Knob & Tube rewire - DIY?

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  #1  
Old 08-23-13, 07:32 AM
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Knob & Tube rewire - DIY?

Recently had our bathroom upgraded from knob & tube. I was home while the work was completed and from what I observed it did not appear to be too difficult.

I am thinking as long as I am careful and patient, I could do the rest of the house myself. I have rewired switches, lights, etc. in the past with positive results.

The only challenge I can see is correctly mapping out the circuits. Can someone recommend a good resource for this?
 
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  #2  
Old 08-23-13, 09:02 AM
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I would not worry about how the current circuits are layed out but instead run new circuits the way they should be laid out. Example the bathrooms and kitchens have very specific wiring requirements under modern code that K&T usually doesn't adhere to. In K&T wires for receptacles often spidered out from the overhead lights. Best practice now is to daisy chain each to the next. In K&T the spacing of receptacles is to great to meet modern code. The list goes no but bottom line you shouldn't use the current layout but what is correct and best practice today.

A method I'd suggest is to take it a room at a time and just install all new receptacles ignoring the existing receptacles and boxes. When the receptacles are complete and working disconnect power to the old boxes and receptacles and remove. It may be necessary to leave some receptacles till other rooms and lighting is done.

Wiring Simplified Available online from places such as Amazon and in the electrical aisle of some BigBox stores is a good place to start learning.
 

Last edited by ray2047; 08-23-13 at 09:36 AM.
  #3  
Old 08-23-13, 01:30 PM
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The most challenging part of rewiring an existing home is usually getting the new cables into the walls. Is your house all one story? Do you have access to the spaces above and below each room, through an attic, basement or crawlspace?

I would, as Ray suggests, set a completely modernized electrical system as my goal. That would include both AFCI and GFCI protection where needed, receptacles at the required spacing or closer, accessible power outsider and in the garage, a hard-wired interconnected set of smoke or heat detectors, etc. It may include upgrading your service and is likely to include replacing your main distribution panel, if it's as old as the K&T wiring.

It's definitely something you should do. A modern electrical system is light-years ahead of one installed in the 1920s in safety and reliability, as well as convenience. It's also something you can do yourself with a resource like Wiring Simplified and the advice you can receive here.

I would map out what you want to wind up with. Include all of the outlets - receptacle, switch and wall or ceiling lighting - and all of the heavy loads like a water heater or A/C compressor. At that point you can do a residential load calculation to see how your planned system compares to the service you have now. Unless you already have a 200A service, that is.

Should you map out your existing system? I think I would. Having that will tell you what you need to replace before you can kill one of your existing circuits and give you ideas about the most effective way to stage the work.

One point where I'll differ with Ray is this: I would not add a new receptacle (or switch box or light fixture box) next to an existing one and then remove the old ones once I had the new ones finished. For one thing, the lighting outlets and switch boxes that you have now, and probably most of the receptacles too, are right where you want to have them. Id you install a new one nearby, you'll not only have one slightly out of place, you'll have the old location to patch and paint after you demo it. No thanks. I'd replace the wiring, boxes and devices right where the old ones are, for the most part. This is where knowing what's on each existing circuit will come in really handy.

Two points: Your existing system probably feeds to a point for each circuit and then spiders out to the devices from there. Your new system will be wired as daisy-chains for the most part. Also, If you wire receptacle-only 20A circuits and separate 15A lighting-only circuits for your new system, you'll increase the odds of always having light in a room as you work and going forward. If you plan the receptacle circuits so that each room has at least two of them feeding it, you increase the chances of always having power in a room.
 
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Old 08-23-13, 02:17 PM
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For one thing, the lighting outlets and switch boxes that you have now, and probably most of the receptacles too, are right where you want to have them.
Most rooms in my 1947 wired house had only one receptacle per room. It was my house as a model I was thinking of. Hard to agree all the receptacles are where you want them if there are only one per room. If though the receptacles are where you want them and meet spacing codes I agree with Nash.

Here is an ad from the K&T era. Notice the appliances have Edison based screw-in "plugs" that screw into the nearest light socket.. Providing receptacles wasn't a priority.

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Source: Retronaut.com
 

Last edited by ray2047; 08-23-13 at 02:35 PM.
  #5  
Old 08-23-13, 09:18 PM
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The house is a single story with attic and crawlspace access. The guy that did the bathroom cut holes near the floor, drilled down through to the crawlspace and then fished wires up to the switches, then ran wire up to the fan and vanity light.

All of the high demand items (washer/dryer, fridge, microwave, furnace, A/C) have been rewired so what I would do seems like basic wiring. Breaker is 100 amps, so an upgrade may be needed.

All of the rooms have at least 3 receptacles. My plan was to utilize them or replace them with larger boxes, they are pretty tight for wiring purposes.

Strategy was going to be one room at a time, circuit by circuit. Only receptacles and lights.
I will likely leave the kitchen for a pro when/if we ever get around to a remodel.
 
