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old house lighting fixture install - no ground - knob and tube...

old house lighting fixture install - no ground - knob and tube...


  #1  
Old 11-18-07, 03:41 PM
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Question old house lighting fixture install - no ground - knob and tube...

Hey folks,

I am working on replacing some old light fixtures in my 107 year old house, one with a ceiling fan. The feed from the switch to the ceiling box is knob and tube, so as you can imagine I have nothing to ground to up there. The feed to the switch is grounded though. It seems like the three options I have in decreasing invasive order are...

-Run a new feed up to the light and tear up the room in the process.
-Put a GFI upstream of the feed and have the light GFI protected, but not grounded (the feed is readily exposed in the basement).
-Do nothing and not have a grounded light.

Would the GFI give me a fair bit of protection from the entire fan energizing due to a fault of some sort without the need to tear up perfectly nice walls?

Thanks for all of your help!
-Bob
 
  #2  
Old 11-18-07, 03:54 PM
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I would install it ungrounded. No one can reach up and touch the fixture. It would not be a risk.
 
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Old 11-18-07, 04:03 PM
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Unfortunately this one's for a ceilng fan with the pull chains

I'll have to get in the routine of checking the fixtures for current when changing lightbulbs. This issue is all over the place in my house. It's definitely not worth it to rip up all of the walls. For this one fan though, the difference is I could wire in a GFI in the basement I believe. Perhaps I could eliminate the chains and have this fan run off the switch only, plus the wireless remote that came in the box. What do you all think?

Thanks for the reply!
 
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Old 11-18-07, 04:32 PM
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Checking the fixture enclosure for voltage when changing light bulbs?? As in dragging an extension cord up the ladder/stool with you for the ground? Wow, you don't fool around do you.

I'd say you're more likely to have a problem just from disturbing all that K&T than getting bitten from a hot fixture. Instead of checking for voltage every time I changed a light bulb I'd just make sure my other hand wasn't somewhere it shouldn't be... like a ground.

There is a 4th option, if you're that concerned about all these fixtures. Swap out your lighting circuit breaker(s) for GFCI ones. This has the advantage of not requiring the addition of any wiring at all.
 
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Old 11-18-07, 04:42 PM
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There is very good possibility that if this is a 100+ year old house and it still contains K & T wiring then the house is probably wired with a fuse panel not a breaker panel, therefore the best option (IMHO) is to install the gfci somewhere at the first of the circuit. Personally, I would try to install a faceless GFCI right at the panel and then feed the circuit from the load side of the CFCI.
 
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Old 11-18-07, 04:53 PM
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Yes, good point. I guess when he said the feed to the switch was modern wire with a ground I made the assumption that they may have done what they did in my 100+ y/o house: Redid everything that was easy to get to (panel, floor level receptacles) but left the light fixture wiring alone.
 
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Old 11-18-07, 05:00 PM
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I've seen that done also but I think you simply misread his post. He mentioned running new Romex to the fixture as a possible ( although last resort) solution to his problem.

My normal response to anyone who mentions K & T wiring is to replace it (all at once or over time) but rewatters seems to want to keep the walls undamaged.
 
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Old 11-18-07, 05:45 PM
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You asked a question that needs to be addressed. You asked, " Would the GFI give me a fair bit of protection from the entire fan energizing due to a fault of some sort..."

The answer to that question is no. No GFCI prevents a fault from occurring . Further, if a fault does occur a GFCI may not catch it. What the GFCI will do is to prevent that fault current from causing death should the current try to find it's way back to the source via something other than the the neutral.

For example, in your situation the metal parts of the fan could become energized. This in and of itself will not trip the GFCI. Should you touch an energized metal part of the fan and be grounded, say through an aluminum ladder, then the fault current would trip the GFCI. However, should you contact the an energized metal part of the fan with one hand and contact the neutral wth your other hand, you will get 120 volts through your body.
 
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Old 11-18-07, 05:59 PM
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Originally Posted by Rollie73 View Post
I've seen that done also but I think you simply misread his post. He mentioned running new Romex to the fixture as a possible ( although last resort) solution to his problem.

Nah, not that part, the part where he said "The feed to the switch is grounded though.".

Well, rewatters, we're dying to know! (Ok maybe not dying) You got modern a breaker box down there?
 
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Old 11-18-07, 06:03 PM
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Thank you, racraft, for that excellent explanation of the operation of a GFCI on a circuit without ground.
 
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Old 11-18-07, 06:39 PM
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Originally Posted by core View Post
Nah, not that part, the part where he said "The feed to the switch is grounded though.".

Well, rewatters, we're dying to know! (Ok maybe not dying) You got modern a breaker box down there?
Yes I do! I should have mentioned that as well. Thanks for all of the responses guys! I'm all ears! The GFCI breaker option sounds attractive as well.
 
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Old 11-18-07, 06:50 PM
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Originally Posted by 594tough View Post
Thank you, racraft, for that excellent explanation of the operation of a GFCI on a circuit without ground.
Ditto! In spite of the GFI acronym, I had forgotten the difference in protection between a fault and "completing" the circuit. Maybe I shouldn't have tried to give up coffee this weekend.
 
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Old 11-18-07, 09:40 PM
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Since he has a modern breaker box perhaps an AFI breaker might be considered to in case some of the disturbed K&T insulation finally fails. Just a thought , could be wrong.
 
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Old 11-19-07, 05:05 AM
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Good point. I'm curious how the arc fault interrupter would fit into this situation as well. Would that be a worthwhile upgrade for all of the knob and tube circuits?
 
 

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