Is 1970s wiring "safe"?

[fan-of-fans]

Our house was built in 1976 and from time to time I wonder about the wiring. I assume it's ok, it's never been messed with and it's not overloaded to my knowledge.

The strange thing is I've been told the entire house is wired with wire gauge that is for a 20 amp circuit, even on the 15 amp circuits. Also some of the distribution of the circuits is a little strange, for instance rooms that share walls such as the hallway and bedrooms tend to have their outlets on the same circuits. So for example, the 20 amp circuit marked washing machine also turns off outlets in the hallway that shares walls with the laundry room. Found that out when trying to vacuum and do laundry.

Also the refrigerator outlet and the outlet in the pantry behind the freezer are on same 20 amp circuit.

The outlet on back porch is on same circuit as the living room?

Otherwise, everything looks pretty good. We've replaced a few old outlets and switches here and there if they wore out or to change colors. Hadn't noticed anything that looked bad.

I think I've always been a bit paranoid of having the house burn down. Even as a kid I used to have dreams about my house catching fire.

All of the wiring is plastic coated romex, so I assume what I can't see in the walls should be ok. Usually when I hear of wiring problems it's knob and tube or cloth romex. But the plastic romex is getting close to 50 years old so I do worry about it getting old and unsafe.

One thing that I do recall that was concerning about the outlets is, they have no ground wire attached to them. The ground is connected to the metal wall boxes and they are grounded through that. The old outlets were all wired with push in wiring, there were no terminals on them. As they've been replaced we've used the terminal method, as it seems more secure. I'm getting the idea it might be best to replace all the remaining old outlets as well with terminal wired ones.

 

[jamiel]

There was, about 30 years ago, a scare with aluminum wiring which seemed to be a 1970s thing...don't recall much about it except what I read in Popular Science.

 

[mattl]

Typical mid 70's wiring, not optimum, but workable. Oversizing wire is not an issue, 20 amp rated wire in a 15 amp circuit is fine.  What I don't like  is the fridge sharing the circuit with a number of other things, but if you're not tripping breakers, odds are it's OK.

 

Grounding to the meal box is fine, pretty common.  

 

[turquoisedude]

Indeed, aluminum wiring from the 1970s is a big scare. The trouble with aluminum wiring was not the wiring itself, but if the wiring was attached to non-compatible devices (outlets, switches, light fixtures, etc etc) - the terminals would corrode and cause poor connections; these could then overheat and burn. There is a designation CO/ALR on devices that are safe to use with aluminum wiring.

It is surprising that as late as the 1970s there was as much daisy-chaining of outlets as there had been in the 50s. I've seen a number of houses where the circuit for the refrigerator was also serving other outlets, but on a 20-amp breaker. I hope the lighting circuits are separate at least!!

 

[norgeway]

Truthfully

Its fine, as are many houses wired with braided Romex and even knob and tube, Its allin how it was installed.

 

[philcobendixduo]

Watch Out For Crimped Connections

My tract home was built in 1967 using "crimped" connections at outlet boxes and switch boxes. Over time, these connections can and do become loose due to heating and cooling of the wires. This is especially an issue with circuits with "high draw" items like space heaters, hair dryers, large motors, etc. I had two crimped connections "burn up" in 2 different outlet boxes. Thankfully, these failures didn't start a fire - just cut off the power to the outlet and others down the line. A few years ago, I had an electrician re-do ALL the crimped connections with "In-Sure" wire connectors.

My home also had up to 8 outlets (4 in one room and 4 in another) on one circuit. I also had this situation corrected. There are other "issues" that remain like the furnace being on the same circuit with the garage and bathroom outlets, the refrigerator not having it's own circuit, etc. I've had no issues so far but am always vigilant!

 

[oliger]

My house was built in 1910. It has original, undisturbed knob and tube wiring with the old style screw in fuses. Many of the outlets share circuits with other outlets. Most of them were meant for a lamp. And, there being one or two outlets in a room, most of them are overloaded. I think your wiring from the 1970's is probably much, much safer.

 

[DADoES]

 
<blockquote>... or instance rooms that share walls such as the hallway and bedrooms tend to have their outlets on the same circuits.</blockquote> My house built in 2004 has some of that.  It hasn't exhibited as a problem but I suppose could be in some instances.

For example if I have the two desktop computers and a space heater in winter running in my office room and at the same time was to run a vacuum at an outlet on an adjacent wall in the living room or hallway.

The one outdoor outlet by the patio feeds on the same circuit as (at least one) of the outlets in the adjacent master bathroom which is a GFCI outlet, which is the outlet I use to run the washers in the bathroom.

All the major appliances are on separate circuits.

All branch 120v circuits have 20a breakers.

