OK, skip this if you don't like longwinded explenations.
Actually started up my laptop to write this cause I couldn't be bothered touch-typing this, so sorry for any spelling mistakes. No auto-correct here...
And if you don't care much for somewhat know-it-all explenations, just skip the post entirely.
So. All this is what I know about the EU-programming. The US might operate differently based on them being hot fill and such.
PowerWash consists of a couple of steps.
First is saturation and distribution of detergent. Spinning and spraying and all.
Then comes heating. Here the machine drains first so there is a known water level in the sump. Then it fills by volume (any PW equipped washer has a flow meter). Then it heats that water to steaming temp - about 85C. During this stage no recirculation happens. The laundry is soley heated by the steam rising up.
Once a certain amount of energy has been used to heat (yes heating here happens not by temp but purely by expended energy) the washer starts recirculating every 2 mins for a couple of seconds. Problem here is that there isn't necessarily any water to recirculate. If the laundry is very absorbent, the intial amount of water might not be enough to fully saturate the load. The recirculation is just there to get any water that might have dripped of the clothing into the sump back into it.
Finally the washer adds cold water to a low water level. This stage dilutes the wash water out of the clothing and is the first point in the cycle where you know for certain the load is fully saturated.
So now to the limitations:
1) Pre-Wash. Pre-Wash in Mieles logic is ment not technically for heavy soils as in stains and such, but for large amounts of soils like sand, dust etc. For heavy soils, soak is supposed to be used.
So, a pre-wash selection means a high dilution power is needed. Thus, a very low water main wash dosen't make much sense. It's not the re-saturation that is the issue, it's the performance wanted in that case.
The soak is done in deep water as soaking clothing - no matter if in a machine or in a tub - requires enough water to submerge all fibres to be effective.
Best way to think about it here: You pre-treat stains with a spray. If there are many heavy stains or lots of loose dirt you don't use a spray, you soak. PowerWash is like super charged stain treating with a spray - just for the entirety of the load.
2) No spin: In europe the limit set for this is 600rpm actually. So if you select anything lower than 600rpm PW is cancelled. If you select such a low spin speed you have a reason you select it - laundry care. And if you do that, you wouldn't want it spun it at all.
A spin during the main wash is just as "damaging" to clothing as during the final spin.
They limit the thermo spin on their W/D as well if you select a low spin speed. Same idea.
3) Cap-Dosing: 2 reasons here. First, they always load at least 5l via the cap to fully flush it. This would be way to much for PW-prepping.
The stain agent I think is added somewhere mid main-wash. Adding it during the dilution stage of PW dosen't make much sense since it only has 10min of action then, and mid wash you can't ensure it will get properly distributed.
4) Water Plus: So, actually, kind of a communication issue there. There are 2 kinds of washers with PW: Those that just have a water plus button and those with both water plus and an extra rinse option.
In Europe, you can set up the first of the two to either add a rinse, raise the water level in all stages of the cycle or both.
On top of that, ALL machines here offer the option to pin the water level in the rinses to max.
If you have set up either the max rinse water level or add a rinse (be that via the extra rinse option or the water plus option programmed to act that way) the machine will still run PW as normal.
If you select water plus (either by setting up the option that way or just using water plus instead of extra rinse) the assumption is that you have a reason to have a deep wash - not just a good rinse. Thus, PW is skipped.
Logic here: Good rinsing does not require much water - it's much better to run an extra rinse. If you actually need more water (for bulky items like blankets or towels or such) you would want it in the main wash aswell.
Water Plus basically acts as a PW kill switch.
5) Something that actually dosen't come up in the US. PowerWash isn't active for any temp over 60C and not for any cycle that requires temp holding.
So a boilwash cycle wouldn't use it since the hotter the laundry needs to get, the longer the heating takes.
On a normal wash for a full load, a Miele takes about 30-35min to heat to 60C over here. That is a full load and that uses about 20l per fill.
On the max PW-load (about 6kg), the machine takes a good hour to heat to 60C - and that only has to heat half the amount of water. The heating element is only on about 1/3 of the time in total due to it cycling and thus you save about 10% of energy in total, but the heating takes double the time.
Heating the same load to 40C takes only about 25min max in PW. Thus heating those last 20C takes more than twice the time.
Heating to 30C is done in max 10min usually.
From there on, the machine can't actually monitor the actual wash temp. There is no direct correlation between the water temp in the sump and in the laundry. The machine actually just calculates how much it has to heat to get all water in the machine to a certain temp. If you interupt the machine right after heating and open the door on a PW cycle, you'll be abled to feel that some areas of clothing will be warmer than others. The temperature only levels out to an even level after 10-20min of continued tumbling.
