panel... is there something I can put over the end of the sleeve?

Thank you!

Answer 1

Use a EMT-to-NM (or GRC-to-NM) combination coupling

They make fittings specifically for transitioning from conduit to a cable, such as an Arlingtion 8600 or equivalent. One of these can be used to keep detritus out of the end of the EMT and strain-relief the cable where it exits the EMT sleeve.

Answer 2

Electrical insulation putty (duct seal) is ideal for this. Most bugs aren't going to have the perseverance to chew through it.

You could also run through a junction box and use a strain relief clamp to close things off where the cable exits.

Answer 3

Get two fittings of the kind that screw into knockouts or threaded junction boxes:

• one for your size conduit into that same size of knockout.
• a common strain relief as you would use when that type of cable enters a junction box, of the same knockout size.

Then add a Rigid conduit coupler of that same size. Use the first one to give your conduit a threaded end, then the coupler, then thread in a strain relief.
Remember, no more than four cables per conduit, and no more than three if any 30A circuits are involved.