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Old 09-10-2008, 07:47 AM   #1
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Safety of old wiring


Hello,

I'm new here and I honestly don't know much about wiring so please excuse my ignorance.

I live in a 100 year old home with wiring that has been incrementally upgraded over the years. I have a 100 amp breaker box in an addition that was put in during the 1980's. The house has a combination of knob-and-tube, cloth NM, and plastic NM wiring. The majority of the knob-and-tube was replaced over the years but there are still a few runs of it in the attic and leading to lights on the second floor. There is an old fuse box in the attic, which is on its own circuit from from the breaker, and I believe it acts as a subpanel. I also believe this is the origination point of the knob-and-tube.

My insurance company notified me that they are raising my rates because of the presence of the fuse box. I bought the house a few years ago and the home inspector made a few notes regarding issues. Primarily, this involved two non-working outlets, a non-working light fixture, and splices that occur outside of a box.

Right now, I have a certain dilemma. My research on the internet seems to indicate that knob-and-tube is potentially very dangerous and should be removed in its entirety. But, I've spoken to multiple electricians and they all indicated that there is nothing inherently dangerous regarding knob-and-tube nor fuse boxes. They all recommended avoiding a complete rewiring of an older house and suggested dealing with individuals issues.

So, I basically have two options: a) Complete rewire of the house and b) Replace the fuse box with a subpanel and address each electrical deficiency individually.

Does anyone have any advice?

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Old 09-10-2008, 08:28 AM   #2
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Assuming the rest of the wiring is in good shape and there are no other issues, I would tackle the items individually.

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Old 09-10-2008, 09:19 AM   #3
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Safety of old wiring


Knob and tube that is in good condition will continue to serve you just fine. It is necessary though to get a look see at all of it that you can to determine its condition. Frayed clothed covering or deteriorated cloth covering that exposes the bare wire is not good. Frayed sheath covering or bare showing at insulators is not good, as is wire strings being buried in insulation. One particular place of problem is in light fixture boxes where the sheath becomes discolored from heat and basically will disintegrate to the touch.

Something like a receptacle that doesn't work can be many things other than the fact it is served by knob and tube.
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Old 09-10-2008, 09:49 AM   #4
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I had nearly an identical situation in a 100 yr old house. I eventually replaced all the wiring. I hired an electrician to do much of the second floor to get the bulk of the work out of the way. He also updated the main panel to 200AMP. I then tackled the more difficult runs like the 3-way lights at bottom/top of stairs, the front porch and all wiring on first floor.

My 3 quotes for the second floor work ranged from about $3000 to $7000. The electrician that worked by himself was the cheapest.... This was back in year 2001 or 2002.

The main problem that we discovered was not the K & T wiring. Copper does not go bad so the wire itself was fine. Most of the cloth insulation was in OK condition. The problem is that K&T wiring cannot be covered with attic or wall insulation because it can overheat (it was covered with fiberglass batts in the attic). In addition, there were may splices and J-box connections to new wiring throughout the house. Previous homeowner connections and splices were made in inaccessible places behind plaster walls which was kind of scary.

I felt much better getting rid of all of it.

Paul
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Old 09-10-2008, 03:12 PM   #5
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Safety of old wiring


You cannot put insulation in between knob and tube, it is not code...

also there could be j-boxes in between walls that is not code either.
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Old 09-10-2008, 04:17 PM   #6
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The main problem that we discovered was not the K & T wiring. Copper does not go bad so the wire itself was fine. Most of the cloth insulation was in OK condition. The problem is that K&T wiring cannot be covered with attic or wall insulation because it can overheat (it was covered with fiberglass batts in the attic). In addition, there were may splices and J-box connections to new wiring throughout the house. Previous homeowner connections and splices were made in inaccessible places behind plaster walls which was kind of scary.

I felt much better getting rid of all of it.

Paul
I, too, own a 100+ year old home. There are remnants of the knobs and tubes in the floor joists, but none of the cloth covered wiring, my mom had that replaced with 12/2 back in the late 1960's.

