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other people
Jun 27, 2004
Associate Christ
Ah, what I did seems to work, but looking at that diagram, it isn't actually correct.

There are three sets of wire coming in. One goes straight to the outlet. The other two I joined with a lug along with the four inch wire that connects them to the outlet.

Correct would be to join all three sets together in lugs with a fourth short wire going to the outlet? Like so:
http://imgur.com/Pzgbm ?


And now, I have realized that it might not be such a big deal for me to double the size of the box and add a proper switch for the lights. I forget I own a dremel now and that it should quite easily cut the tile backsplash with the correct bit!

Also also, if I have two of these under cabinet lights next to each other, can I have power enter one, then go out to the other, in a chain? So they are all controlled by the same switch? Assuming I use the proper romex wiring and wire clamps, etc?

Any idea how to wire this??

lol

other people fucked around with this message at 19:26 on May 8, 2012

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kid sinister
Nov 16, 2002

Kaluza-Klein posted:

And now, I have realized that it might not be such a big deal for me to double the size of the box and add a proper switch for the lights. I forget I own a dremel now and that it should quite easily cut the tile backsplash with the correct bit!

Also also, if I have two of these under cabinet lights next to each other, can I have power enter one, then go out to the other, in a chain? So they are all controlled by the same switch? Assuming I use the proper romex wiring and wire clamps, etc?

Any idea how to wire this??

lol

Depending on your dremel, then make a kit that is perfect for the tile... Before you start cutting however, you would still have more problems to solve.

1. How will you fish wire from this new box to the lights?
2. Romex isn't allowed in exposed installations. You would have to protect it wall-to-fixture and fixture-to-fixture with wiremold.

Also, a "compact hacksaw" is a lifesaver for cutting out an existing box through its existing hole. Stick the blade between the box and stud, then saw through the nails above and below the box holding it to the stud.

kid sinister fucked around with this message at 21:12 on May 8, 2012

other people
Jun 27, 2004
Associate Christ

kid sinister posted:

Depending on your dremel, then make a kit that is perfect for the tile... Before you start cutting however, you would still have more problems to solve.

1. How will you fish wire from this new box to the lights?
2. Romex isn't allowed in exposed installations. You would have to protect it wall-to-fixture and fixture-to-fixture with wiremold.

Also, a "compact hacksaw" is a lifesaver for cutting out an existing box through its existing hole.

I bought their tile cutting bit and it made quick work of the tile. The single box in there now is an aftermarket one that is only held in by plastic tabs, so it was very easy to remove. I replaced it with the same style, just double the size.

I wasn't sure if I would have to get ductwork or not for the wire. Not the end of the world to use it if I have to.

I thought I knew how to wire this, but I guess I don't :/.

kid sinister
Nov 16, 2002

Kaluza-Klein posted:

I bought their tile cutting bit and it made quick work of the tile. The single box in there now is an aftermarket one that is only held in by plastic tabs, so it was very easy to remove. I replaced it with the same style, just double the size.

I wasn't sure if I would have to get ductwork or not for the wire. Not the end of the world to use it if I have to.

I thought I knew how to wire this, but I guess I don't :/.

How about some pictures? One of your wall and one of the underside of the cabinets? We can help with ideas. If the box is directly under the cabinets, it should be easy to fish cable directly down now that you have a hole in the wall big enough to reach your hand in.

other people
Jun 27, 2004
Associate Christ
The lights are already installed and wired! I am just not sure how to wire box/switch/outlet.

The box has two original romex wires and an outlet, and I have added a single pole switch and a romex that is going to the lights.

http://img2.timeinc.net/toh/i/steps/undercabinet-Over.jpg

This is close to what I have, except I am not using a dimmer and there is another existing romex wire to deal with.

By the way, it is absolutely brutal trying to get all that solid copper wire in the loving box!