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Old 08-24-13, 01:16 AM
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The guy that did the bathroom cut holes near the floor, drilled down through to the crawlspace and then fished wires up to the switches,
Why the extra holes, I wonder? Normally you can drill straight up into the wall from underneath or straight down into the wall from the attic.
 
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Old 08-24-13, 10:40 AM
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not sure. My guess is it was easier to find the wire from under the house with the wire exposed from the bathroom. I think this resulted in more patchwork than was necessary.

He had another guy here so he could have just had that person tap on the area while he was under the house. This is what I plan to do.

What size grommets would I use for running the wire up through the floor boards?
 
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Old 08-24-13, 10:53 AM
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I think this resulted in more patchwork than was necessary.
That is why I pointed it out.

My guess is it was easier to find the wire from under the house
Ceiling or floor you drill up or down next to the wall directly below/above the hole for the new box. An eighth inch drill bit is large enough. Then you insert a long stiff wire and go above or below and look for where the wire is. That tells you where to drill in the wall cavity for the cable. You want to drill the center of the wall cavity. Always cut your hole for your old work box first. That lets you precisely line up the cable hole with it and keeps you from drilling into a stud. The opening allows you to actually reach in and grab the cable after you have pushed it down/up. If an uninsulated wall you won't even need a pull tape usually.
 

Last edited by ray2047; 08-24-13 at 02:39 PM. Reason: Clarity
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Old 08-24-13, 12:27 PM
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What size grommets would I use for running the wire up through the floor boards?
There are no grommets used as part of installing electrical wiring. The cables (not individual wires) are run through 3/4" or 7/8" holes drilled through the center of framing members, one or two per hole. To enter or exit a wall, the hole is drilled through the top plate or sole plate of the wall, not through the finished floor or ceiling.
 
  #10  
Old 08-24-13, 04:01 PM
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can you explain daisy chain? I have seen wiring done the way Nashkat describes when the framing is exposed. I am trying to do this with minimal damage to the walls. The surface is textured plaster and lath, could be difficult to patch and repair.
 
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Old 08-24-13, 04:53 PM
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can you explain daisy chain?
Daisy-chaining just means that the wiring - the cable - goes from the panel to the first device on the circuit, from there to the next, then to the next, and so on. It's a different layout from the one that was used with K&T systems. In your existing wiring, it would be typical to find a hot/neutral pair run to a ceiling outlet and, from there, a pair dropped to each receptacle. If you draw it, it looks a bit like a spider web, hence the term "spidering." Switching was done by taking one conductor to the switch and back, and that was done with the neutral as often as with the hot.

I have seen wiring done the way Nashkat describes when the framing is exposed. I am trying to do this with minimal damage to the walls. The surface is textured plaster and lath, could be difficult to patch and repair.
What I described is the standard method of installing electrical cable for branch circuit wiring. It's the method I used when I rewired our two-story plaster-and-lath 1908 house. I didn't open one square inch of wall or ceiling finish for wiring. It was nearly all K&T when we bought it. When finished, there were a couple of K&T runs left, but only because I wanted to tease the inspector (the stuff is actually still as legal as daylight if a list of conditions longer than both your arms is met).

We had two switches and maybe 16 receptacles in the house when we started. We had at least 20 3-way switches a month or so later, plus on/off switches as needed, 60-odd receptacles, invisible GFCI, central A/C, radiant heat in the bathrooms, door-activated switches on the closets, restored light fixtures in restored locations, a new 200A service and two subpanels. That's not counting HVAC controls, security, fire protection, data and communications. The only holes made in finished surfaces for all of this were for device boxes or outlets.
 
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Old 08-24-13, 05:04 PM
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Just to add to what nash explained in new construction to daisy chain you run the cable horizontally. In old work you run it vertical. The cable goes down then back up if coming from the attic (up then back down if from below). Uses more cable but no destruction of the walls. There is a way to use less cable by using Jboxes at the beginning of each drop (or rise) In that case only a single cable is run to the receptacle and the daisy chain connection is made in the Jbox.

I prefer to remove the old boxes because that gives you a hole to make fishing new cables easier.
 
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Old 08-24-13, 06:11 PM
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Yes. I probably ran 2000' of cable in our old house. Less than 100' of that was run crossways, and all of that was in ceilings. All of the wiring in the walls, for receptacles, controls, sconces, etc., was run vertically.

I didn't do any T-tap boxes in the attic or basement because I didn't want to have to go open any of those if I needed to troubleshoot something. Not to mention the hassle of keeping them in the open with insulation being placed.

I prefer to remove the old boxes because that gives you a hole to make fishing new wires easier.
Boxes? What boxes? The first boxes in that 3600 ft.[SUP]2[/SUP] pile were the ones I installed in 1983. Two cases of gangable metal OW boxes w/ NM clamps inside. The original devices were mounted to the lath or the trim or the old gas pipes, and the wires ran straight into them. In the air. Typical K&T work.
 
