Electrical question regarding 240v---grounding?

[BrainOGrefuGee]

I have a question for the electricity gurus... I am setup in a big house with a fuse box, there is a sub-panel/sub fuse box that is 30A 240v that was put in to run a big AC that is not in use. That is a 3 wire 240v outlet. I disconnected that branch circut and ran my cable to the sub box and hooked up. 10/2 romex....got me so far?

now my question is this...How do I ground it? I should have put it in bx right? Its 2 outlets in a metal box but just the romex. should I re run it so its all metal? remember its a 3 wire......when they ran it for the AC it was in bx, but at the receptical it wasnt grounded to the metal box....

Also, my outlet is inces away from the cold water pipe (basement)?????

 

[apartmentblower]

rather than give advice (im not qualified to); ill ask-- why didnt u run regular 10/3????

 

[madpenguin]

Not sure I understand your question. 240v. 10/2 romex. No problems. 2 insulated conductors for the hots and then a bare copper wire for the ground.

Tie the ground in with your neutrals back at the fuse box.

There are other grounding issues with an old fuse box that I won't go into. I'm assuming you have no ground rod or bonding jumper to your water meter at all.... Just your feeder neutral coming from the meter outside?

 

[PharmaCan]

What is the ultimate use that you want from this circuit? Are you going to run only 240v appliances or are you trying to get 120v from that circuit? A combination of 120v and 240V? Do you actually have fuses or are you calling breakers fuses? 10-2 Romex has two insulated wires and one bare wire. What did you do with the bare wire? If you can take some pics of what you are working with it would help a lot.

PC

 

[BrainOGrefuGee]

A.B...I ran 10/2 instead of to 3 because thats what was already in there. its an older house so no breaker box, its a fuse box with no grounding bus, only a neutral bus..

Penguin....I used the 10/2 so there was no fourth wire for ground. should I run one and tie it into the neutral bus??? is that what your telling me???
I was thinking about running one to the cold water pipe with a ground bushing.
Yes there is a grounding wire from the main fuse box to the cold water pipe, and the whole house is wired with bx. when I test for ground throughout the house it it grounded. But I didnt run bx to my room tho. just romex.

PharmaCan... Im only running 2x 600W on it for now, in the winter I will put 2KW in. all 240v of course. I was going to run a sup panel from it so I could have 120v also, but it was a 3 wire. so Im basically treating this like a 3 wire dryer 240v application..dig? yes this is a fuse box, round fuses no breakers. the bare wire is in the neutral bus bar where it belongs..

I have power and everything seems to be working fine, Im just being careful here because this is an old house...when I touch my recepticals with my meter I have 240v power. red in black on the metal housing I read at 120v which means that Im grounded.... I guess my thing is just that I didnt use bx so Im saying to myself "how is it grounded when its just a metal box on the wood wall" theres no bx back to the box so where does the extra electricity go? does it stay in the box waiting for me to touch it and die? lol...

I just need to make sure Im safe before I actually plug these ballasts in. I have power.
Thanks a lot guys

 

[PharmaCan]

To explain this in the simplest terms possible:

240v doesn't need a neutral. The electricity is just used.

120v needs a neutral to complete the circuit.

A neutral is to complete a circuit - a ground is for safety. The neutrals and grounds both go to earth, which is why they can both use the same bus bar in your main panel, but they serve different functions in your circuitry and receptacle boxes. If you can get a wire from the main panel to outside the house, it would be a good idea to run a second grounding wire from the neutral/ground bus to a grounding rod outside.

There should be some holes in the back side of your receptacle box. Get a green grounding screw and screw it into one of those holes. Attach a wire (color makes no difference to the ground, but for the sake of code use either a bare or green wire AWG12 or AWG 14) to the screw then tie that wire into your ground wire. (You should wire nut together the ground wire from the Romex, the ground wire from the green screw and one short ground wire for each receptacle.) Then your box and receptacles will be properly grounded. It sounds like your box is grounded now, since you are getting 120v from a hot and the box, but it could be that your ground wire is just touching the box and you really need to attach it securely to the box. (It could also be that you are using the type of receptacle that grounds to the box when it is screwed in, thereby giving you the 120v reading, but that's not really pertinent to this discussion.)

PC

 

[madpenguin]

240v is a little hard for most people to understand. You actually get return current on the hot. It alternates to and fro so to speak.

Your old BX uses the outer metal jacket for the ground whereas your new romex uses the bare copper wire. The bare copper wire, as PC says, should be first attached to the back of the metal box with a green grounding screw and then attached to the green screw on your receptacle.

Take your multimeter and make sure you get 240v between both insulated conductors. Don't measure against the ground but between both hots.

Put a piece of black tape around the white wire to indicate it's actually a hot. Do it in the panel and at the receptacle location. If you used 10/2 then you should have a black, white and bare wire. The white wire does not tie into the neutral bus at the panel. It gets fed from a fuse just as the black wire does. The only wire that goes to your neutral bus in the panel is the bare copper wire.

If you read 0 volts between both hots (black and white) then you've got both hot wires on the same phase and they need to be redone at the panel so each hot wire is fed from a different incoming feeder hot. If you read 120v between the black and white wire then that means you tied the white wire into the neutral bus at the panel which means you only have a 120v receptacle.

Hope that makes sense. You should also use a 240v receptacle so you don't accidentally plug a 120v appliance into it....

