I was looking over the conduit at Home Depot. They sell galvanized steel and they sell a grey-colored plastic (PVC?). What are the two different types used for?
I want to add some exterior 115V outlets but don’t know which type to use. The conduit will be mounted on an exterior wall. I was thinking that galvanized was to be used for this. Is the plastic for under soil, or wet conditions, or what?
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Replies
Actually, you missed the 3rd variety of "pipe" available at HD - rigid.
Rigid is a thicker walled conduit which is cut and threaded just like black iron or galvanized plumbing pipe. I digress......
PVC vs EMT (galvanized):
PVC:
Approved for underground or exposed locations outdoors (it will be marked on the conduit - UV resistant, direct burial, etc.). Cut and glue just like PVC plumbing pipe, although with a slightly different glue. Pre-bent fittings available for making bends or can be bent with heat. Hub on one end of each length will minimize the use of couplings. When properly glued and cured it is waterproof. Cheap and easy to work with. Ground wire must be pulled into the conduit. For the same ID (wire carrying capacity), PVC has a larger OD than EMT.
EMT:
Approved for exposed locations outdoors, not positive about underground - will eventually rust if not kept painted. Cut with hacksaw or tubing cutter. Joined with various fittings - some are watertight, some are not. Prebent fittings available for making bends or can be bent as a continous length with a bender. No hubs on ends of pipe length, therefore may require more fittings. Can make a very clean installation - depends upon the skill of the bender operator. When properly installed the EMT functions as your ground wire. Little more expensive than PVC.
For a first timer, I would recommend PVC for your outlets.
Jim
I thought you had to pull a ground wire into emt. Isn't the old bmx cable prohibited in most places because it relies on the coiled jacket for a ground?"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
because it relies on the coiled jacket for a ground
key word there is 'coiled', which can make the impedance of the 'ground' very high both from simply being suddenly a few times longer and smaller area ground 'wire' plus high reactance due to inductance.
With compression fittings, 3/4" dia EMT is a 3 times better ground than a 12 AWG copper wire - even though steel is about 10X higher resistivity, there is more cross section area. Just off the top of my head calcs, 1/2" EMT is about 1.6 times better than 12 AWG wire - with compression fittings.
For me, all bets are off electrically with the screw fittings, I dont use those either unless I'm, just using EMT for physical protection.
there is more cross section area
Thougth I had read somewhwre, long ago, that the current travels on the surface of the conductor, not through the conductor itself. So for a pipe used as ground, the current would travel on both the inside and outside surfaces. "Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
That is certainly true for RF energy and it is true for static charge.
P.S. - I already have the pipe cutters and deburring tool (both tpyes of reamers, tapered and the plumbing type).
I also have a hack saw. ;-)
P.P.S. - I forgot about the little offset bend to get into the box. Do they sell a fitting with that offset built in? I could just "ramp up" but that will look like $%^&.
Edited 11/12/2009 6:29 pm ET by Mike_Mills
Edited 11/12/2009 6:30 pm ET by Mike_Mills
>>Do they sell a fitting with that offset built in?<<
Yes.
JimNever underestimate the value of a sharp pencil or good light.
Rigid is a thicker walled conduit which is cut and threaded just like black iron or galvanized plumbing pipe
ridgid conduit threads are straight as where "pipe" threads are tapered...
although with a slightly different glue.
medium bodied gray or clear...
Cut with hacksaw
needs serious deburring...
or tubing cutter.
not a good plan unless you are familar with the score and snap method of cutting this type... using a tubing cutter tends to roll the wall of the tube to the inside leaving a sharp scraping edge that will tear/cut the snot out of the pulled wire's insulation... special attention needs to paidto the deburing after using a tube cutter...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Ok Marty, I'll bite.......no hack saw / Sawzall, no tubing cutter....
How do you cut EMT?
Portable plasma cutter? Water jet? ;^)
I get my best results using a tubing cutter and a tapered reamer......
Jim
Never underestimate the value of a sharp pencil or good light.
what I was saying was to deburr really well if you use a hacksaw or sawzall... and BTW this is the most common way to cut conduit... that's what yur 9E's are for...
