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Comment by mitthrowaway2 | Hacker News Reader

There's more to the video than just that. For example: you should run your hot water tap before turning on your dishwasher, and you should experiment with the dishwasher settings, because they can make a big difference.

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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.

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!

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

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

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.

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.

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.

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.

You're going to stay below the circuit breaker rating no matter the voltage. Nobody's going to put a 2,400 watt heater in a dishwasher designed to be used on a circuit that tops out at 2,400 watts because:

a.) I'm going to go out on a limb and suggest that most countries will place limits similar to the NEC's 80% rule.

b.) There are other high current draw devices in a dishwasher that will have to run concurrently like the water pumps.

Same with things like electric kettles. You're not going to find 1,800 watt kettles in the US even though they're designed for circuits rated at that. A quick peek at the kettles available in Australia show that most top out at 2,200 watts for the same reasons.

In the context of a dishwasher 240V would only get you more powerful heaters than you could run in the US if the circuits were rated at more than 10 amps. Voltage isn't the issue.

You know what, I didn't read the middle comment in this thread closely enough before my first reply. You're right that an Australian circuit doesn't help much, and the voltage on such a circuit is useless.

A UK circuit on the other hand would fix everything. It has the same number of amps (or maybe more), but double the voltage.

The problem isn't purely amps or volts, but in general home circuits tend to have a similar number of amps, and higher power usually goes hand in hand with higher voltage. That's the sense in which voltage fixes the problem. A US appliance staying well within amp limits has a lot less power than a UK appliance staying well within amp limits.

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.

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.

   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.

I think one of his earlier videos suggested doing what I have always done. Load the dishwasher then do the hand washing. This ensures you have hot water ready to go since you’ve already been actively using it. When hand washing is done, run the dishwasher.

The whole point of getting a dishwasher is to not think about any of this though, for me.

That probably just means you’re using your machine badly.

There's no user error, just bad design.

This is an aphorism, not a truth. But it’s true that dish washing machines are often badly designed, especially when there are multiple opaque options that can be turned on and off. Consider the example presented in this very video, where the “Eco” cycle uses more water and more energy than the normal cycle and where the “High Temp” option adds more wash cycles as well as heating the water for longer. No amount of design can save the user from misunderstanding what these options do. The only way for the user to use the machine correctly is, at a minimum, to read and learn from the service guide (or other documentation) which gives explicit details about what each wash cycle is supposed to do. If you watch the supplementary video you’ll find that even that was incomplete and had errors; full understanding required hacking the dishwasher to reveal which parts of the machine were active (inlet, heater, pump, etc) and for how long.

Therefore I stand by my assertion that if you refuse to learn the details of what your dishwasher actually does then you will probably be using it badly.

I don't understand, though. You make the point that the user needs to read about the machine, but the very fact that the user needs to read about the machine points to bad design. A well-designed machine wouldn't have called a mode that user more energy and more water "eco".

I didn’t say that the machine was well designed. I said exactly the opposite! The very fact that it is not well designed means that you cannot rely on your intuition when operating the machine. If you do not have some idea of how the machine operates then you will operate it badly. In the specific case the video examines, operating it badly means blindly operating it in the default mode when a different mode demonstrably works better.

Oh, then we agree, we need to make up for bad design with lots of work (in learning how the machine works).

Right, and bad design is all around us every day. Learning about how your equipment works is a good idea!

I agree, but telling an overworked parent because their dishes are dirty because they didn't take the time to deeply understand the mechanism of their appliance doesn't tend to go down well.

If a machine doesn’t function correctly or well, then fixing it requires blaming some part of the system that can change for the better. The dishwasher cannot change; it’s just a machine. It could be replaced, but that might be expensive. Much cheaper for the operator to change what buttons they press on the dishwasher instead.

If that requires reading a manual, or carefully timing the actual length of each wash cycle, or making a recording of each of those wash cycles so that you can work out how long they fill for and how many pre-washes and rinses that they each do then so be it.

That's rather odd? The whole point of a dishwasher, I assume, is to save a lot of time and water, and then to get clean dishes. There's nothing unusual at all about spending a bit of time to learn how to use a tool to save time later, like learning an IDE or what have you. Of course, if you're already getting clean dishes then I suppose no further tool learning is needed for you.

My brother the dishwasher could use up 10x more water and 99% of people would still use it. Nobody buys a dishwasher to save water. That you position it like that gives me little confidence in the rest of the analysis.

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