It is a good idea to drive a supplementary ground rod if you feel like it but a ground rod is just that. Supplementary. Your water pipe is a FAR superior ground compared to a ground rod (as long as your pipes are continuous copper throughout the entire house and your incoming water pipe from the yard is metal and extends at least 10 feet into the earth, which it almost always does, especially on an old house.).

What size fuses are you using for these wires anyway?

 

[PharmaCan]

It is a good idea to drive a supplementary ground rod if you feel like it but a ground rod is just that. Supplementary. Your water pipe is a FAR superior ground compared to a ground rod (as long as your pipes are continuous copper throughout the entire house and your incoming water pipe from the yard is metal and extends at least 10 feet into the earth, which it almost always does, especially on an old house.).

You are 100% correct that a water pipe is a better ground, simply by virtue of the fact that there's a lot more of it in the ground than a ground rod. However, the water pipe can be disconnected from earth contact during plumbing repairs, thereby disconnecting it as a ground. That is why both a water pipe and ground rod grounds are required. BTW - many houses are plumbed with iron (galvanized) pipe and it is perfectly acceptable as a ground. It's not necessary that the plumbing be copper for it to function as a ground.

PC

 

[apartmentblower]

rather than give advice (im not qualified to); ill ask-- why didnt u run regular 10/3????

ok i just realized that this was a dumb question

 

[BrainOGrefuGee]

ok. well everything you guys have suggested i have already done. I want you to look at the box.....

ok so my idea is this...do you see the 2 open screws on the bus bar? can I run: 1 line from there to my cold water pipe(extra precaution) and put a clamp on it? then run one more line with my romex to a whole seperate sub panel? so I can have 120v and 240v in the room? because then it would kind of be like a 4 wire 240v line wouldnt it? one would be the ground one would be the neutral but they would go back to the same bus bar, which would then be grounded again just to be safe...follow?

at this point my setup is very simple. I ran the romex from that panel to 1 duplex 20A 120v outlet (I dont want to get new ballast cords). I put it in a metal box and ran a grounding screw to the box, and joined that with another from my recepticle and the third from the bare copper wire in the romex. put it back together and I have power and ground when I test it.. Then I was thinking that if the ground takes the spare electicity back to the fuse box through the metal from the grounding screw on my recepticle box, then where does it go if I didnt run the bx to take it back to the fuse box?...thats when I came on here and tried to ask. ..

 

[PharmaCan]

That is not a panel, that's a disconnect. Where are the hot wires from that box coming from?

PC

 

[BrainOGrefuGee]

it is a panel, the main is a huge fuse box with about 20 fuses in it. The hots are coming from the same place that is feeding the main. the main disconnect box with the big pullout block fuses. that is also where power comes into the house at. so it comes into the house, goes into the box with the pullout fuses(main breaker) then goes into this box which originally was for an AC (70's?) and to the main fuse box with all the fuses for the rest of the house.

 

[BrainOGrefuGee]

it says it right on it. 30A subpanel.

 

[madpenguin]

You are 100% correct that a water pipe is a better ground, simply by virtue of the fact that there's a lot more of it in the ground than a ground rod. However, the water pipe can be disconnected from earth contact during plumbing repairs, thereby disconnecting it as a ground. That is why both a water pipe and ground rod grounds are required.

Yep. That's one reason why you jumper the meter. Water pipes make a better ground because they also hold water. You'd get more resistance were it just an empty iron pipe in the ground versus a used water line.

BTW - many houses are plumbed with iron (galvanized) pipe and it is perfectly acceptable as a ground. It's not necessary that the plumbing be copper for it to function as a ground.

PC

Yep. Iron will do as well. That's what's always feeding the line side of the meter in most cases anyway.

 

[touchofgrey]

That is a funky old panel but you've got a 3-wire 220, 2 hots and a neutral. You just don't have a ground. What are you trying to hook up, a 220 outlet that has a ground? If so, you can just run a single ground wire to a clamp on your pipe and provide grounding for that outlet.

 

[madpenguin]

Brian, make sure those are 20A fuses in there seeing as how your using a 20A receptacle.

Not really anything funky about that box. It's just a fused disconnect. Still provides over current protection. You just have a bonus of having a disconnect handle on the side. Will still work for the OP's purposes.

My dryer is fed from just such a box.

 

[BrainOGrefuGee]

randude. so your saying I could have run a 10/3 from this box to a subpanel in the growroom to provide 120v and 240v. and that I would connect both my bare copper and my neutral to that diamond shaped bus bar? correct?

 

[madpenguin]

If so, you can just run a single ground wire to a clamp on your pipe and provide grounding for that outlet.

I wouldn't do that. Conductors of the same circuit need to be ran together. As PC suggests, what if some plumber comes in down the road and replaces a section of plumbing with PVC? Now that receptacles ground is not making it back to the bonding jumper at the water meter, thus not making it back to the main panel...

 

[madpenguin]

Ugh...... Ground faults need to make it back to the panel location.... All power needs to return to it's source, not just thrown out into the front yard on a water pipe left to it's own devices.....

Think I'll jump out of this one. It's starting to slide downward.

 

[BrainOGrefuGee]

those are 2x25A fuses. I should change them for 20?

so if I ran a 4 wire to this box, and connected the bare to the cold water pipe(inches away) I could put in a sup panel? would it have to be fuse? or can I use a breaker box?