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J2000-9NECRTP High-Leverage Side-Cutting Pliers - Connector Crimping & Fish Tape Pulling
J2000-9NECRTP High-Leverage Side-Cutting Pliers - Connector Crimping & Fish Tape Pulling
deburr yur PVC also...
a burr or a sharp edge will raise cain with the wire's insulator when you pull past them...
if you use a tubing cutter just score the tube till you can snap the score... and this is how I cut mine... hacksaw gets second slot..
Greenlee, Ideal and maybe Klein make tubing cutters designed specificly for this mission... just happen to have one by Greenlee..
http://www.mygreenlee.com/GreenleeDotCom/Products/main.shtml?greenlee_category_id=8&product_category=317&adodb_next_page=1&adodb_next_page=2&portalProcess_2=showGreenleeProductTemplate&upc_number=11915
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okay.. so now off to the supply house for the tubing cutter and a pair or two of 9E's...
don't ferget yur PVC cutters...
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Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
This conduit will be above grade, mounted to exterior wall of house, about 12" above a concrete slab. It will carry wiring to a pair of outdoor, GFCI outlets connected to a single 15A circuit breaker. I was planning on using a green wire ground inside the conduit but also wanted to ground the conduit, itself.
For some reason, I wanted the EMT. With EMT the wires are robustly protected from damage (PVC can shatter). Major impact or cutting tool damage will most likely to result in a short to ground (and blown breaker) rather than live, exposed conductors.
Does that make sense?
All bets are off if I get any significant corrosion of the fittings and lose my conduit ground.
I do live near the shore (about 1/2 mile away), so should use PVC?
it makes sense to us...
since you are near the shore use the PVC you'll do well...
suport /clamp it often...
look into am LLB or LB or a pull EL for yur turn...
remember to deburr the cuts...
this tool works like a charm and it's at the BB's in the plumbing department...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
oops... forgot the tool..
works great on EMT also..
Superior Tool Inner/Outer Reamer
View Image
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Ok, now I'm lost again - what function do the 9E's perform in EMT cutting operations? Knock burr down with the nose and no ream? Or, do they only come into play when the cut-off is too short to snap by hand?
My Klein linesman's pliers are longer with red handles.
Never seen score and snap, but then nobody ever taught me any conduit tricks. Tried it on a scrap of 1/2" with my Rigid tubing cutter. Still have a ridge, but no burr, on the inside -- dull cutter wheel maybe? Too deep a score? Or are the Greenlee / Klein cutting wheels or anvil rollers a different shape?
Reaming tool looks slick - might have to abandon my tapered reamer.
I notice we are back to recommending PVC for the OP, alah, post #2. Good choice. Only drawback is keeping the pipe straight during strapping operations - that 1/2" can be like rubber.
JimNever underestimate the value of a sharp pencil or good light.
ugggh!
If you're new to working with EMT, keep things simple.
Cut with a hacksaw - you'll want a blade with 32tpi. Take care the cuts are straight. Indeed, at this stage, all you should use a tubing cutter for is to score a guide line on the outside of the pipe.
To debur, you can ise a pair of linemans' pliers. Open the pliers, place one jaw inside the pipe, softly close the other against the outside. Spin the pipe, and you've now deburred both the inside and the outside.
(One advantage to using a hacksaw is that the burrs are easy to remove).
You can avoid having to make little 'box offset' bends at the boxes by mounting your pipe with 'minerallacs,' metal straps they hold the pipe about 1/2" off the wall. This will also let you pass over minor imperfections in the wall.
Should you use EMT? Look around you ... just how big of a problem is rust? Does all steel in your area immediatly corrode away to nothing? Look at your meter box ... how rusty is it? If, after a few years, it still looks gray, don't worry about EMT. Also, there's no reason you can't paint EMT.
PVC, if you decide to use it, needs to be supported every few feet, or it will sag and warp untill it liiks like you hung spaghetti out to dry. Then it will get brittle and shatter - so paint it as well.
Ok, now I'm lost again -
how come that's not surprising..
what function do the 9E's perform in EMT cutting operations?
