Wiring Question

[kencombs]

That's not correct.

Working in a facility that has seven of its own substations, indoors, with 15kV feeders, 1200A bus feeds, and bus plugs/drops distributed all over its 400,000+ ft² ceilings, there is NO NFPA limitation on service cord length. There are practical limits, and I/R drop restrictions, but national codes do not prohibit that. Using strain reliefs at cord terminations, suspension at intervals that meet NEC tables, and appropriate caps/plugs for connections will make it perfectly acceptable.

Local jurisdictions' inspectors often have their own opinions, however. To circumvent that, one needs only to ask them for a published copy of their code(s). That usually shuts them up permanently since with the exception of larger counties and cites, most municipalities never truly formalize their "codes' and if they do, anything that contradicts NEC can be disputed, while restrictions that adhere to NEC but are more stringent usually cannot. There again, pointing out the codes published by NFPA including the exceptions and details will often resolve any discrepancies.

Residential inspectors are actually the worst to deal with, since they need to be educated just about every time they show up, and yet can still become a PITA for approvals. Appealing their misjudgements usually only annoys them, so even when they are educated and overturned they continue to be obstacles.

That said, the EMT/THWN solution is certainly "code" about everyw

The issue isn't about length at all. The problem is finding a recpt and cord cap with the appropriate HP rating. All I can find locally either have no HP rating or it is only 2 or 3.

That said, I've successfully used "normal" 30 and 50 amp recpt's with 5hp motors for years, but never had them passed by an inspector. Recpts were there at inspection, but not cord plugged in.

I don't consider it a practical issue as they are fine as long as they are never unplugged under load. My understanding of the motor rating is to withstand plugging or unplugging when loaded. Just don't do that and it should be OK.

EMT is allowed to be used as the safety ground. One must take care to make excellent connections though. I use only compression connectors and grounding bushings at both ends.

 

[TerryfromSWIowa]

The issue isn't about length at all. The problem is finding a recpt and cord cap with the appropriate HP rating. All I can find locally either have no HP rating or it is only 2 or 3.

That said, I've successfully used "normal" 30 and 50 amp recpt's with 5hp motors for years, but never had them passed by an inspector. Recpts were there at inspection, but not cord plugged in.

I don't consider it a practical issue as they are fine as long as they are never unplugged under load. My understanding of the motor rating is to withstand plugging or unplugging when loaded. Just don't do that and it should be OK.

EMT is allowed to be used as the safety ground. One must take care to make excellent connections though. I use only compression connectors and grounding bushings at both ends.

Nwever heard of HP rating for plugs or receptacles. Always went with Full load amp rating.

 

[Watthour]

Nwever heard of HP rating for plugs or receptacles. Always went with Full load amp rating.

... At an 80% load factor.

As for cord caps and connectors, there are offerings from Hubbell, Meltric, and all their clones up to 200A off the shelf and more with special order. These are at supply houses, not home centers. They are made to conduct and decontact (vacuum break) loads up to their full rating, as in a running piece of equipment -without flashover. Most of then are available with wall mounts pipe mounts, and cord grips for instances like this.

 

[Geo-TH,In]

Is it ok to run 10-3 rubber jacketed wire from a breaker box to a 220 volt air compressor, or do I have to run Romex to a box with a receptacle and from the box to the compressor with rubber coated wire with a plug? I have a bunch of rubber covered 10-3 I could use but the romex is very expensive. I have a 30 amp 220v breaker.

I would use what I have. I Run my welder off a 50 ft 10-3 extension cord and use a 30 amp breaker

 

[kencombs]

Nwever heard of HP rating for plugs or receptacles. Always went with Full load amp rating.

They are available. The need and code requirement is buried in Nec article 430. Way to many detailed references to to list, but it's in there.

Here is some info from one business that handles them:
RS America, part of RS Industrial Solutions & Electronic Components, offers a variety of motor-rated plugs, which are robust industrial power connectors. These plugs come in different NEMA and IEC configurations, featuring various voltage and amperage ratings (e.g., 20A, 16A, 15A) and are built for heavy-duty applications with durable housing and sometimes IP-rated protection against dust and water. Common options include NEMA L6 twist-lock plugs for secure connections and industrial power plugs with screw terminals or quick connects, available at the RS website.


Types of motor-rated plugs

• NEMA Plugs: These are used for AC mains electricity in North America and other countries following similar standards.
  • NEMA L6 twist-lock: Designed for secure connections in industrial settings where vibration is a factor. They are rated for up to 250V and are available in 20A and 30A versions.
  • NEMA 5-15P: A common 3-pin USA plug rated for 15A and 125V.
  • NEMA L21-20P: A 20A plug rated for 120/208V, available as a cable mount.
• IEC Connectors: These are standard power connectors used in a wide range of equipment.
  • IEC C14/C19/C20: Available as both plugs and sockets, with various current and voltage ratings. For example, a C20 cable mount plug rated for 16A at 250V or a C19 panel mount socket rated for 16A at 250V.

Key features

• Voltage and Current: Plugs are available in a range of ratings, such as 125V, 250V, and higher voltages, with common amperage ratings including 15A, 16A, 20A, and 30A.
• Durability: They often feature robust housing made from durable materials like Nylon 6 and ABS, suitable for challenging industrial environments.
• Protection: Some plugs have an IP rating, such as IP44 or IP67, which indicates protection against dust and water.
• Connection type: Available with different connection types, such as screw terminals, quick connect, or solder/faston terms.

