Switching a 3-prong outlet to 4-prong outlet

[Diggy]

I am wanting to change my brewing system from gas to electric and I already have a 240v 30amp 3-prong dryer outlet near where I want my brewing system. It looks like this:

I know for a 4-prong outlet I need 2 hots, a neutral, and a ground wire. So I thought I would open up the existing outlet and see what wires were already inside and saw that I had all 4 wires already:

Since I already have 4 wires to the box, can I just swap the outlet to a 4-prong dryer outlet?

 

[Brumateur]

Yes, you can. However I'd double check if green wire really connected to a ground.

 

[Diggy]

Yes, you can. However I'd double check if green wire really connected to a ground.

Thanks!

I am guessing that entails breaking out the multi-meter and confirming:

when circuit breaker on:
white to red measures 120 V
white to black measures 120 V
black to red measures 240 V
green to red measures 120 V
green to black measures 120 V
green to white measures <1V

when circuit breaker off:
all wires measure infinite ohms/not connected except
green to white measures ~0 ohms?

Or is there a different test I should do to confirm it is wired properly?

 

[itsnotrequired]

you can also take a look at the cable at your panel, to ensure black and red are attached to the breaker, white to the neutral bar (where all the other white conductors should be) and ground to the ground bus.

 

[Brumateur]

Thanks!


green to red measures 120 V
green to black measures 120 V
green to white measures <1V

when circuit breaker off:
all wires measure infinite ohms/not connected except
green to white measures ~0 ohms?

Or is there a different test I should do to confirm it is wired properly?

Looks fine. So just wire a 4 prong receptacle and that's it.