Washing Machine Fill Times

[John.g]

I have two Zanussi washing machines, one is a 2006 model ZWF1221G, the other, a 2013 model ZWG6141P.
I can run both from the CWST or the mains, recently was doing a bit of pipe re routing and noted the following.
On the older machine if the water supply is changed from the CWST to mains then the fill time falls from 259 secs to 114 secs as expected due to the increase in water pressure but on the newer machine the fill time of 120 secs is exactly the same on either CWST or mains fill which seems very strange as I thought that the pre determined drum fill level is monitored by a pressure switch as is apparently the case with the older machine.
If the water supplies are turned off before start up, both machines will go into alarm (flashing run light) after 5 minutes.

 

[Chuck]

What's your question?

Flow vs pressure is nonlinear. Once the flow becomes turbulent it's relatively insenstive to driving pressure.

Fill level in many (possibly all) washing machines is measured by a pressure gauge. Traditionally an empty hollow tube with an open lower end dips into to the drum housing and the air inside compresses as the height rises. This has the advantage that the sensor is only in contact with air. Disadvantage is that the end of the 'dipping tube' can get clogged up with lint and cause overfilling.

 

[John.g]

My question?....does this model use some sort of flow switch?, even if the pressure switch is relatively insensitive it surely can't explain this. The CWST head is 0.45 bar and the mains is 2.3bar this corresponds exactly to the reduced filling time for the older machine, 259*(sqroot 0.45/2.3), 114 secs. If the newer machine pressure switch is faulty this should be reflected in some change in the filling time but there is absolutely nil after testing multiple times.

This appears to be the analogue pressure switch replacement.

https://www.partmaster.co.uk/washing-machine/zwg6141p-91490601501/analogue-water-level-pressure-switch-type-7640/product.pl?pid=4825862&shop=zanussi&path=108446&model_ref=2573806

 

[Ric2013]

'I think', as Michael Howard said, 'the question we should be asking is whether' the water fill level changes between the mains pressure fill and CWSC-pressure fill.

If you are not able to see the fill level, I would suggest you measure the quantity of water being accepted using a water meter if you have one. If not, at least remove the dispenser drawer and see if the flow rate is about the same irrespective of pressure. It is not right to assume (however intuitive it may be) that 10x the pressure will result in 10x the flow and there may be some form of flow regulating device that means it makes no difference.

To answer the question you are actually asking, I'm not aware of any washing machine that monitors the quantity of water flowing into the machine. If there were, and if the flow rate varied with pressure, I would expect to see a change in fill time. My hunch, however, is that there is no change in flow rate or fill level.

 

[John.g]

Yes, I think they all use a pressure switch and while it is too inconvenient just now to measure the actual vol of water from this machine I can and did measure it on the other machine, whether I use the CWST with a fill time of 259 secs or the mains with a fill time of 114 secs, the pump out vol (tests with empty drum) is almost exactly the same at 16 litres, with CWST fill and if I stop the fill at 120 secs the pump out vol is 7.5 litres.
The other machine, for whatever reason, gives exactly the same fill time on both CWST & mains fill so it simply can't fill to the same levels. When it stops filling after 120 secs on CWST I can open the door and measure the level at 6" above the drum bottom, when I pump it out it takes 8 litres to fill it manually to the the same 6" above. On the 120 sec mains fill it rises above the bottom of the drum door so cannot open the door to measure the level.
The only explanation I can now come up with is that it is a timed fill of 120 secs, (full stop) and if the pressure switch detects any level, the programme continues, if no level detected, it then holds the programme and alarms after 5 minutes and shuts the solenoid(s).
As stated above, both machines go into alarm after 5 minutes if started with water supply off.,

 

[Ric2013]

When it stops filling after 120 secs on CWST I can open the door and measure the level at 6" above the drum bottom, [....] On the 120 sec mains fill it rises above the bottom of the drum door so cannot open the door to measure the level.

start star star dot (above) is supposed to be a four dot ellipses!

So the level is different then.

I've noticed a lot of modern machines add some water (perhaps a timed fill, as you say), then alternate agitation of the washload with additional fill stages, presumably to compensate for different levels of fabric absorbency. If the water levels are significantly different, however, this does not seem right to me. I know you can't measure accurately, but only will you will know how different the levels are.

I wasn't sure what you meant about a flow switch before, but now I get you. Some of those fill valves rely on the water pressure to open/close them (in fact, they often won't shut if the pressure is very low), and it is not inconceivable that they may incorporate a sensor or electrical contact that will detect a no-pressure situation.

