Plug In Cord/ 20A Circuit Breaker

[fifty60]

I am trying to figure out what regulations would apply to a machine that plugs into a 20A wall outlet. The power chord/plug is the only means of disconnect. Does every wire in the device have to be at least 12AWG to coincide with the 20A wall outlet? I am familiar with UL 61010-1, but I would like to know what non-UL approaches I can take to sizing conductors inside of this kind of machine. Thanks in advance.

 

[mgookin]

I am trying to figure out what regulations would apply to a machine that plugs into a 20A wall outlet. The power chord/plug is the only means of disconnect. Does every wire in the device have to be at least 12AWG to coincide with the 20A wall outlet? I am familiar with UL 61010-1, but I would like to know what non-UL approaches I can take to sizing conductors inside of this kind of machine. Thanks in advance.

Q: Does every wire in the device have to be at least 12 AWG to coincide with the 20A wall outlet?
A: No. That 20A wall outlet is there because you're in a commercial/ industrial environment and that's the minimun standard by NEC but NEC stops at that outlet. Your cord and everything after the cord (inside the machine, for example) are sized based on the load going through the conductors with insulation or spacing between exposed contacts relative to the voltage. Is this a one-time build in an industrial plant? Or something you're submitting for UL Listing on as a product to be sold?

The main concern is going to be temperatures in either case. For our products going to market, we use an environmental test chamber to test junction temps throughout the rated operating range to verify our designs before submitting for UL Listing. As far as a conductor size, it's simple physics. How long is your wire, what is the resistance, what's going through it, etc. Insulation type is a function of the environment/ exposure which could include high temps, oil, solvents, etc. depending on what you're building.

 

[fifty60]

The eventual interest is to meet the UL standards. The particular machine plugs into the 120V 20A receptacle. The machine consists of control components, small motors, and a heater. The motors have integral thermal protection, so I know they are protected using #16AWG MTW. The heater draws 6A. Do I have to supply a seperate fuse for the heater if I want to use #16AWG for the heater? It sounds like you are saying no, that it only has to be sized to the circuit load.

 

[templdl]

I am trying to figure out what regulations would apply to a machine that plugs into a 20A wall outlet. The power chord/plug is the only means of disconnect. Does every wire in the device have to be at least 12AWG to coincide with the 20A wall outlet? I am familiar with UL 61010-1, but I would like to know what non-UL approaches I can take to sizing conductors inside of this kind of machine. Thanks in advance.

This is my interpretation of your question:
If the plug in cord is sized to carry the device that it is supply it may be viewed similar to a tap conductor. The device/load Determines the load that the cord carries. If you have a 20a circuit and then plug in a device with a cord rated 15a then it is the device that determines the load. Cords/plugs that are actually rated 20a would have a different male plug configuration as does the female receptacle. A cord that is rated 20a would have a plug that can not be plugged into a receptacle rated 15a.

Now, the caveat is should an extension cord be used which is where one's intelligence must be used.

 

[fifty60]

So where can I see rules that govern beyond the plug of a 20A receptacle? Does the NEC really stop at the 120V 20A receptacle? Is this a special case? Are 120V receptacles above 20A governed by a different set of rules? I am just trying to figure out why I do not have to fuse the individual conductors inside of the machine that plugs into a standard 20A outlet. I know there are definitely space limitations involved with smaller machines. I would like to find the code section that explains this.

 

[GoldDigger]

So where can I see rules that govern beyond the plug of a 20A receptacle? Does the NEC really stop at the 120V 20A receptacle? Is this a special case? Are 120V receptacles above 20A governed by a different set of rules? I am just trying to figure out why I do not have to fuse the individual conductors inside of the machine that plugs into a standard 20A outlet. I know there are definitely space limitations involved with smaller machines. I would like to find the code section that explains this.

Many of these situations are governed by UL standards rather than government adopted codes. You have to pay to see those standards.

 

[fifty60]

What if my machine does not require a UL certification? The conductors need to be sized to the load they carry, with no extra overcurrent protection other than the 20A breaker protecting the wall receptacle? If so, does anyone know why?

 

[Volta]

So where can I see rules that govern beyond the plug of a 20A receptacle? Does the NEC really stop at the 120V 20A receptacle? Is this a special case? Are 120V receptacles above 20A governed by a different set of rules? I am just trying to figure out why I do not have to fuse the individual conductors inside of the machine that plugs into a standard 20A outlet. I know there are definitely space limitations involved with smaller machines. I would like to find the code section that explains this.

In my interpretation, no. There are many instance in the NEC where the NEC considers loads connected to a receptacle outlet. If an appliance or industrial machine however, other codes will apply.

 

[cadpoint]

Many of these situations are governed by UL standards rather than government adopted codes. You have to pay to see those standards.

This in not exactly true I just went to UL.com and went to Standards and read all about UL 61010-1.

I beleive the OP can't beleive that the NEC stops at the device.

The wire gauge 16AWG MTW is not listed in what equates to a set of wires (From NEC Table 310-16), but this is the circuit that makes up the cord, not the circuit that it connects too...

A AWG chart

 

[fifty60]

The power chord is 12/3 cable. The plug of this cable connects to the 120V 20A wall receptacle. The load end of the cable connects to terminal blocks inside of my machine. Inside the machine I have several seperate runs of 16AWG MTW. We do not use any seperate fusing inside of the machine, and I am wondering why this is. I would like to know if all of the seperate conductors inside of the machine need to be protected. Since the only OCPD for the entire machine is the 20A breaker at the receptacle, my initial question was why the conductors inside of the machine do not have to be at least #12AWG.

For small motor loads inside the machine that have internal thermal protection, that makes sense to me why they would not have to have any other protection because their conductors are protected by the thermal protection. But for the remaining resistive load circuits inside the machine, can I really use #16AWG for them and not have a 10A OCPD to protect the #16AWG wire?