None in the actual cutting...
Knock burr down with the nose and no ream?
yes and ream too...
Or, do they only come into play when the cut-off is too short to snap by hand?
that too..
My Klein linesman's pliers are longer with red handles.
get the blue handles...
super tuff jaws...
the cutter pocket is tailored for deburring...
and the same for the nose for reaming...
Never seen score and snap, but then nobody ever taught me any conduit tricks.
practice..
Tried it on a scrap of 1/2" with my Rigid tubing cutter.
get those greenlees.. nice item...
those Rigids you have more than likely have a copper cutting wheel rather than a steel cutter...
Still have a ridge,
too much cutting force and you cut a fuzz too deep.....
but no burr, on the inside --
good start..
dull cutter wheel maybe?
more likely a copper wheel reather than a steel wheel...
if it was a copper wheel it's probably toasted now...
Too deep a score?
yup..
Or are the Greenlee / Klein cutting wheels or anvil rollers a different shape?
yup.. steel cutters too...
Reaming tool looks slick - might have to abandon my tapered reamer.
cake and pie...
US made..
cheap too... at Lowes...
I notice we are back to recommending PVC for the OP, alah, post #2. Good choice. Only drawback is keeping the pipe straight during strapping operations - that 1/2" can be like rubber.
pop a talcum or baby powder line and use that a sight/elevation contol line...
put two holers every two feet... place one of clamp's screws into the control line..
cake and pie...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
>>Ok, now I'm lost again -
how come that's not surprising..<<
It's my plot to drain your portable hard drive! Thanks!
Saw the Greenlee cutters last night, wheel has a built-in depth stop in the form of a flat shoulder. My Rigid's wheel has a longer tapered cutting profile to fully penetrate the wall of black iron or galvanized, but it may be getting dull.
Jim
Never underestimate the value of a sharp pencil or good light.
the rollers are flat too... no groove...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Flat rollers vs groove - wunner what that does or does not do....
Now I know why you thought I was using a copper tubing cutter.....
Poor spelling of brand name by me.....mine is a Ridgid pipe cutter not a Rigid....
there is a difference!
Jim
PS: How come you ain't woikin'? Theoretically, I am doing paperwork at home today as the regrouped remnants of Hurricane Ida blow through, DE coastline is getting pounded, rain and wind (~35 or 40) here. If it did not have already have a name we would just call it a nor'easter.
Never underestimate the value of a sharp pencil or good light.
Edited 11/13/2009 8:31 am ET by JTC1
Flat rollers vs groove - wunner what that does or does not do....
helps to keep the cut from rolling out...
Now I know why you thought I was using a copper tubing cutter.....
Poor spelling of brand name by me.....mine is a Ridgid pipe cutter not a Rigid....
there is a difference!
yup...
Jim
PS: How come you ain't woikin'?
had some serious surgery a few weeks back and been on a roller coaster...
Theoretically, I am doing paperwork at home today
just drinking coffee and goofing off....
as the regrouped remnants of Hurricane Ida blow through, DE coastline is getting pounded, rain and wind (~35 or 40) here. If it did not have already have a name we would just call it a nor'easter.
summer time.. almost 70 degrees and sunny...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
had some serious surgery a few weeks back and been on a roller coaster...
Hope you heal soon!
just drinking coffee and goofing off....
No, no, no - drinking Mountain Dew and goofing off - never learned to drink coffee.
summer time.. almost 70 degrees and sunny...
Lucky dog!
Sunny? What's that, sun last seen here on Monday evening. Raining since Tuesday night.
Wind gusts up to 60 at the beach now, rain starting to slack off here. Plenty of street flooding, beach erosion, etc. Tide comes in and does not go back out during nor'easter - worst case is when there are multiple high tides before the wind slacks off - don't think that will happen with this storm.
Governor just declared a state of emergency for the two counties to my south, I think primarily because this lets the DE NG to mobilize and, if needed, start hauling people out of the underwater beach areas with their duece-an-a-half trucks - tall they are! Throw a big wake too!