When you guys bend the tabs on the blue plastic electric boxes to input cable, do you break the tab off or leave it? It does a good job of holding the wire in place, and maybe that is why it is there, but it makes it hell to pull in a bit more or push some back out after the fact.



edit: gently caress I am not having fun any more >:(

I wired it all up, flipped the breaker, and nothing. After turning the breaker off, I removed the outlet and switch, and then connected white to white, ground to ground, and black to black, using only the two original romex wires. Turn the breaker back on, and still nothing! What have I done?!

edit edit: There is an uncovered outlet box buried in the lower cabinet that I have never noticed before. It has two romex going into it and a bunch of exposed wire :/. Jiggling the wires in the box I have installed wiggles the wires down in this box. I wonder if I knocked something loose, and why is there an uncovered electrical box here!

edit edit edit: Removing everything from the cabinet I found a wire nut sitting on the floor that is missing its metal insert. I stuck a fresh net on the two wires that were obviously twisted together and all the circuits have power again! I guess I am glad that I have learned about this exposed box and can cover it correctly, but I am really mad I took apart all my wiring thinking it was wrong when it was just a loose nut somewhere else. gently caress.

other people fucked around with this message at 00:16 on May 9, 2012

ncumbered_by_idgits
Sep 20, 2008

Kaluza-Klein posted:

The lights are already installed and wired! I am just not sure how to wire box/switch/outlet.

The box has two original romex wires and an outlet, and I have added a single pole switch and a romex that is going to the lights.

http://img2.timeinc.net/toh/i/steps/undercabinet-Over.jpg

This is close to what I have, except I am not using a dimmer and there is another existing romex wire to deal with.

By the way, it is absolutely brutal trying to get all that solid copper wire in the loving box!

When you guys bend the tabs on the blue plastic electric boxes to input cable, do you break the tab off or leave it? It does a good job of holding the wire in place, and maybe that is why it is there, but it makes it hell to pull in a bit more or push some back out after the fact.



edit: gently caress I am not having fun any more >:(

I wired it all up, flipped the breaker, and nothing. After turning the breaker off, I removed the outlet and switch, and then connected white to white, ground to ground, and black to black, using only the two original romex wires. Turn the breaker back on, and still nothing! What have I done?!

edit edit: There is an uncovered outlet box buried in the lower cabinet that I have never noticed before. It has two romex going into it and a bunch of exposed wire :/. Jiggling the wires in the box I have installed wiggles the wires down in this box. I wonder if I knocked something loose, and why is there an uncovered electrical box here!

edit edit edit: Removing everything from the cabinet I found a wire nut sitting on the floor that is missing its metal insert. I stuck a fresh net on the two wires that were obviously twisted together and all the circuits have power again! I guess I am glad that I have learned about this exposed box and can cover it correctly, but I am really mad I took apart all my wiring thinking it was wrong when it was just a loose nut somewhere else. gently caress.

nm: I can't read and am an rear end

ncumbered_by_idgits fucked around with this message at 01:22 on May 9, 2012

babyeatingpsychopath
Oct 28, 2000
Forum Veteran


Kaluza-Klein posted:


By the way, it is absolutely brutal trying to get all that solid copper wire in the loving box!

When you guys bend the tabs on the blue plastic electric boxes to input cable, do you break the tab off or leave it? It does a good job of holding the wire in place, and maybe that is why it is there, but it makes it hell to pull in a bit more or push some back out after the fact.


Leave it there. It's the required cable clamp. Pull more than you need and cut some off. Don't ever try to push any back; it won't work.

quote:

edit: gently caress I am not having fun any more >:(
edit edit: Previous electricians were derps.
edit edit edit: But I'm not.

You're doing great. You fixed a problem it would have taken a professional $100 to find (10 minutes, but billed by the first hour (no partials) +showup fee)).

Also, romex is allowed for exposed use where protected from physical damage. Above/under a cabinet usually counts. I don't have my code book on me to double-check this for 100%, but I have run exposed romex in finished garages with inspectors' blessings. Just make sure it's stapled/secured within 18" of your light, and at least every 3' thereafter, and use listed romex cable clamps.

kid sinister
Nov 16, 2002
Kaluza-Klein, it sounds like you got it done. Good work! There's still one extra step you need to do though... All boxes need covers. Get one for that junction box in the cabinet and everything should be up to code.

edit: nevermind, it sounds like you figured that out.

kid sinister fucked around with this message at 02:10 on May 9, 2012

other people
Jun 27, 2004
Associate Christ
I got it done alright, finally!

A few remaining quirks, one is that the box is flush with the drywall, but there is 1/4 inch tile on top of that, so the faceplate and outlets/switch are far from flush!

I created some fat plastic washers out of drywall anchors to use between the outlet/switch and the box. It "works," but there has got to be a better way!

