On Saturday, 11 June 2016 08:32:15 UTC+1, harry wrote:
On Thursday, 9 June 2016 13:09:41 UTC+1, Robin wrote:
On 09/06/2016 07:15, tabbypurr wrote:
On Thursday, 9 June 2016 06:59:42 UTC+1, harry wrote:

The pumping out is not a timed operation, the pump runs until the machine is empty.

bzzt wrong answer

Can you expand on that please? I ask as on the few machines I've used
the pumps seemed to operate until the machine is "empty"[1], not for a
timed period. My main evidence for that is their behaviour (a) when
used on different cycles with different water levels; and (b) when used
to spin stuff put in wet, or to spin after being paused. In those circs.
the pump operated for a varying periods before starting the spin cycle,
not for a fixed time.

[1] taking empty to mean "negligible more water can be pumped"

There are water level switches in the machine.
One controls fill to the desired level.

Yes, 2 fill level switches, one for most washes and one for deep fill for delicates etc

Another controls the pump ("tells" the programmer that the machine is empty.)

The water level switches are pressure operated. It's not workable to create a switch this way that tells the programmer when the tub is empty.

The programmer controls the pump. It's timed.

Another stops the heater coming on if there's no water in the machine.

The heater doesn't come on unless water has reached wash level. There is no 'empty' detection.

Another stops the spin function from working if there is water in the machine/pump fails.

nope. In a pump failure scenario the water doesn't drop below wash level, which is detected. If for some unusual reason there is some water in the tub when it goes into spin, it just doesn't spin as the water provides a lot of resistance.


In practice these are usually in the form of two multi switches.
They used to work on air pressure from a chamber mounted low on the tub.

they do indeed. It used to be a thin pipe from low on the tub, but scale tended to block those resulting in flooding, hence a small airbottle is now added to prevent that.


NT