Mini-split

J

Jimmy7

Senior Member
Location
Boston, MA
Occupation
Electrician
I did my first mini-split system for a relative of my wife a while back. Locally it seems that all of the hvac contractors run all the cables between the inside and outside units. This system had two indoor units, so the contractor ran two runs of duktstrip cable. In any case, I thought I would do a good thing and sleeve it non-metallic liquidtight from where it exits the house to the back of the outdoor unit. The thing is that I used metal bell boxes to transition the non-metallic liquidtight, so I forgot about grounding the metal boxes. Since it’s a relative I was thinking I should change out the boxes to plastic. Is there some other way to do this, or would you even bother?
IMG_2737.jpeg
 
Jimmy7 said:
Is there some other way to do this,
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If the pass-thru MC emerges from bottom of J-boxes, metallic connectors at both ends of MC should bond boxes.

If MC dives into wall just before the boxes, you could run external EGC between equipment, per 250.130(C).
 
ramsy said:
If the pass-thru MC emerges from bottom of J-boxes, metallic connectors at both ends of MC should bond boxes.

If MC dives into wall just before the boxes, you could run external EGC between equipment, per 250.130
Click to expand...
Could I actually use regular metal liquid tight to ground the boxes, or would I still have cut into the duktstrip cable to ground the boxes?
Original version of this cable was used I believe.
IMG_2738.jpeg
 
Jimmy7 said:
Could I actually use regular metal liquid tight to ground the boxes, or would I still have cut into the duktstrip cable to ground the boxes?
Original version of this cable was used I believe.
Click to expand...
See NEC article 350.60
 
I do this all the time, I strip back the cable put a MC connector and bell box on, then attach the bell box to the wall. I loop the EGC around the ground screw in the bell box and feed the conductors thru the liquid-tight.
If I have two cables I sometimes use a double barrel mc connector.
Not sure if thats code but as others mentioned the duct-strip does have a bending limit.
 
ramsy said:
If the pass-thru MC emerges from bottom of J-boxes, metallic connectors at both ends of MC should bond boxes.

If MC dives into wall just before the boxes, you could run external EGC between equipment, per 250.130(C).
Click to expand...
Its interesting stuff but its not coated MC no metal jacket, from what I gathered 'duckt-strip' comes in a few types and appears to be dual listed NMC/UF cable with stranded? conductors, its, damp / wet rated with a optional signal pair.
It does not seem intended for direct burial the way regular UF is, but designed for running outside in a raceway or indoors.
There used to be a listing for 'NMS', S as in signaling. I think the 2020 NEC removed type 'NMS' designation from Article 334 so any NM or NMC can now contain signaling wires as 334.104 still provides construction specifications as such.
I dont think 340.104 has the same construction specifications as NM for signal wires.
 
Its interesting seeing new, old and rare kinds of wire and cable you all come across and I have not seen 'duct-strip' in the wild here locally, I think I have only seen NMC and NMS only a handful of times.
 
tortuga said:
Its interesting seeing new, old and rare kinds of wire and cable you all come across and I have not seen 'duct-strip' in the wild here locally, I think I have only seen NMC and NMS only a handful of times.
Click to expand...
I haven’t seen or heard of it either, I had to google it to see what it was. Looks similar to trolley wire.
 
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