Hi,
I’m in the process of rewiring – replacing the old knob and tube – and would appreciate any thoughts of whether old BX cable and some older Romex (it has Anaconda markings on it – my impression is that they went under back in the 70s) should be replaced at the same time. The house was built in 1941. The BX is used in three circuits #1 is supplying the oven (50A circuit, #6 wire), #2 the water heater (30A circuit I believe, haven’t checked guage) and the dryer (30A circuit also). The old romex supplies the heater. The oven circuit is currently 3 wire. I understand the logic of going to 4 wire and the oven is new enough that it should accomodate the ground.
Any thoughts/advice here would be appreciated. Seems as though it would be a good time to get everything up to snuff. At the same time it doesn’t make sense to throw out good parts.
Thanks,
John
Replies
I did the same thing you are considering recently. I opted to replace the old bx that relies on the metal jacket for grounding with mc that has the ground wire inside the armour. My philosophy is to do it once and do it right. Won't you feel bad if one of those circuits fails later on and you are forced to revisit the situation?
Conrad
When I updated my house, the choice was easy. The romex was installed incorrectly (grounds cut off, spliced in plaster patches, etc.); the BX was the old type and did not register a ground on the meter; and while the knob & tube was actually functional and relegated to lights, dimmers, and new fixtures requiring 90-degree wire, oh, and that mess of K&T in the new shower wall meant it had to go. Plus it was left in insulated exterior bays, violating one more code item.
...that's not a mistake, it's rustic
Your major concern is probably not the wiring method itself- there's no reason knob and tube can't last for centuries- but, rather, "improvements" made over the years, and our changing needs.
The only real drawback to knob & tube is that there is no ground wire. Apart from safety issues, many items have electronic components that need a good ground to work properly. The oldest type of romex also lacks a ground wire, so it has the same problem.
When there is a mish-mash of different wiring methods, you will usually find other problems as well- everything from incorrect splices to circuits that hop all over the house.
Today, we need many more outlets, and dedicated circuits, than we did- even in the '70's. It is likely that some of the stuff you see is the result of a half-hearted attempt to keep up with the times.
So, what should you do? First of all, have a plan. Then, break the job into smaller bites. Oddly enough, I would first replace the newer stuff; that is more likely to have been properly installed.
Quite simply put, you will likely end up replacing everything. I suspect that you will want to run the dedicated circuits completely from scratch as a starting point: Here's a short list of dedicated circuits you might want:
- Furnace (even if gas);
- Bathroom
- Kitchen (2 for counter, plus 1 for fridge and 1 for dishwasher / disposal)
- Each bedroom
- Smoke alarm
- Computer
- Laundry area / washer
- Outdoors / Xmas lights
- Garage
If the house has distinct sections, such as an addition, you might want to serve these areas from a sub-panel. This will, among other things, keep the mess of attic wires more manageable.
Why the smoke on a separate circuit.I like the idea that it is on some commonly light. Hallway, master bedroom, or master bath.Makes it less likely to disabled, either accidently or on purpose by an off breaker.
I say "smoke alarms on a separate circuit" for two reasons:1) The fire alarm code strongly favors such an arrangement; and,2) Smoke alarms are generally required to communicate with each other; when one sounds, they all sound. This is most easily done when the alarms are all on the same circuit.
Edited 10/18/2006 8:42 pm ET by renosteinke
"I say "smoke alarms on a separate circuit" for two reasons:1) The fire alarm code strongly favors such an arrangement; and,2) Smoke alarms are generally required to communicate with each other; when one sounds, they all sound. This is most easily done when the alarms are all on the same circuit."As for #2, all the smoke alarms I install have to be wired together with 3 conductor wire. I prefer 14-3 for these runs.For several years now I do put some lights on the smoke detector circuit as a circuit "on" indicator for the homeowner. Also, now that all the jurisdictions I work in have AFCI requirements, it is easier to put the smoke detector circuit on an AFCI breaker circuit that already feeds one or more bedroom lighting circuits.
Frank DuVal You can never make something foolproof because fools are so ingenious.
Since the BX appears to me to be dedicated circuits, if the insulating jacket around the individual conductors is ok, I don't see a reason to change it (provided the gauge is correct). There isn't anything wrong with using the armoured jacket as the ground, as long as it is done properly. That means metal boxes with tight connectors at both ends, and a ground wire at the junction box for the recepticle/hard wire.
I don't know if any of the armoured cable came with aluminum wiring (I doubt it) but I suppose you should check that too.
The old romex, I don't know.
Don't forget to make certain all the common's run home to the load center. In an old house the most frequent problem is that the weekend warrior will grab any old white wire to make a circuit. That isn't the worst.
The worst problem is joined "hot leads" from separate circuits (same 'phase'). Go crazy ringing out the circuits. Zero volts to ground, needs to be zero volts. If it isn't zero then you've probably got a phantom connection that is bleeding.
As for your BX. if that is the only problem you have then don't fret too bad.
The first thing I would check is if the wire insulation is still OK. After so many years, some insulation gets very brittle, and any motion will cause it to crack and fall off; sometimes leaving a bare "hot" wire for you to deal with. If the insulation is good, and you can get a proper ground, I see no reason why these wires cannot be re-used.
As for dedicated circuits, where I am, smoke detectors are not allowed to be on a seperate circuit. Code requires them to be on a regular lighting circuit, so people are not tempted to shut them off because they go off whenever "George" starts smoking that giant stogie.
locolobo
Edmonton, Alberta, Canada
Only thing I'd add is that where I live (Boston area), K&T is very frowned upon by home insurance companies, many/most will simply not cover you, or if you already have it and they found out, they'll ask you to convert or cancel you. I've had 2 different co's cancel me for much lesser risks (because of some renovations on my house).
You see, they want to increase profits (premium) while lessening their risks & claims, great business model.
'41 could be a year where they still used natural rubber with the (ahem) fabric coating (that doesn't burn).
I have that type of wire in my old house built in the early 30's. One writer mentioned that it crumbles. That is straight info. It is also tinned 12 ga copper that is pretty resilient and still working fine. Having a bare conductor is an awful issue that could cause the opening of a wall to re run BX. so do this...
I replaced all of my duplex outlets and found grounds, hopefully you will too. However when you open up the faceplate and remove the old device move slowly. Undo the screws with as little wrenching and twisting as possible. Then take your needle nose pliers and straighten out all of the conductors in as gingerly manner as possible. Then take 1/4" dia. shrink tubing and put a 6 inch piece over the conductor. Color code it too. ie white or black. It is 600 volt rated and with a hairdryer to shrink it on it makes the conductors really easy to work with. I slide the tubing into the bx til it stops. It is a great way to keep the old copper running.
best of luck.
Thanks to everyone for their input - my takeaway is that while I could keep the old BX and romex I'm probably better off spending the money (it works out to about $150 or so in wire to replace the old stuff with new romex. As for the thoughts folks had on knob & tube I appreciate those also. I had made the decision to replace it throughout the house for several reasons
1) the only insurance company I could find who would write a new policy on it was Farmers, nothing wrong with Farmers but its nice to have choices
2) the insulation crumbled right off when I when to put in a new fixture
3) we're in the middle of renovating the house so now is time to do it
4) I already finished the 2nd floor of the house and while it took time it wasn't as bad as I had thought. I should mention that I was able to snake the wires through attic for the second floor. The first floor is requiring that I open up the 2nd floor floor (old lineolum over 6" t&g subfloor) in spots. So far, so good.Again, many thanks!