Metal Boxes in Residential???

[B4T]

They do make 3" deep plastic boxes if you think that a dimmer might melt a standard box.. :roll:

 

[LEO2854]

Generally, my only use of metal boxes in houses is for dimmer switches, as I saw on other posts here, they help to heat sink some overly hot dimmers. I sometimes use them to gang up what I can't buy in plastic.

Plastic is cheaper, lighter, easier to nail up, don't have to tape terminal screws, etc. The few customers that have asked me, I've told them plastic has been standard for over 20 years. I agree with most previous comments about better space and grounding as well. I do notice that some of the speedlock or "quickclick" boxes don't securely hold device screws for a sturdy install. Sometimes have to up them to 8-32 screws. The ones without quickclick hold well, but are often a tight go with a screwdriver. Sometimes I even drill a 6-32 tap into them to loosen them up.

I do use metal for anything surface mounted on a porch, utility room, etc. where physical damage is a consideration.

I cant' imagine doing a house in EMT, as the Chicago guys posted. My cousin's apt in Chicago was wired in NM, what I saw in her attic. Older building though, in Irving Park area. Don't know when EMT became code there.

I cant' imagine doing a house in EMT

It is just like an Office bulding that is speced out for all EMT and Rigid You run the pipe inside the Rough walls,

in a house you would do it the same way smaller scale and of cource you would have wood studs instead of metal studs.

If you can the next time your roughing out a house do one room in pipe just for kick's:grin:

 

[K8MHZ]

I cant' imagine doing a house in EMT,

I've done a couple of them.

No fun. The EC llost his butt.

But it sure looked pretty before they covered it all up with drywall.

 

[K8MHZ]

It is just like an Office bulding that is speced out for all EMT and Rigid You run the pipe inside the Rough walls,

in a house you would do it the same way smaller scale and of cource you would have wood studs instead of metal studs.

If you can the next time your roughing out a house do one room in pipe just for kick's:grin:

It's not that simple. In a house there are turns that need to be made that are really tough to do with pipe simply due to it's inherent physical limitations. There are other issues as well, but it's way easier to run EMT in a commercial building than in a wood frame house, and I speak from actual experience.

 

[LEO2854]

It's not that simple. In a house there are turns that need to be made that are really tough to do with pipe simply due to it's inherent physical limitations. There are other issues as well, but it's way easier to run EMT in a commercial building than in a wood frame house, and I speak from actual experience.

I agree with you.And i have done both it is not an easy task .
But it would be fun just to pipe in a room just for kicks if you have the time.
When you the owner you can make the time if you want

 

[LEO2854]

They do make 3" deep plastic boxes if you think that a dimmer might melt a standard box.. :roll:

I agree i read somwhere that the plasic boxes disapate heat better.
Where steel boxes get hot as well as the dimmer switches.

Good Point:grin:

 

[jmellc]

It is just like an Office bulding that is speced out for all EMT and Rigid You run the pipe inside the Rough walls,

in a house you would do it the same way smaller scale and of cource you would have wood studs instead of metal studs.

If you can the next time your roughing out a house do one room in pipe just for kick's:grin:

I know to do it. But in a cutthroat market, few would be willing to pay for it.

 

[Smart $]

I agree i read somwhere that the plasic boxes disapate heat better.
Where steel boxes get hot as well as the dimmer switches.

...

Given conditions are the same other than steel or plastic box, the steel box will dissipate heat better. Dissipation is directly related to the material's thermal conductivity. I don't know of any plastic which conducts heat better than steel.

 

[LarryFine]

But it would be fun just to pipe in a room just for kicks if you have the time.

Then you have the wire-EGC-vs-EMT debate.

 

[peter d]

I've never heard of the "heat sink for a dimmer" argument in favor of metal boxes before now. There must be at least a billion dimmers installed in non-metallic boxes. I think that kind of reasoning is limited only to electrical forums.

 

[don_resqcapt19]

I've never heard of the "heat sink for a dimmer" argument in favor of metal boxes before now. There must be at least a billion dimmers installed in non-metallic boxes. I think that kind of reasoning is limited only to electrical forums.

There was a post that said the non-metallic box would be a better heat sink.

Smart is correct, there is no way that with everything else being the same that a non-metallic box would be a better heat sink than a metallic one.

 

[hurk27]

PVC plastic as well as most plastic used in a box construction, along with bake lite is a thermo insulator, used for years in aluminum cased windows and doors as a thermo break between the inside and outside to prevent thermo transfer, are there plastics that can dissipate heat? yes NASA has been using them for years in heat sinks aboard space crafts to save weight, but if a single gain box was made of this stuff I would hate to see the price tag, If I remember right its a high silicone composite and very expensive.

I'm not even sure you can call it a plastic?


If you want to test this theory, just grab a small propane torch and hold a metal box on one side and try to heat the other, bet you will let go way before you get that box very hot, now try this with a plastic box, you will melt almost the whole box away before your fingers start feeling the heat from the box.

 

[tryinghard]

Aren't all plasitc boxes 1 hour rated now-a-day's?

 

[hurk27]

Aren't all plastic boxes 1 hour rated now-a-day's?

the ones I use say 2 hour, and are for the most part flame retardant, I would expect some amount of Teflon being used in the mix for them, as Teflon can stand high temps, but is still considered an insulator when it comes to thermo.

 

[hurk27]

I guess there are other compositions being played with to make plastic thermo conductive:

http://www.ledsmagazine.com/news/7/9/2

 

[sameguy]

It isn't that the box will melt, it is to transfer heat from the dimmer to the box keeping the dimming out put device from over heating. Like the fins on the front if reduced to fit you need to derate the dimmer.
If plastic was better then wouldn't the fins be made of plastic?

 

[electricmanscott]

It isn't that the box will melt, it is to transfer heat from the dimmer to the box keeping the dimming out put device from over heating. Like the fins on the front if reduced to fit you need to derate the dimmer.
If plastic was better then wouldn't the fins be made of plastic?

If it mattered wouldn't we be required to install dimmers only in metal boxes.

It doesn't so we're not.

 

[readydave8]

I've never heard of the "heat sink for a dimmer" argument in favor of metal boxes before now. There must be at least a billion dimmers installed in non-metallic boxes. I think that kind of reasoning is limited only to electrical forums.

I've had customers complain about cover screws getting hot at dimmer switches 1/2 a billion times, they must have called someone else the other half.

 

[peter d]

I've had customers complain about cover screws getting hot at dimmer switches 1/2 a billion times, they must have called someone else the other half.

I've heard the same complaint. I just tell them "It's normal."

 

[peter d]

Smart is correct, there is no way that with everything else being the same that a non-metallic box would be a better heat sink than a metallic one.

I agree, but is this really an issue? If the heat sink on the dimmer itself is designed for it to operate correctly, does it need additional heat sinking? :-?