Leviton OBC AFCI Receptacle Is Sensitive to Amateur Radio Transmissions

[gary]

I recently installed three of the new Leviton AFTR1 receptacles in my 1977 era condominium. I had to slightly modify the existing wiring to position them as the first device in each of three circuits, but found I was able to provide AFCI protection for all of the bedroom and living room receptacles and all of the lighting circuitry. If this quote from a Leviton brochure is accurate, we will be required to install a lot of these in the future:"Leviton?s Smart lock Pro OBC AFCI receptacle can also be used to meet the NEC requirements for replacement receptacles that take effect in 2014.
NEC 406.4(D) states, "Arc-Fault Circuit-Interrupter Protection. Effective January 1, 2014, where a receptacle outlet is supplied by a branch circuit that requires arc-fault circuit interrupter protection [210.12(A)], a replacement receptacle at this outlet must be one of the following:
(1) A listed outlet branch circuit type arc-fault circuit interrupter receptacle
(2) A receptacle protected by a listed outlet branch circuit type arc-fault circuit interrupter type receptacle
(3) A receptacle protected by a listed combination type arc-fault circuit interrupter type circuit breaker."
Although something of an AFCI skeptic, I have to admit that it felt good to know that my 35 year old wiring was now being protected by this state of the art safety technology. That was before I found out that the AFCI protecting the circuit in my bedroom / home office / ham shack tripped immediately whenever I tried to use my 100 watt amateur radio transmitter. I found that transmitting with as little as 5 watts could cause the bedroom AFCI to trip! The cord on my transceiver is long enough to reach an exterior receptacle on another non-AFCI circuit and I was sure that would solve the problem, but again I found that a low power transmission would instantly trip the bedroom AFCI. I called Leviton and asked for a suggestion. A CSR suggested that I swap two of the AFTR1's to make sure I didn't have a defective device. That seemed like a reasonable suggestion, but I found it didn't alter the problem. The AFCI is apparently reacting to electromagnetic energy induced in the house wiring by these radio transmissions. I called Leviton again and talked to another CSR who seemed quite interested because he said this was the first time anyone had reported a problem like this. That was late on a Friday afternoon and they were getting ready to close for the weekend but he assured me I would get a phone call or email from someone from their engineering department on the following Monday. I never heard back from them, of course, but wanted to put the word out that radio transmissions from a nearby ham or CB operator can definitely cause these things to trip. Due to restrictive CC&R's, many amateur radio operators have been forced to use "stealth" antennas hidden in attics, under eves, or disguised as flag poles, so it may not be obvious that random false tripping is being caused by the ham next door.

 

[GoldDigger]

The AFCI is apparently reacting to electromagnetic energy induced in the house wiring by these radio transmissions.

This has been mentioned here in the context of public safety handheld radios too. But probably not cell phones.
In some cases putting the AFCI receptacle in a metal box with metal cover plate may help. If the problem really is from signal conducted over the power wires, you may be able to add specific frequency traps to the wires in and out of the box without compromising the AFCI function. But that sort of field constructed power line filter will not be listed equipment.
A 100 watt transmitter is a pretty strong signal source. The earlier thread involved a 5 watt (?) handheld UHF radio.

 

[gary]

This has been mentioned here in the context of public safety handheld radios too. But probably not cell phones. <br>
In some cases putting the AFCI receptacle in a metal box with metal cover plate may help. If the problem really is from signal conducted over the power wires, you may be able to add specific frequency traps to the wires in and out of the box without compromising the AFCI function. But that sort of field constructed power line filter will not be listed equipment. <br>
A 100 watt transmitter is a pretty strong signal source. The earlier thread involved a 5 watt (?) handheld UHF radio.

100 watts probably sounds like a lot of power, but that is the typical rating of an average HF band amateur radio transceiver. Properly licensed, hams can legally use up to 2000 watts PEP on certain frequencies. As long as they are properly licensed and are not using defective equipment, they can legally ignore the fact that their hobby is causing interference to their neighbor's TV or causing their AFCI breakers or receptacles to trip. That's because those devices are required to be designed and built to withstand lawful radio transmissions. I currently have the problem outlet connected as just an AFCI receptacle, with the line & load conductors both connected to the LINE terminals. Connected this way, the AFTR1 is immune to my radio transmissions, so I don't think placing it in a metal enclosure would make any difference. Of course, it is kind of pointless to use it this way because AFCI protection is limited to what ever load is plugged into this one outlet and offers no benefit to the house wiring at all. In an unrelated mater, I noticed in the installation instructions that there was a warning not to use it on a circuit that powers life support equipment because if the AFCI trips it will shut down the equipment. I don't recall seeing a warning like that on any of the AFCI breakers I've installed and I don't think there is an exemption in the NEC that would allow for non AFCI protected receptacles in a residential bedroom. I have a brother-in-law with a sleep apnea problem who relies on CPAP breathing machine to get through the night. Any thoughts on this particular issue?

 

[GoldDigger]

I don't recall seeing a warning like that on any of the AFCI breakers I've installed and I don't think there is an exemption in the NEC that would allow for non AFCI protected receptacles in a residential bedroom. I have a brother-in-law with a sleep apnea problem who relies on CPAP breathing machine to get through the night. Any thoughts on this particular issue?

Just a power failure alarm to make sure he wakes up to reset the breaker. At least that way he can sleep securely for the rest of the night.

 

[texie]

Well, it seems to me to be just yet another example of AFCI vodoo. If you push hard enough, the manufacturer(s) and UL will come up with a million reasons why your application is not stable-it's not the AFCI but rather your situation. But that is no help to the user. This whole AFCI situation is an embarressment to the trade.