Jim
These are some good questions that have me looking at this thread in a different light.
First let me clear up the fact of testing. It is the National Recognized Testing Lab that sets forth the type of test to be done on a product. This product will be tested according to the purpose the manufacturer says the product is to be used. An example will be sliding glass doors and windows. The testing for sliding glass doors takes into consideration a child in a walker but the window will not. Both are glass.
In the example you gave of the coupling and the EGC it would be the flex that would have to conform to the requirements of the EGC not the coupling. If the flex does not meet the requirements then the use of the coupling to transition would not be allowed. There would be no need to test the coupling as a transition device if the flex would not meet the requirement therefore no testing is done.
Any appliance that comes with an EGC in the cord of the appliance will have exposed metal somewhere on that appliance. There are some appliances that have exposed metal that do not have an EGC included with the cord such as toasters. Why not toasters? It is a safety issue. Should the user of the toaster try to remove a piece of toast using a metal utensil while holding the toaster would complete a path from hot to the metal and should the metal be connected to the neutral in the service the person would be completing a conductive path and dead therefore no requirement for an EGC.
Both the National Electrical Code and the International Code Council has provisions for the use of a three wire appliance on a system that has no EGC. This can be achieved by the use of a GFCI device that protects the three wire receptacle in the absence of the EGC. These provisions allow the use of a three wire appliance without an EGC therefore anything wrote in the installation instructions that it must be connected to a receptacle that has an EGC is nullified. The use of a three wire receptacle without an EGC is allowed as long as it is GFCI protected.
The instructions that the appliance be connected to a receptacle that has an EGC is taking into consideration that the system already has an EGC installed. It is not there to say that the appliance has to have an EGC or it can’t be used on a system that has no equipment grounding conductor that has been installed in a compliant manner (GFCI protected as outlined in the NEC)
If the appliance that has an EGC is allowed to be used on a compliant installation that has no EGC in that system then how can the manufacturer mandate that this appliance cannot be used on the older systems that have no EGC within the system? They can’t.
There has been many times over the years that I have been asked to do an evaluation of an electrical system in older homes. Should there be three wire receptacles that have no EGC but are protected by a GFCI device I don’t have but one choice. I refer to section 406.4(D) of the National Electrical Code and report that the system is in compliance with the codes in effect and therefore no safety hazard.
Does this mean that the user can now use an appliance that has an EGC in the supply cord on this system? Most certainly. Well what about all that talk in the instructions of the appliance about a receptacle that is grounded? It is covered by the use of a GFCI which is far safer than an EGC.
Now let’s take everything into consideration concerning this recommendation to only use a receptacle that has an EGC attached. The codes allows the use of GFCI on receptacles that have no EGC so does this now mean that the use of an appliance that comes with a three wire cord is a violation? No.
As to seeing the installation instructions that are included with the listing and labeling of any appliance these Standards can be obtained for a piece and they are not cheap.
It would be much easier to just use the codes in effect at the time of the installation to make an inspection. The codes allow the installation of three wire receptacles without an EGC therefore any appliance that contains an EGC in the supply cord can be safely used on this systems that are in compliance with the codes.
So the question stills remains about a manufacturer mandating the use of a grounded receptacle for their use. The answer is so simple that we tend to overlook it. For future reference see 406.4(D) of the National Electrical Code.
(D) Replacements. Replacement of receptacles shall comply with 406.4(D)](http://code.necplus.org/document.php?field=jd&value=necss:70-2011:id02011009172#70-2011:id02011009172)(1) through (D)(6), as applicable.
(1) Grounding-Type Receptacles. Where a grounding means exists in the receptacle enclosure or an equipment grounding conductor is installed in accordance with 250.130©](http://code.necplus.org/document.php?field=jd&value=necss:70-2011:id02011004494#70-2011:id02011004494), grounding-type receptacles shall be used and shall be connected to the equipment grounding conductor in accordance with 406.4©](http://code.necplus.org/document.php?field=jd&value=necss:70-2011:id02011009166#70-2011:id02011009166) or 250.130©](http://code.necplus.org/document.php?field=jd&value=necss:70-2011:id02011004494#70-2011:id02011004494).
(2) Non–Grounding-Type Receptacles. Where attachment to an equipment grounding conductor does not exist in the receptacle enclosure, the installation shall comply with (D)(2)(a), (D)(2)(b), or (D)(2)©.
(a) A non–grounding-type receptacle(s) shall be permitted to be replaced with another non–grounding-type receptacle(s).
(b) A non–grounding-type receptacle(s) shall be permitted to be replaced with a ground-fault circuit interrupter-type of receptacle(s). These receptacles shall be marked “No Equipment Ground.” An equipment grounding conductor shall not be connected from the ground-fault circuit-interrupter-type receptacle to any outlet supplied from the ground-fault circuit-interrupter receptacle.
© A non–grounding-type receptacle(s) shall be permitted to be replaced with a grounding-type receptacle(s) where supplied through a ground-fault circuit interrupter. Grounding-type receptacles supplied through the ground-fault circuit interrupter shall be marked “GFCI Protected” and “No Equipment Ground.” An equipment grounding conductor shall not be connected between the grounding-type receptacles.