Vent fan: no ground wire with K & T.

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Old 10-12-16, 06:22 PM
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Vent fan: no ground wire with K & T.

I have a house built in 1929. I'd like nothing more than to replace all the old wire with three wire. That way I could have grounded outlets. However I'm not ready for that; the old wires simply disappear behind the plaster where it begins a knob and tube lay out.

I recently redid our bathroom and added a fan to pull out moisture, however I've only got a hot and a neutral wire to work with. Can I ground to a water pipe? what is the best option?

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Old 10-12-16, 06:57 PM
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No, you can not just bond to a water pipe.

Extending an ungrounded circuit is not allowed in the NEC. What did you tie the fan into? Did you have an existing circuit/wires to connect the fan to?
 
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Old 10-12-16, 08:58 PM
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I haven't done anything yet. I have a hot and a neutral wire; knob and tube. The picture I loaded is what I have available. It is the circuit that powers the whole upstairs of the house sadly. Yet it is all that I have.

We don't really use a lot of power though so I don't expect this fan to make or break this line's capacity.
 

Last edited by benw3; 10-12-16 at 09:03 PM. Reason: Add thought
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Old 10-13-16, 02:58 AM
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There is a section of wire spliced into the two wires which were mounted about 12" apart. Whoever tied into the circuit simply scored off insulation and wrapped some electrical tape around the connections. I did however cut out that old connection and use some wire nuts to connect redo what was already present.

I haven't moved forward on wiring this vent/light. Can I simply tie into the circuit on the romex wire which was spliced into the knob and tube source? Perhaps omit the ground? Will this be problematic.

QT130LE Bath and Ventilation Fans - Broan
 
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Old 10-13-16, 03:23 AM
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Can I simply tie into the circuit on the romex wire which was spliced into the knob and tube source?
No. The Romex wire in its self was probably a code violation. As Tolyn said you can NOT extend an ungrounded circuit. You will need to run a new circuit from your fuse or breaker box.
 

Last edited by ray2047; 10-13-16 at 04:18 PM.
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Old 10-13-16, 09:59 AM
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Well thank you. I'm glad that I asked. I will see what I can do.
 
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Old 10-13-16, 10:58 AM
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Other than the code reasons to not extend an existing K&T wiring, it is probably a good opportunity to run a new grounded, 20A circuit into the bathroom to bring it up to current code. The 20A circuit can be GFI protected and run a receptacle, lighting, and the fan in the bathroom.

With today's high-wattage hair dryers, straighteners, and other hair-care devices, a dedicated circuit is probably well worthwhile.
 
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Old 10-13-16, 02:05 PM
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Legally you can't do anything with K&T other than leave it alone. If you change or modify the circuit it needs to be replaced up to modern code.
 
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