I swear I had some other issues but I have forgotten them all overnight. Yay!

let it mellow
Jun 1, 2000

Dinosaur Gum
There is another option, but I've always just used washers to prevent me from over tightening the faceplate screws too.

ncumbered_by_idgits
Sep 20, 2008

These work pretty good too.

http://www.erico.com/products/CADDYcfcDvcLvlrRetnr.asp

other people
Jun 27, 2004
Associate Christ

ncumbered_by_idgits posted:

These work pretty good too.

http://www.erico.com/products/CADDYcfcDvcLvlrRetnr.asp



Oh, that looks nice! Ordered!

Now I have to power wash the deck, paint the kitchen and bathroom (including ceilings) and whatever else my wife can think up while I am on vacation :/.

kid sinister
Nov 16, 2002
I've used these too:

edit: if you have to shim any devices out so far that their screws no longer reach the screw holes on the box, you can just use longer #6-32 screws.

Only registered members can see post attachments!

kid sinister fucked around with this message at 01:23 on May 10, 2012

babyeatingpsychopath
Oct 28, 2000
Forum Veteran


Kaluza-Klein posted:

I got it done alright, finally!

A few remaining quirks, one is that the box is flush with the drywall, but there is 1/4 inch tile on top of that, so the faceplate and outlets/switch are far from flush!

I created some fat plastic washers out of drywall anchors to use between the outlet/switch and the box. It "works," but there has got to be a better way!

I swear I had some other issues but I have forgotten them all overnight. Yay!

I'm taking that drywall-anchor-as-a-shim idea. That's good stuff. Normally, we just twist a piece of wire into a coil around a #6-32 and cut the length we need, but anchors are way easier to cut.

crocodile
Jun 19, 2004

crimp sleeves work really well for that, too.

NewcastleBrown
Mar 15, 2004
The One and Only
Ok, please forgive me as I know this is brought up with some regularity. I don't know if I just wasn't reading well enough or what, but I still have questions after reading some other posts on this topic.

I just moved into a 100+ year old house that was converted into 4 rental apartments. Virtually all of the plugs in the house are 2 prong. There is a 3 prong in the bedroom that my surge protector tells me isn't actually grounded and there is a 3 prong in the kitchen (that the fridge is plugged into) that I haven't gotten around to testing for ground yet.

I'd like to convert all the sockets to 3 prong so I can use my surge protectors for my computer/tv/etc. Also, other than in the kitchen there is only one outlet per room so I'll need the extra socket space the surge protectors provide. I gather all this means that I'll need some GFCIs, though they'd still leave my computer equipment ungrounded.

I guess the first question is that as a renter (in CA, if that matters) should I even be attempting anything like this, or should I leave it up to the landlord to take care of?

If I do end up doing it myself, is there any way I can protect my computer from shorting without running a ground? From what I've read you only need a GFCI on the first socket in the line. How do I determine which one of my plugs that is?

I'm beginning to feel like I'm in a bit over my head.

corgski
Feb 6, 2007

Silly goose, you're here forever.

NewcastleBrown posted:

I guess the first question is that as a renter (in CA, if that matters) should I even be attempting anything like this,

No.

NewcastleBrown posted:

or should I leave it up to the landlord to take care of?

Good luck.

NewcastleBrown
Mar 15, 2004
The One and Only

thelightguy posted:

No.


Good luck.

These were the exact responses I expected and feared.

I'm currently running extension cords from the ungrounded bedroom socket to the living room (for the tv) and another to the "office" where I have the computers. I'm pretty sure this isn't a terribly good idea.

Hopefully my new landlord isn't a shitheel!

corgski
Feb 6, 2007

Silly goose, you're here forever.

Just buy a bunch of these things.

http://www.google.com/products/cata...ed=0CLMBEPMCMAI

grover
Jan 23, 2002

PEW PEW PEW
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:

thelightguy posted:

Just buy a bunch of these things.

http://www.google.com/products/cata...ed=0CLMBEPMCMAI
No! Those things are dangerous and illegal 99% of the time, and it amazes me they're still allowed to be sold. You should not be considering using an ungrounded adapter with a metal-bodied appliance that requires grounding (like a computer) without at least a GFCI power strip.

NewcastleBrown
Mar 15, 2004
The One and Only

thelightguy posted:

Just buy a bunch of these things.

http://www.google.com/products/cata...ed=0CLMBEPMCMAI

Hopefully the wiring is new enough that the boxes are grounded. Worth a shot, at least. Should I get an outlet tester, or will my surge protector that shows ground status be enough?

