On Wed, 26 May 2021 10:09:21 -0600, bud-- wrote:

On 5/25/2021 11:01 PM, Clare Snyder wrote:
On Tue, 25 May 2021 23:28:17 -0600, bud-- wrote:

On 5/25/2021 4:56 PM, micky wrote:
A friend of mine bought a house in Baltimore County 5 or 10 years ago
that still had knob and tube wiring, at least in the attic. My friend
says you can't get a mortgage if you don't pass inspectinon and you
can't pass inspection with k&t wiring.

What do you think happened?


I think it is modern redlining - an excuse to not mortgage (or insure)
old houses.

Example:
http://web.archive.org/web/20040825060154/http://www.maine.gov/pfr/ins/hearing_2003-13680.htm
An insurance company was sued by a homeowner. Insurance was not renewed
because the home had some K&T. The homeowner provided evidence the
installation was in good condition. "The company provided no
justification for its position that knob and tube wiring per se
automatically provides grounds for nonrenewal." The court ruled against
the insurance company.

Years back the NEC prohibited insulation in contact with K&T. I don't
think there was ever any evidence that had caused problems. The head
electrical inspector for Minneapolis, where a lot of insulation has been
added, provided a comment that he saw no "record of hazard". After the
provision was enacted California was sued and could provide no record
of a problem. California and a few other states now allow insulation.

K&T is still in the NEC although permitted uses are very limited.

In Minnesota, State Farm put a surcharge on houses that did not have the
service replaced in some time period (don't remember what it was). They
were reversed by the state insurance regulator. There was no insurance
casualty data that supported the surcharge.

I would rather have K&T than some of the early 2-wire Romex type stuff
with tar-paper(???) jacket. Particularly embedded in insulation you have
2 wires together heating up instead of 1.

OK. The problem with K&T is mofifications.A house wired with K&T
usually had less than a 60 amp service with 2 or 4 circuits. Most of
those circuits were lighting cirguits

The US does not require "lighting circuits". K&T powered whatever was
installed at that time.

- and MOST of the devices were
surfacxe mounted with no boxes.

Maybe where you are. I have seen a lot of K&T and NEVER seen that.

All connections were hidden (except
those in open basement ot attic structures) soldered and taped
connections. Shorts were uncommon because the wires are separated by a
minimum of 8 inches..

Wiring in open basements is "open wiring on insulators"


A lot of the buildings were also "ring topology" - both live and
neutral had both ends connected to the panel. (Not all - but a
significant number)

That may be how you do it. It is common in the UK. Maybe the queen told
your electricians to use ring circuits.

I have never even heard of that in the US.


Adding "modern" loads required adding to the wiring - and how THAT was
done is the important elephant in the room. If the K&T is not touched
and new romex circuits are added FROM THE PANEL it is not a problem.
The right way is a new panel with the existing K&T panel set up as a
sub panel - and otherwise NOT TOUCHED!!!..

A subpanel just for K&T is another nutty Canadian idea? Also never seen
that. Existing K&T is just refed from a new service panel.

The NEC allows "extensions of existing installations". (That is probably
uncommon.)

My mothers house had K&T. I survived in it for 20 years (Perhaps a
miracle??). At some point she replaced the service with a 100A fuse
panel and added some receptacles and other wiring. That is likely very
common. If a house has only original K&T wiring the Smithsonian museum
is probably interested.

When new lighting fixtures
etc need to be added, run new circuits from the new panel according to
current code. Decommission the circuits no longer used.

So lighting fixtures can't be replaced? Or is this just new wiring,
where lighting is not unique (except apparently in Canada).


Tapping into the original K&T in ANY WAY will generally trigger a
fail under an electrical safety authority inspection

The NEC allows "extensions of existing installations".

- as will
ANYTHING other than lighting circuits on K&T.

The US does not require "lighting circuits". K&T powered whatever was
installed at that time.

It is a safety and fire
safety issue as virtually NO living electrician is competent in K&T
technique

I guess I am not a living electrician. Minor changes are not that
difficult (like refeeding, which is common with a new service).

and the old rubber/cloth insulation doesn't respond well to
manipulation.

Rubber I have seen is generally in good condition. Original wiring in my
house is rubber (in rigid conduit).


My Dad was an electrician and did a LOT of renovation wiring in older
homes and saw a LOT of extremely badly done "modifications" to K&T
systems - and had to remedy the problems caused including complete
rewires of houses where the modified K&T had not QUITE managed to burn
the house to the ground.

My kid's house had a lot of "extremely badly done" wiring. There was no K&T.
So argue about wiring of any type that is in bad condition.

As I wrote I have more concerns about the early 2-wire stuff before Romex.

I have heard of no data that says K&T is intrinsically a particular hazard.

Note the court ruling and multiple states allowing insulation around K&T.

And the NEC is trying to put most EXISTING residential circuits on AFCIs.

Also 2-wire circuits can be connected downstream from a GFCI.

I see a few errors in this thread as for insulation the code says

"394.12 Uses Not Permitted.Concealed knob-and-tube wiring shall not be
used in the following:
....
(5)Hollow spaces of walls, ceilings, and attics where such
spaces are insulated by loose, rolled, or foamed-in-place
insulating material that envelops the conductors".

It must also be concealed in most cases or covered by running boards.

"394.23 In Accessible Attics. Conductors in unfinished
attics and roof spaces shall comply with 394.23(A) or
(B).Informational Note: See 310.15(A)(3) for temperature
limita-tion of conductors.(A) Accessible by Stairway or Permanent
Ladder. Conductors shall be installed along the side of or
through bored holes in floor joists, studs, or rafters. Where
run through bored holes,conductors in the joists and in studs
or rafters to a height of not less than 2.1 m (7 ft) above the
floor or floor joists shall be protected by substantial running
boards extending not less than 25 mm (1 in.) on each side
of the conductors. Running boards shall be securely fastened in
place. Running boards and guard strips shall not be required where
conductors are instal-led along the sides of joists, studs, or
rafters.(B) Not Accessible by Stairway or Permanent
Ladder.Conductors shall be installed along the sides of or
through bored holes in floor joists, studs, or rafters"


You should also check with your AHJ because plenty of jurisdictions
hate K&T and will impose even stricter standards.

Personally I would remove it if I had it.