Same goes with dampness: Right after spinning and spraying, the laundry often isn't 100% evenly wet. Both water, detergent and heat are ment to migrate throught the laundry over time.
This though means as well that if you need to keep a wash temp for stain removal or for sanitizing, you can't warrant that on a PW cycle. Thus, for example, Hygiene/Sanitize don't run PW cycles even though they are just cottons cycles with long temp holding and slightly lower agitation to compensate for the longer main wash.
And then another final addition to this:
There were 4 major generations of "PowerWash" up to now:
1) PowerWash: That was just the recirculation. No fancy highly efficent ultra-low water level washing with heating via steam.
2) PowerWash 2.0 - First version: These machines only used the PowerWash 2.0 method on Cottons and Easy-Care. They had some teething issues. PW-sensing was sometimes very inaccurate. The machine could not abort PW once PW was decided on. Means that if you had a very light load that absorbed a lot of water, the machine could potentially not saturate the load enough to get decent results on PW mode with steam heating. For example with certain kinds of towels, you could end up with dry spots even after 90min of main washing.
3) PowerWash2.0 - Second version: This version added a lot of things though it was still labeled the same. At this point Miele just kept the 2.0 suffix to make sure any first gen PW machine that didn't have the heating by steam functionality was sold before changing the naming again. Here PW was added to certain cycles like at first Delictaes and Shirts, later on Automatic Plus. Cycle times under PowerWash were extended in general - the shortest PW Cottons 40C cycle without options now was over 2h vs. the 1:30h version that it could sense to before.
Here the PW cycle was still capped at a max of 8l of water used for saturating the load, but it could switch out of PW into a normal cycle if it had to add any more water than that to saturate the load for PW.
This is also where SingleWash shows up for the first time.
4) PowerWash: Now, the machines are only labeld PowerWash again. Any machine that is on sale that has 2 pumps and a QuickPowerWash cycle from this point on also washes with what now has become the key feature of PW - the indirect heating. There actually was one exception maybe kinda - some M-Touch machines might have been labeled PW2.0 even though they might have used this version of the programming, but only very briefly.
This version adds another thing to PW: variable saturation targets.
Beforehand, all PW cycles aimed at about the same residual moisture - the same as the Cotton cycle would use, or about 80-100% for the main wash heating part.
For certain cycles - like Shirts and Delicates - that could lead to insufficent moisture retainment on small loads. You would than see for example that most of the shirts in a load had come pretty clean, but certain areas in random spots would still have some reminants of a stain on them.
To combat this, in certain situations, the speed the machine spins to during the preparation to the heating stage might be reduced or it might be skipped all together and it just distributes. The first spin up for load sensing however remains untouched.
This leaves you with actually dripping wet items compared to the wet but not fully saturated items in the Cottons cycle for example. This version is used for example in Delicates and Shirts.
One way you can actually check if you have this version (at least in Europe) through an update for example: This is what enables the QuickPowerWash cycle to run 4kg in 49min. The machine runs this higher saturation version in that case - not to save energy, but simply because you gain an ever so slight advantage time wise through the lower amount of water needed to heat and the considerably higher detergent concentration. Togehther with a slightly adapted rinse procedure, you can save the 10min for load up to 4kg.
PowerWash isn't dumb programming.
Until the newest series of BSH machines this was the most complicated and innovative wash system on the EU market - and even now I'd give it an edge over those machines.
They weren't perfect from the beginning - but Miele never was.
By now they have covered so many edge cases that they run PW cycles on most programms anybody ever uses and they are the only ones I know that run such an efficent system even on their short cycles.
Alone the idea of takeing the basis of cleaning clothing - the Sinner's circle (Sinner was a german chemist, so Sinner is a name, not like sinning) - to it's very basic terms was more than anybody has realised in a long time.
PowerWash is the basic idea of "just throw everything you need together and somehow it will work out".
They realised that you just needed the chemicals, the energy, the mechanics and the time in total.
They will mix enough on their own.
Thus, they realised that you don't actually need to heat all that water.
And you don't have to actually monitor the temperature in the clothing.
You don't have to be sure that you have everything 100% saturated from minute one.
As long as there is enough water and chemicals to cover everything, it will eventually spread out and cover everything.
As long as there is enough energy to heat everything to a certain temp, eventually everything will be that temp.
And as long as you give it enough mechanical action and time on top of that, everything will eventually come clean.
All you have to make sure you exactly know how much you need.
And that can be easily calculated.
You can easily calculate how much water you need. How long you have to heat. How long you have to tumble.
They took cleaning clothing and broke it down into some math.
They established edge cases where the math didn't work (thus those exemptions) and always operated within that confine.
Don't say I didn't warn you this was gonna be a novel...