Looks like I'll only be able to use one of those per outlet? Or do they make "top" and "bottom" outlet adapters?

Thanks for your input, by the way.

Edit:

grover posted:

No! Those things are dangerous and illegal 99% of the time, and it amazes me they're still allowed to be sold. You should not be considering using an ungrounded adapter with a metal-bodied appliance that requires grounding (like a computer) without at least a GFCI power strip.

My quick amazon search shows only a handful of GFCI power strips and they're all 3 prong. If I can't get my landlord to install GFCI sockets what options do I have other than selling my electronics?

E2: and GFCI anything still doesn't fix my lack of grounded outlets...

NewcastleBrown fucked around with this message at 00:06 on May 11, 2012

kid sinister
Nov 16, 2002

NewcastleBrown posted:

Hopefully the wiring is new enough that the boxes are grounded. Worth a shot, at least. Should I get an outlet tester, or will my surge protector that shows ground status be enough?

Looks like I'll only be able to use one of those per outlet? Or do they make "top" and "bottom" outlet adapters?

Thanks for your input, by the way.

Edit:


My quick amazon search shows only a handful of GFCI power strips and they're all 3 prong. If I can't get my landlord to install GFCI sockets what options do I have other than selling my electronics?

E2: and GFCI anything still doesn't fix my lack of grounded outlets...

I wrote a big post about legally upgrading to 3 prong outlets.

As for your questions, the grounding light on surge protectors is just a little light that tests for a circuit between the hot and grounding prongs. Don't trust them, they can be fooled by a neutral-ground shorts that would indicate an outlet was grounded when in fact it's not. Get a $2 circuit tester.

I have seen 3-to-2 prong adapters that use a short wire to attach to the outlet screw. You could probably use those for other receptacle.

And GFCI themselves offer similar protection to grounded outlets, so they're a pretty good and the only legal alternative.

kid sinister fucked around with this message at 01:14 on May 11, 2012

ncumbered_by_idgits
Sep 20, 2008

kid sinister posted:

I have seen 3-to-2 prong adapters that use a short wire to attach to the outlet screw. You could probably use those for other receptacle.

These do absolutely nothing unless the box is grounded.

kid sinister
Nov 16, 2002

ncumbered_by_idgits posted:

These do absolutely nothing unless the box is grounded.

Neither do the ones with the screw down tab. Nor do the grounding prongs on 3-prong outlets that are piggybacking off a GFCI via 2-wire NM. I'm not saying he should use them, I think they're completely dangerous. Their only use is saving people from needing to cut off the grounding prong from plugs just so they will fit, even though that grounding prong is there for a good reason.

corgski
Feb 6, 2007

Silly goose, you're here forever.

grover posted:

No! Those things are dangerous and illegal 99% of the time, and it amazes me they're still allowed to be sold. You should not be considering using an ungrounded adapter with a metal-bodied appliance that requires grounding (like a computer) without at least a GFCI power strip.

Like anything else, they're illegal if installed permanently, but they're an absolute necessity for any audio equipment that would share a ground with, well, practically anything.

Dangerous is a homemade ground neutral bond. A floating ground is nothing.

randomidiot
May 12, 2006

by Fluffdaddy

(and can't post for 11 years!)

I found a small fridge (2.7 cubic foot) by the dumpster the other day. Specifically, this one.

It was clean, so I brought it back. Plugged it in and it wouldn't start until I smacked the thermostat, then it got good and cold... until the thermostat cycled off. Smacking the thermostat again brings it back to life. If I set the thermostat to its coldest setting, it runs nonstop and gets down to about 5F. So obviously, the thermostat is bad.

Problem I'm running into is only one distributor stocks this exact thermostat, and they've given me a hell of a runaround, including double billing my card then telling me "oh even though the website said we have 50, we actually ran out a month ago, it's on backorder".

The fridge is actually made by Haier. The data plate states it pulls 6.3 amps at startup, and 1.5 amps while running.

This thermostat looks absolutely identical, except I can't make out what's on the sticker. The one I have now is rated for 5 amps @ 250 volts (this is a 120 volt unit). Think I would be safe ordering that particular thermostat? It appears to be for a somewhat larger minifridge (4.5 cubic ft), but I'm thinking the only difference may be in the sensitivity.

