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Comment by znpy | Hacker News Reader

This.

We had a consumer-grade coffee machine at the office once, along with free coffee capsules for the employees.

Whereas in somebody's home that machine would have made 4-5 cups of coffee a day, that machine was making in the order of hundreds a day.

Of course it broke quite often.

But having worked at a restaurant as a waiter in my youth, I can tell: industrial (even entry-level) professional dish-, washer are on another league, completely different. If anything, for having the dishes done in 40 seconds (!)

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> ...for having the dishes done in 40 seconds (!)

While my next home dishwasher will be an industrial / commercial-grade dishwasher after one too many services calls for a supposedly premium residential make (Bosch, and I've heard rumblings Miele fares no better), I also have to acknowledge there are trade-offs.

1. I need to supply higher voltage and amperage than most homes plumb for dishwashers. Fortunately not three-phase for the smaller units I'm looking at.

2. I cannot put my more delicate dishware into them, and hand wash them.

3. While there is more energy and water use, I'm okay with that. That marginal inefficiency is more than made up for by keeping a residential dishwasher from entering the landfill in just a few years. Under residential use, I can reasonably expect to run it until parts run out, which for the better brands like Hobart, does not appear to happen for decades.

4. While I have to use detergents that are not available at the grocery store, I'm okay with that.

I sometimes wish there were open source reference blueprints for the big ticket household appliances built around a design dimension that will not change for the foreseeable future: human planiform scale. And manufacturers plug into that frame so the basic core like the tub of a laundry machine or dishwasher doesn't change common mounting points and dimensions while everything around it changes and swaps Ship of Theseus-style over the decades, radically reducing the footprint of these machines entering the waste stream. What I'm really wishing for is more cradle-to-cradle design however, and I should leave the actual implementation to the domain experts.

Tips for a long lasting Dishwasher:

1: Demand that it's attached to the hot water (machine need less power to heat it up, less chalk...AND Cheaper(your boiler is better at producing hot water))

2: Clean it once a month, especially the pump intake (has often sand like stuff on the ground)

3: DONT use tabs but powder.

However, Industrial grade stuff is more expensive (from the power standpoint), but better for the water (not stupid aromas)

> 1: Demand that it's attached to the hot water (machine need less power to heat it up, less chalk...AND Cheaper(your boiler is better at producing hot water))

Most machines actually specify that the water entering the unit has to be at least 49C. To meet this you usually have to run the hot water on the kitchen sink—which then wastes water. (And may be where people get the mistaken idea for pre-washing: they're running the sink anyway.)

AFAICT, the only brand that can officially be connected to the cold water (10C) supply is Miele, which have an internal heater. And the official specs show that they actually use less overall power with cold water. This is probably because (a) some of the cycle can use cold water, and (b) a smaller quantity overall needs to be heated up compared to running the tap. It does take longer, time-wise (~30m), though; see page 45:

* https://www.miele.com/pmedia/ZGA/TX2070/10544640-000-03_1054...

BSH says cold water is okay, warm water only up to 60 °C (!).

I'm under the impression most dishwashers follow pretty much the same design. There's an inlet valve, usually just the aqua-stop itself, which feeds into the water/ducting plate, which also acts as a heat-exchanger between waste water and water intake. Another two valves control the water softener (to switch between normal operation and regeneration using salt water, which is what the salt you put into it is for). Fresh water runs into the pump sump, which contains the waste water pump, which is controlled by a water level switch connected to the inlet (which also turns the aqua-stop off). The pump sump has a third connection, going into the pressure pump, followed by the water heater, that then goes to the washing arms. The water-clearness sensor (which is just a light barrier) is located in this path.

So overall there are remarkably few actuators and sensors:

    - Three valves
    - Two pumps
    - One heater
    - One solenoid to release the powder / tab latch
    - Outlet temperature sensor at the heater
    - Thermal cutoff integrated in the heater
    - Water clarity sensor
    - Level sensor

I have never had a dishwasher connected to the hot water (which at 60C would be too hot).

I've never heard of a dishwasher that did not have a water heater.

They all worked very well for years. I've had Bauknecht, Siemens and Miele.

Can you elaborate on tabs vs powder?

Technology Connections has got you covered:

> Ever wonder how dishwashers work? Are you ever bummed by the performance of yours? Well, this video can answer your question and possibly provide you with a solution!

* https://www.youtube.com/watch?v=_rBO8neWw04

Oh Technology Connections. What a good channel!

Something about pre-wash routines not getting soap to clean some of the grimes.

There's actually not a lot of parts in a dishwasher, I'm curious what gave you trouble with your unit.

Since I have a parade of technicians coming through to fix the issue, I had the opportunity to talk with them. The high-end units of all brands these days have sensors everywhere to save water and energy, and simultaneously monitor cleaning effectiveness as they are all competing on advertising the least utilization with the most cleaning power (monitoring cleaning power and cleaning results is another aspect of saving water and energy). It reminds me of Apple's "you can never be thin enough" focus.

In my case, it has led to an issue that is still stumping the techs, where something is causing the unit to believe it has finished the session well before it even gets under way with the hot water cycle sometimes, and other times to not even start after the initial tub fill. The diagnostic code thrown indicate a malfunctioning sensor they've already replaced twice. Maybe if I call them out enough times, Bosch will just offer to replace the entire unit for me. While I don't get charged labor for subsequent tech visits for the same issue, I still pay for parts, so maybe Bosch's dastardly plan is I'll Ship of Theseus pay for a new unit part-by-part and end up paying 10X what a normal unit would cost before it works again.

In the meantime, it has been fascinating getting an inside look at the design decisions. Lots of incredibly clever engineering has gone into these beasties, which screams to me as a software guy of a ton of refinement over decades of accumulated experience, much of it learned the hard way in the field. Kind of like when I see a software system where the sharp edges have been burnished away into a smooth patina of refinement, and there are still odd bugs that pop up now and then.

AFAIK commercial dishwashers are very diverse: some are rugged equivalent of a consumer dishwasher, some can only sterilize pre-washed dishes, and some do the quick 40 seconds wash... but use really a ton of electricity.

Yes, for smaller cafe-style commercial establishments, I've seen the "ruggedized consumer" type models, but chatting with repair techs, I got the impression from them they feel those units are nearly as corner-cutted-into-not-BIFL as their consumer brethren. I did forget to mention that another tradeoff others might not be aware of is having to scrape off food before it enters these commercial units. I already do that.

My style of cooking is wash as I prep and cook, so I'm constantly in motion while prepping and cooking. I dynamically figure out ahead of time whether what I'm using at that moment is needed the rest of the session, and wash it the moment I get a "let simmer for N minutes" break, and everything that is dirty that doesn't land on the meal table lands in a sink of hot soapy water. I scrape for a compost pile as I go as well.

This minimizes clean up time and food waste at the end of the meal, but I have since found out few people do this. I learned it when I worked back of house. While I had dedicated team members for various clean and prep activities, there was still plenty to do with not a moment wasted, so building that habit was the only way to keep up with the service rush. Having just learned queuing theory gave me a leg up over a couple old salts who learned the same through brute force intuiting the habit, and I taught the less-experienced team members by giving them rote expert-system-like if-then procedure.

It was a glorious feeling when my entire shift team had only a few minutes of cleaning and tidying at the end of the shift well before the cleaning crew arrived (thank goodness we did not have draining and cleaning the fryer on our duty list), and we could relax a few minutes over a snack and shoot the breeze just before clocking out.

Our office has worked out that it's still cheaper to buy replacement consumer-grade applicances than one really expensive industrial-grade and pay for servicing and maintenance. It's really wasteful but made more financial sense.

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