• RS PRO 8606738 NEMA 5-15P 3-Pin USA Main Plug, 15A, Cable ...
  RS PRO 8606738 NEMA 5-15P 3-Pin USA Main Plug, 15A, Cable Mount, 125 V ac, Simple Connect.
  RS – Industrial Solutions & Electronic Components

​

​

​

Electrical Connectors, Power Out​

• 
  
  
• RS PRO 7769113 C14 Cable Mount IEC Connector Plug Screw ...
  Overview * RS PRO 488191 C14 Panel Mount IEC Connector Plug Solder Spade Term. Rated At 10A 250 Vac. * RS PRO 7769125 C20 Cable Mo...
  RS – Industrial Solutions & Electronic Components
  
  
• 
  
  
• RS PRO 8179375 NEMA L6 Twist Lock Main Plug, 20P, 20A USA ...
  NEMA connectors are power plugs and receptacles used for AC mains electricity in North America and other countries that use the st...
  RS – Industrial Solutions & Electronic Components
  

 

[Jim.ME]

They are available. The need and code requirement is buried in Nec article 430. Way to many detailed references to to list, but it's in there.

Here is some info from one business that handles them:
RS America, part of RS Industrial Solutions & Electronic Components, offers a variety of motor-rated plugs, which are robust industrial power connectors. These plugs come in different NEMA and IEC configurations, featuring various voltage and amperage ratings (e.g., 20A, 16A, 15A) and are built for heavy-duty applications with durable housing and sometimes IP-rated protection against dust and water. Common options include NEMA L6 twist-lock plugs for secure connections and industrial power plugs with screw terminals or quick connects, available at the RS website.


Types of motor-rated plugs

• NEMA Plugs:These are used for AC mains electricity in North America and other countries following similar standards.
  • NEMA L6 twist-lock: Designed for secure connections in industrial settings where vibration is a factor. They are rated for up to 250V and are available in 20A and 30A versions.
  • NEMA 5-15P: A common 3-pin USA plug rated for 15A and 125V.
  • NEMA L21-20P: A 20A plug rated for 120/208V, available as a cable mount.
• IEC Connectors:These are standard power connectors used in a wide range of equipment.
  • IEC C14/C19/C20: Available as both plugs and sockets, with various current and voltage ratings. For example, a C20 cable mount plug rated for 16A at 250V or a C19 panel mount socket rated for 16A at 250V.

Key features

• Voltage and Current: Plugs are available in a range of ratings, such as 125V, 250V, and higher voltages, with common amperage ratings including 15A, 16A, 20A, and 30A.
• Durability: They often feature robust housing made from durable materials like Nylon 6 and ABS, suitable for challenging industrial environments.
• Protection: Some plugs have an IP rating, such as IP44 or IP67, which indicates protection against dust and water.
• Connection type: Available with different connection types, such as screw terminals, quick connect, or solder/faston terms.

• RS PRO 8606738 NEMA 5-15P 3-Pin USA Main Plug, 15A, Cable ...
  RS PRO 8606738 NEMA 5-15P 3-Pin USA Main Plug, 15A, Cable Mount, 125 V ac, Simple Connect.
  RS – Industrial Solutions & Electronic Components

​

​

​

Electrical Connectors, Power Out​

• 
  
  
• RS PRO 7769113 C14 Cable Mount IEC Connector Plug Screw ...
  Overview * RS PRO 488191 C14 Panel Mount IEC Connector Plug Solder Spade Term. Rated At 10A 250 Vac. * RS PRO 7769125 C20 Cable Mo...
  RS – Industrial Solutions & Electronic Components
  
  
• 
  
  
• RS PRO 8179375 NEMA L6 Twist Lock Main Plug, 20P, 20A USA ...
  NEMA connectors are power plugs and receptacles used for AC mains electricity in North America and other countries that use the st...
  RS – Industrial Solutions & Electronic Components

I believe you use the motor HP and other information of the motor to select correct plug to meet or exceed the voltage and amperage for the motor you are dealing with. All the plug specs you just posted are referring to voltage and amperage, I don't see one that calls out that it is for a certain horsepower motor.

 

[kencombs]

I believe you use the motor HP and other information of the motor to select correct plug to meet or exceed the voltage and amperage for the motor you are dealing with. All the plug specs you just posted are referring to voltage and amperage, I don't see one that calls out that it is for a certain horsepower motor.

That section of the company's product listing begins " RS America, part of RS Industrial Solutions & Electronic Components, offers a variety of motor-rated plugs," as noted in my last post.

All of them those listed motor rated. That company sells lots of others that are not motor rated, but that list are all so rated. All plugs that are rated for motor service say so on the product, package or specs. They are designed to withstand not only the rated amperage but the input surge of a motor start, over and over. They can also be connected and disconnected under load, without failing.

Of course, you, I, and anyone else is free to use whatever we want and can get inspection approval for. I've used a 30 dryer cord and receptacle many times for my air compressors over the years, even a 50a range version for a bigger compressor. Nothing burned down (or up) but that doesn't mean it was 'up to code.
NEC 430 is a long read, but contains a lot of good info.

Even Geo's welder hookup mentioned earlier is OK per code, not in 430 but other sections. My welder also runs on a 30A breaker,but 10ga wire, just because I had 10. Duty cycle for welders allows such.

I

 

[TheBartman47]

I believe you use the motor HP and other information of the motor to select correct plug to meet or exceed the voltage and amperage for the motor you are dealing with. All the plug specs you just posted are referring to voltage and amperage, I don't see one that calls out that it is for a certain horsepower motor.

1 horsepower = about 735 watts, and wats = voltage times amperage, so size cable and breaker accordingly for a given horsepower rating motor.