This is the thermostat I pulled out of it:

kid sinister
Nov 16, 2002
A thermostat that can be "reset" by hitting it could just be a loose connection. Did you make sure all the terminals are good and tight?

randomidiot
May 12, 2006

by Fluffdaddy

(and can't post for 11 years!)

Yeah all the terminals were fine - nice and tight, no evidence of arcing. It could also be "reset" by turning the knob to 0 then back to 8 (9 is the coldest setting), even if the fridge was room temp.

The thermostat made an audible click every time it turned on or off, including when I hit the thermostat. Even with the thermostat out, it only clicks if I turn it all the way to the coldest setting or otherwise tap it. It's the exact same click that the thermostat on my other mini fridge makes when it cycles.

Also, the schematic on the back shows that the thermostat doesn't contain any sort of overload protection - there's a relay on the compressor for that.

Just trying to figure out if the one I linked to will work properly, being that it's for a slightly larger unit (no fan inside on either the one I have now or the one I linked to). I may try the local appliance shops to see if they stock one a bit cheaper.

babyeatingpsychopath
Oct 28, 2000
Forum Veteran


some texas redneck posted:


Just trying to figure out if the one I linked to will work properly, being that it's for a slightly larger unit (no fan inside on either the one I have now or the one I linked to). I may try the local appliance shops to see if they stock one a bit cheaper.

I think it'll be fine. If you can find one locally for cheaper, go for it. t-stats are basically interchangable.

Farside
Aug 11, 2002
I love my Commodore 64
How close can I run romex next heating ducts? I want to fish some up through a wall cavity that is mostly filled with a rectangular duct that only leaves like 0.75" to 1.0" for me to pull through. The run next to the duct will only be 6' if it makes a difference.

grover
Jan 23, 2002

PEW PEW PEW
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:

Farside posted:

How close can I run romex next heating ducts? I want to fish some up through a wall cavity that is mostly filled with a rectangular duct that only leaves like 0.75" to 1.0" for me to pull through. The run next to the duct will only be 6' if it makes a difference.
I would not run romex in close proximity to an uninsulated heating duct as the elevated temperatures can reduce the ampacity to the point where it becomes a fire hazard, but if the duct is insulated or an uninsulated return plenum, it shouldn't be an issue.

dwoloz
Oct 20, 2004

Uh uh fool, step back

grover posted:

You're not supposed to double-lug, so if this is the 3rd cable in the box, you'll need to make a pigtail: remove one set, and wirenut it to your new wire plus a ~4" piece of wire to run back to the receptacle. Black is hot, white is neutral, and the receptacle is rated for pass-through, so it doesn't matter which set you use.

What's the reasoning for this?
I can understand not having two wires on one screw but not sure why you can't have wires on separate screws if you're not using it as a duplex outlet

grover
Jan 23, 2002

PEW PEW PEW
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:

dwoloz posted:

What's the reasoning for this?
I can understand not having two wires on one screw but not sure why you can't have wires on separate screws if you're not using it as a duplex outlet
You can put one wire on each screw, but not two on the same screw. This limits you to 2 connections on most receptacles. So, when you add a 3rd, you need to pigtail it. You only need to remove one for the pigtail; you can leave the other on the receptacle. Most electricians will just cable-nut them all the together in the back of the box for simplicity, though, and *just* run the pigtail to the receptacle.

It it was #14 could you technically use the backstabs to get 4 wires per receptacle, but you don't ever want to use backstabs unless they're screw-tightened (like on most GFCIs).

grover fucked around with this message at 03:19 on May 13, 2012

dwoloz
Oct 20, 2004

Uh uh fool, step back
Im talking about using the jumper tab on a duplex receptacle to essentially replace the wire nut and pigtail. Power would come in and be connected to (lets say) the top two screw terminals then the the bottom two screw terminals would have wires running to the next receptacle in the series.
I've seen it done this way, just wondering if it's allowed and if not, why

ncumbered_by_idgits
Sep 20, 2008

dwoloz posted:

Im talking about using the jumper tab on a duplex receptacle to essentially replace the wire nut and pigtail. Power would come in and be connected to (lets say) the top two screw terminals then the the bottom two screw terminals would have wires running to the next receptacle in the series.
I've seen it done this way, just wondering if it's allowed and if not, why

I can't remember the code reference now but I was always taught that the current from one device (receptacle) should not pass through another.

