On Fri, 05 Feb 2016 14:15:30 -0700, Don Y
wrote:

On 2/5/2016 2:31 AM, Texas Kingsnake wrote:
I am having my electrician buddy help me replace an old circuit box in a
fairly old house. Much of the wiring is old and cloth covered from the
40's.

Knob and tube?

What happens if one of the wires we are replacing breaks or is too
short to reach the breakers in the new panel?

This is what makes electrical work "interesting"! (not)

Do your homework and try to reshuffle the placement of the breakers
so you can attach each branch circuit to *a* breaker -- even if it
is not in the same physical position as previously.
Lots of attention to detail can also be a win when selecting a new
panel -- to minimize the distance the wires "need" to travel to
reach their corresponding breakers (don't forget about the neutral
connections, as well!)

A lot easier here in Canada where inspectors don't look ascanse at
panels mounted "sideways" I was able to replace my old Consolidated?
fuse panel with a new Square D QO panel without having to pull a
single staple or move a single wire - and had wire to spare by simply
laying the QO panel on it's side with the main to the left.

The electrician was a bit of a ditz and used the top neutral buss for
circuits that were on the bottom breakers - which made foe some fun
when I went to install an arc fault breaker in the bottom side of the
panel because "sparky" had cut the neutral to make it a neat fit to
the top buss. I called the inspector and he said no problem using a
Marrette 65 to tag a length of #12 or #14 copper to the aluminum
neutral to extend it to the bottom of the panel, so that's what I did.

Coulda skinned "sparky" for telling me I didn't need to upgrade to
GFIs and AFCIs with the panel upgrade when I was doing it for
"insurance inspection requirements" - and I asked him NUMEROUS times,
just to be sure.

So I had to upgrade it all after he was done when the inspector said
it was needed - meaning I needed to pull another permit and get
another inspection.
Thankfully the inspector was very understanding and he got me a "no
charge permit and inspection"
Do those broken wires have to
be spliced with wire nuts to a new piece of wire and then the splice section
mounted in a new junction box outside of the new panel? That could get ugly
very quickly but my limited knowledge of the NEC says splices have to be
with approved connectors and inside junction boxes.

Have you considered using one or more subpanels as a "cheat"?

Will he have the tools to determine if any of the wiring in the house has
decayed enough to present a fire hazard? Do you measure the resistance of
the wire from the panel to the eventual load?

The "wire" (i.e., "conductor") won't degrade/decay (when copper "rusts",
it forms a greenish oxide layer) but, rather, the insulation may be
a problem -- especially where it may have experienced mechanical wear
(like in the panel and terminal Jboxes -- lots of flexing as it is
connected/reconnected)

I know that one very long run
to the kitchen reads 105 volts with the microwave on when the voltage at the
breaker serving that run is at 119 volts. This is a run that has been used,
apparently, for years with a 20A breaker even though the wire apparently is
only 14 gauge. We will be correcting that by wiring it to a 15A breaker

frown Sure to get flagged by an inspection. For "efficiency", you
typically only want a 3-5% voltage drop under load. Wire is "sized" so
the heat generated in the conductor is safe for the insulation chosen
(the wire won't melt but the insulation will degrade).

SERIOUSLY consider running two new 20A countertop feeds into the kitchen.
Most of a home's AC is consumed in the kitchen. You'd also like to avail
yourself of GFCI and AFCI protections.

[I think we have 5 or 6 circuits feeding our kitchen, not counting the
oven/refrigerator/lighting]

And, chances are, you have all "two wire" circuits -- no earth/safety ground
available at your loads.

Also, he talked about "balancing the load" within the panel. Why is that
important?

The AC line feeding your residence is really two 120V lines wired one "atop"
the other. Sort of like putting two 120V batteries in series:

120V 120V
+XXXXXX- +XXXXXX-

A N B

The "neutral" wire is connected to the middle -- at 0V. So, you can think
of one "leg" as being +120V (i.e., at 'A') the other as being -120V (at 'B').

But, as this is AC and not DC, the 'A' point is really continuously varying
("alternating" as in "alternating current") between +120V and -120V while, at
the same time, the 'B' point is alternating between -120V and +120V!

[there's a bit of a lie, here, but not one that is material to the discussion]

For a 120V appliance, it "sees" the 'A' (or 'B'!) leg alternating between
+120 and -120 with the other wire connected to neutral (0V). Thus, 120V AC!
The load current flows "from" the 'A' (or 'B') to the load, through the
load and then returns on the neutral. (all of the electricity flowing OUT
the A -- or B -- ends up coming *back* on the neutral. A "closed loop")

For a 220V (240) appliance, it sees one leg alternating between +120 and -120
while the other leg is alternating between -120 and +120. So, there's
240V AC *across* the device -- and the neutral wire is not involved!

Because A and B are "opposites" (A is positive while B is negative and A is
negative while B is positive), the "neutral current" from an appliance fed
from the 'A' leg is "opposite" what the neutral current from an appliance
fed from the 'B' leg; one is "going" while the other is "coming".