Jim
My wood turning guy just called - my reproduction 200 YO casing corner medallions are done for the latest museum project. That project is one county south - think I'll stay here. It'll be better travelling tomorrow......
Never underestimate the value of a sharp pencil or good light.
Edited 11/13/2009 11:50 am ET by JTC1
Hope you heal soon!
me too...
if they quit opening back up I'd like that a lot...
this is screwing wid da fishin'....
but look at the bright side... it's keeping me off of the golf courses...
No, no, no - drinking Mountain Dew and goofing off - never learned to drink coffee.
isn't it about time ya started???
summer time.. almost 70 degrees and sunny...
Lucky dog!
Sunny? What's that, sun last seen here on Monday evening. Raining since Tuesday night.
Wind gusts up to 60 at the beach now, rain starting to slack off here. Plenty of street flooding, beach erosion, etc. Tide comes in and does not go back out during nor'easter - worst case is when there are multiple high tides before the wind slacks off - don't think that will happen with this storm.
Governor just declared a state of emergency for the two counties to my south, I think primarily because this lets the DE NG to mobilize and, if needed, start hauling people out of the underwater beach areas with their duece-an-a-half trucks - tall they are! Throw a big wake too!
a week ago or so the snow was waist deep...
hardly any left....
what do you suppose is happening with all that water???
in another day or two winter will return with a vengence...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
rummaged around and found some replacement cutters for tubing cutters (copper and PVC) and pipe cutters...
the PVC cutter is reallly thin with a long taper to the cutting edge...
the copper cutter is a little thicker with a little bit faster taper...
the iron cutter is really quick wih the taper and noticeably thicker body..
if you do a bunch of EMT this gizmo is made to order... reams and deburrs.... the driver tip fits the set screw fittings like a paint job...
slicker than deer guts on a door knob..
Conduit-Fitting and Reaming Screwdriver
Hooded-blade design keeps tip from slipping out of screws, especially when tightening hard-to-reach conduit fittings. Thicker hood is designed for rugged use.
Reams and smoothes 1/2" (13 mm), 3/4" (19 mm), and 1" (25 mm) thin-wall conduit ends to protect wire and permit correct installation of fittings.
Reams both the inside and outside of the conduit at the same time.
Longer Cushion-Grip handle provides comfort and more torque for reaming.
Replaceable reaming blade is now held in place with a 1/16" hex socket set screw.
View Image
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Have seen that gizmo.
Figured I don't do enough EMT to justify buying and, more to the point, hauling around in my electrical bags.
Most of my EMT work is for "protection only" in basements, etc. Some Carflex and Greenfeld for miscellaneous applications.
My conduit work is primarily PVC for buried runs and outdoor outlets / lights.
JimNever underestimate the value of a sharp pencil or good light.
So, my next question is this, what wire type do you guys use inside the conduit? Do you pull the appropriate single conductor wires or pull the romex stuff or,...?
rarely Romex...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Conduit, of any type, gets individual wires of the appropriate colors. That's one of the advantages of conduit; you can put in any assortment of sizes and colors.
The wire mist commonly used today is called THHN. For outdoor / wet area use, you want to use THWN, which is almost always the same wire as THHN - the spool will have both markings on it.
As others have already said, for your exterior application --- THHN / THWN, or just THWN as marked on insulation of individual wires.
You should be buying and pulling black, white and green -- all insulated - no bare grounding wire. Stranded wire is easier to pull than solid but both are legal. You could use red, blue, purple, etc. instead of the black (No gray, white or green for "hot" wire). White or gray neutral required, green ground required - no re-color coding on the small sized wires you will be using (#14 or #12).
You will find the better quality outlets and box mounted GFCI's which have integral back clamps for their wire connections work very nicely with stranded wire. Not to be confused with the cheapy back-stab connections.
Only time I ever pull Romex into conduit is an "all interior" application where the conduit, generally EMT, is being used for "cable protection" only. Exposed work in a basement or garage which are likely to be hit, or an aerial drop to a oil/gas furnace are a couple of examples.
JimNever underestimate the value of a sharp pencil or good light.
