City allows a bag full of 20 amp breakers on a new 200 amp main service to an 80 year old house.
Knob and tube appears to be as fresh as 80 year old wiring can be, but I can’t help but think most existing wiring would be better off with 15 amp breakers and leave the 20 amp circuits for new 12g wire.
Along same lines, is 14g romex allowed on a 20 amp breaker? I can’t ever remember 14g on anything but a 15 amp breaker. The under cabinet lighting I’m building into some new cabinets is being fed with existing 14g wire from a remodel 10 years ago tied into a 20 amp kitchen circuit.
Cheers
Beer was created so carpenters wouldn’t rule the world.
Replies
14G wiring must be on a 15A or smaller breaker, except in a few very special circumstances.
In theory K&T is good for whatever the wire size is, but prudence would suggest that you limit it to 15A, especially since you never know if the same size wire has been used throughout a circuit.
There's generally nothing wrong with using a breaker that's smaller than the wiring would allow -- it gives you a little extra protection against malfunctioning appliances, overloaded extensions, etc.
# 12 = 20 amp
# 14 = 15 amp
I wouldn't chance it, especially with some of the crazy older wiring and splices I've come across over the years.
"Preach the Gospel at all times; if necessary, use words." - St. Francis of Assisi
I can't speak for that application but when I tore my house apart the wire size on my knob and tube was over 10 guage.
The problem is, the feeds to individual outlets are apt to be smaller.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
I'm not so sure of that.. My whole house appears to have been wired from one spool of wire. Remember when knob and tube was popular there were far fewer outlets plus most homes were much smaller in size..
Yep Martha ,We have lights in 3 rooms! Our house is electrified!
The problem is that a sort of primitive romex is often used for the last few feet from the K&T wiring to the outlet. That stuff is apt to be a smaller diameter.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
I lived in an old house and I remember some of the wiring appearing to be lighter than 14 gaugeIs there such a thing?this was wiring in the walls going to outlets, lighting circuits, etc
They used to play pretty fast and loose with the rules -- and there were no rules. I wouldn't doubt that there are some old circuits on #16. Often the "backbone" would be heavier and the drops would be something light.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
In my bookshelf I happen to have a copy of the "Minnesota Farmstead Wiring Regulations", effective March 15, 1938 (it's a 20 page pamphlet the size of an index card...a far cry from the codebooks of today.) This book was used in lieu of the 1937 NEC for rural communities.
Anyway, it says that wires shall be 14awg minimum for lighting circuits, and 12awg minimum for appliance branch circuits. That applies for knob and tube, NM, armored cable or conduit wiring methods.
1938 was pretty late, wiring-wise. Lots of earlier stuff exists, with all sorts of things that would scare the sith out of you if you knew they were present in your house.
The mark of the immature man is that he wants to die nobly for a cause, while the mark of a mature man is that he wants to live humbly for one. --Wilhelm Stekel
Hi
Our first house we bought in 82 it was moved on to the lot in 1917, and planed to tear it down in a couple years and rebuild, nice lot. Well!! l big storm next june and our 628 sg foot of pleasure fell into it to a washed out block crawl space. So the tear down came real soon.
As we started up to rip the second storey stoop we hit some K+T and it was black in between the wires in many spots. splices into romex were all charred and insulation burned and wires just a hair away from each other in an attic with wood shaving insulation. Showed my friend who was with the local utility. Sort of a dead run to see you hit the main breaker first. Still get the odd chill from that sight.
I'm not sure but I believe it is against code here in SK. Canada. If you see it! out it goes. That was a ticking time bomb and I'm sure glad mother nature did the deed before the wiring did.Working now on a condo reno, the buried junction boxes and wiring ran in a notch on a studs.
Todays best was a electrician dam near nicked a gas line with an auger bit. Have you wired in smoke detecters? we a bitch about codes but guess there is a reason for them.
Regards
BB
Well done man.
I happen to have the 2006 code right here and K&T ain't in it...anywhere...at all...ever.
