is flexible conduit required between disconnect box and air compressor pressure switch?

[sabinoerc]

I am installing 230V 5HP compressor. I put a new subpanel in garage and ran 8/2 romex from there to a disconnect box on wall by compressor. The disconnect box about 3' to 4' from the compressor pressure switch. Do I need to put the 8/2 romex in a flexible conduit between the disconnect box and compressor switch or can I just use the romex with some restraint at the disconnect box & pressure switch? (as is done for electrical connection between motor and pressure switch on the compressor)
Thanks!

 

[Knight511]

You ran the Romex on the outside of the wall? The wire must be protected from damage. Based on what I have learned reading around, you can use conduit as a sleeve for protection. Others will be along to answer shortly though.

 

[sabinoerc]

I ran the romex inside wall to rafters, across garage in rafters, down in conduit on outside of wall to cutout box.

 

[Cruzan80]

Technically, Romex should not be in conduit, or outside at all. Romex in conduit is bad due to heat buildup, and outside is bad due to possible wet conditions. You should use a junction box inside, to transition to THHN in conduit to the disconnect.

From the disconnect to the pressure switch, you need something that is both protected as well as rated for outside use. I would use either armored cable or Liquid-tite with THHN inside.

 

[mikedodge]

Technically, Romex should not be in conduit, or outside at all. Romex in conduit is bad due to heat buildup, and outside is bad due to possible wet conditions. You should use a junction box inside, to transition to THHN in conduit to the disconnect.

From the disconnect to the pressure switch, you need something that is both protected as well as rated for outside use. I would use either armored cable or Liquid-tite with THHN inside.

I think he means outside of the wall, not building. Romex on the wall is ok but you need something more flexible from the disconnect to the compressor.

 

[Cruzan80]

Yes, sorry. I read it as outside the garage entirely.

 

[Wrench97]

Simplest way is a #8 wire whip> https://www.amazon.com/dp/B0756MLLD9/?tag=atomicindus08-20

 

[alfredeneuman]

Technically, Romex should not be in conduit, or outside at all. Romex in conduit is bad due to heat buildup,

NM (romex) is perfectly acceptable in conduit and doesn't a "heat buildup".
It's a dry conditions only wire and can't be used outdoors. Type UF cable is suitable for use outdoors

 

[wyliesdiesels]

I am installing 230V 5HP compressor. I put a new subpanel in garage and ran 8/2 romex from there to a disconnect box on wall by compressor. The disconnect box about 3' to 4' from the compressor pressure switch. Do I need to put the 8/2 romex in a flexible conduit between the disconnect box and compressor switch or can I just use the romex with some restraint at the disconnect box & pressure switch? (as is done for electrical connection between motor and pressure switch on the compressor)
Thanks!

NM-b is not permitted for use in that regard. You should either use THHN/THWN in FMC or flexible cord....

You ran the Romex on the outside of the wall? The wire must be protected from damage. Based on what I have learned reading around, you can use conduit as a sleeve for protection. Others will be along to answer shortly though.

There is no prohibition against using NM-b surface mounted on the outside of a wall. "Subject to damage" is highly subjective as well.... there is no hard and fast rule in the NEC for what defines subject to damage... your AHJ may have stricter code however...

Technically, Romex should not be in conduit, or outside at all. Romex in conduit is bad due to heat buildup, and outside is bad due to possible wet conditions. You should use a junction box inside, to transition to THHN in conduit to the disconnect.

From the disconnect to the pressure switch, you need something that is both protected as well as rated for outside use. I would use either armored cable or Liquid-tite with THHN inside.

Technically youre incorrect. There is no prohibition on running NM-b inside an indoor conduit. there is no such thing as heat build up due to NM-b being inside conduit either. That is all misinformation.

and while NM-b is not permitted for use outdoors, I dont think the OP meant exterior when he said outside the wall so that has no bearing on the OPs situation....

Liquid tite is also not needed. FMC would work perfectly fine...

 

[Cruzan80]

NM (romex) is perfectly acceptable in conduit and doesn't a "heat buildup".
It's a dry conditions only wire and can't be used outdoors. Type UF cable is suitable for use outdoors

Yes, sorry. I was trying to post after a few rough days, and what I thought =/= what I typed. What I meant to say is that NM in conduit needs to use the 60deg C rating, whereas THHN does not.