My dilema right now involves my desire to upgrade the electrical system so I can use GFCI and ASCI outlets in the house. I did recently upgrade the home's service from 100 amps to 200 amps, paid dearly for underground service to avoid tearing the old walls out with the weight of the larger 200 amp overhead service wire from the pole, and ran some additional circuits down into the basement for future expansion, but the 12/2 without ground does not support GFCI/ASCI, so here I am looking at the need to upgrade my current wiring yet again.....

The owner of the local hardware company says the 12/2 is just fine, no need for GFCI's or ASCI's, but as long as I'm upgrading the electrical and plumbing systems I might as well do it right this time. Sure wish my mom hadn't been such a tightwad back in the 60's and had spent the extra $5 per roll of wire to get the 12/2 with ground .

So, as long as we have a thread regarding the safety of the wiring in older homes, I'm hoping somebody will have some ideas regarding the need for me to upgrade from 12/2 to 12/2 with ground as it relates tyo the need (????) for GFCI/ASCI outlets.............needless to say, I wouldn't go through the trouble if I weren't worried about safety .

Thanks!

Dugly
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Old 09-10-2008, 04:47 PM   #7
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Safety of old wiring


In the jurisdiction where I live, the code has been amended this year, to allow the replacement of non-grounded recepticles, fed by non-grounded cable with ground fault receptacles.
No need to have a ground wire run in.
Perhaps this would be allowed in your area, also!
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Old 09-10-2008, 05:41 PM   #8
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In the jurisdiction where I live, the code has been amended this year, to allow the replacement of non-grounded recepticles, fed by non-grounded cable with ground fault receptacles.
No need to have a ground wire run in.
Perhaps this would be allowed in your area, also!
Anything is allowed in my area, the town is 4 blocks long and 3 blocks wide, there are 118 people in the town and the entire county doesn't have any codes or inspectors.

I didn't realize it was an issue of codes, I thought it was an issue of not having a ground wire and the GFCI wouldn't work without a grounding circuit.

If you can turn me on to a source for the GFCI outlets that will work without a ground wire, I'll be all over that. The Arc Sensor Circuit Interrupters would have been nice in the bedroom, but those GFCI breakers sound like a must near the kitchen sink and the bathroon sink....maybe in the garage?

Thanks, please tell me more about these GFCI receptacles that would work with my current 12/2 wiring .

Dugly

Last edited by YerDugliness; 09-10-2008 at 05:43 PM.
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Old 09-10-2008, 07:25 PM   #9
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All GFCI receptacles will work without a ground. The GFCI measures current between the hot and neutral and trips when an imbalance of 5mA or more is detected. The presence or absence of a ground has no effect.
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Old 09-10-2008, 07:40 PM   #10
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Originally Posted by YerDugliness View Post
Anything is allowed in my area, the town is 4 blocks long and 3 blocks wide, there are 118 people in the town and the entire county doesn't have any codes or inspectors.

I didn't realize it was an issue of codes, I thought it was an issue of not having a ground wire and the GFCI wouldn't work without a grounding circuit.

If you can turn me on to a source for the GFCI outlets that will work without a ground wire, I'll be all over that. The Arc Sensor Circuit Interrupters would have been nice in the bedroom, but those GFCI breakers sound like a must near the kitchen sink and the bathroon sink....maybe in the garage?

Thanks, please tell me more about these GFCI receptacles that would work with my current 12/2 wiring .

