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I have a water pump, it works fine. Motor is rated for 115/230 and draws 9.6 or 4.8 full-load amps depending on voltage. Its cord has a plug that appears to be vintage NEMA 10-20, but I'm not certain as I've never seen one before. The receptacle is on its own 30-amp dual-pole breaker, and I verified that the wiring is two hots and a ground.

I want to run this pump from my generator, which is an older 5000 watt Troy-Bilt with standard 240v L14-30 and 120v 5-15/20 receptacles.

The problem: I can't find any adapters for 10-20 plugs anywhere. Is this just because they're obsolete? Or because they're ungrounded and super-dangerous?

Main question: Should I bother making a custom adapter cord for this setup or just upgrade the plug and receptacle to something newer? Is one option obviously better/safer/easier?

Pump motor is a 1986 Dayton 5K658B 3/4HP 115/230 3450 rpm. I found this tech sheet but I'm not 100% sure it's the same model.

nema 10-20 plugdayton pump faceplate

receptacle wiring

Conclusion:

Based on the discussion in the comments, this whole situation is more complex and sketchy than I had anticipated. I have other electrical work I need done so I'm going to add this plug/receptacle to the list and seek professional help.

meetar
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Is that plug safe, yes when properly wired there is no issue with that plug. What would a best practice be when setting up a direct connection to a generator. Change the plug to the appropriate 3 wire twist lock. The old plug will work but with motor loads vibrations can allow the plug to work out of the receptacle moving the plug from one source to another increases the chance the plug can vibrate out because of the stress on the wire being different.

The only real difference in today’s plug / receptacles is the ground lug each voltage hi / low has the ground lug pointing in or pointing out on twist locks. a 120v 5-15 standard receptacle and plug 120v would work Or a 6-15 240v 15a would also work but there is a higher chance for this plug to fall out, this is why I would suggest twist locks.

If you want to get fancy you could pay more and go to a 4 wire plug that is 120/240 rated but that is a waste because you won’t be changing your motor configuration but some folks have asked me to do this.

Last you are using a 5000w 240v generator, to power a pump with a book value 1657w (book values not nameplate is used for load calculations). I would suggest to put in a simple interlock kit on your panel and an inlet to the panel and you could run your pump, refrigerator, Freezer and some lights off of that generator (my small backup generator is a 5000w welder and it runs all these loads) I turn the other breakers in the panel off and have had this setup for years. The issue I see with that large of a generator is fuel usage when not pumping.

Ed Beal
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The NEMA 10 configurations is a 240v receptacle for appliances that ground via the neutral conductor conductor, and cannot be properly wired to a single pole breaker, and even if wired for 240v as far back as I can recall it was never a legal configuration for that motor anyway.

I would attempt to change the receptacle and cord cap to a NEMA 5-20. The code requires replacement with GFCI's where GFCI's are required*. I wouldn't recommend changing the wall receptacle to a twist lock because the L14-30 configuration to match the generator shouldn't be wired to the existing 20A breaker or fed by the #12 wires probably feeding the receptacle.

A first thought might be that swapping wire for wire to a NEMA 5 which should work, but it's anybodies guess if the wire colors would actually comply with Code. Since it's improperly wired to begin with what colors are present is anybodies guess.

A NEMA 10 should be a white (or grey), and two other colors besides green. A Nema 5 should be a ground (green, bare, or raceway), white (or grey), and one hot (none of the aforementioned colors). There are some minor exceptions, but it is best to determine what you have before going down that path.

NoSparksPlease
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If you were not doing other electrical work, I would leave it and make a custom adapter cord. I would lean toward the cord especially if you have any distance between the generator and the pump motor. Even a one foot or shorter cord could be cheaper than changing breaker, outlet, and possibly some wiring.

Now, since you mention other electrical work, I would at least match the breaker to the outlet. The nema 10-20 has two hots and a ground. It does not have a neutral. You say double-pole breaker, so two hots with ground and no neutral means you could change to a 6-20r or even a 6-15r. Keep in mind that if you have a 20 amp plug, you really should have a 20 amp breaker to match the plug and wiring.

That said, you may prefer to install a generator interlock kit as an easier method and put your whole breaker panel legally on your generator.

Jason
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