 

[alfredeneuman]

Liquid tite is also not needed. FMC would work perfectly fine...

I understand it as being outdoors, which is a wet location
NEC2017 >
348.12 Uses Not Permitted. FMC shall not be used in the following:
(1) In wet locations

 

[wyliesdiesels]

I understand it as being outdoors, which is a wet location
NEC2017 >
348.12 Uses Not Permitted. FMC shall not be used in the following:
(1) In wet locations

umm where did the OP say the compressor is being used outdoors? Or that he ran the wire on the exterior of the building?

 

[nadogail]

I am unable to intelligently comment because I have not seen the job.

 

[Jim greengo]

Or a piece of emt and a couple of minnies,if you dont know how to bend pipe.

 

[sabinoerc]

Thanks for the replies, sorry for not providing enough detail to prevent confusion!
Everything is inside garage, not outdoors. The subpanel is mounted in an interior wall of garage. I ran the nm-b (I think Romex is a brand name?) inside the wallboard to ceiling where I used staples to hold to rafters to run to other side of garage. The other wall of garage is unfinished slump block so I ran the nm-b inside conduit down from rafters to the cutout box which is mounted to block wall next to compressor.

I had looked for flexible conduits with conductors inside but all the ones at HomeDepot/Lowes were too long. I didn't want a long loop hanging down between compressor and wall/cutout box.

after reading replies (thanks!) I decided to run the nm-b inside waterproof flexible conduit just because I could buy it by the foot @ HD and get it done today. I've read the yes/no nm-b inside conduit posts and hmmm? For better or worse, I thought since I oversized the conductor (8 gage for a 5HP motor) I'd just use the nm-b in the conduit and not worry about it.
Thanks again

 

[u2slow]

I usually run AC cable (type w/copper bond wire) from the jb or disco to the machine.

 

[Jim greengo]

Thanks for the replies, sorry for not providing enough detail to prevent confusion!
Everything is inside garage, not outdoors. The subpanel is mounted in an interior wall of garage. I ran the nm-b (I think Romex is a brand name?) inside the wallboard to ceiling where I used staples to hold to rafters to run to other side of garage. The other wall of garage is unfinished slump block so I ran the nm-b inside conduit down from rafters to the cutout box which is mounted to block wall next to compressor.

I had looked for flexible conduits with conductors inside but all the ones at HomeDepot/Lowes were too long. I didn't want a long loop hanging down between compressor and wall/cutout box.

after reading replies (thanks!) I decided to run the nm-b inside waterproof flexible conduit just because I could buy it by the foot @ HD and get it done today. I've read the yes/no nm-b inside conduit posts and hmmm? For better or worse, I thought since I oversized the conductor (8 gage for a 5HP motor) I'd just use the nm-b in the conduit and not worry about it.
Thanks again

The ac whips usually come with 1 end not made up,so they can be shortened if need be.

 

[wyliesdiesels]

Thanks for the replies, sorry for not providing enough detail to prevent confusion!
Everything is inside garage, not outdoors. The subpanel is mounted in an interior wall of garage. I ran the nm-b (I think Romex is a brand name?) inside the wallboard to ceiling where I used staples to hold to rafters to run to other side of garage. The other wall of garage is unfinished slump block so I ran the nm-b inside conduit down from rafters to the cutout box which is mounted to block wall next to compressor.

I had looked for flexible conduits with conductors inside but all the ones at HomeDepot/Lowes were too long. I didn't want a long loop hanging down between compressor and wall/cutout box.

after reading replies (thanks!) I decided to run the nm-b inside waterproof flexible conduit just because I could buy it by the foot @ HD and get it done today. I've read the yes/no nm-b inside conduit posts and hmmm? For better or worse, I thought since I oversized the conductor (8 gage for a 5HP motor) I'd just use the nm-b in the conduit and not worry about it.
Thanks again

So you used the NM-b from the disco to the pressure switch? thats not kosher... NM-b is not supposed to be used in that manner. either get a short piece of FMC and some THHN or some cordage...

 

[Compressed]

Simplest way is a #8 wire whip> https://www.amazon.com/dp/B0756MLLD9/?tag=atomicindus08-20

That is what i have used for my waterfall and pool pumps, personally i'd use MC for an air compressor just because it's that much tougher.
i was debating on which cable casing to use since i have some WT here.

