new 220v 4 wire to an older 3 wire socket
 

need to hook up a convection oven
it has a 4 wire plug so I bought a 4 wire socket
but my house is old 3 wire 220v

now what do I use the metal shell of the socket and box pipes ect as #4
or do I need a new 4th wire run from the main breaker box ? or elsewhere ?

I think #4 wire is ground not neutral for 220v return from the 2 110 lines =220
so the box pipes ect is the ground with two existing hot wires and a return wire ?
but is anything else needed at the main or do I need a 4th wire run in and not use the box pipes ect ground ?

When you say three wire are you saying black, white, bare ground or black, red, white?

black is hot, red is hot

green & white & bare are all grounds

black to black
red to red
all the others together

understand the two hots
problem is N and/or grounds side

got red black hot
and a white return
think pipes/box are grounds
got the 4 wire plug in wall mount
and could use a very short box to female plug for 4 th wire
question is that good or do I need something else ?

You should run the 4 th wire. That's code. The technical side of this is the white neutral sends current to the neutral buss as you likely have 120v controls and fans in the new oven. Not always but the schematic on the oven will tell you.

AFA the equipment ground, has to be green or bare, that goes to the grounding buss in the panel. Grounding is usually referred nowadays as the equipment ground while bonding is another thing. One thing for sure is that conduit of any nature is not considered a ground path oi most cases. However, if the conduit is bonded at each junction, it can serve as an EG. Rigid conduit schedule 40> is considered the min requirement, not some spiral flex.

^this, besides the safety factor, as Zeke says the neutral is needed for any 110v powered components.
Ground and neutral is NOT the same thing.

spiral flex OUT OF THE WALL under the counter think the in wall runs are hard pipes
they are in the attic where I see them

while tying the 2 N and G may work

I do NOT think it is a good way to do
or what the new 4 wire plug wants to do
to protect from problems

is there any reason if a new 4th bare wire ground is run
to put it thru the pipe with the other 3 existing
or just run it outside the exist pipe as it is JUST a ground and never hot ?

Is this "pipe" emt (conduit)? Seems like you could use that for the ground, assuming it has a good bond all the way back to the box. In a commercial job I did I was required to bond all the device boxes to the EMT and they tested for continuity all the way to the breaker box. Most of the runs were FMC (flexible metallic conduit). It passed inspection, so I assume it is NEC compliant. I would definitely make sure you have good connections all along the run.

Our new electric clothes dryer came with instructions on how to connect it to 3-wire service. Red to hot, Black to hot, white to neutral, and a jumper from the frame of the dryer to the same lug the white wire is on.

"Our new electric clothes dryer came with instructions on how to connect it to 3-wire service. Red to hot, Black to hot, white to neutral, and a jumper from the frame of the dryer to the same lug the white wire is on."

I saw a video (the "Internet Electrician", I believe) explaining this option. He advised best practice is to properly convert the receptacle to 4 wire, but acknowledged properly converting the appliance plug to 3 wire was sometimes appropriate.

I hope he explained "properly." That would include rewiring the circuit with 4 wire cable. Changing the receptacle isn't going to help anything.

Nota, if you want to do it right, picture of both ends would be good, panel and outlet box.. Need wire size, breaker size, gauge of wire(awg) size of conduit, current demand of appliance.

What year was house built? 1980's and before, emt served as the ground in florida. Ive fouind some emt corroded so bad, or loose connections in the walls, that GFIs don't work. I've been pulling new grounds, or running new homeruns back to the panel when possible.

Also, If the conduit is running through concrete, I strongly recommend pulling new wire(s). I've seen some so corroded so bad they no longer conduct, and spalling (concrete guys) splicing wires and covering with cement.

Oh yes, he went through it in detail.

HOUSE BUILT IN 55

three wires in the box red black are hot white return or common
and the FLEX STEEL TUBE IS A GROUND
hooked to a new meile convection wall oven [got a SUPER deal from habitat for humanity store] THEY ASKED 800 BUT DISCOUNTED TO 400 THEN 200 AFTER IT SAT
I GOT IT FOR A 100 , IT WAS 3 K LIST NEW but a few years old UNUSED
so I want to do the hook up to spec to not damage the new oven

NO FLOOR SLAB WIRES
everything runs up in the attic and down the int walls
old fuse panel bypassed to a newer breaker panel
oven needs 20 amps but shares a circuit with the glass top 4 burner cook plate
it is on a 60 amp breaker for them at the main box so that should handle the loads
of both wires are plastic coated and look to be replaced when the breakers were redone [after andrew 92 ? likely]

the cook top has only the 2 hot wires so may add a ground to the metal base on the cook top a ground to the box flex tube

the problem with conduit as a ground is that the connections may not be good,.


make sure all wiring is sized for the breaker.
even though the oven is 20amp it should not be connected to wires that are 12g (20amp wire)

I get the same volts if I read from the two plugs on a 110 line wall plug on my fluke meter
or one side of the 110 line to grounded box the new oven plug will be placed in
or what I think is a good connected ground in place on the existing box and flex line

so am I good to go to ground at the box with a short wire to #4 lug on the new socket ?
or do I really need a new wire run to ground on the main breaker panel

yes the emt is the steel pipe to a box in the wall then a flex 5' run to the plug box and grounded by meter readings of
so I get the same volts from a 110 plug in on both sides meter probes
or the single side 110 plug in to the emt on the box same reading

what totally confuses me is the 4 wire as a non-return ground side

but tied at the main panel to semi hot N or return side, right ?
and the dam A/C alternates so that why I call the N line semi hot
as does not the current flow both ways on both lines ?

The question is do you want to follow code. Whether you 'have' to or not is academic. For a long while, manufacturers shipped 240v appliances with instructions to do what yours said. The NEC would allow it, but no longer does.

So, if you were having a licensed electrician hook this up, he would not do it unless he pulled a ground wire. Then comes the matter of insurance. If the time line can be established that you installed this appliance in 2018, you would be found non compliant.

Many thousands of us do our own work and do what we need to do but not always what we have to do. And we get away with it. There are parts of the country where there are no inspections — you're on your own. And the fact is, there are more fires on those structures than the average. Not saying this about you, just in general.

Now that you know this, really, how can you not do it right?