[y-curious]

I am not an electricity/wiring guy so maybe you can help me understand. I thought aluminum is dangerous to wire with because it is a fire hazard (I bought a home this year and this was a prominent warning in my reading). Is that because it needs to be done very carefully? I imagine most data centers would not mess with a fire risk on such a scale.

[crote]

That's the "a pain to work with" part.

Residential aluminum is a Really Bad Idea because DIY Dave will inevitably do something wrong - which then leads to a fire hazard. Copper is a lot more forgiving.

But a large scale datacenter, solar farm, or battery storage installation? Those will be installed and maintained by trained electricians, which means they actually know what a "torque wrench" is, and how to deal with scary words like "corrosion" and "oxidation".

Like I said: it's what's used for most of the power grid. With the right training it really isn't a big deal.

[jabl]

Aluminum got a bad rep due to a lot of poor installations made in the 1960 and 70'ies. Subsequently new alloys (AA-8000 series) for wiring, new installation and termination procedures etc. have been developed, and AFAIU the situation today is much better. It's still trickier than copper wiring, so probably not a good option for DIY, but for some industrial installation with competent personnel and where the savings can be substantial it could certainly be an attractive option.

https://en.wikipedia.org/wiki/Aluminum_building_wiring

[scherlock]

Aluminum oxide has high resistance and if you mix aluminum wiring with copper outlets, etc the impedance mismatched is what causes fires. You need to either have special copper pigtails installed or use fixtures that are rated for aluminum wiring.

For commercial installs, it shouldn't be a problem as long as it's planned for.

[auxym]

It's because aluminium has a higher coefficient of thermal expansion. It expands and shrinks more as it heats, and as those cycles add up it tends to loosen electrical connections. Loose connections have higher resistance, heat up and can cause fires.

That said, there is no reason we can't design better connectors that can withstand the expansion and shrinkage cycles, like spring loaded or spring cage connectors.

[quickthrowman]

Wiring devices have almost all been universally rated for Al/Cu conductors for the last 50 years, what you’re talking about only lasted a handful of years in the early 1970s.

Go look at the terminals on any light switch or receptacle at Home Depot, they’re all Al/Cu rated.

[_heimdall]

Unless I'm mistaken, the risk with aluminum is that it can expand and contract if it gets too hot. Aluminum sized properly with the correct connectors torqued to spec would be fine, aluminum wires in a residence with a DIYer working on it can be riskier and is why inspectors will always note it.

[u8080]

Aluminum wires became brittle over time(tens of years), fluid which requires some maintenance for screw terminals and inducts galvanic corrosion when coupled with copper without special care. If wiring was properly done and maintained, it is okayish.

[quickthrowman]

If you apply antioxidant paste, torque the terminations to the correct value, and use wiring devices rated for Cu and Al conductors, there are zero problems.

Most homeowners know none of the requirements of aluminum wire installation so I don’t recommend using it, oxidation is bad and can cause fires. Just pay for copper NM cable, it’s dirt cheap anyways.

FWIW I sell and run electrical work for a living. I assume crote and amluto work in the electrical industry, since they’re the only other posters in this discussion who know what they’re talking about.

[Analemma_]

It’s a fire hazard in residential houses where people frequently do their own wiring, because it needs more expertise to wire correctly. Copper wiring is a lot more forgiving to being hooked up by amateurs.

The biggest reason is that aluminum oxidizes, and unlike copper, the oxide layer has high resistivity. In theory that shouldn’t be an issue in datacenters hiring expert technicians.

[pixl97]

Yea, in a data center setup the cost difference can justify the things like soldiering connections rather than mechanical connectors with a higher resistance.

[MSFT_Edging]

Old aluminum wiring in your walls with cloth insulators, designed for a time where electricity consumption was a small fraction of today's electrified usage is dangerous because you're overloading an old, unprepared system.

Aluminum bus bars(solid, often exposed) would be designed for the required power levels and installation criteria.

[Aurornis]

Aluminum home wiring was from the 60s and 70s. It’s not the same as cloth covered knob and tube from earlier years. It has its own problems, but I’d take a house with knob and tube over a house with aluminum wiring.

[margalabargala]

Household electrical usage has decreased, not increased, since that time. Your scaling is backwards.

Old aluminum wires in your walls were designed for a time when you lit your home with 100 watt incandescent lamps rather than 12 watt LEDs.

[quesera]

Only true for lighting circuits though, and most household circuits are mixed.

The quantity and (edit: aggregate) power draw of modern appliances is far greater now than 60 years ago, so the overall load on the old wires is much higher.

[Jblx2]

> power draw of modern appliances

Here's a article that claims that refrigerator energy efficiency has improved dramatically from 1972 to 2012.

https://appliance-standards.org/blog/how-your-refrigerator-h...