RMC (Rigid) has the same taper as water pipe. It is the fittings like romex connectors that have straight threads.344.28 Reaming and Threading.
All cut ends shall be reamed or otherwise finished to remove rough edges. Where conduit is threaded in the field, a standard cutting die with a 1 in 16 taper (3/4-in. taper per foot) shall be used.
FPN: See ANSI/ASME B.1.20.1-1983, Standard for Pipe Threads, General Purpose (Inch).I like cutting EMT with a side grinder. The "burr" problem is pretty much nonexistent.
got it...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
meant to ask ya...
after you useyur sidegrinder what do you do about the cooked galv???
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
I haven't noticed it being that "cooked". If you use the thin cutoff wheel it goes pretty fast. There may be a 16th or so that is damaged to some extent but you are giving away the corrosion protection on the cut end anyway.
ridgid conduit threads are straight as where "pipe" threads are tapered...
Wrong. I thought the same thing for years, but:
NEC 344.28 "..........Where conduit is threaded in the field, a standard cutting die with a 1 in 16 taper (¾-in. taper per foot) shall be used.FPN: See ANSI/ASME B.1.20.1-1983, Standard for Pipe Threads, General Purpose (Inch)."
got that earlier...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Should also note that PVC should be protected from damage where it might get bumped by a lawn mower or whatever.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
Dont forget to factor in the cost of the grounding conductor when using PVC, it can cost more than using EMT. Plus if you have a bender, EMT requires many less fittings for bends and stuff if you have anything other than straight runs and simple 90s.
I usually use whatever I still have left in a pile, but usually stay with pvc for underground ...
... (or simply bury old extension cords <G> )
The run is a simple 90 degree L shape with approximately equal leg lengths. I was thinking of using a 90 degree elbow fitting at the corner to make the turn. It would terminate in a junction box at each end. I thought I'd be using galvanized, so I will proceed with that.
I've never used the plastic and was wondering where it was required. That it is used in contact with the ground makes a lot of sense.
I will look out for the rigid conduit next time I'm there. What is rigid conduit used for, as opposed to EMT?
Thanks for the info.
Rigid is used when there is more protection required than you get from EMT. You can also bury RMC 6" down. PVC has to be 18". As for the grounding with BX, they fixed that in type AC with that little bonding strip. It is only there to shunt out the "coil" effect.
use the plastic...
simple and clean...
won't rust either..
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
If any of the 90's are not below grade you may want to consider a pull box, it can make it easier with heavier gauge wire.
need to pull the bond wire also along with using bond collars..
so go with PVC...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
There are quite a variety of different wiring methods, each attempting to strike a balance between protection, ease of installation, standardisation, and economy. You just noticed a few of the more common.
Cutting to the chase, heavy steel is used wher maximum protection is needed; light steel where you have less of a need for protection yet still want some ability to make changes later; plastic where conditions will rust away steel, and romex where the wiring is simple it doesn't need any protection at all.
Each wiring method requires it's own types of tools, and installation details vary somewhat. Which method to use is most often a design, rather than a code, issue.
Chances are, if you hired an electrician to do this job, he would most likely use the light steel (EMT) tubing. Only if you were at the sea shore would he opt for PVC in an exposed location.
stay tuned....
this thread may go fer a bit...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
Mike,
PVC conduit is listed for exterior and direct burial. PVC is much easier to work with but be mindful to strap at approx. 36" intervals to prevent a"scalloped" look after expansion and contraction.
Galvanized is a good choice, a bit harder to install and requires threading and factory bends.
Thanks, guys, lots of good info herein.
This question is an old one and probably answered elsewhere on this site, but it seems apropos for this thread.
Are there limitations on pulling romex in conduit? Specifically, is heat build up and issue. If so, at what point do you have to derate the wire?
Jon Blakemore
RappahannockINC.com Fredericksburg, VA
Just do everyone a favor ... and don't do it. Sure, the issue has been debated endlessly, but one thing remains: it's a lot more work than you need, it cancells out many of the advantages of using pipe, and few things scream "DIY" as much as romex in pipe.