As a practical matter I would not do it this way anyway. At least with wirenuts/pigtails if you have a bad connection at the receptacle it affects that receptacle only.

grover
Jan 23, 2002

PEW PEW PEW
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:

dwoloz posted:

Im talking about using the jumper tab on a duplex receptacle to essentially replace the wire nut and pigtail. Power would come in and be connected to (lets say) the top two screw terminals then the the bottom two screw terminals would have wires running to the next receptacle in the series.
I've seen it done this way, just wondering if it's allowed and if not, why
?? You can still only put 1 wire per screw, it should be shaped like a J, not a |. Lets you splice 1 in and 1 out, 2 total sets per receptacle. If you pull a 3rd piece of romex to the box, you MUST pigtail to connect it legally.



ncumbered_by_idgits posted:

I can't remember the code reference now but I was always taught that the current from one device (receptacle) should not pass through another.

As a practical matter I would not do it this way anyway. At least with wirenuts/pigtails if you have a bad connection at the receptacle it affects that receptacle only.
Pretty sure the receptacle tab is UL listed as a pass-through for 15 & 20A circuits, and what you're describing isn't a code requirement, just good practice. For DIY, though, I would think using the receptacle as a splice would be safer & more reliable than trying to nut 4 wires together. poo poo takes practice, and 3 is a lot easier to do.

grover fucked around with this message at 13:22 on May 13, 2012

Farside
Aug 11, 2002
I love my Commodore 64

grover posted:

I would not run romex in close proximity to an uninsulated heating duct as the elevated temperatures can reduce the ampacity to the point where it becomes a fire hazard, but if the duct is insulated or an uninsulated return plenum, it shouldn't be an issue.

Ok I'm confused. My wire has a temp rating of 90 deg C (194 deg F). At temps up to 60 deg C (140 deg F) there is no need to derate the cable, or at least that is my understanding. My ducts don't get anywhere near that hot. Hell my attic gets a fuckton hotter than my ducts and I have wires all over the place. The only thing I found in regards to ducts were about flue gas exhaust and type 'b' were I need 1" of space.

Not saying that I don't believe you its just that it seems like I should be able to do it and I couldn't find anything that explicitly forbids it.

Might be a moot point anyway. The duct is insulated with a wrap of some sort (looks like super thick wallpaper and is probably asbestos) and I got a better look at the space the wire is going to be running through by widening the holes a bit. The space I have to work with is 2" at its widest and 1.5" at the narrowest.

I would still like a more specific answer though. I'm sure I'll run into similar problems in the future. Or is it not really a rule but more like its technically ok to do but you shouldn't really do it type of thing?

I appreciate the help.

grover
Jan 23, 2002

PEW PEW PEW
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:
:circlefap::circlefap::circlefap:

Farside posted:

Ok I'm confused. My wire has a temp rating of 90 deg C (194 deg F). At temps up to 60 deg C (140 deg F) there is no need to derate the cable, or at least that is my understanding. My ducts don't get anywhere near that hot. Hell my attic gets a fuckton hotter than my ducts and I have wires all over the place. The only thing I found in regards to ducts were about flue gas exhaust and type 'b' were I need 1" of space.
A 90C temp rating on a cable means the insulation is rated for 90C TOTAL, but wires are like little strip heaters. That cable will heat from 30C ambient to 90C (60C rise) if you put 100% of the rated amout of electricity through it. If you tried to heat "90C" wire to 90C and put full normal-rated through it, it would heat up to 150C, the insulation would melt, it would short out, and you would start a fire.

NEC table 310.15(B)(2) provides temperature derating tables that you can use to oversize the wire if necessary to use a "hot" chase.

grover fucked around with this message at 02:59 on May 14, 2012

Farside
Aug 11, 2002
I love my Commodore 64
Thanks for the more detailed explanation. I knew I was missing something which is why I asked. The wire is only going to a wall sconce for accent lighting. I'll have to open up some more wall to see if I can find an alternate route to use.

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babyeatingpsychopath
Oct 28, 2000
Forum Veteran


Farside posted:

Thanks for the more detailed explanation. I knew I was missing something which is why I asked. The wire is only going to a wall sconce for accent lighting. I'll have to open up some more wall to see if I can find an alternate route to use.

In that case, you know your current, and you can figure out if derating for heat still leaves you with enough ampacity in your wire. Of course, the current you use is the wattage rating of the socket on the sconce. Note that derating #14 wire 90% still leaves you the ability to run a 100W light bulb.

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