Bosch dishwasher high performance pumps

[gelaundry4ever]

If Bosch pumps in their dishwashers are high performing, why do they speed up and slow down during wash when filled with water? You'd think it would run at full speed at all times like the older single-speed ones did. I assume the new pumps have the water pressure at a weak spray at certain points. Then at other times, the spray is at full blast.
Why do they soft start instead of turn on immediately with bursts like their older ones and most dishwashers do?[this post was last edited: 8/1/2024-21:37]

 

[Chetlaham]

Good question, I don't know Bosch's reasoning but my guess is primarily two fold:

 

1) Achieve various pressures based on load type- ie pots and pans get strong pressure, everyday cycles medium pressure, china cycles deliver low pressure. GE for example would either introduce air into the sump boot or do a reduced fill to soften the water on the china crystal cycle.

 

2) Compensate for the tall tub low water design-

 

a) To prevent drawing in air or cavitation, the pump slows down as water is returning into the sump then speeds up to deliver it to the wash arm. As soon as the pump starts to draw in air, it slows, waits for the water to return, then ramps up. Its a way of using less water with the same sump, pump and spray arms.

 

b) To purge trapped air bubbles out of the pump and sump.

 

c) To warm the air inside once the door has been opened or the machine has drained and re-filled. The rapidly expanding cold air can force water out of the bottom vents where the door linear meets the tub floor- so by warming the air inside through brief bursts of water there is less cold air to expand at start of wash. 

 

I'm sire there are other reasons, but these 4 come to mind.

 

[gelaundry4ever]

auto cycle

I noticed mine does it on every cycle. What about the auto cycle? The first pre-wash is at low pressure, while the main wash is at high pressure. The final rinse is at low pressure too. Why is that?

 

[Chetlaham]

Not sure- maybe energy. It takes less pressure to rinse dishes than to clean them, in theory, so running the pump at low speed saves energy without sacrificing performance. 

 

Me personally I like across the line motors. VFDs add complexity and various failure points.  Electrolytic caps have a finite lifespan, so if those are present in a machine its a given expiration date.

 

[gelaundry4ever]

active water

I wonder if my dishwasher is based off the active water or variable pressure wash system technology that Bosch is known for. There's nothing wrong with it, but I have been taking observations to the behavior of the dishwasher. I'm wondering if the water flow is still active. With the turbo clean option during the intermediate rinse, the heater comes on and the pump is at full pressure for a few minutes, then it lowers it minutes later. Sometimes, my dishwasher will run the pump at full pressure depending on how full and dirty the load is. It really is a workhorse and I don't see myself planning to quit using it. I'd rather use it since it's there. Side note: I'm enjoying Finish Ultimate due to its performance. I really like the fresh smell it gives my dishwasher. The corresponding rinse aid works well too.

 

[gelaundry4ever]

pumps

Back to the pumps, I wonder if electricity is increased or decreased when changing pump speeds, or if it's at constant full charge and the electricity goes to different phases. Either way, my dishes still get clean completely regardless. I'm just used to single speed pumps.

 

[Chetlaham]

A pump running at lower speed when driven by a typical VFD will definitely consume less electricity. If its a 3 phase motor, as are most VFD motors, current equally goes up or down on all 3 phases. 

 

[gelaundry4ever]

to chetlaham

I believe mine is a 3 phase pump. You can hear the water flowing throughout the dishwasher at both pressure levels. And, it sounds fairly strong when the dishwasher is empty at both pressure levels too. As a side note, check out my thread about dishwasher detergent fragrances and another one regarding shrimp Alfredo casserole.

 

[Chetlaham]

If the machine works for you, if it makes you happy, then I am happy. If the Bosch works for you then it works for you, thats all that matters. 3 phase induction motors are the best out there. They have the lowest vibration, smoothest power output, great torque and are among the most efficient. I don't know what the slip on that motor is, but if driven by a high frequency that motor may not even get super hot to the touch making is bar none while extending its life. 

 

Thanks for bring those threads to my attention, I will check them out!  

 

[cfz2882]

Bosch BLDC motor

permanent magnet rotor,so no "slip" and runs cool-no cooling provisions besides(normally hot) water going through pump.

 

[Chetlaham]

Ah, ok, that makes sense. I was thinking a dry rotor induction pump. My mistake in assuming.  

 

[neptunebob]

3 phase?

But how can a Bosch dishwasher have a 3 phase motor if residential electric service is only single phase? By they way, our Bosch makes a low rumbling sound, it is quiet so I really don't notice any change in running.

I will post a review of our Bosch this weekend.

 

[Chetlaham]

3 Phase

Can be produced from a single phase service via a variable frequency drive. AC power comes in, is rectified to DC, smoothed, then converted to 3 phase out-power via semiconductor switching. 

 

[cfz2882]

the inverter in the dishwasher can take in single phase power and output 3 phase AC power or-with BLDC motors-3 phase switched DC.Single phase fed 3 phase AC out inverters driving 3-phase induction motors is common on a lot of 2010s belt-driven front load washers and certain top loads like the GE Hydrowave.

 

[gelaundry4ever]

Kenmore by Bosch running smoothly

Oh, I see. That may explain why my Bosch dishwasher which is under the name Kenmore runs so smoothly. Maybe it's the variable spray feature that keeps the water active even when changing pressure.

 

[gelaundry4ever]

dishwasher power up sound

One thing I forgot to mention is that when you press the power button to turn the machine on, you'll hear 4 clicks then you'll hear power being applied to the pump as if it's about to start. Why do Bosch dishwashers do that? Mine which is a Kenmore does that.

 

[appnut]

After pushing start at the beginning of the cycle, the pump is checking to see if there's any appreciable amount of liquid in the sump which needs to be oumped out. And it will even if there's ajust a small amount that hadly any consequence.

 

[DADoES]

 
Fisher & Paykel SmartDrive motors are 3-phase in both topload washers and DishDrawers.  SmartLoad dryer also has a 3-phase, reversing motor.  And AquaSmart's SmartPump.

DD603 DishDrawer motor description from the service doc:  The motor is a fully electronically controlled 80V, 60w, 3 phase, 6 pole brushless DC motor, running on wash at between 2300-2850rpm depending on the cycle selected and at approximately 4200 rpm on Drain.

Series 9 DishDrawer:  The motor is a fully electronically controlled 80V, 60w, 3 phase, 6 pole brushless DC motor, running on wash at between 2200 - 2800 rpm depending on the cycle selected, and at approximately 5000 rpm on drain.

AquaSmart pump:  The motor is a fully electronically controlled 325V, 3 phase, 6 pole, brushless DC motor.  The speed of the motor will vary depending on whether it is draining or recirculating the water.
Motor Resistance per Phase:  8.1Ω +/- 10% (16.2Ω +/- 10% across any two phases).
Maximum Wattage:  200W
Nominal Wattage:  60W
Drain Speed:  2500rpm
Recirculation Speed:  2000 rpm

 

[gelaundry4ever]

high pitch motor drive

If anything, the only thing you'll hear is the high pitch pump motor drive. It's the best dishwasher I've ever had. The noise you'll hear the most is water splashing around. It does sound like a thunderstorm in the dishwasher.