Benefits of DC pumps

[mussel and hate]

I couldn't really say if there are higher voltage DC pumps for the hobby though I'd be surprised if there were. I was just dispelling myths regarding AC vs DC. There are some low voltage AC pumps though. The Koralia controllable are 12V AC for instance.

Brushless motors possess superior longevity and a brushless DC motor is just a brushless AC motor with an inverter and rectifier. Not all DC motors are brushless btw.

If you're using AC power from your wall plug an AC motor will be more efficient. Conversion to DC requires you to give up some electricity as heat. If you're running your DC pump off of solar panels and batteries then that would be pretty efficient.

 

[BeanAnimal]

I don't see why someone would use ac to convert it to dc then back to ac to use in a pump.

It is done all the time... That is how many VFDs work.

The VFD takes an ac Voltage at 60Hz, rectifies it, then feed it to an inverter to create a sinewave at the desired frequency.

It's cheaper to use a dc motor to vary the speed then to use an ac motor. Less components. The motors that I have seen use resistors in series to vary the speed for ac.

You have it somewhat backwards

There are several types of AC motors, but in general using resistance to speed control any of them (Lets ignore universal motors) is not effective due to severe loss of torque causing phase slip and therefore heating issues. That said, some small desk fans, blower motor, etc use an autotransformer, or a triac and a resistor to do just that (cause loss of torque and phase slip) to give some degree of speed control.

A universal motor (a motor with an armature and brushes) is a different beast... but lets ignore it simply because it has no place in our hobby.

Resistors:
Large "variable speed" DC "traction" motors in industrial applications (to power underground track equipment in coal mines, street cars, rail locomotives, etc) use huge banks of resistors to vary speed. The speed controller drops in or pulls out banks of resistors to change the speed by varying resistance in series with the motor. The resistor banks are often used in dynamic braking systems (both regenerative and rheostatic).

In any case...

I have been using a few DC pumps for several months. While the motor itself may be a bit more efficient, the losses in the power supply abd speed controller (switch mode in my case) pretty much cancel the savings. That said, I am happy with the pumps and would rather have the wasted heat in the controller and PSU instead of the field windings, core and magnets.

 

[steve9]

I there any ac pump even close to the spec of a dc10000.

 

[BeanAnimal]

Steve,

I use both the DC-10000 and the DC-5000. I have been happy with both, but ran into some problems with the DC-10000. Waiting for it to be replaced right now.

To answer your question: The spec power:flow ratio are derived from power measured AFTER the controller and therefore do not take into account the losses in the power supply or driver. When those losses are accounted for that 98W is closer to 130W The pump is still great. It has a speed control, feed timer, etc.

Comparing "apples to apples", I replaced a Velocity T4 with the DC10000. Both draw roughly 140W from the wall. However, the DC10000 only has 98W at the motor, so at best 98W can be transfered to the water. The ohter "heat" is at the power supply and therefore does not make it to the water. The T4 had 140W at the motor. Real world, the heat transfer of the T4 was much greater.

Hope that helps.

 

[biodegraded]

Bean, have you considered dumping the stock controller and going for something you can throw a PID loop on? I'm wondering who's already got their Waveline closing on flow rate.

 

[BeanAnimal]

Yes, that was a consideration, but too many other projects ahead of it. To that end, it is my understanding that Waveline should (will) be releasing a controllable version of the pump shortly.

 

[Kawi9_cf]

Bean I noticed on your site that you said the waveline 5 and 10k pumps accept threaded 1.5" fittings. I have two separate volutes for my 5000 and I can only get the threaded fittings to thread onto the input side and not the output side. I contacted RLSS and they said that was normal. Have you experienced this? If so how did you overcome the issue?

 

[Kawi9_cf]

It seems recently there has been a large influx of DC controllable pumps into the aquarium market. I have heard various claims being thrown around about the benefits of using DC pumps over AC including:

• Safer, electrical shocks are lass of a concern
• Longer life
• More torque
• Can be controllable and have a 'soft start' feature
• More efficient

How many of these are true and to what extent? Are there any benefits or drawbacks I have missed?

One thing I have noticed about my waveline is how quiet it is. I know this wasn't on your list but the cost or the waveline pump compared to a waveline pump of the same quality seems to be a lot lower.

Why have so many skimmer manufacturers jumped on the DC bandwagon recently?

Cheers!

One thing I have noticed about my waveline is how quiet it is. I know this wasn't on your list but the cost or the waveline pump compared to a waveline pump of the same quality seems to be a lot lower.

 

[BeanAnimal]

Bean I noticed on your site that you said the waveline 5 and 10k pumps accept threaded 1.5" fittings. I have two separate volutes for my 5000 and I can only get the threaded fittings to thread onto the input side and not the output side. I contacted RLSS and they said that was normal. Have you experienced this? If so how did you overcome the issue?

I used the supplied adaptors and hose barbs, as the pumps are not "permanent" yet. I have a lot of changes to make (new ATS, remove the chiller, etc). I did test fit standard PVC fittings onto both volutes and if I remember correctly, the dicharge was somewhat snug. I attributed it to the casting mold not lining up perfectly and causing a slight misalignment in the threads. I assumed this was an issue corrected in the production run, as I was told my pumps came from the prototype or first batch.

 

[Kawi9_cf]

That was the issue I ran into. It was very misaligned on the volute that came on the pump and salty supply sent me a replacement free of cost but it was misaligned as well (so much so that I couldn't get the fitting to thread at all). I found a way to adapt it but I was just curious to see if you had run into this issue at all. I wonder if this is something they are going to correct or if they will continue to release the pumps into production like that.

