Life expectancy of electrical systems

[designer82]

I know that Elec Distribution Equipment (Panelboards, Switches etc.) have a life expectancy of 50-70 years, depending on installation conditions.
This is based on information from Schneider Electric.

What about cables, what is their life expectancy?

The actual application is a 4 unit multi-family building built in the 40's. We're replacing all electrical distribution equipment with new since they're past the 70 year mark.
-Is it smart to also replace all the cables within the dwelling units with new?
-Would this necessitate ripping out all walls or can an electrician replace all cabling with minimal cutting/patching & fishing new wires?


Thank you

 

[petersonra]

I think 70 year old wiring is probably past its prime.

It is hard for anyone to give you good advice about your specific situation but it seems likely that if you ripped out all the existing wiring whatever you put back in it's place will likely have to meet the version of the electrical code you currently are required to follow.

Gfcis, afcis, aic ratings, sa circuits, 3 wire receptacles etc. none of these things existed 70 years ago. Even the quantity and placement of receptacles required has changed.

 

[tom baker]

The type of wire insulation is likely RHW, or similar rubber. This type insulation dries out and cracks. If the wire is in a raceway and can be removed then do so. Also wiring of that age had small boxes, no egc, etc. As petersonra pointed out the quality of devices is much better today

 

[Fred B]

It is generally not an issue with the copper conductor but the insulation that becomes an issue when it ages. Repeated overloads or even just getting to the edge and high temperature, all enhance the degraging of the insulation. 70 yr old wire I've encountered have all been really well past it's prime and in most cases dangerous to even work on as the insulation is brittle and doesn't take well to manipulation needed to make updates/repairs of devicies that will go bad way before any wire limitation.

 

[PillarOfAutumn]

I would replace the wiring if only to add equipment grounds to circuits. But I think what everyone else has said is correct, that the insulation on the wiring is almost certainly past its life expectancy.

As far as the walls and ceilings go, you wouldn't have to rip them all out in order to get the new wiring and boxes in but it definitely won't be a small job to patch and paint/refinish everything afterward. One thing to consider with this too is what are the existing wall materials? If they're also from the 40's I would not make any assumptions about todays materials easily matching up.

 

[petersonra]

One thing to consider with this too is what are the existing wall materials? If they're also from the 40's I would not make any assumptions about todays materials easily matching up.

Probably lead paint and asbestos issues as well.

Once you open up the walls you have no idea what you will find and in a lot of places if you open the walls up enough when you put them back together you have to insulate them to today's standards.

The point is that it is not about just replacing some wires.

My suggestion is leave the wiring downstream of the panelboards alone so the owner can make a rational decision about the scope of the project he is getting into. It may even involve having to upgrade plumbing depending on what is found in the walls.

If you are looking into replacing the panelboards for each tenant give serious consideration to a 42 circuit replacement regardless of what is there now.

 

[petersonra]

One other thing, when estimating the cost don't forget the cost of having the power company come out to shut off the power and then to turn it back on.

 

[letgomywago]

Probably lead paint and asbestos issues as well.

Once you open up the walls you have no idea what you will find and in a lot of places if you open the walls up enough when you put them back together you have to insulate them to today's standards.

The point is that it is not about just replacing some wires.

My suggestion is leave the wiring downstream of the panelboards alone so the owner can make a rational decision about the scope of the project he is getting into. It may even involve having to upgrade plumbing depending on what is found in the walls.

If you are looking into replacing the panelboards for each tenant give serious consideration to a 42 circuit replacement regardless of what is there now.

Something to consider is 42 space panels are overpriced now. Since the 42 space isn't a limiting factor anymore 40-80 space and 60 space full size are becoming the standard large size loadcenter

 

[electrofelon]

Something to consider is 42 space panels are overpriced now. Since the 42 space isn't a limiting factor anymore 40-80 space and 60 space full size are becoming the standard large size loadcenter

Personally, I don't think I would ever use a load center with over 40/42 spaces, that just sounds miserable. As it is a full 40 is not that much fun to make up. I'd go with 2 partly full 40's or better yet a panelboard

 

[ActionDave]

Making up an eighty circuit panel with dedicated neutrals for each hot and a green wire for each pipe has a level of joy and satisfaction one would associate with an afternoon of babysitting a classroom full of undisciplined toddlers old enough to walk, but not potty trained who have been given sugary snacks right before nap time.

 

[letgomywago]

Personally, I don't think I would ever use a load center with over 40/42 spaces, that just sounds miserable. As it is a full 40 is not that much fun to make up. I'd go with 2 partly full 40's or better yet a panelboard

I like the siemens 3048 personally. It's my favorite resi 200 amp panel.

 

[petersonra]

Making up an eighty circuit panel with dedicated neutrals for each hot and a green wire for each pipe has a level of joy and satisfaction one would associate with an afternoon of babysitting a classroom full of undisciplined toddlers old enough to walk, but not potty trained who have been given sugary snacks right before nap time.

I am not suggesting that but if you are putting in new stuff might as well give the electrician who has to upgrade the circuits to today's code a fair chance.

 

[__dan]

I know that Elec Distribution Equipment (Panelboards, Switches etc.) have a life expectancy of 50-70 years, depending on installation conditions.
This is based on information from Schneider Electric.

What about cables, what is their life expectancy?

The actual application is a 4 unit multi-family building built in the 40's. We're replacing all electrical distribution equipment with new since they're past the 70 year mark.
-Is it smart to also replace all the cables within the dwelling units with new?
-Would this necessitate ripping out all walls or can an electrician replace all cabling with minimal cutting/patching & fishing new wires?


