It depends. Outlets are manufactured so that both sockets are powered from a single source - one hot wire and one neutral wire and a ground wire for safety.
On almost all outlets, those sockets are connected by small tabs of brass that feeds the connections from one socket to the other. If you attach the hot and neutral wires to the screws for one socket, these brass tabs carry that connection to the other socket. It works the same way if you use the press in connections which are holes on the back of some outlets (but many pros and DIYers do not favor using press in connections). The brass tabs on the side carry the power from one socket to the other.
You can change this. If you break off the brass tab on the hot side, the hot wire you attach to one socket does NOT carry over to the other socket within the outlet. This technique is often used to have an outlet with an always live socket (for clocks, etc,) and a switched outlet (for bedside lamps). The outlet is wired with two separate hot leads, one that is always hot and one that goes through a switch. They could be on the same or different breakers depending on several factors. The neutral side may or may not be connected depending on several factors that are not critical here.
You can also separate the sockets if you wanted a dedicated socket for a high draw device, such as a heater, and run a separate line from the panel. (This generally would require a separate neutral).
In your example, if the sockets are set up conventionally, that is powered from a single line, there is no difference, except plugging into a socket is a marginally safer approach than multiple splitters. Be sure that the overall load that is likely to be used at one time does not exceed the capacity of the surge protectors or the circuit breaker on the line.
You're going to have to either get a washer that accepts 240V, or change the circuit.
New Washer
Getting a new washer will depend on the manufacturer, dealer, and other factors that are off topic here.
Change the circuit
Modifying the circuit will require knowledge of electrical safety practices, and general electrical wiring principles/standards/codes. If you lack this knowledge, or are not comfortable working with electricity, please contact a local licensed Electrician.
If you decide to tackle this project yourself, here is an overview of what needs to be done. You'll be going from a configuration with two ungrounded (hot) conductors, and one grounding conductor (NEMA 6-20). To a configuration with one ungrounded (hot) conductor, one grounded (neutral) conductor, and one grounding conductor (NEMA 5-20). To do this you'll have to swap out the double pole breaker for a single pole breaker, and repurpose one of the conductors.
At the Panel
- Before you begin, you'll need to purchase a 20A single pole circuit breaker that is compatible with your service panel, and a blank panel cover insert.
- Start by turning the power off by flipping the main breaker to the
OFF position, then verifying that power is off using a non-contact voltage tester.
- Remove the service panel cover (be careful working in the open panel, the main lugs are still energized even when the main breaker is in the
OFF position).
- Locate the breaker for the washer.
- Remove the wires connected to the breaker (should be either black & red, or black & white).
- Remove the breaker from the panel.
- Install the new single pole breaker in one of the slots where the old double pole breaker was.
- Install the blank panel cover insert in the panel cover, so that is covers the empty space left.
- Connect the black wire that you removed from the breaker in step 5, to the new breaker.
- If the other wire from step 5 is white, connect it to the grounded (neutral) bus bar. If the wire is red, mark the wire with a bit of white tape, or a white marker, then attach it to the bus bar.
- Reinstall the panel cover.
At the receptacle
- Before you begin, you'll have to purchase a 125V 20A receptacle.
- Uninstall the old receptacle.
- Connect the black wire to the brass screw terminal on the new receptacle.
- If the other wire is white, attach it to the silver screw terminal on the new receptacle. If the other wire is red, mark it with white tape or a white marker, and attach it to the silver screw terminal on the new receptacle.
- Attach the bare or green grounding wire to the green grounding screw on the new receptacle.
- Mount the receptacle in the box, and install the cover plate.
Once everything is finished, you can flip the main breaker, and the new breaker to the ON position.
WARNING:
This answer is only applicable in the US, and possibly Canada.
Best Answer
I think for what you want to do:
You could consider building a 220V 30A power strip. Without knowing your welder, I'll list parts from Home Depot that might work but you have to confirm their suitability for your use.
Please review this URL to determine your plug NEMA type. It will probably be NEMA 10-30 or 14-30. Make sure the plugs, receptacles and dryer cord all match.
Note this is for standard 30A dryer. If you need 50A, you will need different receptacles and cord. Probably a range cord. But I assume that since you are currently plugging your welder into your dryer receptacle, 30A will be sufficient.
Raco 2-Gang 42 cu. in. Square Boxes Model # 8257 Internet # 202058366
You should screw this to the wall if possible for safety, as that will reduce stress on the dryer cord.
6 ft.10/4 4-Wire Black Dryer Cord Model # AW20009 Internet # 100672788 Store SKU # 601004
(two) Leviton 30-Amp 2-Pole Flush-Mount Outlet Model # R50-05207-000 Store SKU # 621336
wire, wire nuts, box cover, cord clamp etc.
If your box can be mounted close enough to the existing outlet, you can cut the excess off your dryer or range cord and use that excess wire to connect the two new outlets. This is just a very minor optimization and you might figure it out as you assembled the box but this way, you'll know before you go shopping.