As you bring the loads on the 'A' and 'B' legs into balance, the neutral
current from that 'A' loads cancels out the neutral current from the 'B'
loads thereby reducing the current flowing in *THE* neutral (from the
power company).

If you consider the "two batteries in series" example, above, you can
see that the electric utility would prefer that you "load" each battery
similarly; why include the second battery if folks are just going to
put EVERYTHING on the first??

[The batteries are really transformers -- technically, a *single* transformer
with a "tap" in the center. If you're only using one half of the transformer,
then all of the heat is generated in that "winding" while the other is just
taking up space, so to speak]

This may sound like a stupid question but why are the breakers staggered? I
thought the A hot coming in on the left fed all the breakers on the left and
the B hot of the right fed all the breakers on the right. Apparently not.
Why?

When you remove the panel (or, when it has had all of the breakers
removed), the reason will be obvious. : It's just easier to make it
that way!

Any other pointers on panel upgrades or sites where I could learn more about
the process? I've been watching a bunch of so-so YouTube videos, but they
don't seem to answer the questions I have.

I've already gone through the panel and marked down which wires go where by
shutting each breaker off in turn and making note of what outlets and lights
were no longer powered. My buddy said that's often the worst part of a
panel replacement.

Methinks he exaggerates! : It's just tedious, not really "bad".
I prepared a scale floorplan of this house and adorned it with notations
of each Jbox, circuit number, etc. just so I could KNOW where everything
went. I.e., which breaker controls power to the smoke detectors??

When you are done, be sure to walk through the house and verify you have
identified the breaker for EVERY outlet/switch -- to make sure you haven't
missed something (which you might want to *change* in the process!)

I.e., did you remember the outlet behind the refrigerator? For the garbage
disposal? Garage door opener? Front porch light? Dishwasher? etc.

I assume the wires have to be properly labeled as they
come off the old panel and get attached to the new one.

Yes. Otherwise, you will have the panel disconnected (no power in your house!)
while you run around trying to figure out what each wire does. Easier to
do this BEFORE you turn off the power (and inconvenience the occupant)

Would a Brother label printer do the job?

Pro'ly. You might find it difficult to get the label tape to stick to the
(cloth/asphalt) wires. As such, you might want to use a "flag" sort of
attachment (wrap label around wire and adhere it to *itself*).

Note that you probably want the power off on the panel if you're going
to be messing around with individual conductors. It only takes an
ohnosecond to cook yourself!

Would it pay to get the kind of labeling tape
that's actually heat shrink tubing?

No. That would require you to disconnect each wire before labeling.
I.e., you'd only be doing that when you'd shut off power to the panel
(and then you're back to the "inconvenience" issue, above).

Would it be code-worthy to label each
wire like that permanently?

No. Labels can be flammable.

Some of the cloth covered original wiring looks awfully frayed. I am
guessing that it's not code to sleeve them with plastic shrink tubing but I
suspect the real fix is to replace the wire which would about quintuple the
price of this job.

Presumably, you have a basement and/or attic? I'd probably leave most of
the living area outlet and lighting circuits "as is". But, would seriously
consider redoing the kitchen/meal prep circuits. More capacity is usually
a good investment. Even if you don't upgrade the service, you might
find it convenient to be able to run an electric skillet AND the microwave
at the same time (by moving them to different circuits). Or, not having
to worry about tripping the breaker for the refrigerator (food spoilage)
because some other appliance happened to be on at the same time, etc.

You will probably also discover that your existing wiring is not up
to code (kitchens, bathrooms, garages and basements see lots of code
revisions -- 70 years is a LONG TIME in code terms!). Recall that
the code is there for YOUR safety, not just as an excuse to "make work"
for electricians!

Here, I've considered running a new branch circuit into the bedrooms
as I use one for my office (and have LOTS of electronic equipment in
there; so much that I am cautious about what I turn on at any given time!)

Would this be a good time to check the house's grounding system? How do you
measure the quality of the house's ground?

Always a good idea as this is what keeps you safe. Of course, if everything
is 2-wire, you're already bucking a headwind.

I'm assuming that he's going to know all of this stuff, but I'd like to be
as well-informed as I can about what problems we might be facing since I
will be assisting (mostly holding the flashlight or heading out to Home
Depot if we don't have everything we need).

I was also wondering if it would be prudent to place an externally mounted
shutoff for the whole house between the meter and the box? As it stands now
any work on the panel involves disconnecting the smart meter and a shut-off
would eliminate that step.

Dubious value. Unless you want to anticipate a whole-house genset in the
future!

Have fun. *Plan* on things going wrong/taking longer than expected/etc.

[You might also want to carefully investigate the panel chosen -- particularly
wrt the breakers! Will you be able to purchase replacements in the future
when these "new ones" fail? Or, will you be scouring the used building
supplies/surplus shops hoping to stumble across one that fits YOUR panel
20 years hence?]