 

[sarahperdue]

Knob, tube and screw in fuses

I’ve seen one house with intact and functioning knob & tube wiring. It was a beautiful, immaculately preserved. Modern circuits had been added for major appliances.

If your breakers are working properly, that vacuum or extra waffle iron isn’t going to do any lasting damage. The breaker trips, you reset the breaker then move the offending device to an outlet on a different circuit.

The problem with screw in fuses was not so much the design but the ease with which they could be bypassed. Keep blowing the same fuse, no problem, just screw in a higher rated on. Run out of replacement fuses in the middle of the night, no problem, just put a penny in the socket and screw the blown fuse in on top of it. Then either forget about the penny or decide it’s working fine and leave it in. My great grandmother’s gorgeous turn of the 19th century house was destroyed by a lowly penny.

(Some screw in fuse boxes had different sized sockets for different fuse ratings. I speculate that those were newer.)

 

[wayupnorth]

My house was originally our family's summer place with all old ungrounded wiring on 2 screw in fuses. I tore every bit of it out and completely rewired the whole house when I made it year round in 1995. Every room has at least 3 separate circuits and kitchen alone has 5. In all those years I have never once tripped a breaker. My first apartment had 7 outlets total on one 30 amp screw in fuse. When the refrigerator turned on, the tv picture closed up.

 

[thomasortega]

I just had a contractor rewire my father's house in Brazil.

Just in case, to be on the safe side, we abandoned EVERYTHING that was existing there, even the meter (the power company replaced it by a digital one at no extra cost, so my father doesn't need to open the gate every month to "read" the meter.

The contractor is a retired electrician from Itaipu (the biggest power generation dam in the world, in production records).

He went strictly by the codes and with some light OCD overdimensioning just to be on the safe side.

Absolutely everything has an exclusive circuit breaker.

His electricity bill dropped by 70% compared to the old wiring he had. The power company even sent somebody to inspect his house thinking he did something to tamper the meter and steal electricity.

Pictures later as they are in my phone.

 

[Ultramatic]

 

 

If it was built in the 1970's and never given any issues chances are you are fine.

 

All but one of the circuits in my home are 20 amp. With the exception of one 15 amp circuit. Breakers rarely tripped prior to the 1980's. Afterwards, with more and more appliances we had to do a balancing act. It was particularly bothersome during Christmas with all the exterior lighting. Since I switched over to LED's years ago, it's only an issue if I inadvertently run the microwave and the convection oven at the same time.  Otherwise we're good.

 

[fan-of-fans]

Refrigerator circuit

Yep, the outlet behind the refrigerator and the one in the pantry that the freezer plugs into are both on one circuit marked "Refrigerator/Freezer". I don't believe anything else is on that circuit, but there is a hall closet that backs up to the pantry and it has an outlet in it too, so it's likely on that circuit. We never used that one though except when we had a stereo in that closet. That circuit never trips, though.

Oh yes, I've heard about the aluminum wiring. I think it was mostly used in mobile homes, but I have heard of site built houses having it too. Wonder if there is any around here. Another issue is some of the fan motors that GE built in the 70s had copper and aluminum windings mixed together, and those do often catch fire. I think they even brought up using aluminum windings for the motors in today's hybrid and electric cars to save weight but it was decided it wasn't a good idea.

Another problem I've heard of with 70s wiring is the circuit breakers. Some of these used Pushmatic and possibly other brands of breaker panels which are a fire hazard. Our house has its original panel but it's a Square D QO series which I believe is one of the better panels. Some of the breakers have failed over the years and have been replaced with spares that came with the house or in some places newly bought ones.

 

[wayupnorth]

Speaking of Aluminum wiring, my first house I bought has aluminum going to the main breaker from the meter. One night it majorly shirt socketed and kept throwing the main breaker because that goop wore away. Paid an electrician dearly to re goop the main breaker and all was well in the middle of a snowstorm. No aluminum wiring in this place. But I knew of many older mobile homes with aluminum to copper outlets to burn down, as copper and aluminum dont mix.

 

[sarahperdue]

Power consumption

Wow. I had no idea that rewiring could lower power bills. Thanks for sharing, Thomas.

Sarah

 

[combo52]

Home Electrical Situations

Some Thoughts

 

1 Rewiring an underwired home will never reduce your electric consumption [ bill ] if fact having proper wiring where no wiring is being overloaded will actually increase your total power use, [ replacing an old meter that over reads will reduce your bill, this is very unusual at least in this country however ].

 

2 Aluminum wiring was used in all kinds of houses all over the country from the late 60s through the mid 70s because of very high copper prices during this time.