So, in an unfinished basement with a wall receptacle, you install a junction box and run THHN from the JB to the receptacle instead of placing the Romex in the conduit?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
An unfinished basement is a classical case where you might run romex in conduit. Conduit from ceiling level down to the outlet box, a fitting on the top end of the conduit (as a "bushing" to prevent cutting the romex), but no box, the romex run inside the conduit then into the ceiling without conduit.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
That would be the 'class' way to do it. Another variation is to combine fittings - romex connector, threaded coupling, EMT connector- and just strip the outer jacket off the Romex. (By stripping off the jacket, you avoid that whole debate about conduit fill, heat, etc.)
Though ... I'm going to pause here .... and wait for the rest of the shoes to drop. I say this because when you say unfinished basement, I start imagining a furnace with a disconnect, and that dedicated circuit being tapped off from to do all manner of forbidden things. I start remembering all the basement horror stories I've encountered.
So ... lets forget the abstract discussion. Let's put aside all the 'maybes' and 'what ifs.' Just exactly what are you trying to do, that putting the romex inside pipe seems such a fine solution?
Note that using stripped romex in conduit is supposedly verboten since the wires "aren't labeled for individual sale", as they like to say. Of course, if the wires are still attached to a piece un-stripped romex then it's probably legal.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
I don't know where you get that from; you just have to assume a 75 degree rating for your calculations, as they're not individually marked as to the insulation type. Since there's no splice and no junction box, you really can't do it any other way - especially if the transition is in a place that would conceal a junction box.
There's an infinite number of possibilities. Since I have no desire to be dancing in circles or playing word games, I asked for a more specific question from the OP.
"So ... lets forget the abstract discussion. Let's put aside all the 'maybes' and 'what ifs.' Just exactly what are you trying to do, that putting the romex inside pipe seems such a fine solution?"
You like to jump to conclusions, don't you?
I'm asking about running a conductor to a device, whether it be a receptacle, switch, or something else. I know that a cable in an unfinished basement needs to be protected by conduit, but I wanted to know to what extent I should be concerned with the heat.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
surface mount or wall internal cable???
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Surface mount.
Jon Blakemore RappahannockINC.com Fredericksburg, VA
you need to protect that cable...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
"Some days it's just not worth chewing through the restraints"
Not a matter of jumping to conclusions, as much as the difficulty of hitting a moving target.
For an ordinary device (receptacle) on a convenience circuit, the issue of having to derate on acount of heat is unlikely to ever become an issue. Simply put, there's so much 'cushion' in the code for 15 and 20 amp convenience circuits that it's nearly impossible for that much heat to accumulate.
While you would be allowed to have the romex enter the protective pipe for that short run, take care to have a fitting of some sort on the end of the pipe, This will protect the tire from rubbing against the end of the pipe.
Running a short length of romex through pipe is a common, and accepted, practice in this specific instance. Indeed, it's one of the very few such instances. Using 1/2" pipe for a single cable might even be within conduit fill rules, and such a short run (with few bends if any) is likely to be an easy pull.
Change the question, and the answer changes. As an example, I recently saw a house where an outside light (in a damp location) was located about 30ft, form where the wire came out of the house, and it was romex that simply entered the pipe inside the house. Here's an instance where doing so was improper, and a junction box should have been used to change wiring methods.
I'm on my way to Home Depot to buy some THWN wire for my outlets - black, white and bare for ground bare.
Mike, Home Depot doesn't have THWN (around here anyway). Only THHN.Jim x 3
It will be dual rated THHN/THWN
Fret,I checked further - the HD spools here are only labelled "THHN". But the wire itself is rated MTW, THWN and THHN. I knew wire was often multiply rated, but I guess I figured that the manufacturer would advertise the multiple rating on the spool packaging.And when I had asked the HD "customer associate" for THWN, he said THEY DON'T HAVE THAT KIND OF WIRE.So I learned 2 things. Thanks.Regards,
Jim x 3
Edited 11/17/2009 8:10 pm ET by jimjimjim
Interesting. I looked at my spools of wire and they all say THHN-THWN-MTW-AWM.Note that AWM rating also allows this to be used in 105C applications inside appliances.http://gfretwell.com/electrical/Wire%20spool%20label.jpg
Same here, jimjimjim, the packages were labeled THHN but the wire inside is also labeled as THWN.
