Why do modern dishwashers pause so much during the cycle?

[maytaga806]

Hello all, so Im still waiting on the water inlet valve to come as it should be here this week. Anyway, Im aware that newer style dishwashers seem to pause quite frequently during the cycles, as my Maytag Jetclean Plus does. I know its supposed to, as the manual says so, but they dont give a specific reasoning. Why does it pause during its cycles for about 15-20 seconds? Whats the point of it?

 

[lorainfurniture]

Sometimes it pauses to re heat the water, other times it pauses because there is a diverting valve that sends water to the upper,or the lower spray arm. It is a slow moving valve. I'm sure there are more reasons, but that's the 2 that I know of off the top of my head.

 

[stevet]

Sensing time!

The main reason today's machines will pause is to allow the soil sensor in the sump/pump area to read the condition of the water and how much soil is suspended in it. It is an optical sensor so the water basically has to remain still. It will then signal the controller to adjust the cycle to the soil levels. There are times when my K/A tall tub will go right from the prewash to the main wash without draining because the water is "clean" and other times during the cycle it will partially drain and fill as it attempts to rid the water of the soil in it.This will happen during the main wash as well but rarely in our case.
They call it Automatic Purge Filtration and it seems to work well.

 

[appnut]

Daniel, your Maytag is similar to my old Kenmore Elite.  Yours does not alternate between top and bottom rack spraying.  It runs both wash arms simultaneously.  Toward the end of the main wash cycle it stops & starts several times.  Pausing for about 5 to 10 seconds and starting up again.  This was a software change from the very first generation of tall tub Whirlpool designed dishwashers to overcome the lack of enough spray power to effectively clean taller glasses in the 4 corners of the top rack.  It pauses to have all the water gather back down in the sump and then the pump comes back on and has quite a bit of initial spray power.  My current Kenmore Elite, which alternates between top & bottom rack spraying, does not do this. I've had my new one for about 18 months and had forgotten about this. 

 

[seedub]

Curiously, my BOL Whirlpool WDF120PAF not equipped with a soil sensor, carries out these same pauses only during pre-rinses. This topic may finally help me get to the root reason for this. Is this a tall-tub model and I don't know it, making one of Bob's observations​ applicable? During Normal and Heavy cycles, pre rinses are accompanied by a purge along the lines of what Andrew describes​ in Post 64218 - tub fills with a tiny bit of water, then the pump pulses on and off. So then, could intermittent spraying while rinsing be some maneuver to ensure maximum cleanliness of the filtration system? Or, is it simply Bob's other point: it's a software function, and the software is programmed to do this on all WP machines?

Another poster's surmise re: water heating was true for a 2010 Frigidaire machine I used at a duplex I rented: there's a pause before the main wash and the final rinse begin during which time the heater element switches on and reaches max temperature. Then, while switching from the upper wash arm back to the lower, a longer than usual pause occurs I'm guessing to keep the burner at that max...or possibly as some primitive steam generation on the cheap - during the no-action intervals, water drips onto the element, generating steam?

 

[yogitunes]

my Kitchen Aid tall tub does the 'pulsed/burst' of water sprays during the Soak N'Scour if that cycle is selected....

I believe its heating the water in-between these short burst....very effective wash program if you ask me...

could also be part of any given machine, as some motors, especially pumps, are not designed for continuous duty, its around 45 seconds ON, and 15 seconds OFF type of setup....

 

[washerdude]

No Soil Senor?

That sure sounds strange...at the time my Kenmore 15113 came out, it was the BOL model and even it features a soil sensor. I did note after multiple replacements of the main board (which was incorrectly diagnosed and was the wrong part replaced 2-3 times) the dishwasher seems to pause a LOT more than it did when it was new during the wash. Sounds like they defiantly modified the programming in the newer revisions of the board.

All I can make sense of this is that its the soil sensor taking the status of the water and looking to see how dirty the water is, based off of the waters cleanliness it either increases or decreases wash time.

It only appears to do this on the main wash and not the rinses, on the 1 hour wash cycle it never pauses other than the pre-washes.

 

[logixx]

Mine never pauses. The pump simply slows down a little for a few seconds as it alternates between lower, middle and ceiling sprayer.

 

[maytaga806]

Yes, my Maytag is a soil sensing model.

 

[lordkenmore]

Maybe it's pausing to catch its breath. Just like a non-athletic kid might need to pause a moment in PE class when he or she is being forced to run a long distance...

 

LOL

 

[henene4]

Nice

Now we can actually equal HE-haters do bullies: People who hate people (or things) because... Yeah, why again when any rational view would devalid their statements?

 

[panthera]

It makes sense that they'd

Pause to measure the amount of soil in the water.

It also makes sense that a system with a low-power pump and low-level of water would occasionally let what little water there is gather in the sump to be thrown out with (relatively speaking) force to clean dishes outside of the reach of the regular minimal spray coming out of the slowly revolving arms.