I can understand why UL inspectors would probably not like to see a 5A resistive load using #16AWG with no other protection than the 20A breaker from the receptacle. But outside of UL or CSA, is there anything that says I cannot use #16AWG inside of the machine without a seperate OCPD (10A) to protect the wire?

 

[GoldDigger]

This in not exactly true I just went to UL.com and went to Standards and read all about UL 61010-1.

Reading all about a standard (in the case mentioned, UL 61010-1) is a lot different from reading the standard!
If I am not a UL Certification Customer (which I am not), I can pay the trivial sum of $576.15 for a print version or more for an electronic version. A bit pricier than the NEC, which you can still read for free as long as you do not want to be able to carry a copy or do detailed searches.

 

[Little Bill]

Q: Does every wire in the device have to be at least 12 AWG to coincide with the 20A wall outlet?
A: No. That 20A wall outlet is there because you're in a commercial/ industrial environment and that's the minimun standard by NEC but NEC stops at that outlet.

Where does it say in the code that you are required to have a 20A receptacle in a commercial/industrial environment?
I know the 20A receptacles are usually a little "beefier" than 15A ones, but even if the circuit is 20A, you can still use a 15A receptacle per table 210.21(B)(3)
I will say the norm is to install 20A in commercial/industrial, but don't see where they are required.

Unless you are talking about a single receptacle which must be rated the same as the branch circuit. But then you could use a 15A single receptacle if the circuit was 15A.

 

[cadpoint]

One could make any requirement for work from the manufacture via, Article 110.3

 

[mgookin]

Where does it say in the code that you are required to have a 20A receptacle in a commercial/industrial environment?
I know the 20A receptacles are usually a little "beefier" than 15A ones, but even if the circuit is 20A, you can still use a 15A receptacle per table 210.21(B)(3)
I will say the norm is to install 20A in commercial/industrial, but don't see where they are required.

Unless you are talking about a single receptacle which must be rated the same as the branch circuit. But then you could use a 15A single receptacle if the circuit was 15A.

Change the word receptacle to circuit. My appologies.

 

[mgookin]

UL cares if it's going to electrocute someone or catch fire. UL = Underwriter's Laboratories = Insurance Companies. They only care about insurance claims. They lobby the hell out of legislators and that's why you need insurance on everything in your life so Warren Buffet gets richer and you get poorer.

Now as the manufacturer if you want to protect the equipment from damage from events such as rotor lock, overload, etc. you can put fuses inline with those conductors. But that's your choice. UL does not care unless that fuse is to prevent electrocution or fire.

As a manufacturer you set the specs for the equipment. If you say it's only rated to operate from -200 to -150 degrees C, you can get by with some pretty light wiring. You have to design it for your needs and the needs of your customers if you're selling it.

 

[fifty60]

I am still having trouble with this one. I know some applications require no less than 14AWG even if the amp draw is sufficient for #16AWG. But if the circuit can use #16AWG, I am free to use #16AWG wiring without a fuse as long as the load is less than the ampacity of the #16AWG wire? Are fuses only REQUIERED on circuits that require 14AWG ampacities and above?

 

[GoldDigger]

I am still having trouble with this one. I know some applications require no less than 14AWG even if the amp draw is sufficient for #16AWG. But if the circuit can use #16AWG, I am free to use #16AWG wiring without a fuse as long as the load is less than the ampacity of the #16AWG wire? Are fuses only REQUIERED on circuits that require 14AWG ampacities and above?

You seem to be approaching this from the wrong direction. Fuses (or other overcurrent devices) are REQUIRED by the NEC where the code says they are required. That would be within the wiring system itself, as covered by the NEC, which may work in conjunction with load devices that either will or will not have their own internal overcurrent protection.

Within load equipment, UL (not NEC) may have specific requirements for various types of equipment, and in addition any manufacturer has an obligation under civil law not to produce something they know is unsafe.
Only you (or your engineer) know what constitutes a safe way to build equipment to do what you want done.

The NEC is not a design tool.

 

[suemarkp]

What is the ampacity of your 16 AWG wire? Is it in free air or in a big bundle? Does it have 105C insulation, 90C, or 75C? There are many factors that will determine how much current can go through those wires without causing a problem. Go small enough, and your wires are now a fusible link. If they melt, and are contained in a metal box, that still may not be a problem.

Many areas are now requiring just about anything that plugs in to be UL or NRTL listed/certified. We've got that to deal with here in WA. The only trouble is enforcing it. I can buy a Chinese blender that isn't listed and plug it into my kitchen. That would be a violation of the WAC, but there's no inspector here to catch it. They try to stop it at the seller, but they can't with online sales. I still see stuff at Home Depot that isn't listed (e.g. generators). We also get stopped when pulling a permit to do something (e.g. move an old hard wired drill or mill to another building). Being hard wired on its own circuit, we need to pull a permit. The inspector will check that old device for a UL or NRTL label and fail the install if it isn't listed/certified.

 

[Volta]

I am still having trouble with this one. I know some applications require no less than 14AWG even if the amp draw is sufficient for #16AWG. But if the circuit can use #16AWG, I am free to use #16AWG wiring without a fuse as long as the load is less than the ampacity of the #16AWG wire? Are fuses only REQUIERED on circuits that require 14AWG ampacities and above?

In my opinion one large reason for the smaller limit of building wire generally being 14 AWG is mechanical in nature rather than purely from an ampacity position.

 

[Little Bill]

In my opinion one large reason for the smaller limit of building wire generally being 14 AWG is mechanical in nature rather than purely from an ampacity position.

Can you explain what you mean by this? I'm not following the "mechanical" part.:?