Thread Number: 70581
/ Tag: Modern Dishwashers
Why do modern dishwashers pause so much during the cycle? |
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Post# 935263 , Reply# 3   4/29/2017 at 08:12 (2,525 days old) by appnut (TX)   |   | |
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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. |
Post# 935302 , Reply# 4   4/29/2017 at 13:09 (2,525 days old) by seedub (South Texas Hill Country)   |   | |
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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? |
Post# 935303 , Reply# 5   4/29/2017 at 13:35 (2,525 days old) by Yogitunes (New Jersey)   |   | |
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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.... |
Post# 935309 , Reply# 7   4/29/2017 at 14:08 (2,525 days old) by logixx (Germany)   |   | |
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Post# 935320 , Reply# 8   4/29/2017 at 15:55 (2,525 days old) by maytaga806 (Howell, Michigan)   |   | |
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Yes, my Maytag is a soil sensing model. |
Post# 935333 , Reply# 9   4/29/2017 at 17:07 (2,525 days old) by LordKenmore (The Laundry Room)   |   | |
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Post# 935335 , Reply# 10   4/29/2017 at 17:14 (2,525 days old) by henene4 (Heidenheim a.d. Brenz (Germany))   |   | |
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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? |
Post# 935340 , Reply# 11   4/29/2017 at 18:22 (2,525 days old) by panthera (Rocky Mountains)   |   | |
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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.
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Post# 935389 , Reply# 12   4/30/2017 at 00:21 (2,525 days old) by seedub (South Texas Hill Country)   |   | |
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Post# 935458 , Reply# 14   4/30/2017 at 09:24 (2,524 days old) by panthera (Rocky Mountains)   |   | |
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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. |
Post# 935461 , Reply# 15   4/30/2017 at 09:48 (2,524 days old) by appnut (TX)   |   | |
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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. |
Post# 935503 , Reply# 18   4/30/2017 at 14:37 (2,524 days old) by Johnb300m (Chicago)   |   | |
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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. |
Post# 935522 , Reply# 19   4/30/2017 at 16:22 (2,524 days old) by washman (o)   |   | |
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My contractor grade Frigidaire does this during the normal cycle. There is no soil sensor in this unit, it runs on the preset cycle times, heats water if needed, then dries. |
Post# 935626 , Reply# 21   5/1/2017 at 05:14 (2,523 days old) by logixx (Germany)   |   | |
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Post# 935662 , Reply# 22   5/1/2017 at 09:54 (2,523 days old) by panthera (Rocky Mountains)   |   | |
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Post# 935666 , Reply# 23   5/1/2017 at 10:57 (2,523 days old) by Iheartmaytag (Wichita, Kansas)   |   | |
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I always assumed the pauses were due to sensing. Because, when you choose one of the cycles that are sensor cycles, Normal, Heavy, Light/China. The Machine will fill pause, until the correct amount of water is obtained. Then there are several pauses during the cycle, which again I assumed were due to the sensor.
If you choose the 1 hr cycle, no sensor. The machine fills to the maximum amount washes, drains, fills. No pausing. Also goes to mention that the 1 hr cycle does not allow options so it doesn't have need to pause to heat water etc.
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Post# 935757 , Reply# 24   5/1/2017 at 22:29 (2,523 days old) by volsboy1 (East Tenn Smoky mountains )   |   | |
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Besides the senors and heating .They also pause because the motors a lot of them that I have worked on Whirlpool and Frigidaire the ones with the Askol pumps say on the side of the motor. 15 mins on then 3 mins off or 15 min on 5 min off..They put such cheap motors in them now compared to the loud continuous duty type of the good days . |
Post# 935810 , Reply# 25   5/2/2017 at 09:37 (2,522 days old) by johnb300m (Chicago)   |   | |
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I must partially disagree with the reason machines pause is due to the ON-OFF duty cycle time of the wash pumps.
Granted, on many drain pumps they can overheat and must have rest periods. But....we have seen several pieces of evidence on modern dishwashers already, that have these "wet rotor" motors with duty cycles stamped on their labels, yet they WILL run nonstop for a whole cycle segment and be perfectly fine. I cannot explain why they have duty times on them and not abide by them. Yet some do, such as drain pumps. But the pausing due to the duty cycle? I have to disagree. Especially since whatever pausing does occur, never seems to be long enough to match the OFF duty time of the motor call-out. |
Post# 935813 , Reply# 26   5/2/2017 at 09:56 (2,522 days old) by panthera (Rocky Mountains)   |   | |
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Assume certain conditions. I'd guess those conditions are considerably less well ventilated/not conduction cooled/hotter/closer to stall than what these motors are doing in modern dishwashers. It's not as if they were actually moving any great volumes of water or being subject to tremendous thermal load without any cooling. Be interesting to research the conditions behind those rating tags.
Same with the infamous solenoid and GE's pump. I've had some vintage potscrubbers which hold it down for longer than 15 seconds (Twenty-Eight Hundred, Twenty-Five Hundred) and some which do not. Same solenoid. Just, with that humongous fan blowing right on it in the shaded-pole motor version, who'd worry about it getting warm, much less hot? |
Post# 1125700 , Reply# 28   8/13/2021 at 11:44 (958 days old) by GELaundry4ever (Nacogdoches, TX, USA)   |   | |
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It pauses repeatedly to allow water to soak into the soil of the dishes for better removal. |
Post# 1125714 , Reply# 29   8/13/2021 at 18:15 (958 days old) by Seedub (South Texas Hill Country)   |   | |
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