Our old place up in Maine (in the family since 1788) we upgraded the panel with arc fault breakers feeding juice to the old Buss Fuses so that as the wiring continues to degrade we at least have some assurance that when they go sparky on us they'll shut themselves off. One circuit did so when the house was un-occupied in the middle of the winter two years ago and we just let it be dead rather than tear up the house looking for the fault. I just left a bad fuse in the suspect circuit with tape on it saying that the circuit was bad and went on. It's a really old farmhouse and we don't really need all the outlets to be live if the alternative is spending a ton of cash or burning the house down.
m
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"You cannot work hard enough to make up for a sloppy estimate."
The standard logic I've heard from a number of trusted electricians is knob and tube is safe if all is in good condition, not covered, and fused with a 15a breaker.
So I agree with your thoughts to keep the existing on 15a's and leave the 20a for the new 12g wire. It's nice if you can kill the existing recepticles and make them all new 20a. Lighting circuits usually work fine with the existing 15a K&T. Vic
Don,
You recall right: 14 gage copper wire, 15 amp breaker (or fuse).
You can protect a 12 gage circuit with a 15 amp breaker, and that's a very good idea for old houses. It's what I do when replacing the old panel in an old house: protect the branch circuit wiring with a 15 amp breaker, even if it's an AWG 12 copper conductor leaving the panel. You never know if some yahoo has extended a 12 gage circuit with #14, or for that matter, 18 gage zip cord. Or phone wire--no kidding, I've seen that.
The NEC has always required that 14 gage copper wire be protected at no more than 15 amps (except in some uncommon situations, like motors that have a heavy startup current, and you wouldn't see this in old houses). Again, that doesn't mean that uninformed people didn't put a 20 amp fuse or breaker on a 14 gage circuit, to keep the fuse from blowing/breaker from tripping under overload, or extend a circuit with wire too small.
Generally, the wiring in old houses ( circa 1890 to 1950) that were wired by professional electricians was done very well. The NEC came to exist within the first few years of electricity being installed in houses. People were rightly scared of electricity--not that it was any more dangerous than gas, or kerosene for lighting, mind you, but it was new--and the electricians of the time typically were very good craftsmen.
Also, in very old houses, knob-and-tube wiring was typically set up with one neutral shared by two circuits. In the earliest days, this was in houses with 30 amp, 120 volt service. The neutral was fused as well (usually for the lighting circuits, and at 15 amps), so that if the sum of the current on the two circuits exceeded 15 amps, the neutral fuse would open the circuit and protect the wiring from overloading. This worked because the loads were usually very light (only a few 40-watt or 60 watt lamps on one lighting circuit at any given time), and so an overload of the shared neutral was rare.
In the 1920s, as electrical appliances became common (toaster, waffle iron, mixer, electric fan), the loads on circuits increased. Consequently, people over fused (or by passed the fuse with a penny) the neutrals so as to not be inconvenienced, and there were fires.
So, some time in the late 1920s, , the use of a fused neutral (called the grounded conductor, for you semanticists) was prohibited in new construction. Shortly prior to thehis change, sometimes a 10 gage copper conductor was used for the shared neutral, and was not fused. I don't know if this was allowed by the NEC, but I've seen it often enough (and in different areas), to think that it was.
This was also when 240/120V, 60 amp services started to be used for houses, so the shared neutral circuits (called Edison or multiwire circuits) didn't require a fused neutral. With the two hot conductors coming off the different legs of the 240/120V service, the neutral carries the difference in the current of the two, not the sum (as with a 120V service).
From a practical standpoint, anyone who upgrades wiring needs to know a lot of history, or they can get things really messed up (as in, "burning the house down" messed up.)
Cheers,
Cliff
"The under cabinet lighting I'm building into some new cabinets is being fed with existing 14g wire from a remodel 10 years ago tied into a 20 amp kitchen circuit."
I was called out to fix dead kitchen outlets in a condo. The tenants complained that they couldn't make toast and coffee until it was fixed. There was also an electric grill and a toaster oven.
The outlets were actually plug mold installed under the cabinets where tile back splash covered the wall right up to the cabinets. I traced the problem back to a duplex outlet upstream from the under-cabinet plug mold. Wires were 14ga. Half of the duplex outlet's plastic body had melted, forming plastic stalactites. Somewhere in the wall behind all that tile the 14ga was spliced to a 12ga wire from the original 20A kitchen circuit.