30A receptacle with 20A circuit breaker

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at our yacht club we have outside boat storage. the smaller craft have a panel serving 20 pedastels each with an oulet. The standard boat outlet is 30 @120. My inspector made me remove the 30 a receptacles and replace them with a 20. This was about 4 years ago.Each was served by a #12 thhn and protected by a 20 amp breaker. The 30 a receptacles were for the convenience of plugging in the standard cords. The result was that a receptacle adapter device or a 20/30 patch cord had to be made up for each boat using the standard cord. The reality was that after a period of time these receptacles began mysteriousy morphing in the middle of the nite back to thier original 30 amp state. Dont know how that happened and will never admit it if i did.
 
I often find 10-50's on a 30A with #10 TW wire to a dryer.
I used to have all these 30A L15-30R receptacles in a large bakery every where. Some on 20A ckts with 12 AWG THHN some on 30A ckts with 10 THHN some on 15A ckts with 14 or 12 THHN.

In all these cases they were individual branch circuits. In the bakery I observed large hobart mixers requiring a 30A circuit being moved and plugged in to a different receptacle. Now you have a 30A piece of equipment on a 15A ckt with a 30A receptacle.

I generally replace the receptacle with the one of correct rating. The guts of a L15-30 are the same as a L15-20 open up some old ones.
If the centrifuge comes with a moulded L15-30 cord cap and MFR instructions dont spec a 20A max OCPD then I pull in 10's and put it on a 30.

Sure you cant plan for what stupid is going to come around and do later but in a lab you have people with common sense when they go to get a different centrifuge some day they will probably look at the rating of the twistlock to see what they can plug in. Perhaps a label on the cover plate "20A load max" if you cant get them to pay you to re pull the circuit.
 
cpiper said:
I observed an existing installation with 30A 208V receptacles with 3/12 MC cable spliced to #10 THHN wire that runs back to the panel that lands on a 20A/2P breaker. A centrifuge is plugged into the receptacle and the nameplate data lists its ampacity at 20A. While this doesn't seem like a good design, is it Code compliant? Is there anywhere in the Code that says you can't have a 20A circuit connected to a 30A receptacle? Also, I believe the 20A circuit breaker would need to be 100% rated. Opinions?
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In 1968 language was added to 210.21, sub-section (b), that said,
"Grounding type receptacles shall be installed only on circuits of the voltage class and current for which they have been approved."

Maybe someone with electronic version of recent codes can do a search for "Noninterchangeability". 2008 406.7 isn't the phrasing I remember. But previously there was wording that precluded intergangeability between plugs and receptacles having different circuit characteristics on the premises.
 
stew said:
The reality was that after a period of time these receptacles began mysteriousy morphing in the middle of the nite back to thier original 30 amp state. Dont know how that happened and will never admit it if i did.
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What's it worth to you that they don't find out? :cool:
 
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