You can safely cut off the ground wire. It would serve no purpose at all unless the entire circuit was grounded at the entrance box.

thanks for response. so, what if the entrance box is grounded? would the ground serve a purpose and is there a way to.connect the wires, one with and the other without ground?

thanks for response. so, what if the entrance box is grounded? would the ground serve a purpose and is there a way to.connect the wires, one with and the other without ground?

The entrance box would be grounded, probably to a copper alloy rod driven into the ground. That's not the question though. Prior to changes in the electric codes, all residential wiring used only two wires, the black hot wire and the neutral white one. This is what you have. When the codes changed a third grounding wire was required. From that point onward entrances boxes contained a strip where the third grounding wire for each circuit could be attached. All outlets and other devices also began to have a place where the grounding could be attached. Thus you would have a continuous path to ground from any point on all of the circuits serving the house - a significant safety improvement.

In your case, your entrance box may or may not have a grounding strip, but the only way it could be utilized in the way intended would be to replace the entire two wire circuit with a three wire one. What you need to do is connect white to white, black to black and disregard the grounding wire.

If you are not confident in your ability to do this safely, call an electrician or at least someone with experience. The splices can be made using wire nuts, but the whole thing needs to be placed inside an approved junction box. Your fan will not be grounded so electrical shock from the metal housing is possible but highly unlikely - this would only happen if somehow the insulation on the wires were so damaged current entered some other part of the fan or its housing.

thanks so much. I do have the older white/black wiring all over the house. guess im just a little paranoid of electric issues, such as lightning and such if not properly grounded. I do have the junction box with nuts and someone briefly explained the process, but wasnt too sure I.understood. for example, I have the original old wire laying up in the attic , which is too short to make it to the fan. so im gone go up to.the attic with this new wire (after shutting off main electric from panel) and the junction box with nuts and junction box cover. I already popped the hole in the junction box. I understand the junction box is so that if there is a short the fire is contained in the box, or something like that.

so im gone nail or screw box onto a stud. I suppose I will run the original wire through the hole.......and this is where im.stuck. do I join the wires at this point, do I ground here?

thanks so much. I do have the older white/black wiring all over the house. guess im just a little paranoid of electric issues, such as lightning and such if not properly grounded. I do have the junction box with nuts and someone briefly explained the process, but wasnt too sure I.understood. for example, I have the original old wire laying up in the attic , which is too short to make it to the fan. so im gone go up to.the attic with this new wire (after shutting off main electric from panel) and the junction box with nuts and junction box cover. I already popped the hole in the junction box. I understand the junction box is so that if there is a short the fire is contained in the box, or something like that.

so im gone nail or screw box onto a stud. I suppose I will run the original wire through the hole.......and this is where im.stuck. do I join the wires at this point, do I ground here?

fhorta-
With all due respect, you're getting in over your head. Do you have any friends with electrical experience? I can tell from your questions that you don't have the background to end up with a safe installation and may not even have all the parts you need to make this code compliant. If this involved just one technical issue, I'd provide more detail, but I'm worried that there is no way I can responsibly empower you to get this right. I'm all for do-it-yourself, but not when there's the potential for an unsafe result.

understand. thanks.

Thanks for not taking offense. I just wanted to keep you safe and not end up with a dangerous result. I remember some of the unknowing mistakes I made when I was first learning wiring and so I know how easy it is to mess up. If you don't have a friend who can help, at least get a book on basic wiring at the library. Good luck.

understand. thanks.

fhorta: At this point, I'm with kudzu9 on this one. There are too many questions involved here: The wire is just lying up in the attic? Where does it go? Are you even sure it carries any current? What kind of junction box are you using? Will the circuit involved have the capacity to run the fan? Further, you are confused about the difference between lightning protection and grounded wiring. Everyone starts out knowing not very much at all. Electrical work is the wrong place, however, for trial and error learning. I just can't encourage you to proceed without some on site help.

appreciate it. and I guess I left.some things out. the wire up in the attic was in the bathroom a.nd prev iously powered a vanity light. wires were just sticking out of the wall and I hook it to the new fan , turned on the switch and the fan turned on. this told me there was power on the wires and could turn on the fan. I will try to.find.someone who.can help. thanks for.concern.

What you are missing is that if there is no ground wire in the existing cable, there will be no ground for the circuit and any extension of that circuit. The new cable's ground wire can therefore be ignored because if it were connected it would not be doing anything. Connecting it would only mislead someone who was working on the circuit later.

The purpose of the ground wire is to trip the breaker if the housing of the exhaust fan came in contact with the wiring and would shock someone who touched it. It is unlikely that someone would be touching the housing unless there is a light in the fan housing. I'm not sure what the electrical code says about extending a non-conforming circuit to a new fan but I doubt it is allowed. Of course, it is also likely that only a licensed electrician is allowed to do this work. In any case, if the installation caused a fire it is unlikely you would be insured if there was evidence the fan was not installed by a previous owner.

Also, if the new junction box is metal you must use cable clamps where the cables enter through the knock-out holes. The box not only provides isolation of the connection but secures it so it can't be pulled apart. The cable must also be stapled to the framing at certain intervals; it can't be lying loose in the attic.

2 wire ungrounded non-metallic sheathed cable is rare in my area. Post knob & tube, home wiring was metal armored (AKA "BX") and the metal provided a ground to the metal boxes although it was not always reliable for long circuits. In the 60's an aluminum strip was added inside the cable to improve the continuity of the ground. Non-metallic (plastic) sheathed cable (AKA "Romex") became popular in the 50's and in 62 the electrical code made a bare ground wire mandatory for all branch circuits. For your wiring to have only 2 wires and no ground it would probably have been installed in the 50's by someone who didn't want to use BX cable. But this is not all bad because the insulation on BX wiring tended to crumble when exposed to air and is more dangerous than any other kind of wiring wiring.

For any further help you should post photos of the original cable and the main panel with the cover off. Tripping the main breaker is wise but NEVER assume a branch circuit is dead without using a voltage detector. If a breaker can be turned off, it can be turned on again by someone else. Always put a note on the panel. A 120v wire can stop your heart instantly. A voltage detector is the smartest $10 you will ever spend.

Here is a link that might be useful: voltage detector

thanks.for all this information, I really do appreciate it. will keep you posted and try to take pics.

A 120v wire can stop your heart instantly.

If voltage is what kills, you'd be dead every time you discharged a static electrical charge, 20,000 volts.

Ten milliamps 'll do ya in.

BTW, my electrical instructor taught us to never rely on a voltage detector, but to also physically short out any wiring we planned on working with. I've got a large screwdriver with the marks to prove the wisdom of that advice!

Here is a link that might be useful: Fatal Current

Just a couple of corrections:
Home owners can legally do electrical work in their own detached home that they live in (ie. landlords can't work on their rental properties). Multi-family dwellings are different and require an electrician. Some areas may have more stringent conditions, but this is the general rule.

And while insurance may TRY to deny claims if you are proven to have done something against code that caused a fire, they can't actually deny it. You are protected against your own stupidity or ignorance. Unless you did something intentional to burn down your house, you are covered. Just like if you left a candle burning and it tipped over and caught your curtains on fire. Insurance covers that. If you doused the room in gasoline before lighting that candle, then you will be denied coverage.
Insurance companies will try to deny your claim for any and every reason, whether it makes sense or not. If it prevents only 1% of their customers from pursuing a claim, then they still come out ahead. Fight it and you'll get what you are entitled to.
Having said that ... you obviously don't want to burn your house down even if you are covered, so figuring out the correct way to do this is important. And if you aren't comfortable, hire someone.