Have you tried the Washerhelp forum?

 

[John.g]

Have submitted it now to the above Washerhelp forum.

 

[John.g]

Got one reply but nothing really other than saying that all washing machines have a pressure switch to give the proper fill levels in varying pressure conditions.
I will take the top off my magical machine sometime and have a look inside.

How Does Washing Machine Control Water Level | Whitegoodshelp

All washing machines control water levels using the same system, which works on air pressure. It's reasonably reliable but several things can go wrong

www.whitegoodshelp.co.uk

 

[John.g]

Just to confirm that one of my wash machines, the Zanussi ZWG 6141P is indeed apparently a timed fill, I installed a slightly different sensor which I picked up for a few euros, its a 545-AA-017 (0-380mm H2O) and I get exactly the same fill times/volumes as the 545-AA-016 (0-300mm H2O).

A bit ironical really that a simple pressure switch in my older machine gives exact fill water volumes irrespective of the water pressure vs the fancy analogue sensor in the newer machine.

Open a close the link a few times to see how this works, I think this is also used in some dish washers.

 

[John.g]

I think I may have figured out this Zanussi (6141P) 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 6 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.

 

[Ric2013]

That's probably it. I have a 20 year old Miele that fills a bit, agitates a bit, fills a bit more. Probably it fills 5 times to maintain a certain water level as the washload absorbs the water.

The fact that your machine seems to fill excessively (perhaps you have high mains pressure too) at times isn't great, but then machines are designed to work best at full load and possibly the aim was to make it work efficiently at full load and leave the user to blame himself if it does not work all that well when not fully-loaded. If you consider that in 1990 a machine could cost £350 (which is what my mother paid for an ex-display Philips model), and factor in 30 years of inflation, then I think you'll see that we are lucky modern machines work at all, given what they cost us. Quite possibly your older machine is better: domestic washing machine manufacturers seem to be racing each other to the bottom at present and quality is taking a battering, probably with Zanussi too.

 

[John.g]

That's probably it. I have a 20 year old Miele that fills a bit, agitates a bit, fills a bit more. Probably it fills 5 times to maintain a certain water level as the washload absorbs the water.

The fact that your machine seems to fill excessively (perhaps you have high mains pressure too) at times isn't great, but then machines are designed to work best at full load and possibly the aim was to make it work efficiently at full load and leave the user to blame himself if it does not work all that well when not fully-loaded. If you consider that in 1990 a machine could cost £350 (which is what my mother paid for an ex-display Philips model), and factor in 30 years of inflation, then I think you'll see that we are lucky modern machines work at all, given what they cost us. Quite possibly your older machine is better: domestic washing machine manufacturers seem to be racing each other to the bottom at present and quality is taking a battering, probably with Zanussi too.

That's probably it. I have a 20 year old Miele that fills a bit, agitates a bit, fills a bit more. Probably it fills 5 times to maintain a certain water level as the washload absorbs the water.

The fact that your machine seems to fill excessively (perhaps you have high mains pressure too) at times isn't great, but then machines are designed to work best at full load and possibly the aim was to make it work efficiently at full load and leave the user to blame himself if it does not work all that well when not fully-loaded. If you consider that in 1990 a machine could cost £350 (which is what my mother paid for an ex-display Philips model), and factor in 30 years of inflation, then I think you'll see that we are lucky modern machines work at all, given what they cost us. Quite possibly your older machine is better: domestic washing machine manufacturers seem to be racing each other to the bottom at present and quality is taking a battering, probably with Zanussi too.

The above Zanussi also gives the exact same filling times of 127 secs on either mains or attic supply when doing the rinse so clearly something not right here. I gave away my 2006 machine to a old neighbour as his old machine had packed up and he only does one/two washes/week, his machine was attic tank fed and my old machine will give ~ 16 litres fill on this supply (or on mains). I purchased a new 7 kg Zanussi ZWF7254B4PW and carried out some tests ...... this machine does change the filling times a little to 74 secs on mains fill and 84 secs on attic but the attic fill time should be 170 secs, however it works exactly as I think it should on the rinse cycles, ie a rinse filling time of 60 secs on Mains and 138 secs on attic , a factor of 2.3 (sqroot 2.3/0.45) to gives the same filling volume.
So there you have it, a 2006 machine with the old type pressure switch that works perfectly on all water pressures, a 2013 machine that seems to work on fixed filling times with different fill levels and the new machine that works to a fashion. I did change the analogue pressure transducer on the 2023 machine but it made no difference.