On 3/25/2012 8:13 AM, The Daring Dufas wrote:
On 3/24/2012 6:14 PM, RBM wrote:
On 3/24/2012 6:54 PM, dpb wrote:
On 3/24/2012 4:26 PM, Doug wrote:
I thought about buying an older home built in the 50's in around
Houston, Texas but I was wondering about the electrical wiring.
a) does anyone know if aluminum wiring was used, when this area
switched over to copper wiring?
b) briefly what advantages does copper have over aluminum?
c) without pulling off outlet/switch plates, is there an easy way to
tell if the house has aluminum or copper wiring? Can aluminum wiring
use a breaker box or only fuses?
d) for a 1 story 1500 sq foot home circa 50's, what an electrician
might charge to switch wiring?
e) advice buying an older home with respect to electrical wiring?
The Al branch circuit wiring craze was generally in the mid-60s; the
chances of it in a 50s house are nil.
Not exactly nil, but pretty close. As with a number of electrical
materials, some things were available long before anyone cared to use
them. Small gauge aluminum building conductors were around since the
40's, possibly because of the war, but the era of aluminum wiring that
strikes fear in homeowners, is primarily from 65' to 73'. Sometimes
earlier conductors with tinned copper is mistaken for aluminum.
Al tends to oxidize and has higher thermal coeff of expansion so tends
to loosen connections w/ time more than Cu. The biggest issue is the
oxidation layer and contact resistance at connections that acts as a
miniature heater and eventually can reach combustion temperatures if
gets bad enough.
You'll have a home inspection done, anyway, wiring is just one of the
many issues to have verified and discover if there needs to be either
work done prior to the sale or discount the offer to cover the cost to
yourself after the sale.
--
A lot of early copper house wiring was tinned because connections were
soldered then wrapped with friction tape.
I read tinning was to protect the copper from the rubber insulation
(sulfur?). (I don't know.)
I've found this in a lot of
older homes during remodels and the insulation appears to be tar
impregnated cloth which will often crumble away when disturbed
especially if it's been exposed to heat as in light fixtures. I worked
for an electrical supplier in the early 1970's during the oil shortage
and a copper shortage when many electrical manufacturers switched to
aluminum for Romex and they added a lot of fillers to petroleum sourced
plastic insulation to keep the electrical industry alive. I was glad I
owned a car that had an 1108cc engine during that time. The problem with
aluminum house wiring showed up even then because the manufactured
housing industry was using a lot of it and when the trailers bounced
down the highways for delivery, the aluminum wiring had a tendency to
fail because it lacked the ductile properties of copper and could not
tolerate mechanical and thermal stress the way copper could.
Thermal expansion is part of the problem. The "old technology" aluminum
wire was too ductile - it would extrude and creep. Probably a larger
problem is an insulating aluminum oxide layer that very rapidly forms on
any 'clean' aluminum surface. The actual metal-to-metal contact area in
a connection may be very small. For large wires, tightening the
connection deforms the wire which breaks the oxide layer.
Electricians of the day weren't used to working with small aluminum
conductors and the connections would often burn up setting homes,
especially mobile homes on fire. Over the years I've found a lot of
failed connections in aluminum Romex and had to add the special
connectors and copper jumpers in order to replace damaged wiring
devices. The special connectors containing antioxidant grease are
available at most home improvement stores and you can use them to add
copper jumpers to your aluminum house wiring.
Another post has a link to:
http://www.kinginnovation.com/pdfs/R...Fire070706.pdf
which was written by the engineer that supervised extensive testing of
aluminum connections for the CPSC. A basic element in connections is
abrading the wire to remove the oxide and applying antioxide paste. He
does not particularly like the Ideal 65 wirenuts that come with
antioxide paste in them. They are, last I heard, the only UL listed
wire nuts for aluminum. They are not more effective than some other
wirenuts with antioxide paste added, and have some negative features.
http://www.kinginnovation.com/produc...cts/alumiconn/
may be the best splice for small branch circuit aluminum wires. The
screws should dig through any oxide layer, like on larger aluminum wire
connections.
--
bud--