View Full Version : knob and tube wiring

08-03-2007, 11:42 AM
I am helping my friend with his old house with some of the old wiring, knob and tube, part of the house. The house inspector told him to change that because it were not grounded. (only two wirings). My questions:
What is my best solution to change its to 3 wiring system?
To rewire the whole house it going to cost time and money, any other suggestion?

08-03-2007, 12:24 PM
If the old wiring isn't disturbed, it is still usable. Any time you have access, it is best to update...and a whole house update, while expensive, is a good idea. It is also likely that the system has fuses rather than circuit breakers and the main supply line may be limited in total power it can bring in, so a new panel, including drop from the power pole may be called for. One of the pros will have some ideas, when they get home from work.

08-03-2007, 09:24 PM
A fire, or injury, will also cost time and money. Either rewire what you have to now, or do the entire system and get it over with.

08-03-2007, 10:54 PM
It's not clear from your question whether the walls are open. If the walls are open, replace it.

If the walls are intact, and rewiring the whole house is not in the budget... there are differences in the canadian and american electrical codes, but I've heard that you can provide protection to an ungrounded receptacle, by putting in a gfi.

Near as I understand, it will NOT provide GFI protection, because there's no ground; and the test button won't work; but it does protect as much as a ground connection would...

Mike (JWelectric) knows more about this - hopefully he'll drop in on this thread & explain the details better.

It's also not clear from your post, exactly what the inspector had to say. If the receptacles are 3-prong, they MUST be grounded. It would be a safety violation to have them in a 2-wire system, because they're giving the illusion of ground protection where there isn't any. If that's the problem, the bare minimum you can do is replace those receptacle with 2-prong receptacles.

08-04-2007, 06:41 AM
The wall is not open and that P.I.T.A. I might have to tear down the basement ceiling.
The house inspector advise are to remove those wire because of the house insurance demanded. But the house with updated circuit breakers, only part of the house with knob and tubes wires.

Bob NH
08-04-2007, 09:32 AM
If you install a GFCI receptacle as the FIRST outlet on the circuit, and connect the outgoing circuit to the LOAD terminals of the GFCI receptacle, then the whole circuit is GFCI protected. You should then add a little sticker (several are furnished with the GFCI receptacle) to the other receptacles saying that they are GFCI protected.

The GFCI receptacle measures the difference between the current in the hot wire and the neutral. If that difference exceeds about 0.006 Amps, then it trips the GFCI to shut off the power. It DOES NOT depend on a ground wire.

You or your buddy should invest in the tools you need to fish wires through walls and plates, and some "old work" boxes, and rewire where you need to. It isn't that hard. Some people use long flexible drills to drill through plates from access at the outlet or switch plate holes. I usually find a way to get at the plate from above or below.

While you are learning it is easier to use 15 Amp circuits with #14 wire. There may be some cases where you need #12 for 20 Amp kitchen and bath circuits.

08-04-2007, 10:56 AM
Depending on your friend's insurance company, you may have to re-wire the whole house; seems some companies won't insure you if there's any knob & tube in the place.

Although it got off-topic very quickly, this thread from JLC is where I heard about using GFI's:


Another potentially useful thread:


(warning: that website, JLConline, is a great source of info; but it's strictly "pro-only". Feel free to lurk, read, search... but do not post questions there unless you're in the construction industry. You won't get answers, you'll just get flamed.)

08-04-2007, 11:01 AM
What kind of tools called "fish wires through walls and plates""?
How it works?

08-04-2007, 11:20 AM
Looks like this:


there another type, called fish sticks, that are more rigid (like a fishing pole), you screw the 4' sections into each other to the length you need.


You use these to "fish" your new wires through the wall.

Bob NH
08-04-2007, 12:50 PM
Check out this link to see flexible bits for fishing expeditions.