Shop Electrical setup in a Japanese system

[leehljp]

I am wiring my 9 X 12 workshop _from_ the 200V circuit for the oven/stove circuit in our house and am having a little bit of trouble understanding this Japanese system.

Setup:
Under the house (good spacious concrete crawl space) where the wire goes to the (would be) electric stove, I cut the wires and connected it (screw type clamp for electric wires) to a set going to the shop. The wire to the stove, and from there to the shop, are 2.6mm. Total run from main house circuit breaker to shop is about 50 feet. The wire from house to shop (8 feet distance) is in water proof conduit under ground.

Most Japanese 200 Volt house systems have 2 hot wires and NO Neutral wire for 200V AC or etc.. There is/was a ground wire going into the wall to the outlet for the stove. (BTW we are not using an electric stove, so the circuit is not in use.)

Shop setup:
I have a small 4 switch (20 amp each) circuit breaker in the shop. I brought the 200 volts in and set two circuit breakers to be 2 separate 100 volt lines (opposite sides of the 200 volt main switch). The two other switches are also set up this way, but are sent out as one 200V line for a very small 200V welder.)


My Problem: With two hot wires and no neutral wire, the 200 Volt welder works. But when turning on ANYthing on either of the 100 volt sides will trip the _House_ Main circuit breaker.

I brought the "ground" green wire (ran from the stove ground wire) in with the 200V. This ground wire was added to the "neutral" of the shop circuit breaker. I found out that this is a no-no inspite of two Japanese electrician's advice to do that. This was the problem that caused the main circuit breaker to trip when turning on anything.

The Main house circuit breaker does have a "Neutral" side and all 100V runs have this "neutral" wire. I found a 100 V wire (2.0mm) under the house with a neutral wire and "spliced" into it (neutral/white), then ran it in a conduit to the shop and hooked it up to the Neutral of the shop's circuit breaker.

Now, the 100V sides work fine. The 200V circuit works for the welder, but it does not use the neutral wire.

The PUZZLING part: Wanting to be safe and do like the house was set up with the 200V stove, I hooked the ground wire onto what looked like the "ground" screw of the shop circuit breaker. Now, the problem of tripping the main circuit breaker started again when turning anything on. I took the gound wire off and the problem went away. The circuit breaker did not trip upon hooking something up (which would indicate a short) but when turning it on.

With the neutral (white) wire by itself, everything works fine (so far) on the 100 Volt side, and 200V side.

200V welder work fine with 200v with the plug's green wire attached to a "grounded" outlet - but without a neutral wire at all.

100V will not work with green ground wire in lieu of neutral.

I wish they would put neutral wires in all of their 200V systems! A pain.

I don't understand this system over here! Thanks for letting me rant!

A bit of humor: over here, the ground is called "earth" and pronounce "assu".

[stewchi]

Maybe I can share some knowledge with ya.

Definitions:
Ground: wire is a wire that should never carry any electricity, if it ever does it means it just saved you from the electricity going though you. It is not the same as a neutral. The Ground wire should always be green or in some cases bare copper.

Neutral: wire in most cases is white (can be gray). This is the wire that attaches to the center tap on the transformer that provides electricity to your house or neighborhood. This is always used for any circuit needing 100V (120V)

Hot: this is the black, red, yellow or other color wire that will kill you. Your house has two of these and you use both for 200V (240V) circuits. You only need 1 Hot and 1 neutral for 100V circuits. In 200V circuits there is no need for a neutral. Many appliances however need both 100v and 200v, the heating elements of the stove will use 200v while the clock and light bulb will be 100v.

You generally will not see a neutral for 200V circuits unless they have a device on them that needs 100 V. As for the ground tying the ground to the neutral is a bad thing to do. It can create parallel paths and induce return current to run down the ground wire which is bad. And may trip ground fault breakers in certain cases. There is only 1 place in the house the ground and neutral can be tied together and that is at the main panel were your house gets its electricity. All modern US panels (the box with the circuit breakers) have a green screw (Bonding screw) that if you remove isolates the neutral bus (bar that all the neutral wires (white wires in US)connect to) from the case or frame of the box. This isolation is required for you subpanel (a second box with breakers that gets it power from the first box). Since neutral and ground can only be connected at the main panel they have to be separated at the subpanel. This means you need 4 wires from the main panel to the subpanel 2 hot, 1 neutral and 1 ground. The wires also have to be of a size that can support the amount of currents (Amps) that you will use on them.

What you describe makes since, the welder will not need a neutral since it only uses 200v
I am a little concerned about the neutral wire that you are using to power you subpanel. As it may get overheated and be a potential fire hazard.

The best setup is to have as I mentioned four wires coming from the main panel that are connected to a breaker say 60A. The 4 wires will go to your subpanel and then separated into two 100V circuits. Each 100v circuit shares a the neutral going back to the main panel but since the circuits are smaller than the 60A breaker and the wire that is used is rated for 60A the breaker will protect the wire from overheating. There is also a low probability you will max out the neutral since this setup is also called (Mulit Wire) since the 2 hot wires are opposite in phase if you are using 2 equal devices say (both using 12A) one connected to breaker which is getting power from Hot #1 the other from Hot#2 then the return current from each cancels each other out since they are out of phase.

The problem here is we do not know what the neutral you are using is rated for, or what the other devices in the house are using that neutral, when you begin using stuff in the house and in the shop you may over heat the neutral.

Your best bet is to run a new neutral the same size as the other wires for the stove all the way back to the main panel (or were ever the stove wires go). By US codes this neutral can not be run separately from the Hot wires so keep that in mind.

If this just made thing more confusing I apologize and will be happy to clearly anything.

If I got anything less that 100% correct I bow to the expertise of Don and Loring or other knowledgeable people on the forum.

[leehljp]

Thanks Stewchi. You cleared up a lot for me, much better than the electricians did.

I am a little concerned about the neutral wire that you are using to power you subpanel. As it may get overheated and be a potential fire hazard.

That is my concern also since I am running off of a 2.0 mm wire and the hot wires are 2.6mm. My plans are to run a separate 2.6 neutral all the way from the main curcuit breaker. AS to overload, the only simultaneous machines I use are a 12 amp dust collector and the BT3000. I did not mention in the original that the lights are on a totally separate circuit, so that any usage is not being co-used with the light system.

I think that 2.0 mm wire is equal to 12 gauge and 2.6 mm is that same as 10 gauge wire. Not totally sure.