They didn't have stranded wire in small quantities (500 ft minimum), so I bought solid. I have only a few short runs and it's easier to use at the outlets, anyway, so I'm okay with that. They had no bare wire for grounding, so I bought some green.
I also bought some offset elbows so I don't have to bend my EMT or have it stand -off the wall and look worse than it already will.
Edited 11/17/2009 9:05 pm ET by Mike_Mills
>>They had no bare wire for grounding, so I bought some green.<<
That was a good choice as bare ground wire in conduit is a no-no. Green = good. Solid is fine, just a little harder to pull.
Bet they only had bare copper in #6 and #4 for ground rod / pipe bonding uses.
JimNever underestimate the value of a sharp pencil or good light.
Why is bare wire in conduit a no-no? The 30 year old conduit running to my detatched garage has bare copper ground in it. Adam
Didn't used to be a no-no. Relatively recent change.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
I would like to hear about that "bare wire" thing too. The only place I know that requires an insulated ground wire in conduit is feeding a swimming pool.
See ####.81 - new and improved.
JimNever underestimate the value of a sharp pencil or good light.
"See ####.81 - new and improved."So now certain number combination are among the censored "words"..
William the Geezer, the sequel to Billy the Kid - Shoe
You better not be looking at BT on a LCD screen made by Matush(eye)tu, or it wont work.
Guess I should not have used "X"'s to fill in unknown numbers...........
:^0
JimNever underestimate the value of a sharp pencil or good light.
Thanks for your response.So, for a "typical" application (either 15a receptacle or switch leg), a single cable run of less than 10' with no bends is not worth any concern. Right?
Jon Blakemore RappahannockINC.com Fredericksburg, VA
I'll go along with that.
Look at it this way .... any theoretical violation will be more than cancelled by the obvious concern you had to protect the cable.
The general answer is that romex should only be pulled into conduit when the conduit is needed for (relatively) short distances to protect the romex from damage. Appropriate fittings must be installed at each end of the conduit to keep the conduit end from cutting the romex sheath.There have been arguments here on the derating issue. My vague recollection is that derating is not required if a SINGLE romex is pulled in the conduit, but derating IS required for more. (But, as I said, that's only a vague recollection, and my NEC book is 25 years out of date.)
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
You are correct. It is called the "skin effect".
Without an equipment grounding conductor, you need to bond EMT connectors. This is code. We always used to just pull the equipment ground.
My favorite way to cut EMT is with a porta-band. My cordless sawzaw is my least favorite, but it is usually all I have on hand. Blade bounces around too much.
> I want to add some exterior 115V outlets but don't know which type to use. The conduit will be mounted on an exterior wall.
Perhaps we should go back to the top and start with a broader picture. What's this exterior region like? Is it the end of a driveway where somebody might back a truck into the conduit? Is it the back patio where minimum ugliness might be a goal? What kind of wall surface does it mount to, and what's the surface below, bare dirt, wife's favorite flowers, concrete, ....? The more we know, the better we can narrow it down to the most appropriate candidates.
-- J.S.
The skin effect only applies at high frequencies.
And when the skin effect is in effect the inside surface doesn't conduct.
The more I think about the skin effect the more I realize I am not sure when it applies.
I first heard about skin effect in the context of RF.
I know that the static charge on a metal ball all resides on the surface, too. Static charge is a frequency of zero and a current of zero.
With copper being as conductive as it is, I bet the current does distribute itself internally. I bet it isn't uniform.
Hmm,... an interesting analysis is coming. Now, where's my copy of Jackson?
