I'm finishing up a residential install on some Mitsubishi Mini Split units where the mfr spec calls for a 3 pole Leviton MS303-DS disconnect switch for each indoor unit (req'd by AHJ). I roughed in the 14/3 NM that supplies these units into deep plastic boxes, only to find out later (meaning after the drywall is finished) that the MS303-DS is an UNGROUNDED switch and has no ground terminal. I get it, most of these are used for motors in industrial applications in which the switch is housed in a metal enclosure. Art 404 requires the yoke on all snap switches to be grounded. Is there an exception I'm missing, or am I going to have to find a way to ground these (as in cutting out the plastic boxes to replace with old work metal ones)? I have a hard time understanding how these got their UL rating with no ground terminal. Mini-splits: always a PITA.
Grounding disconnect switch without a ground terminal
- Thread starter ckelley3
- Start date
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wow ! wonder I would have ever caught that ?
It is my understanding that the requirement for the switch is for motor disconnecting therefeore
what about using a two pole switch (with grounding means) and not breaking the "control" wire ?
It is my understanding that the requirement for the switch is for motor disconnecting therefeore
what about using a two pole switch (with grounding means) and not breaking the "control" wire ?
wow ! wonder I would have ever caught that ?
It is my understanding that the requirement for the switch is for motor disconnecting therefeore
what about using a two pole switch (with grounding means) and not breaking the "control" wire ?
Breaking only 2 poles does meet code, however, can cause this units to fault out, as the control wire needs to be disconnected as well to prevent this
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
The code allows for this where there is no existing EGC (404.9(B) Exception) if you use a nonmetallic plate and non conductive screws. I realize this does not technically fit your case but your AHJ may accept. You can get nylon 6/32s at the Orange or Blue store.
Let that be a lesson to always use a metallic box for the more commercial/industrial type devices going into a resi NM job.
kwired
Electron manager
- Location
- NE Nebraska
The code allows for this where there is no existing EGC (404.9(B) Exception) if you use a nonmetallic plate and non conductive screws. I realize this does not technically fit your case but your AHJ may accept. You can get nylon 6/32s at the Orange or Blue store.
Let that be a lesson to always use a metallic box for the more commercial/industrial type devices going into a resi NM job.
But he ran a new circuit that does have an equipment grounding conductor.
One easy solution may be to add a Wiremold extension box - they usually have a place for a grounding screw and then the switch yoke will be bonded through the extension box.
It appears, from the pics they have online, that there is in fact a ground screw terminal. Praise God, and thank you kwired! Now, let's just hope the huge switch actually fits the wiremold extension.
kwired
Electron manager
- Location
- NE Nebraska
I have had trouble with those extensions when using GFCI's. Another similar option that should have no trouble with a large device is a 4x4 extension designed to extend from a 1 gang device box.
If you are stuck on the wiremold option, you can use the back plate of the extension box and install the main body of a deeper box to it - I have done that before.
They make a deep extension, part 5751A that is 1-3/4" deep. The switch is 1-1/2" deep. I'll have to see how readily available it is here, otherwise I'll be doing the swapping as you suggested.
I've never seen a 4x4 extension from a single gang enclosure. Obviously a mud ring works the other direction. Do you have a link that shows one? I'm intrigued.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
kwired
Electron manager
- Location
- NE Nebraska
They work great for transitioning from concealed to exposed wiring, even in cases where you run concealed, need a disconnect switch then a flex to the equipment.
kwired
Electron manager
- Location
- NE Nebraska
There usually is not a ground screw hole, but I have drilled and tapped one many times.
In Australia you rarely see EMT,RMC,or enclosed outlet or switch boxes,we leave everything open behind the plate.The code allows for this where there is no existing EGC (404.9(B) Exception) if you use a nonmetallic plate and non conductive screws. I realize this does not technically fit your case but your AHJ may accept. You can get nylon 6/32s at the Orange or Blue store.
Let that be a lesson to always use a metallic box for the more commercial/industrial type devices going into a resi NM job.
but your electrons run countercloskwise rather than our (US) clockwise flow
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
That's only when you are flushing them down the toilet....but your electrons run countercloskwise rather than our (US) clockwise flow
- Status