[bakje]

Running the hot water tap beforehand assumes that the dishwasher is hooked up to the hot water in the first place, which isn’t common everywhere.

Where I live this feature is called hot fill, I believe, and a lot of dishwashers don’t even support it. For those that do support its still generally not recommended to use it since the dishwasher now can’t do any rinsing with cold water, which is not only wasteful but I’ve heard the hot water can damage the water softener in your dishwasher.

But if you do hook it up to hot water (which is a lot more common in the US, I think) this makes a lot of sense.

[mitthrowaway2]

And lo, there is verily even more information presented in the video than this thread has yet revealed. For what Alec says in the video is that this purge-the-cold-water advice is specific to North America, and he even explains the reasons why!

[bakje]

Haha I have to admit I didn’t watch the whole video.

In which case my comment still stands for those who also haven’t watched the whole video, which is probably a fair amount of people

[krige]

He does mention it has to do with voltage and heating systems. I think it's something he covered on his kettle vid.

[inferiorhuman]

He mentioned that it's not due to voltage but rather low current circuits. A 15 amp circuit translates to around 1,800 watts in the US and if you derate it to 80% of that like the NEC requires a continuous load you'd have around 1,440 watts available.

His argument is that appliance manufacturers are trying to simplify their lineup by making models that would work in homes without a dedicated circuit (15 or 20 amp). Although I can't think of a better argument that still doesn't quite sound right to me. The NEC has required dedicated circuits for dishwashers for quite a while now and IIRC that requirement has been for a 20 amp circuit for a few decades. Even though you typically only see 15 amp receptacles, kitchens have required 20 amp circuits for somewhere north of forty years.

I think a lot of his video is simply based on testing with crappy Whirlpool and AEG dishwashers. There's a reason why Bosch (and these days LG) dishwashers are pretty much universally recommended.

[Turskarama]

It's the same issue, if you have a higher voltage then you can get more power without increasing current.

For example in Australia a standard house circuit is 10 Amps, but because it's at 240V we can get 2400 Watts (realistically more like 2300) out of a _standard_ wall outlet that is in every room of your house.

[inferiorhuman]

It's not the same issue. The vast majority of kitchens in the US have 20 amp circuits (so 2,400 watts peak, 1,920 watts continuous) exclusively. It's a bog standard receptacle (NEMA 5-20R instead of 5-15R) that's backwards compatible with 15 amp plugs. In fact these days most 5-15R receptacles have identical guts to their 20 amp counterparts save for the additional provision for a horizontal blade.

The electrical code (NEC) has started moving towards requiring 20 amp circuits in other rooms and more 20 amp circuits in kitchens.

[Dylan16807]

But they're staying shy of the amp limit on purpose. So designing for 20 amps would be somewhat of a boost but not enough. While doubling voltage would actually fix the problem.

[mschuster91]

Meanwhile, here in Germany, we have 230V, but every standard wall outlet is rated for 16A continuous load over 1 hour so you can get 3.6 kW on each circuit.

Your standard home has a supply of 3 phase power @ 35A (southern Germany) or 63A (northern and western Germany), I think only the former GDR is at standard 3x25A, because like in many former Communist countries they had to save on expensive copper and aluminium, and since a lot of the GDR was heated by steam-based central district heating systems, you didn't need that much power anyway.

[whatevaa]

Lot's old homes and flats here limited to 5A or 3A 220v. If you don't use electric heating your power demands go down substantially, though 3A is a bit small these days.

[inferiorhuman]

   the hot water can damage the water softener in your dishwasher

Most dishwashers in the US don't come with water softeners. AFAIK European made American market Bosch 500/700 series ones do, but the American made ones do not. Both would be designed for connection to a hot water supply.

As heated air drying (in the US) has fallen out of favor, hot rinse water will help things dry faster. To that end my Bosch dishwasher has an option to increase the temperature of the rinse water.