I'd bet that modern TVs are more efficient that CRT televisions. Do most people even have desktop computers anymore, or have they mostly been replaced by laptops, tables, and phones? I'd be interested to see the efficiency numbers for electric clothes dryers over time. I wouldn't be surprised if they are also slightly more efficient than older models, even if they are still using resistance heating. Due to smarter electronics that automatically turn the unit off after the clothes are dry (air humidity sensor). I think electric ranges, dish washers, toasters and coffee machines have been ubiquitous since the 1960s (but are probably about the same energy-consumption wise). Air conditioning units are one thing that I'd believe are much more common today than in the 1970s and 1980s. Household sizes are also smaller, so less electricity used for electric water heaters, and the oven, etc.. Electric vehicles are an up and coming user of electricity. What other appliances are likely to be using more now than before?

[quesera]

These are good points, but having worked on a few older houses, I usually see overextended and overloaded circuits, not the opposite.

Standard small-house service used to be 60A, sometimes as few as 4 circuits! It's now 100A minimum by code, with 200A common.

Ovens/ranges have gone from 30A to 50A (dedicated) circuits by code. Microwaves also require dedicated circuits now. Gaming computers with big GPUs are common. Air fryers and electric pressure cookers are newly-common countertop appliances. People definitely use resistive electric space heaters more now (very cheap, much safer than the older options). And there's a trend away from gas and to electric ranges and water heaters. Heat pumps are also increasingly common. You mentioned air conditioners and EV chargers. Kitchens and bathrooms are now required to have dedicated (and GFCI) circuits. Household sizes are smaller, but houses are larger.

So I guess I'd say that, properly expanded, individual circuits should carry less current than they used to. But very often, appliances (AC, microwave, gaming rig, air fryers), are just "plugged in" to an unexpanded system, with varying results.

If you're lucky, they pop a breaker and you call an electrician. If you're not lucky, they push the power draw into uncomfortable zones, esp for Al wire.

[Jblx2]

>Gaming computers with big GPUs are common.

Is there a good way to quantify this?

[quickthrowman]

This is absolutely not true in areas where heating the air and water and cooking are done with natural gas. Every single appliance in a house is more efficient today than in 1970 due to advances in motor speed control, without exception. The only thing that didn’t get more efficient is electric resistive heat and it’s impossible to improve on that anyways.

I can’t think of a single appliance from 1970 that consumes less energy than its modern equivalent. Anything with a pump or fan is more efficient and so is lighting. LCD TVs use less energy than CRTs.

I also can’t think of an appliance that has become common in households that draws more than 100 watts of continuous load since the 1970 aside from just ‘computers’. An ancient 500W 80% efficiency PSU at max load only has 5.2A of current at 120V single-phase.

If you convert your natural gas furnace to a heat pump, you will use more electricity but excluding that and NG to electric HPWHs leaves only more efficient equipment.

[quesera]

Sure, but there are more appliances plugged in today than there were. The simplest evidence for this is that there are never enough outlets in an old (unrenovated) home.

In a renovated house, you won't have aluminum wire at all, so these concerns are null.

My original statement should be qualified. Since we were talking about aluminum wire it's relevant -- an updated house will have new (copper) circuits that can handle all this stuff. An NON updated house might have Al wire and be overloaded in a more severe way than it was in the 60s.

But FWIW, new >100W appliances:

  - microwaves (1200+W)
  - air fryers (1500W)
  - electric pressure cookers
  - rice cookers (mine claims 610W on the plate)
  - stand mixers (old: 80W, new: 475W)
  - desktop computers (esp gaming rigs)
  - resistive space heaters (1500W)
  - *bigger* TVs (compare 72" LCD to 19" CRT?)
  - air purifiers (mine clocks 175W on high)
  - towel warmers? :)
  - and the ubiquity of 10-20W small stuff has of course exploded, and it all adds up

[quickthrowman]

> Sure, but there are more appliances plugged in today than there were. The simplest evidence for this is that there are never enough outlets in an old (unrenovated) home.

Perhaps, but none of them are continuous load, which absolutely matters.

Rice cookers, microwave, stand mixers, air fryers, pressure cookers, etc are all short duration usage, not continuous load. If homeowners decide not to add dedicated kitchen circuits and instead use a 120V 12A load on a 120V 15A shared circuit and trip the overcurrent protection, that’s their own fault.

These loads don’t really matter in the way a heat pump, air conditioner, furnace fan, or water heater does, it’s a bunch of random kitchen appliances that you won’t be using simultaneously. Your utility does not even take the full non-continuous load into account when calculating the kVA demand of your electrical service. IIRC a random convenience duplex receptacle for non-continuous loads only adds like 180 VA (this is 1.5A at 120V with a power factor of 1) to the demand calculation.

You are correct in a technical sense that people have more devices they plug into a wall, but most of the power consumed by a home is to devices that are hardwired in, aka continuous loads, not cord and plug connected appliances.

The continuous load of a home should be lower than ever without electrifying heat. Every continuous load (which are almost exclusively motors and lighting) in a home is more efficient now than in the past due to variable frequency drives and electrically commutated motors.

[knollimar]

Old aluminum is dangerous. Modern aa-8000 series aluminum is fine. Bigger pipes though.