 

[alfredeneuman]

For Pete's sake use stranded THHN wire.
Premade whips are made with stranded wire
Solid wire isn't used because of vibration.

 

[wyliesdiesels]

For Pete's sake use stranded THHN wire.
Premade whips are made with stranded wire
Solid wire isn't used because of vibration.

Well he did use stranded wire as he used #8 NM-b which is stranded. But NM-b is not kosher in this manner.

 

[mikedodge]

If this is in a residential garage it's probably closer to being correct then a lot of them are.

 

[alfredeneuman]

Well he did use stranded wire as he used #8 NM-b which is stranded. But NM-b is not kosher in this manner.

That's why I said to use stranded THHN wire
It was just a warning to others that are thinking that it's OK to use MC or NM

 

[Norcal]

NM cable 8 AWG & 6 AWG has stranded insulated conductors, but the grounding conductor is solid.

 

[sabinoerc]

Thanks for all the responses.
Yes - it is a residential garage. I had the #8 nm-b in hand as there was exactly the length needed for the run from disconnect box to compressor switch left over from the 50ft roll I bought to run from subpanel to disconnect box.

My main goal was to have the permanent wiring be to code so when I eventually sell house it doesn't stick out as something which has to be addressed. All the advice on this forum has been fantastic for someone like me who is a DIYer. I've done little "add an outlet" sort of stuff before but this is first big electrical job.

I read many, many posts on nm-b in conduit yes/no and found it a bit confusing. Regardless, in the end I made the decision which allowed me to finish without the 49th trip to Lowes for another thing I forgot, realized I needed, wrong thing, wrong size, etc. Plus, if I sell the house the whip/connection from disconnect to compressor is removed and not a potential code question.
Thanks again

 

[wyliesdiesels]

NM-b can go in conduit, indoors only, however using nm-b as a whip for a motor is not kosher

 

[sabinoerc]

NM-b can go in conduit, indoors only, however using nm-b as a whip for a motor is not kosher

Thanks - to clarify, I put the nm-b in a flexible conduit for the whip. I didn't leave it exposed. All indoors.
Just curious - still technically not kosher?

 

[wyliesdiesels]

no still not kosher. NM-b is not permitted for that use.... putting it in conduit doesnt change that.... thats why alfred said to use THHN in post #20... plus #10 THHN wouldve been way easier to work with that trying to stuff NM-b in LFNMC

 

[sabinoerc]

Thanks - appreciate the education (and yes, also learned #8 is a pain to get into tight connections...)

 

[sparky 1971]

Just go to a box store and buy a 6' pre made whip with #10 wire for about $15. Cut to length. With a sharp knife, you can cut it with the wires in it. If you're not comfortable doing it that way, take the wire out and cut it.

 

[Syberia]

Can also use a tubing cutter to cut it with the wires inside, and you can limit the depth of the cut so you don't damage anything that way. I've had to do this with EMT as well.

 

[AP514]

Do not think he will change it...

 

[sabinoerc]

As I've mentioned, I really appreciate all the advice and opinions which have been provided. It allowed me to do a project in an area where I have little expertise. At this point in my life, I could pay someone to do this stuff but the fun is in learning something new and gaining an appreciate for the skills & knowledge required. For me, that's the fun in projects and hobbies. Some people do crosswords - I do projects.
I like to think I return the favor to the universe in the areas in which I do have a depth of knowledge and experience in other forums in which I participate (if you have first gen camaro, an early 90's GM TBI, or data storage questions - I have your back!). When I offer opinions or advice, I've do so without strings attached not thinking about whether someone is following my advice - just hoping I might help someone solve something I've previously learned how to solve. That's one of the great things about the internet age - it allows us to connect with people who have knowledge and share. (I guess one could also say there is a dark side to that also -but I don't want to detract here).
When I read the comment

Do not think he will change it...

it made me wonder if my views on offering advice are same as others.
I definitely do not want those who generously took the time to answer my questions, offer advice, or opinions that I dismiss or don't value your advice!. If anyone who offered me advice/opinions/answers to my questions would like to know what I've done or plan to do - please don't hesitate to send me a PM or ask. I'm happy to detail! Thanks again!