NEC & Adapters

TuckerD

Active Member
Joined
Mar 1, 2012
Location
Rochester, NY
Hello all,

Some questions about adapters as defined by section 520 of the NEC.
520.2 Definitions.

Adapter.
A device used to adapt a circuit from one configuration of an attachment plug or receptacle to another configuration with the same current rating.

520.67 Multipole Branch-Circuit Cable Connectors. Multipole branch-circuit conductors shall be constructed so that tension on the cord or cable is not transmitted to the connections. The female half of shall be attached to the load end of the power supply cord or cable. The connector shall be rated in amperes and designed so that differently rated devices cannot be connected together; however, a 20-ampere T-slot receptacle shall be permitted to accept a 15-ampere attachment plug of the same voltage rating. Alternating-current multipole connectors shall be polarized and comply with 406.7 and 406.10

520.69 Adapters. Adapters, two-fers, and other single- and multiple-circuit outlet devices shall comply with 520.69(A), (B), and (C).

(A) No Reduction in Current Rating. Each receptacle and it's corresponding cable shall have the same current and voltage rating as the plug supplying it. It shall not be utilized in a stage circuit with a greater rating.

(B) Connectors. All connectors shall be wired in accordance with 520.67

(C) Conductor Type. Conductors for adapters and two-fers shall be listed extra-hard usage or listed hard usage (junior hard service) cord. Hard usage (junior hard service) cord shall be restricted in overall length to 2.0 m (6.6 ft).
One of our local venue's power distro has some pigtail boxes with the aforementioned 20-amp T-type receptacle. If I want to plug in a fixture with the common 5-15 type connector, I could plug it in directly if it was close by. According to the exemption given by 520.67 this is fine. If I want to plug it into that circuit over some distance, however, then I will need an extension cable. If that cables male end is the 5-15 type connector then it's female end must be the 5-15 receptacle (no reduction in current rating). Is it acting as an adapter in this case since it is being used to convert from a T-type configuration to a PBG type configuration (and due to the 520.69 exemption the male 5-15 is allowed to connect with the 5-20 receptacle).

Once the connection to the load is made is this adapter being used in a circuit with a higher rating (a violation of 520.69 (A)? What if I used an extension cable with 5-20 T-type connectors; I assume this would be fine because the extension cable would not be an adapter and the cable on the fixture (5-15) is allowed to connect to the T-type receptacle.

If my pigtails had stage pin connectors and I used a stage-pin to NEMA 5-20 adapter would I then be allowed to use a more 'normal' 5-15 extension cord to get to my fixture with a 5-15 type plug? In that case is the circuit considered a 20a circuit, in which case there are now underrated plugs?

To clarify, I know what is done most places. And I know that the 5-15 and 5-20 connectors are almost identical. My questions are really more about standards interpretation.
 
Last edited:

Apmccandless

Active Member
Joined
Oct 20, 2013
Location
Missouri
I cannot speak to the code compliance but I would warn against using 5-15 plugs for 20 amp loads. A company I used to work for used them in this way then we started to notice a higher failure rate than expected in our connectors. We traced the issue back to the 5-15 plugs we were using being only rated to 1800W. We were loading them higher than that and over the course of events the connectors would become soft and then fuse together. When we checked even though the connectors looked the same as the 5-20's of the same brand the thickness of the blades was less and the plastic housing melted at a lower temperature. Just a warning even though it may seem like they are the same that does not mean that all of the components are made to the same spec.
 

MNicolai

Well-Known Member
Fight Leukemia
Joined
Mar 30, 2008
Location
Sarasota, FL
Sort of two things at play.

1) Don't exceed the rating of your weakest connector in the chain. You are permitted to plug a 15 into a 20, but shouldn't operate it above the rating of the 15.

2) Don't build adapters that reduce the cable ampacity from one end of the cable to the other. To get a little silly here, let's say you made a cable with a 50A 2P&G male and a 20A 2P&G female and then plugged it into a 50A receptacle. It would be very easy to drive the cable over the ampacity rating of the 20A connector and your connector would melt into oblivion well before your overcurrent protection would trigger and kill power to that circuit. If you put 35A onto the cable, it's likely your upstream circuit breaker wouldn't engage until after your connector and cable had already melted into goo. There are a number of cables out there that qualify as "suicide cables", and this is one of them.
 

STEVETERRY

Well-Known Member
Joined
Aug 12, 2007
Location
New York
Hello all,

Some questions about adapters as defined by section 520 of the NEC.


One of our local venue's power distro has some pigtail boxes with the aforementioned 20-amp T-type receptacle. If I want to plug in a fixture with the common 5-15 type connector, I could plug it in directly if it was close by. According to the exemption given by 520.67 this is fine. If I want to plug it into that circuit over some distance, however, then I will need an extension cable. If that cables male end is the 5-15 type connector then it's female end must be the 5-15 receptacle (no reduction in current rating). Is it acting as an adapter in this case since it is being used to convert from a T-type configuration to a PBG type configuration (and due to the 520.69 exemption the male 5-15 is allowed to connect with the 5-20 receptacle).

Once the connection to the load is made is this adapter being used in a circuit with a higher rating (a violation of 520.69 (A)? What if I used an extension cable with 5-20 T-type connectors; I assume this would be fine because the extension cable would not be an adapter and the cable on the fixture (5-15) is allowed to connect to the T-type receptacle.

If my pigtails had stage pin connectors and I used a stage-pin to NEMA 5-20 adapter would I then be allowed to use a more 'normal' 5-15 extension cord to get to my fixture with a 5-15 type plug? In that case is the circuit considered a 20a circuit, in which case there are now underrated plugs?

To clarify, I know what is done most places. And I know that the 5-15 and 5-20 connectors are almost identical. My questions are really more about standards interpretation.
A 5-15P is allowed to connect to a 5-20R. That is not considered an adapter. However, the 5-15 cable may never carry more than the rating of the 15A connectors, providing the cable in the extension is rated up to that load.

ST