3 wire 240v system to a 4 wire dryer outlet

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rappell

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Advice please. I moved to a new house and do not have a 240v outlet in my garage but am not using the dryer outlet. Can I make an adapter to go from 4 wire to 3 by pairing the ground and neutral wires together at the 3 wire plug? Want to make sure it's safe. Breaker is 30a gfi.
 

doug293cz

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I assume your control system is 240V only (no 120V usage at all), and that the three wires are GND, HOT1 and HOT2. Is this correct? If not there are issues with the panel that will need to be addresses before using it again.

The four wire receptacle is most likely a NEMA 14-30. A drawing for both 14-30 receptacles and plugs is below. What you want to do is make a short extension cord using 10AWG cable. On one end will be a NEMA 14-30 plug, and on the other end will be a NEMA 6-30, NEMA L6-30, or NEMA 11-30 receptacle (drawings also below.) The green wire will connect to the "G" terminal in both the plug and receptacle. The black wire will connect to the "X" terminal in both the plug and receptacle. If you have a four wire cord, the red wire will connect to the "Y" terminal in both the plug and receptacle. If you only have a three wire cord, then you won't have a red wire, so connect the white wire to the "Y" terminals. In this case you should wrap some red electrical tape around both ends of the white wire so anyone who might get inside the connectors on the cord knows that the white is not neutral (the normal use of a white wire.) If you have a four wire cord, the white wire connects to the "W" terminal in the 14-30 plug, but is not connected in the (L)6-30 or 11-30 receptacle. The unconnected end should be insulated with electrical tape.

NEMA 14-30.png

NEMA 6-30.png

NEMA L6-30.png

NEMA 11-30.png

Brew on :mug:
 
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rappell

rappell

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Doug, thanks for the info. I am using an L6-30 plug on 10awg, 3 conductor cord and the wall plug is a NEMATODE 14-30 outlet. My thought processes was that since ground and neutral are all connected on the same bar in the panel that connecting the two in the adapter would be ok. I need to run the "adapter " about 10ft to reach the outlet. Already planning on using 10 awg wire.
 

doug293cz

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Doug, thanks for the info. I am using an L6-30 plug on 10awg, 3 conductor cord and the wall plug is a NEMATODE 14-30 outlet. My thought processes was that since ground and neutral are all connected on the same bar in the panel that connecting the two in the adapter would be ok. I need to run the "adapter " about 10ft to reach the outlet. Already planning on using 10 awg wire.
Ground and neutral are connected in the main panel BEFORE the neutral goes thru the GFCI breaker. Connecting the ground and neutral at the dryer outlet will remove some of the protection the GFCI provides to your circuit, and may cause the GFCI to malfunction. The neutral is very fussy on the load side of a GFCI. Don't connect ground and neutral.

Brew on :mug:
 

ajdelange

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The neutral is there to return current to the service entrance. The ground wire is there to hold things connected to it at ground potential for safety. If you join neutral and ground at an appliance part of the appliance's return current will flow through the ground wire and part through the neutral wire. That which flows through the ground wire is termed 'objectionable current' because, unless the ground circuit has 0 impedance back to the service entrance it will cause the voltage at the appliance to rise above ground potential leading to the possibility that someone touching said appliance will be shocked.
 

itsnotrequired

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if i understand correctly, you have 240/120v available at the outlet via a 14-30 receptacle but you only need 240v for your brew panel (no 120v required). is this correct? if so, you will either need to replace the 14-30 receptacle with a L6-30 receptacle (to match your existing plug) or replace the plug on your brew panel cord with a 14-30 plug (to match your existing recep). if going the former route, simply leave the neutral wire unconnected at the receptacle (place a wire nut on the end of the neutral wire). if going the latter, you don't need to do anything with the existing recep although you may want to disconnect the neutral at the receptacle anyway, just to eliminate a potential additional path to ground.

and if my above assumption on the existing configuration is incorrect, please describe your existing installation in more detail. in any event, do not tie neutral and ground together at the recep.
 
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