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From the hardware store I bought a NEMA 14-30 power cord, to which connected a NEMA 5-15 receptacle so I can plug in a 240V appliance.

enter image description here

https://www.amazon.ca/AC-WORKS-Generator-250Volt-Flexible/dp/B083YYCBRH/ref=sr_1_54?th=1

^ DIY-ed the above adapter cord.

enter image description here https://commons.wikimedia.org/wiki/File:NEMA_simplified_pins.svg

I'm not sure about the wiring, though. The red & black wires in the NEMA 14-30 has 240V across them, so I connected them indiscriminately one to NEMA 5-15's neutral & hot. I then proceeded to joining each's respective grounds. As for the NEMA 14's neutral, I just left it floating.

enter image description here

I really don't understand what I apparently think is Split-phase electric power that our dryer had been installed in. I take it it's a lot like a transformer with the 2 ends at full voltage (hot -- red & black) & the middle (neutral -- white) is the center tap?

So now, is it alright to draw full load while the NEMA 14-30's neutral is left floating? Doesn't it need to keep carrying current?

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  • \$\begingroup\$ A nema 5-15 should not supply 240v. It's a 120v socket. Assuming you want to connect a conventional 120v appliance to it, you should not be using both hots \$\endgroup\$ Oct 20, 2023 at 10:07
  • \$\begingroup\$ An adaptor like this should connect one of the phases and neutral to get 120V. Putting 240V on the 5-15 is asking for trouble. What appliance are you connecting? \$\endgroup\$
    – Finbarr
    Oct 20, 2023 at 11:32
  • \$\begingroup\$ Tempus Nomen - Hi, Please note the site rule which requires that if a post includes content (e.g. text, image, photo etc.) copied or adapted from elsewhere, that content must be correctly referenced. As a minimum, for online material, the source webpage or PDF etc. should be named & linked (see that rule regarding references for books / articles etc.). Therefore please edit your question to include the original source links for those images (and please remember it's your responsibility to do that in future). Thanks. \$\endgroup\$
    – SamGibson
    Oct 20, 2023 at 22:09

1 Answer 1

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What you have done is wrong in several ways.

First, if your objective is to plug in a 240 volt appliance, you should not be using a NEMA 5-x receptacle; it for 120 volts, not 240 volts. If your 240 volt appliance has a 5-15 plug on it, it's wrong. For 240 volts, you should be using NEMA 6-x .

Second, ignoring voltage, putting a NEMA 5-15 receptacle on a 30 amp circuit (which is supplying the 14-30) means that the 15 amp appliance will have to be pulling more than 30 amps to trip the breaker. If something happens to the appliance that it starts drawing 25 amps, it will probably burn up its line cord and start a fire but the breaker will not trip. Wrong again.

A properly designed commercial 14-30 to 5-15 (or 6-15) adapter will include a 15 amp circuit breaker or fuse to protect the 15 amp end.

To actually answer the asked question, your analogy to a center-tap transformer is correct. In fact, your utility service probably has a transformer with a center-tap 240 volt secondary feeding your house. This is stepping down from higher voltage single-phase (or one phase of 3-phase) service. There is no harm to not drawing any current on the neutral; in fact, with a true 240 volt load, even with the neutral connected, the neutral carries no current.

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