 

In point of fact - this is precisely the reason GE 'reinvented' the multi-orbital arm! Exactly, precisely the reason.

 

As I've frequently mentioned, current low-water, low-energy, no-phosphate dishwashers, given several hours and thoroughly pre-scrubbed dishes can do an adequate job of washing them. That they don't rinse adequately is shown by the Bierschaum test.

 

 

[seedub]

@washerdude: nope, no soil sensor. My unit goes through the same sequence per cycle with no variations.

 

[retro-man]

I remember somewhere probably in this group, that one of the reasons for pausing was that this was to allow air to escape out of the system and to fill with water. There was an initial problem before this was put into place, that the system would get an air bubble in the pump lines somewhere and no water would come out or only a small amount. The starting and stopping allowed the air to purge out and work as normal.

Jon

 

[panthera]

Another reason for the pause with the Electrolux system

At least one they used for many years is to reversed the direction of the pump. This drives the ball into the other section of the divider, sending water to the wash arm that was previously not activated.

Of all the awful water saving dishwashers, this early design was by far the worst. Stupid ball was always gumming up with food residue.

 

[appnut]

A couple of other things I've forgotten

My old model, the initial prewash fill would have a 5 second period where it would turn on the pump after it had begun filling for about 20-30 seconds and circulate pulsed water for 5-10 seconds.  As was explained to me by very knowledgeable whirlpool employee, this helps condition and balance hot/cold areas of the tub, especially with households with water heaters set at maximum of 150 to 160 degrees.  My current dishwasher does this on every fill on just about every cycle except pots & pans.  Something else I forgot on my old dishwasher.  Except on pots & pans cycle, the 1st post wash rinse fill was a partial fill and did a 15 second water circulate that sporadically shot water through the wash arms as it gather  back down in the sump.  After a while, I decided I wanted to full fill post wash rinses and pretty much used pots & pans.  Also on my old dishwasher, the 30 minute quick wash, the 1st post wash was also a partial fill and did the 15 second pump on and 45 second pause for 5 to 6 minutes.  On my current on on auto wash or normal wash cycle and normal soil sensed, the first post wash rinse fill does similar for about 7 minutes, all the while alternating wash levels too.  Again, I prefer two post wash rinse fills so I use either Pots & Pans or Smart Wash or Normal  Wash & select high temp wash to get 2 post wash rinse fills.  On Pots & Pans with either TurboZone or SaniRinse, I'll get 3 post wash rinse fills. 

 

[henene4]

Interesting. I never heared of pausing DW in the EU, except for these first alternating arm systems with the ball valve.

What we have now is modular-speed systems. On some Eco cycles, the motor speed is reduced to lower the water throughput and thus allow lower fills.
Further we have watersaver tanks that save the final rinse water, and the sump volumes have be grately reduced.

 

[maytaga806]

Totally makes sense that it would pause to detect the amount of soil in the water, apparently when it detects large amounts of soil in the water after a certain amount of time that its been washing, it will decide to drain. Its like it has a brain! LOL!

The very first fill of the cycle it the pump will kick on for about 10 seconds after its mostly filled up, then stop and continue filling. Only does that once.

Then, after the main wash has drained out of the tub on both Normal and Light cycles, it will fill the tub partially, the pump will kick on for about no longer than 10 seconds, then it immediately drains the water and refills for the final rinse and sanitize. I ALWAYS have sanitize on as an option. So this Maytag Jetclean fills 4 times for Heavy and Normal, and 3 times for Light. My old Hotpoint filled at least 5-7 times. I absolutely LOVE this dishwasher!

 

[johnb300m]

After reading a plethora of dishwasher technical education manuals these past few weeks, there are a few different reasons why some dishwashers will pause during the cycle.

- To calm the water in the sump for turbidity sensors to get accurate soil level readings.
- Time for diverter valves to move to their correct locations and modes.
- Time to allow soils to settle out of the sump or out of the filter mechanisms in preparation for draining.
- Brief, cyclical soak times to loosen soils in pre wash or main wash periods.

***There was no mention of pausing cycles to allow water to recollect in the sumps, in order to fully pressurize the system due to "under fill" conditions in order to save water.
This is a misnomer.

Many machines will purposely do one or a couple "Partial Fills" in order to save some water, or conduct a filter purge, and that's only when planned cavitation will occur.
But one thing ALL the brands have in common, is that they will have long or extra long fill times for maybe 1 pre-wash, definitely the Main wash, and definitely the final rinse, to ensure that the pump will be operating at full pressure.
None of them are designed to run any of their main wash/rinse programs with an underfill situation, unless the user's plumbing pressure is low or there's a fill valve malfunction.
All the fill valves are strategically designed for a specific flow rate, and the controller is timed to use that fill rate to its task.