Safety of 14-50 to 6-20 adapter

[johnfluevogs]

First, I tried searching, but the system ignored the numbers (14, 50 etc) as generic...

Second, I fully understand operating 20a device (ie power tool) from a circuit protected only by a 50a breaker may allow the wires between the 14-50 receptacle and the device to see current in excess of their capacity. Perhaps this risk is low, but I acknowledge the risk still exists.

Therefore, I have concluded simple 14-50 to 6-20 are not a good idea. My question is: are the 14-50 to 6-20 adapters with built-in "surge protection" safe to use?

Final thought, it seems all these adapters are sold on Amazon and likely made from low, or very low, quality materials.....

 

[zbang]

Safe? Maybe if they have an internal overcurrent device; just a surge device doesn't cut it.

 

[winnie]

Safe? Maybe if they have an internal overcurrent device; just a surge device doesn't cut it.

Exactly. The receptacle needs proper overcurrent protection.

Such devices are available from reputable manufacturers.

https://www.homedepot.com/p/Southwire-Gas-Range-Adapter-9042SW8801/302183109 provides a fuse protected 5-15 receptacle from a range receptacle. I wouldn't want to run a power tool with it; the internal fuse is not replaceable. For the intended application of supplying control power to a gas range, it is perfect.

 

[jaggedben]

It's a general principle that a device with a cord and plug should never draw more amps than the cord and plug are rated for, and this is what protects the cord, plug, and device. The branch circuit OCPD does not protect the cord, plug and device in the same manner, it protects the receptacle and the wiring between the receptacle and the OCPD.

So as long as a plug adapter *reduces* the rated amps I don't see a safety issue. If the adapter went the other direction it would invite overloading the circuit tripping the breaker, which isn't good.

 

[Gene B]

NEC 210.21(B)(1) - "A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit."

(exceptions for arc welders etc)

An adapter with fuse is compliant because the "branch circuit" is the part after the fuse.

 

[LarryFine]

An adapter with fuse is compliant because the "branch circuit" is the part after the fuse.

I must disagree for a plug-in item.

 

[johnfluevogs]

NEC 210.21(B)(1) - "A single receptacle installed on an individual branch circuit shall have an ampere rating not less than that of the branch circuit."

(exceptions for arc welders etc)

An adapter with fuse is compliant because the "branch circuit" is the part after the fuse.

Are you saying the plug in adapter is considered a branch circuit?

In my case, the 14-50r would be permanently wired as a brach circuit with the proper breaker and appropriate sized wire.

 

[jaggedben]

Are you saying the plug in adapter is considered a branch circuit?

It's not. (If he was saying that then he's wrong.)

A plug in adapter is pretty much outside the scope of the NEC. Product standards would govern.

 

[johnfluevogs]

So I guess my concerns were unfunded and a 14-50r to 6-20 adapter would be safe to use to run power tools.

Thanks!

 

[jim dungar]

So I guess my concerns were unfunded and a 14-50r to 6-20 adapter would be safe to use to run power tools.

Thanks!

Not necessarily.
We are saying this adapter is beyond the scope of the NEC.
The NEC covers to the end of the branch circuit. It does not cover most equipment that is plugged in.

For example which part of the NEC protects #18 and #16 gauge extension cords feeding corded gardening tools like hedge clippers or leaf blowers?

 

[winnie]

It's a general principle that a device with a cord and plug should never draw more amps than the cord and plug are rated for, and this is what protects the cord, plug, and device. The branch circuit OCPD does not protect the cord, plug and device in the same manner, it protects the receptacle and the wiring between the receptacle and the OCPD.

So as long as a plug adapter *reduces* the rated amps I don't see a safety issue. If the adapter went the other direction it would invite overloading the circuit tripping the breaker, which isn't good.

I partially disagree.

The cords and such are designed with the assumption of a maximum supply OCPD in mind.

Something that plugs into a 5-15 receptacle might only draw 1A and have an 18ga cord. The design and listing assumes a maximum 20A OCPD.

I agree that a 20A OCPD does not protect an 18ga cord from overload, but I assume it does provide short circuit protection. Thus my partial disagreement.

Something that plugs into a 50A receptacle is designed with a 50A circuit in mind.

Jonathan

 

[jaggedben]

So I guess my concerns were unfunded and a 14-50r to 6-20 adapter would be safe to use to run power tools.

Thanks!

I think it's fine for one power tool that is intended to use a 6-20. But if you are modifying anything from its factory state or plugging in multiple tools with unfused distribution or otherwise jerry-rigging stuff then it could be unsafe.

 

[jaggedben]

Typing at the same time as Jon, but I take his point as well. There's an outside chance that a tool designed for 6-20 could be damaged if plugged into a 14-50 using the adapter, and the tool develops a problem that would trip a 20A breaker but doesn't trip a 50.

 

[johnfluevogs]

Thanks for the healthy discussion!

 

[johnfluevogs]

Weird thought....build an adapter with an in-line circuit breaker (20a)...

 

[winnie]

Uncommon to do this for a single converter 'cord'.

But a device called a 'spider box' is quite common. This has a high amp multi-phase input cord, has internal circuit breakers, and supplies a number of lower amp/lower voltage receptacles. For example, you might have a 3 phase 50A 208/120V inlet, then a bunch of 20A breakers, and then a set of 20A 120V duplex receptacles.

Jonathan

 

[retirede]

Typing at the same time as Jon, but I take his point as well. There's an outside chance that a tool designed for 6-20 could be damaged if plugged into a 14-50 using the adapter, and the tool develops a problem that would trip a 20A breaker but doesn't trip a 50.

If a tool “develops a problem” it’s already damaged.

 

[jaggedben]

If a tool “develops a problem” it’s already damaged.

I dunno, I'm imagining a jammed old radial saw that would be fine if a 20A breaker tripped after a few seconds but not fine if it somehow got left on on a 50A breaker for several minutes. Time matters when things are heating up.

 

[johnfluevogs]

Uncommon to do this for a single converter 'cord'.

But a device called a 'spider box' is quite common. This has a high amp multi-phase input cord, has internal circuit breakers, and supplies a number of lower amp/lower voltage receptacles. For example, you might have a 3 phase 50A 208/120V inlet, then a bunch of 20A breakers, and then a set of 20A 120V duplex receptacles.

Jonathan

A very appropriate solution indeed.

Temporary power distribution units are more expensive and possible overkill for someone needing a simple single low cost adapter. I concede, building an adapter will also cost money

 

[jim dungar]

I dunno, I'm imagining a jammed old radial saw that would be fine if a 20A breaker tripped after a few seconds but not fine if it somehow got left on on a 50A breaker for several minutes. Time matters when things are heating up.

Don't these types of saw have internal protection. I remember a red button opposite the blade on the radial saw I used in the 70's.