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Old 12-29-13, 09:46 AM
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getting prepared to do this

I am about halfway through reading Wiring Simplified and have a few questions:

The main breaker is new, but the electrician that installed it ran new wiring from the main to the K&T. I am thinking that this would need to be removed and I would start with a new cable all the way back to the box to my first circuit in each location. Correct?

Switches:

I understand now that switches are not outlets, just a break in the main, controlling power to lights or receptacles. Does it matter where in the daisy chain I introduce the switches into each circuit?

Switch loop:

I don't have any 3-way switches currently. However, I do have 2 locations that have multiple switches.

The front door has 3 switch box that controls a dining room light, the front porch light and a receptacle, which I plan to convert to a spare switch for future install of can lights in the living room.


The laundry room has a 2 switch box that controls laundry room light and an exterior light on the side of the house.

Would either of these boxes require a switch loop? I am thinking they could be pig-tailed to run independently.

I was thinking of running 12/2 wire for all of this. Is this correct? I know I could use 14/2 but read where 12/2 would be worth the additional expense.
 

Last edited by Stumped1; 12-29-13 at 09:48 AM. Reason: clarity
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Old 12-29-13, 09:57 AM
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Whether you need a switch loop depends on how you decide to run your wiring. The newest code requires a neutral at the switch box so a switch loop does not provide any advantage.

Using #12 for lighting circuits is overkill. Rarely is the circuit that heavily loaded.
 
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Old 12-29-13, 10:43 AM
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Well, I can answer the last question at least...lol. There is no reason in the world to use 12ga vs 14 ga unless you plan on changing all your circuits to 20 amp. In fact, it's a bad thing to do on a 15 amp circuit as someone could see the 12 ga later and assume they had a 20 amp circuit.

Why pay extra for 12 when 14 is perfectly adequate. I also believe that many devices won't accept 12 ga for back wiring (not back stabbing!). It's harder to pull, harder to bend loops for the screws (for non-Pros), and costs more....why use it except where required?
 
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Old 12-29-13, 11:17 AM
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Using #12 for receptacle circuits does make sense. You get one third more capacity for a slight increase in cost.

Backstabs are limited to #14 wire.
 
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Old 12-29-13, 11:25 AM
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But you will have to buy all new 20 amp breakers, yes? Do you need to buy 20 amp receptacles? Are 15's rated for higher than 15 feed through? I think pigtails can change that? School me please!
 
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Old 12-29-13, 11:30 AM
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You would use a 20 amp breaker vs the 15, but the cost is the same.

As long as there is more than one place on the circuit to plug into you can use 15 amp slot devices. Both are good for 20 amp feedthrough.

Pigtails can be used regardless, but are not required.
 
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Old 12-29-13, 11:38 AM
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Thx pcboss...........
I guess it makes sense now if you can afford the cost of the 12 vs the 14 and the new breakers. In real life does it make much of a diff if you won't be plugging in heaters or high draw appliances?

I understand for kitchens and baths...but otherwise?
 
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Old 12-29-13, 11:41 AM
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Depends on the expected loads. Some may like to run heaters to take the chill off. Some vacuums also place a heavy load on the circuit and may trip the breaker if other loads are in use.
 
  #22  
Old 12-29-13, 01:20 PM
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Don't forget that kitchen counter receptacles along with receptacles in pantries and dining areas are required to be on a 20 ampere circuit. Same with receptacles in bathrooms. If you foresee using window air conditioners then a 20 ampere circuit near the window is a plus.
 
  #23  
Old 12-29-13, 04:57 PM
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Is 30% more capacity going to make much of a difference in a house? I think you are better off running additional circuits if you need that much for capacity. Having dedicated circuits for window a/c's is certainly preferred anyway.
 
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Old 12-29-13, 05:11 PM
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That 30% gives you more headroom should someone add an unexpected load to the circuit and prevent tripping.x

If heavy loads like window shaker AC I agree that dedicated circuits are a good idea.
 
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Old 12-29-13, 11:18 PM
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the first part of the house I plan to tackle includes the dining room, living room, and front porch light:

Dining room:

1 outlet, 3 switches powering dining room light, front porch light and one outlet in the living room space. I think I will be required to add at least one outlet on one short wall where the switches are located and another if a outlet is required on the wall under the front window. I plan to remove the outlet from the dining room switch and reserve this switch for a future addition of can lights in the ceiling of the living room.

Living Room:

This area has four outlets and no overhead lighting. As stated earlier, one of the outlets is currently powered by the switch in the dining room. I plan to change this so that it is wired as part of the living room space. I think I will be required to add 2 outlets for a total of 6. The walls are very short in length so 2 of the 4 should only require 1 outlet.

I was thinking one circuit would be sufficient for these 2 areas, although I could see the advantage of separating them if one of the circuit breakers were to fail.

Any advice is appreciated.
 

Last edited by Stumped1; 12-29-13 at 11:23 PM. Reason: clarity
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