I am installing a new 240v circuit. As long as I am doing it I am putting
in a 30a breaker and #10 cable in case I ever need it.

At the moment the device I want to use has a 20a plug, and I have some 20a
outlets? Is it alright to use them (analogous to putting a 15a outlet on a
20a circuit) or must I get a 30a plug and outlet?

I have to buy a quad breaker for this, so it is impractical to use a 20a
breaker now and upgrade if I need it.

In article , "Toller" wrote:
I am installing a new 240v circuit. As long as I am doing it I am putting
in a 30a breaker and #10 cable in case I ever need it.

At the moment the device I want to use has a 20a plug, and I have some 20a
outlets? Is it alright to use them (analogous to putting a 15a outlet on a
20a circuit)

NO.

or must I get a 30a plug and outlet?

Yes. Or use a 20A breaker.

NEC Table 210.21(B)(3)
Circuit rating (amperes) Receptacle rating (amperes)
15 not over 15
20 15 or 20
30 30
40 40 or 50
50 50

--
Regards,
Doug Miller (alphageek at milmac dot com)

It's time to throw all their damned tea in the harbor again.

"Toller" writes:

I am installing a new 240v circuit. As long as I am doing it I am putting
in a 30a breaker and #10 cable in case I ever need it.

At the moment the device I want to use has a 20a plug, and I have some 20a
outlets? Is it alright to use them (analogous to putting a 15a outlet on a
20a circuit) or must I get a 30a plug and outlet?

I have to buy a quad breaker for this, so it is impractical to use a 20a
breaker now and upgrade if I need it.

I'm no electrician, but I'm thinking from a safety perspective that if
the circuit is capable of supplying 30A before its breaker will open,
all outlets on that circuit better be able to handle 30A without
melting.

Hopefully someone who knows electrical code will chime in, but I you
have good reason to be asking the question.

Best Regards,
--
Todd H.
http://www.toddh.net/