Washing Machine Fill Level

[stratfordgirl]

Well, I think it shows the pressure sensor is able to read water level correctly. The criteria used to determine fill level in each program and program phase would be determined by the machine’s software, something which none of us have access to.

The advantage of a pressure sensor over a pressure switch is that it allows the development engineers to vary behaviour of the machine according to a variety of factors, not just water level, in order to achieve an optimum balance between cleaning performance and program duration.

This type of more flexible programming when it started to appear in high end machines in the 1980s and 90s was often referred to as fuzzy logic, but is now commonplace. In addition, modern appliances are sometimes capable of machine learning, enabling them to memorise observed parameters over several wash cycles and adapt programs accordingly.

I suspect the quirks you have identified on your more recent machine, rather than pointing to a specific fault, may be a byproduct of these more adaptable technologies.

[John.G]

The Miele required 6.5 litres of water (for your test) which required a fill time of 27 secs from a mains pressure of 3 bar. If the mains pressure reduced to say 1 bar then because the logic determines that 6.5 litres are required then the fill time must increase by a factor of ~ 1.7 to around 459 secs, if the fill time remains constant then only ~ 3.7 litres will be delivered into the drum, one way or the other, one cannot have a fixed filling time which mine has apart from that extra rinse cycle.
You might consider throttling in the filling isol valve on that test and note the filling time with the reduced filling pressure, I would be astounded if it remains the same as for the 3 bar pressure.
“459 secs” read ~ 46 secs.

[stratfordgirl]

I don’t think there is any value in studying the fill time on my Miele. I think it may be worth exploring whether you have any means of increasing the flow rate into your machine, perhaps by checking the inlet filter or renewing the water supply tap.

[John.G]

I think I may have figured out this Zanussi fuzzy logic.
Normal operation: Depending on the selected programme the filling valves will open for a fixed time (different for the various programmes), after this fixed time period if the drum level is at or above the minimum level required to cover the heating element then the heating element is energised and the cycle continues. If the drum level is below this minimum due to say a big load of towels or suchlike absorbing some water then the filling valve will stay open or reopen if the clothes are still absorbing some water, the effect is that, especially with big loads, the water level will be just above the drum bottom for the wash cycle, if the drum only contains a few hankerchiefs or so then the drum level will be higher, it takes a measured 3.5/4 litres of water to cover/energise the heating element on this 7 kg machine.
Again IMO, this is why I am getting completely different initial fill levels with widely varying water pressures due to this fixed initial time period, I assume more sophisticated machines will shut the water off on initial fill once the minimum (heating element) level is reached, at the very least, and may even give higher drum levels depending on the clothes fabric requirements.
If the machine is started with low/no water flow available then the filling valve(s) remain energised until the time out period of 5/6 minutes has elapsed, the valve(s) then close with machine alarm.

A neighbour’s Bosch Serie 4 Vario Perfect appears to operate quite similar to the above except that it will not start if the mains pressure is < 1 bar.

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