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Knob and Tube wiring and replacing outlet.


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Some building code jurisdictions permit a 3-prong receptacle in the absence of a grounding conductor if that device is a GFCI device but I don't recommend it.

Surge devices won't work if there's no ground connection. They use the ground wire to bypass lightning currents to the earth where it can safely disperse. Without a ground, a surge protector offers only the illusion of protection.

Do what Ghent suggested...upgrade the wiring.

Marc

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Good point about the surge protectors being useless, didn't even think about that before. Our two main reasons for not upgrading the wiring are cost and wanting to keep the old plaster walls. Is there a way to run new wiring without damaging the walls (much) to the second floor?

Sure. Google, SURFACE RECEPTACLE ELECTRICAL RACEWAY

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Surge devices won't work if there's no ground connection. They use the ground wire to bypass lightning currents to the earth where it can safely disperse. Without a ground, a surge protector offers only the illusion of protection.

Marc

Marc, are you talking about Point of Entry surge protection or Point of Use type surge protection? Just curious.

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Surge devices won't work if there's no ground connection. They use the ground wire to bypass lightning currents to the earth where it can safely disperse. Without a ground, a surge protector offers only the illusion of protection.

Marc

Marc, are you talking about Point of Entry surge protection or Point of Use type surge protection? Just curious.

I'm referring to duplex receptacles that have GFCI protection built-in.

Yeah, that jogs my memory. Surge protection could be installed in the main panel. Shoulda mentioned it. Thanks.

So Andrea, if you're reluctant to disturb the plaster, maybe just install GFCI protection on all 120V branch circuits, surge protection in the main panel and leave it at that. Try installing just one GFCI receptacle at first because device boxes were much smaller long ago and you might find that a bulky GFCI receptacle won't fit in them. If a GFCI breaker - an alternate solution to GFCI receptacles - won't fit in the main panel either, you're back in square one. Let us know.

Marc

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"One of the biggest mistakes many restorers make is to try to replace every piece of old wiring in the system, says Michael Hedrick of Historic Electric Preservation in Fredericksburg, Virginia. “Most efforts tend to be heavy-handed and replace more than what is truly necessary to an older system. Many parts of an older wiring system, if they have been undisturbed, are still quite usable and reasonably safe,â€

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A 3-hole receptacle on a 2-wire system gives people the illusion of a grounded electrical system. That is why those outlets should be labeled ungrounded, or have GFCI receptacles installed for a bit of protection. I understand an ungrounded GFCI receptacle will still trip, but I haven't tried it myself.

If the house has exposed framing in the basement, it is fairly simple to install new receptacles in the first floor walls. They can go in a few inches above the floor. A hole for a receptacle is large enough that the electrician can reach in and pull the new wiring in from below. Then they can install a junction box that has clamps in it so the box anchors itself in the hole. Sometimes the new receptacles are installed horizontally in the baseboard trim.

With wiring pulled in to the first floor to a hole for a receptacle, it isn't that hard to reach down from the second floor with a fish tape and pull a feeder up to the second floor. From there to the attic. Then you can run across from the attic to the other second floor rooms. That would be my recommendation. Pull in as much new wiring as possible.

Buy a couple of electrician's fish tapes or maybe they are called something different down there. Stiff wire with hooks bent into the ends.

If you don't rewire the home, then technically you should not blow insulation into the walls or the ceiling. Knob and Tube wiring is not designed to be covered by insulation, so it could heat up in an insulated wall.

It's all very well for a guy to write an article saying K&T is OK left alone. It won't be his house that catches fire from undiscovered damaged wiring. The insulation on that old wire is rubber from rubber trees. Some of it is in excellent condition and some is dry and flaking off. Some of it has been attacked by rodents.

We load the system down with 10 times more gadgets than our grandparents ever did. There are no enough receptacles in the house. Are you going to keep the old K&T and run extension cords around the rooms? Plugging in some space heaters, maybe?

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A 3-hole receptacle on a 2-wire system gives people the illusion of a grounded electrical system. That is why those outlets should be labeled ungrounded, or have GFCI receptacles installed for a bit of protection. I understand an ungrounded GFCI receptacle will still trip, but I haven't tried it myself.