Thank you

Cable and conduit are two different things. Conduit, rubber with fabric, RH, or THW, in RGS from that era, as long as the equipment ground is there I would not be in a hurry to change it. I would probably be looking to retain the old feeders in conduit, but run new for the new loads and leave the old feeders to feed something. Reuse would be on my list.

Cable from that time, fabric thermoplastic romex and BX using the armor as the ground, you may end up replacing most of it inside the unit. For one, the 3 x 2 outlet boxes are too small per code for anything and as soon as you start touching it you cannot get around that. Ceiling lights had those old pancake boxes or no box at all.

A minimal renovation I would leave the old wiring in place and try to not touch it, running direct lines for new circuits. If you are doing the entire unit or structure, might have to plan on all new for the get go, may be easier to tackle it production style instead of one at a time.

Feeder type cable to the unit subpanels if they ran those to inside the unit, I would look at them each instance. They may or may not have aged well. Armored feeder cable could be pretty good after stripping back a little. Old SER type, could be failing at sharp bends and pinch points, where mechanically overstressed or hard bent.

Inside the unit the issue would be the 3 x 2 x 2.5 boxes being too small. Other than that the cables could be reusable. If the boxes have to go, you would not be saving the cables.

 

[letgomywago]

Cable and conduit are two different things. Conduit, rubber with fabric, RH, or THW, in RGS from that era, as long as the equipment ground is there I would not be in a hurry to change it. I would probably be looking to retain the old feeders in conduit, but run new for the new loads and leave the old feeders to feed something. Reuse would be on my list.

Cable from that time, fabric thermoplastic romex and BX using the armor as the ground, you may end up replacing most of it inside the unit. For one, the 3 x 2 outlet boxes are too small per code for anything and as soon as you start touching it you cannot get around that. Ceiling lights had those old pancake boxes or no box at all.

A minimal renovation I would leave the old wiring in place and try to not touch it, running direct lines for new circuits. If you are doing the entire unit or structure, might have to plan on all new for the get go, may be easier to tackle it production style instead of one at a time.

Feeder type cable to the unit subpanels if they ran those to inside the unit, I would look at them each instance. They may or may not have aged well. Armored feeder cable could be pretty good after stripping back a little. Old SER type, could be failing at sharp bends and pinch points, where mechanically overstressed or hard bent.

Inside the unit the issue would be the 3 x 2 x 2.5 boxes being too small. Other than that the cables could be reusable. If the boxes have to go, you would not be saving the cables.

If ran in 14 those boxes are fine with cable in and put.

 

[__dan]

If ran in 14 those boxes are fine with cable in and put.

Afaik the volume limit for the 3 x 2 x 2.5 is one 14-2 cable with device and clamp. Cannot daisy chain two cables through them as would be found with the typical install from that time.

Splice and fan fold 6" lead length 2x cables in those boxes ???

 

[letgomywago]

Afaik the volume limit for the 3 x 2 x 2.5 is one 14-2 cable with device and clamp. Cannot daisy chain two cables through them as would be found with the typical install from that time.

Splice and fan fold 6" lead length 2x cables in those boxes ???

Non grounded cables usually.
No clamp for 2 wires clamps if stapled within 8 in
1 receptacle so 2 conductors fill 4
2 14-2 non grounded 8
12 cu device fill.
2x3x2.5 box is 12.5 cu

 

[macmikeman]

Check the local building code to find out if new energy codes affect your area. And if so are retrofits exempt from the same. This is a different thing that has arrived in our land.

 

[__dan]

Non grounded cables usually.
No clamp for 2 wires clamps if stapled within 8 in
1 receptacle so 2 conductors fill 4
2 14-2 non grounded 8
12 cu device fill.
2x3x2.5 box is 12.5 cu

What I would expect to see commonly from that time, the 1940's, balloon framed Victorians worker housing.

Usually armored cable BX with clamps, rarely the fabric RX with undersized EGC.

Metal wall boxes were very shallow, probably not 2.5" deep, then they had a kind of octagonal bend where the cables came in.

Point being you would have to check the presently installed box and get their number for cubic capacity. Maybe probably something less than 2.5 deep is there now.

Very rarely see wirenut splices from that time at outlets. Twist and tape with solder was common and the quality was good. Sometimes see twist and tape with no solder and those are failing. Lesser quality sometimes see both cables run to the outlet screw terminals, 4 wires to the outlet, then no lead length so the outlet barely comes out of the box.

Two cables with a twist and tape splice would barely fold into the box and then minimal for the leads to the outlet. Their technique was good to get it all in there but then you would have to duplicate that high practiced skill just to get another outlet and the wires back in (done that enough times).

If you're in there remaking the splice for pigtails, the wire you start with can be short and your working with wires that barely long enough to themselves come out of the box.

Point being you would have to spot check what's in there now looking for the gotchas. Are the boxes big enough for two cables if you have to rework it, existing splices good already or twist and tape no solder repair everything, existing wires long enough to resplice.

If they're not opening and moving walls and most of it can stay, or, if you have to rework too many and they're a pita, could be easier to demo them and run all new. Depends on how much of what is there now is reusable.

 

[LarryFine]

If I was asked to completely rewire an entire house, I would insist that it be gutted.

 

[PaulMmn]

If I was asked to completely rewire an entire house, I would insist that it be gutted.

You mean rip out all the plaster and lath, still in good shape? That should not be done lightly!