A four wire receptacle would normally be used in a poly phase circuit. For example, a 240 VAC branch will have two "hot" wires (conductors), one neutral (grounded) conductor, and a grounding conductor.
Older circuits for dryers and ovens, for example, used only three wires. New NEC standards allow for the use of a four conductor arrangement so all conductors are delivered to the receptacles on the branch.
When replacing the three wire receptacle with a four wire receptacle, you should run a new branch which includes all of the necessary conductors to make the connection correctly.
Otherwise, connect only the three that you need. This is unsafe, though, since any subsequent homeowner may assume that the receptacle is fully wired (as they should). This would also be illegal in the eyes of the NEC.
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A four blade dryer plug is the new code and should not be changed to a three blade cord. What should be done is to change the three blade receptacle to a four blade receptacle. The only difference in the receptacle wiring is that the position of the neutral wire and the addition of a ground wire being brought out to the dryer on a separate blade to match the ground wire on the plug. Shut the circuit to the dryer to the off position. Opening up the receptacle you will find now two hot wires to the outside blades and a neutral to the center pin. Look in the back of the box and you will see a ground wire wrapped around a screw that grounds the dryer feed wire. From this ground wire add an extension of six inches. This new wire then connects to the fourth terminal on the new four blade receptacle. Looking at the new receptacle you should have the two hot wires on the outside terminals X and Y, white (neutral) to the L shaped W blade and the newly installed ground wire to the U shaped ground G blade. This receptacle is a NEMA 14-30R, 3 pole 4 wire grounding receptacle.
You need two different hots, one neutral and a ground. You can't do it with three wires.
You would first install the required 4-wire cable (or conduit with 4 wires) and proceed accordingly.
Yes, you can always have heavier wire than code requires.
If it does not come with a plug on it, no. If it is made for direct wire, then 99.9% chance is that it is a 240 volt unit. If you plug it into a 120 volt outlet your water will barely get warm.
Generally, if the electrician did it right, the BLACK wire is HOT, and the WHITE wire is NEUTRAL. Meaning that the white wire is the center tap of the main transformer, and the black wire(s) are either leg of the 240 volt output. Since the hot to center tap only takes half of the 240, it ends up being 120 volts at your outlet.
For a 240V with ground outlet you will connect black (hot) to one brass screw, red (hot) to the other brass screw, and bare (ground) to the green screw. Cap white (neutral) with a wire nut. It is for 240/120V appliances. If you don't fully understand this buy a book. This is a very basic question. If you don't understand which wire is which you could make a serious mistake causing fire or death.
There are a couple of catagories for plug descriptions. Straight blade and twist lock blade. The amperage and voltage rating is embossed on the plug (trade name for plug is cap, wall part receptacle). See related links for a chart.
You don't.
you must run the proper size wire based on the ampacity needed, wire must have four conductors including the gound
A three phase four wire commercial distribution service will not give you 240 volts. The nearest voltage you can get is 208 volts. It is a wye connection which gives you 208 volts between the three legs and 120 volt between any of the three legs and ground. This ground point is the systems neutral point.
You might be out of luck. Three phase delta 240 volt services are a thing of the past. As far as I know there never was a 240 volt three phase four wire. The line to neutral voltage would be 240/1.73 = 139 volts which is of no use to anyone. Three phase four wire system for business and commercial use these days is 120/208 volts. A 3/0 copper conductor with an insulation factor of 90 degrees C is rated at 225 amps.
Yes, you can always have heavier wire than code requires.
A four wire plug suggests to me that it is for split voltages. 120/240, hot - neutral - hot - ground will be the four blade connections for shore power in the US. With UK shore power three wire there will be no neutral as you know it. 120 volt equipment will not work. If there is a special berth for 120/240 shore power that is what you will need to tie up to.
Yes <<>> In North America, a three wire 120/240 volt system uses a neutral wire. For 240 volts two "hot" wires are used with no neutral.
You can't do that. An L14-30 is a 240/120 outlet and you cannot "make" 240 volts from two separate plugs; you have to have a hard-wired 240-volt source (either another type of outlet or wired directly to 240 volts).
If it does not come with a plug on it, no. If it is made for direct wire, then 99.9% chance is that it is a 240 volt unit. If you plug it into a 120 volt outlet your water will barely get warm.
You probably mean to change it to a 240 V outlet... either case, you'll need to run a new wire and install a new breaker.
240
Generally, if the electrician did it right, the BLACK wire is HOT, and the WHITE wire is NEUTRAL. Meaning that the white wire is the center tap of the main transformer, and the black wire(s) are either leg of the 240 volt output. Since the hot to center tap only takes half of the 240, it ends up being 120 volts at your outlet.