IIRC, current density decays exponentially as you move from surface to center. That's for any charge on a conductor, whether moving or not. The size wires we are talking about are so small in diameter that you probably couldn't detect much difference between surface & center. When you talk skin effect, you are talking currents induced in a conductor by an impinging electromagnetic field. Then the frequency starts having an effect that is noticeable. The frequency effect is always there, but until you reach RF, it is negligible. From an engineering/academic standpoint, the 4 Maxwell equations that describe electromagnetic phenomena are truly universal for the non-quantum world. We just tend to ignore certain parts when they are negligible.DonDon Reinhard
The Glass Masterworks
"If it scratches, I etch it!"
It's been about 38 years, but my recollection is that the skin effect only becomes a factor in the GHz range. True, static CHARGE will distribute itself on the outside of the object, but CONDUCTION is a different matter entirely.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
skin effect only becomes a factor in the GHz range
Lots lower than that, just a few kHz, even shows up on big cable at 60 Hz. .
60 Hz, table9 of chapter 9 of NEC* shows that 2000MCM cable has an ac resistance 23% higher than dc, due to skin effect at 60 Hz. 0.4% even for relatively small 4/0
*(1980 NEC version, only copy I bother looking at, everything else since then is just marketing by the mfg, but that's another story <G>)
This is an interesting thread in that is does show some great misconceptions ??
Yeah, apparently you're right -- I misremembered the 15 minute lecture I got on that about 38 years ago.http://en.wikipedia.org/wiki/Skin_effect
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
Nobody mentioned UF for outdoors. Lots less work than all the bending, fittings, and fishing. Just bring it into an oversized conduit 18" below grade for the short exposed run up the wall.
Or am I the only one who doesn't expect an overly agressive gardner to hack through my admittedly less protected lines?
Rick
I think the OP had already decided upon conduit of some sort due to appearance considerations.
I use UF very occasionally and generally swear at it, since I have never figured out a good way to strip the incredibly tough jacket off in anything which resembles a short time.
UF makes good money for me though --- everytime I dig it up to find the break in the wire run after someone unwittingly cuts a run which was not buried deep enough to avoid the gardeners! 6" deep seems to be about the normal depth for a HO installation.
The HOs generally want it replaced with conduit......
JimNever underestimate the value of a sharp pencil or good light.
We wired a whole house with UF in Puerto Rico. They used it there because of the rats.
A strong nation, like a strong person, can afford to be gentle, firm, thoughtful, and restrained. It can afford to extend a helping hand to others. It's a weak nation, like a weak person, that must behave with bluster and boasting and rashness and other signs of insecurity. --Jimmy Carter
Rats don't like the taste of UF?
Might be handy information.......
JimNever underestimate the value of a sharp pencil or good light.
Why wouldn't a rat eat UF any faster than RX?
My, my.
Scanned this whole thread and never once saw any mention of whacking the ends of EMT with a hammer, dirlling a hole, and using for shelf support brackets.
Or of using rigid for water pipe.
Or using 2" PVC for building a Van de Graff
Or for closet rods
Or for lally columns
Or......... endless list......
Well, now that you bring it up .... 1" EMT does make an exceptionally fine closet rod. It's also a good post for supporting a bird feeder or bird house.
Outdoor outfitters carry fittings that allow you to quickly assemble blinds, etc., using 3/4" EMT. Also makes a pretty decent walking stick.
Plastic rain gutters make great tool and part trays that you can hang above your workbench - or from the rails of a scissors lift.
My wife's new bedroom curtains are hanging from 1/2" EMT.
Don't know, DanH posted that UF = no rat chewing.
Someone told me that mice / rats like to chew Romex because the outer sheath contains lead which makes it taste sweet. Piffin I think. I have not done a taste test.......
RE: no bare in conduit. Our local inspectors don't like bare in conduit, green only. Sort of makes sense in PVC, very little sense in EMT or rigid. As a result of their possible bias, locally, it is virtually impossible to find bare copper in gauges smaller than #6. #6 & 4 are readily available even at BB stores.
So it may be sort of a self-fulfilling prophesy - not available, so everybody uses green insulated.
JimNever underestimate the value of a sharp pencil or good light.
One thought on bare copper inside EMT is corrosion if it gets wet inside. Granted that's not a super great reason to ban it, but going with green insulated wire instead isn't that much of a burden, either.
-- J.S.