If the house has exposed framing in the basement, it is fairly simple to install new receptacles in the first floor walls. They can go in a few inches above the floor. A hole for a receptacle is large enough that the electrician can reach in and pull the new wiring in from below. Then they can install a junction box that has clamps in it so the box anchors itself in the hole. Sometimes the new receptacles are installed horizontally in the baseboard trim.

With wiring pulled in to the first floor to a hole for a receptacle, it isn't that hard to reach down from the second floor with a fish tape and pull a feeder up to the second floor. From there to the attic. Then you can run across from the attic to the other second floor rooms. That would be my recommendation. Pull in as much new wiring as possible.

Buy a couple of electrician's fish tapes or maybe they are called something different down there. Stiff wire with hooks bent into the ends.

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Listen to Bill. Some electricians know the framing and if this house of yours uses a certain features of balloon framing then it might afford an easy way to get new cables up to the second story from the basement. I've done it myself in the past year. In balloon framing, there's no plate between the lower and upper story, just a rim let-in to the studs to secure the floor joists to the walls.

It's a labor intensive job though, any way you do it.

Don't allow just any electrician do it, they'll insult the house.

Marc

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Another issue with K&T is that it is just not designed to carry the loads our modern electronics will place on those circuits.

Also, if some outlets have stopped working as stated in the OP then I would be looking a little further down that line. A home with K&T is just a prime candidate for the local fire department to practice their skills.

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It's all very well for a guy to write an article saying K&T is OK left alone. It won't be his house that catches fire from undiscovered damaged wiring. The insulation on that old wire is rubber from rubber trees. Some of it is in excellent condition and some is dry and flaking off. Some of it has been attacked by rodents.

We load the system down with 10 times more gadgets than our grandparents ever did. There are no enough receptacles in the house. Are you going to keep the old K&T and run extension cords around the rooms? Plugging in some space heaters, maybe?

Excellent comment. Just an example of the some of the dumb advice that people give online. Where's the Like button?
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A 3-hole receptacle on a 2-wire system gives people the illusion of a grounded electrical system. That is why those outlets should be labeled ungrounded, or have GFCI receptacles installed for a bit of protection. I understand an ungrounded GFCI receptacle will still trip, but I haven't tried it myself.

If the house has exposed framing in the basement, it is fairly simple to install new receptacles in the first floor walls. They can go in a few inches above the floor. A hole for a receptacle is large enough that the electrician can reach in and pull the new wiring in from below. Then they can install a junction box that has clamps in it so the box anchors itself in the hole. Sometimes the new receptacles are installed horizontally in the baseboard trim.

With wiring pulled in to the first floor to a hole for a receptacle, it isn't that hard to reach down from the second floor with a fish tape and pull a feeder up to the second floor. From there to the attic. Then you can run across from the attic to the other second floor rooms. That would be my recommendation. Pull in as much new wiring as possible.

Buy a couple of electrician's fish tapes or maybe they are called something different down there. Stiff wire with hooks bent into the ends.

If you don't rewire the home, then technically you should not blow insulation into the walls or the ceiling. Knob and Tube wiring is not designed to be covered by insulation, so it could heat up in an insulated wall.

It's all very well for a guy to write an article saying K&T is OK left alone. It won't be his house that catches fire from undiscovered damaged wiring. The insulation on that old wire is rubber from rubber trees. Some of it is in excellent condition and some is dry and flaking off. Some of it has been attacked by rodents.

We load the system down with 10 times more gadgets than our grandparents ever did. There are no enough receptacles in the house. Are you going to keep the old K&T and run extension cords around the rooms? Plugging in some space heaters, maybe?

Yes and yes, right after I blow dry my hair...in the shower.

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I've met some pretty good electricians that can update all the knob & tube wiring with limited damage to plaster. If they have a knowledge of the framing methods and "know the tricks" damage and patching is minimal. They ain't cheap though.

Bill, always enjoy your work.

not sure about this though from your link

The hot and neutral wires are always separated by at least 3 inches except near a connection to a box or fixture. At these places, an additional protective woven sleeve, or was used from the last knob.

did you omit loom or have something else in mind?

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We have a few outlets that stopped working and my husband wants to put a grounded outlet in. I have read that you should only have ungrounded outlets with knob and tube, is that accurate?