 

Aluminum wiring had a lot of connection failures because proper connectors were not used, at least at first. Corrosion on aluminum wire is non-conductive and resistance will increase and start heat up and cause failures and sometimes fires. 

 

But do consider that everyone here has aluminum wiring bringing their power into your home and into your service panel.

 

Also aluminum windings in appliance motors is very common, EVERY Maytag washer and dryer motor from about 1960 has aluminum main motor windings [ and all other major US brands as well ] this use of aluminum has caused little problem except for increased power consumption. This is why nearly all new washer motors have gone back to all copper windings.

 

John L.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[thomasortega]

Sarah

Yes, as wires, outlets, ballasts and switches age, they can start "transforming" electricity into heat.

Of course, that's not REALLY significant if it's only one circuit.

But when you make a whole house project at once and you get rid of everything that is old the difference is absurd.

My father's house wiring was a total disaster, a time bomb. You know, every time a different cheap "electrician" (SIC) doing a different jackass repair and my father, scrooge as hell, trying to save every penny most of the times reusing something that should've been replaced 30 years ago and just adding some duct tape.

It reached a point that I had to say "you know what, it will be either I sacrifice my own finances and do something or sooner or later one of my sisters will call me and say my father died in a fire or electrocuted because his house simply decided to kill him."

As it would be horribly expensive to do all at once, I split the house in 3 zones. 1 zone is ready (and I have 4 very unpleasant installments to pay and was the worst because it's the circuit breaker panel itself, kitchen, living room and dining room. The circuit breaker panel was bought huge, waiting for the other zones.

When I finish paying, I'll do the second zone (Bathroom, bedroom and dining room) replace everything. Literally abandon absolutely everything that is there and make everything brand new.

Then the 3rd zone will be his office and the outdoor kitchen. (That will be piece of cake) But I will also get rid of a horrible Hitachi water cooled central air conditioner from 1970's that look like two side by side refrigerators. This AC was reused from our 3500 square meters mansion that was sold some years ago and it almost killed my father in 2015.

That machine remained nearly 20 years completely off, then my father had the stupid idea to install it in his house, just to save money. You know, why buy a new air conditioner if we already have that dinosaur? It turned out that the machine and the ducts (also reused) had an specific and rare type of mold growing inside them. My father had "Old building syndrome" that costed him thousands of dollars in medical treatments for almost 3 years. (until today he's not fully recovered)

Of course when we discovered that (I was still living in Brazil) we never again turned that "thing" on again. A few weels ago, the contractor decided to open the machine and take a look just as curiosity because the last time he saw one of those monsters was decades ago. He ended up discovering that even off, the system had so many jurassic relays and other components that were still using electricity. Also, the water from the chiller (on the roof) evaporated and was continuously being topped off (it also ended the absurd water bill). Only the AC was responsible for most of the electric and water waste.

Calculating roughly, what that AC wasted all those years, even never being turned on, was enough to buy the most modern and impressive central air conditioner money can pay.

The contractor of course didn't think twice before cutting the wires and the supply water pipe. We were lucky enough to find a bank that wanted to buy the machine to replace a very similar machine that reached the end of it's life. They're of course being stupid, but who cares? Money is always welcome! and we got rid of that "thing".

 

[lowefficiency]

Aluminum wiring was (and still is) everywhere - the only way to know is to start opening up switches and outlet wall plates and look. We had some fail in a large apartment building we used to live in - smoke started pouring out of the end of a baseboard heater. A connection had gone bad, and the heat that generated burned the insulation off the wire clear back into the wall. We (and the other apartment tenants) are lucky we were home at the time to turn it off, and that the wall didn't catch.

Unusual wiring patterns were more common in the past, as the craftsmen of the time were quite skilled at conserving wire. Our 1920s house has some really clever single-wire knob & tube loops... and most of the circuits run vertically (serving 2 or 3 floors in a line) rather than fanning out to cover all of the receptacles in a room. Supplying receptacles on opposite sides of the same wall fits well with this style of wire routing.

Be a little bit careful about outlets that are grounded through the conduit. While it may be permissible, not all electrical contractors are perceptive enough to maintain the integrity of those conduit connections over time as circuits are moved, modified, or added upon. All it takes is one disconnect in the wrong place during a service call, such as adding another outlet near the panel, and your "grounded" outlets downstream suddenly are no longer connected the way you thought. Since it isn't a "wire", and modern systems aren't grounded this way, not everyone thinks to ensure that those conduits stay electrically connected.

 

[norgeway]

Aluminum wire.

The problem of aluminum wire is that people didn't use the proper switches etc made FOR aluminum wire, Copper and aluminum have different rates of expansion and contraction, Put a copper screw on a aluminum wire and you can see it does not take long before the connection works loose and can begin to heat up.