Dugly
GFI's depend on the neutral current being equal to the supply current. Has nothing to do with the ground in the cable.
What this means if current flowing through the supply conductor flows through a human body and then via a faucet in the bathroom to ground, there will be no current in the neutral and the GFI will trip.
Or if current flow from another circuit gets crossed to the neutral, it will trip also.
The ground in the cable is used to trip the fuse or breaker, if a short circuit occurs. This is to prevent over-heating that could result in a fire.
If a human is connected from the hot wire, to the ground, he will be fried before the breaker ever trips.
The idea behind the ground wire was in case the housing for a device became shorted to the hot wire, the circuit protection(fuse/breaker) would trip.
Now most tools have double insulated, plastic housings so there is less concern about shorts.
Probably, clothes dryers are most likely have internal electrical probs. The elements are prone to separating and one end falling down to touch the housing.
In this case, the whole cabinet is protected by the cable ground.
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Old 09-10-2008, 10:21 PM   #11
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Quote:
Originally Posted by Wildie View Post
GFI's depend on the neutral current being equal to the supply current. Has nothing to do with the ground in the cable.
What this means if current flowing through the supply conductor flows through a human body and then via a faucet in the bathroom to ground, there will be no current in the neutral and the GFI will trip.
Or if current flow from another circuit gets crossed to the neutral, it will trip also.
The ground in the cable is used to trip the fuse or breaker, if a short circuit occurs. This is to prevent over-heating that could result in a fire.
If a human is connected from the hot wire, to the ground, he will be fried before the breaker ever trips.
The idea behind the ground wire was in case the housing for a device became shorted to the hot wire, the circuit protection(fuse/breaker) would trip.
Pardon my seeming ignorance on this matter, it's been many years since I studied electrical theory, but as I understand this, any GFCI outlet will still work with my 12/2 without ground as long as I connect the hot and the neutral wires correctly. I helped pull and secure the 4/0 service wire into the current Square D electrical panel and I can assure you that there are three wires of equal gauge, one was marked and we were careful to observe that polarity as that one was carefully aligned with the common/ground (?) at the meter box and the common busses on the new electrical service panel. The new circuits I added, which are 12/2 with ground and 10/2 with ground, have both the neutral and the ground wires connecting to the same common bus on the panel--there was another piece of hardware included with the service panel that appeared to be used for establishing yet another separate ground circuit, but it wasn't used. The electrician assured me that a separate ground circuit with grounding rods was not necessary b/c there is a healthy (perhaps 10 gauge solid copper wire) ground circuit at the pole on which the meter box is mounted, and the uninterrupted line from the common buss on the box is (as I understnad it) linked to that ground wire. Therefore, it appears to me that any outlet connected correctly will have a neutral that is connected to the grounding circuit, am I right??????

Sure hope so.....but I'm willing to admit that it might be necessary for me to get GFCI circuit breakers rather than GFCI outlets if my understanding stated above is incorrect.

If I'm right about things, that makes it much easier for sure.....I'll get started wiring in the GFCI outlets in the kitchen and bathroom without worrying about having a ground wire in the circuit!!

There aren't many appliances in this house with metal cabinets, maybe an old toaster oven that doesn't get used much.....thanks to your great explanation I now understand why the owner of the local hardware store said not to worry about rewiring......thanks again, Wildie!

Dugly
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Old 09-11-2008, 05:51 PM   #12
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Pardon my seeming ignorance on this matter, it's been many years since I studied electrical theory, but as I understand this, any GFCI outlet will still work with my 12/2 without ground as long as I connect the hot and the neutral wires correctly. I helped pull and secure the 4/0 service wire into the current Square D electrical panel and I can assure you that there are three wires of equal gauge, one was marked and we were careful to observe that polarity as that one was carefully aligned with the common/ground (?) at the meter box and the common busses on the new electrical service panel. The new circuits I added, which are 12/2 with ground and 10/2 with ground, have both the neutral and the ground wires connecting to the same common bus on the panel--there was another piece of hardware included with the service panel that appeared to be used for establishing yet another separate ground circuit, but it wasn't used. The electrician assured me that a separate ground circuit with grounding rods was not necessary b/c there is a healthy (perhaps 10 gauge solid copper wire) ground circuit at the pole on which the meter box is mounted, and the uninterrupted line from the common buss on the box is (as I understnad it) linked to that ground wire. Therefore, it appears to me that , am I right??????

Sure hope so.....but I'm willing to admit that it might be necessary for me to get GFCI circuit breakers rather than GFCI outlets if my understanding stated above is incorrect.

If I'm right about things, that makes it much easier for sure.....I'll get started wiring in the GFCI outlets in the kitchen and bathroom without worrying about having a ground wire in the circuit!!

There aren't many appliances in this house with metal cabinets, maybe an old toaster oven that doesn't get used much.....thanks to your great explanation I now understand why the owner of the local hardware store said not to worry about rewiring......thanks again, Wildie!