Andrea,

The first thing to do is figure out why the receptacles have stopped working. If the receptacles themselves are bad or if the wiring at the back of the receptacles is bad, then there are probably other locations in the house where this is happening - or about to happen. Figure out the problem and then be sure to address all of the places that are likely to be affected.

The National Electrical Code gives you several choices of what to do with the non-working receptacles.

  • You can replace the ungrounded receptacles with new ungrounded receptacles. This is fine for places where you only plan to plug in ungrounded things - vacuum cleaners, clock radios, lamps, many laptop computers, etc.

You can replace the ungrounded receptacles with grounding-type receptacles, leave them ungrounded, and protect them with GFCIs. In this case you have to label the receptacle faces, "No Equipment Ground." If the GFCI protection is from a remote location, you also have to label them, "GFCI Protected." This choice will protect people as well as grounding will but it won't protect electronic equipment because, as mentioned earlier, surge protectors won't work without a ground to shunt the surge to.

You can replace the ungrounded receptacles with grounding-type receptacles and install a separate grounding conductor that runs from the new receptacle to the service panel or to a point on the grounding electrode system for the house. To do this properly is usually as much trouble as running a whole new cable. (You may *not* run a new grounding conductor to the "nearest water pipe" as used to be allowed in the days of yore.)

Of course, you can also install an entirely new cable to the receptacle and abandon or, better yet, remove the old knob & tube wiring.

Regarding the old knob & tube wiring, it's an obsolete system and you should at least consider replacing as much of it as you can. Always begin with the wiring in the attic because it's usually in the worst condition - particularly the wires directly above ceiling light fixtures, where the heat from the fixtures has burnt the insulation on the wires. The stuff in the attic and basement is easy to replace. Wiring in walls and in ceilings between floors is a little tougher but certainly possible. You can do a lot without disturbing much of the plaster walls if you learn how to use a 10' flexible drill bit.

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We have a few outlets that stopped working and my husband wants to put a grounded outlet in. I have read that you should only have ungrounded outlets with knob and tube, is that accurate?

Andrea,

The first thing to do is figure out why the receptacles have stopped working. If the receptacles themselves are bad or if the wiring at the back of the receptacles is bad, then there are probably other locations in the house where this is happening - or about to happen. Figure out the problem and then be sure to address all of the places that are likely to be affected.

The National Electrical Code gives you several choices of what to do with the non-working receptacles.

  • You can replace the ungrounded receptacles with new ungrounded receptacles. This is fine for places where you only plan to plug in ungrounded things - vacuum cleaners, clock radios, lamps, many laptop computers, etc.

You can replace the ungrounded receptacles with grounding-type receptacles, leave them ungrounded, and protect them with GFCIs. In this case you have to label the receptacle faces, "No Equipment Ground." If the GFCI protection is from a remote location, you also have to label them, "GFCI Protected." This choice will protect people as well as grounding will but it won't protect electronic equipment because, as mentioned earlier, surge protectors won't work without a ground to shunt the surge to.

You can replace the ungrounded receptacles with grounding-type receptacles and install a separate grounding conductor that runs from the new receptacle to the service panel or to a point on the grounding electrode system for the house. To do this properly is usually as much trouble as running a whole new cable. (You may *not* run a new grounding conductor to the "nearest water pipe" as used to be allowed in the days of yore.)

Of course, you can also install an entirely new cable to the receptacle and abandon or, better yet, remove the old knob & tube wiring.

Regarding the old knob & tube wiring, it's an obsolete system and you should at least consider replacing as much of it as you can. Always begin with the wiring in the attic because it's usually in the worst condition - particularly the wires directly above ceiling light fixtures, where the heat from the fixtures has burnt the insulation on the wires. The stuff in the attic and basement is easy to replace. Wiring in walls and in ceilings between floors is a little tougher but certainly possible. You can do a lot without disturbing much of the plaster walls if you learn how to use a 10' flexible drill bit.

Thank you for the detailed response!

I agree with the general consensus, replacing all the wiring would be ideal. However, that won't happen this year or even next. Or at all if we can't find an electrician that will preserve the walls. But for the short term, we would like to address the most pressing issues. Properly replacing the outlets that have gone out. Replacing wiring in basement since one of the breakers keeps tripping after lights are on for 2 mins, and a couple other small things.

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