Dugly
You are welcome!
You are correct in assuming that the GFI will work if connected correctly!
In my area, the neutrals are NOT allowed to be connected to the same bus! The neutral bus must be isolated from the grounds on their own bus!
The neutral gets its ground at the transformer. Here its connected to the center tap of the transformer, that is in turn grounded to a ground rod at the pole.
Don't quote me on this, but I believe its to maintain the same potential relationship with the hot conductors.
To have the grounds on the same bus as the neutrals makes mr cringe. Just the way that I learned, I guess!
The ground at the meter, in my case must be a #6 run to 2 ground rods that are 10' long and are 10' apart.
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Old 09-11-2008, 07:18 PM   #13
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GFCI outlets will not fit in your existing boxes from the K&T era.

GFCI breakers will not work IF the citcuits are multi wire circuits (two hots "sharing" one neutral)

Have it Rewired.
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Old 09-12-2008, 10:50 AM   #14
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GFCI outlets will not fit in your existing boxes from the K&T era.

GFCI breakers will not work IF the citcuits are multi wire circuits (two hots "sharing" one neutral)

Have it Rewired.
The old wiring was replaced in 1966, so it is possible that new outlet boxes were installed. I do know they covered all the old plaster & lathe walls with sheetrock at the time. If so, the GFCI outlets should fit, but I'll keep that in mind as I proceed. I'll probably try just installing the GFCI's in the current boxes first (the path of least resistance ), but I'm ready if I need to do some new wiring.

Would you mind explaining further your comment regarding the two hots sharing one neutral?

This house was rewired with 12/2 (no ground) "romex" (??--it is copper wire, appears to have two insulated leads, one black and the other white, with what I would describe as a tough, white rubberized plastic sheath covering both of the leads).

The house was rewired by a couple of handyman types, there were no electricians in the area back in those days. I'm certain it's pretty much straightforward as to the wiring, although the main house circuit is IMHO overloaded b/c it has both the kitchen and the living room on it. There are no switch controlled outlets or lights controlled by three-way switches--are those the circuits you mean when you mention "...two hots 'sharing' one neutral?

The house has a basement, so I do have access to most of the wiring, which was run in the ground floor joist bays. There is one, maybe two circuits that were run overhead on the main floor, but that section of the house has a dropped acoustic tile ceiling system so there ought to be access for them, too. I'm almost afraid of what I'll find when I get into the ceiling area....maybe no junction boxes, that sort of thing. My mom was well known for cutting corners--hence my original belief that I had a dilema with the GFCI outlets. She did do some things right, though--I was able to replace two ceiling fixtures with rather heavy ceiling fans without any support problems, the current ceiling boxes were firmly secured with 2 X 4 between the joists.....

Thanks for the help, and if you don't mind please expand on the two hots sharing a common issue.

Dugly
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Old 09-12-2008, 12:13 PM   #15
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Had a ceiling fan wiggle its way off of the ceiling mount last weekend. Found it hanging by its fixture wires. Cut it free and told the kids I'd hang it again the next day. My wife notices that most of the receptacles in the upstairs are now no longer working. Understanding that the feed for most of them is derived from this same box, I figured that something got pulled apart when the fan came down. Looking more closely, I notice that most of the wires in this box have lost most or all of their visible insulation (old rubber insulated, cloth covered). Ok, no problem, I'll just move some of my rewiring work up in the schedule and start the next day by pulling out the old wire and replacing it with new. When I remove the light fixture in the bathroom adjacent to the kids' room (their room's wiring derives power from the bath), I am showered with little chunks of insulation. And look-how cute! Arc damage! I wind up rewiring pretty much the entire upstairs using the old steel conduit and pancake boxes (this is temporary until it cools down enough to work in my firebox of an attic). So, a 1/2 hour job turns into a 1-1/2 day job. And I still don't have a light in the bathroom (the kids have learned to use the flashlight that I have available just outside the door but I still can't get them to lift the seat).

Ahh, the joys of old home ownership

Aside: When I was up in the attic briefy (to trace the circuits), I was pleased to notice that whatever chucklehead owned the place prior to us decided to install an exhaust fan for the bathroom. I guess he figured, as long as the air is removed from the bathroom, who cares where it winds up. The thing was simply exhausting all of that warm, moist air right into the attic space (guess that explains why I was noticing ice crystals on the rafters last winter). I will give him credit though. He did cover the fan with an inverted clothes hamper to keep the loose fill insulation from disturbing its operation (the hamper was what cause the initial WTF).

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