 

[dread240]

Safer, electrical shocks are lass of a concern - Untrue.
Longer life - Untrue.
More torque - True.
Can be controllable and have a 'soft start' feature - Possible for both AC as well as DC.
More efficient - Untrue.




The reason you didn't get electrocuted is that it was low voltage not that the voltage was DC. If that were 120V DC and you made the circuit, chances are you'd be dead. At least with AC your muscles clench and then unclench at 50-60hz, you have a chance to let go of whatever is electrocuting you. With DC you just grab on and don't let go. If you don't believe me grab a transformer and a 9v battery and make the circuit.

As a professional in power generation, I simply cannot even wrap my head around where you get some of these assumptions.

Safer, electrical shocks are lass of a concern - Untrue.
We do not run 100v+ dc pumps here. Most of these pumps are maxing out at 24v DC. Furthermore the path to ground is through the rectifier and not a free ride to earth ground. Given the skins normal high resistance, and the low source voltage, I would take my chances ANY DAY of the week with a 24v dc pump compared to 120v AC pumps

Longer life - Untrue.
We do not use any brushes in our pumps, they are all inductive. Therefore true digital boards and control over the motor can and will lead to increased life any day of the week. A nice DC pump through a 4 to 8 winding stator through a rectified circuit is way more controllable. Furthermore lower voltage and less heat will increase the life of the insulation of the stator windings

More torque - True.
You got this one right. A good multi winding stator compared to a 2 pole setup common in most ac pumps does indeed give more starting torque generally.

Can be controllable and have a 'soft start' feature - Possible for both AC as well as DC.
True however it's way easier and more cost effecient with a DC pump. Building true variable voltage/frequency SINE WAVE inverters are not cheap, and that's basically what a VFD is. I've done testing on korallia's with a square wave AC, as well as mag pumps, and they weren't that happy and generated a lot of heat during it. Alot more has to go into the circuit to vary it from say 100v @ 50hz up to 140v @ 90hz to change the speed of the motor. You cannot do it with resistance at all in an inductive motor.

More efficient - Untrue.
this is another hit or miss, depending on the conditions. If you can control the pump and run it in optimal conditions all the time, it's better with a light power loss at the transformer and rectifier compared to running that straight to the pump. That said though, there will always be losses when you start rectifying, and sometimes invertering ac voltage again

 

[mussel and hate]

I think you need to read my posts again. You will see that I haven't made any claims of high voltage DC pumps or claimed that any pumps you use have brushes and you are skirting the truth regarding conversion efficiencies.

Please review now.

 

[BeanAnimal]

Please review now.

Originally Posted by mussel and hate
Safer, electrical shocks are lass of a concern - Untrue.

You asked for a review

So the topic (and direct context to that point) was specifically the 24V DC pump compared to the 120V AC pump. Your bullet points are clearly related and in context to the 24V DC vs 120V AC PUMPS being compared (motor life, motor torque, motor efficiency). So anybody reading along would be expected to take the "Safer, Electrical shocks are [sic] lass of a concern - Untrue" point in the same context.

 

[mcgyvr]

My experience with DC pumps is only limited to one Waveline/RLSS DC5000.

It was a leaky big pile of LOW QUALITY Chinese crap and was returned. An attempt to replace the bad parts by the manufacture resulted in me waiting a long while only to receive parts with the same cracks and manufacturing flaws in them.

It "seemed" fairly quiet and powerful but I only had it running for a few seconds before it sprung a leak each time.

Supposedly the manufacturer is in the process or has done changes to address these issues. But I wouldn't put any faith in that without seeing the "new" pump/housings again. Part of my "real life job" involves injection mold design and let me tell you it was an absolute mess. I offered them suggestions and I hope they implemented them.

 

[BeanAnimal]

I got a sneak peak at the new prototype, and the volute cover is much more substantial. That said I am running my original external and have no leaks, though I am aware of the concerns regarding the origibnal design and to an extent agree with them. To be fair, many of the other pumps in our hobby have similar design issues or flaws, both the mechanics of the seal and/or injection mold issues and meterial strength. Then again, who wants to pay for milled plastic billet wet ends

 

[mussel and hate]

You asked for a review

So the topic (and direct context to that point) was specifically the 24V DC pump compared to the 120V AC pump. Your bullet points are clearly related and in context to the 24V DC vs 120V AC PUMPS being compared (motor life, motor torque, motor efficiency). So anybody reading along would be expected to take the "Safer, Electrical shocks are [sic] lass of a concern - Untrue" point in the same context.

You are mistaken BeanAniaml, there was no voltage amplitude specified in the comparison, merely type AC vs DC. Go back and check.

Claiming that an AC pump is more dangerous than a DC pump is hogwash when both operate on the same voltage which was 12V in my example of the Korallia.

Now re-review.

 

[Kawi9_cf]

I got a sneak peak at the new prototype, and the volute cover is much more substantial. That said I am running my original external and have no leaks, though I am aware of the concerns regarding the origibnal design and to an extent agree with them. To be fair, many of the other pumps in our hobby have similar design issues or flaws, both the mechanics of the seal and/or injection mold issues and meterial strength. Then again, who wants to pay for milled plastic billet wet ends

When will the new prototype be available. Do you think they will have an improved faceplate that fits the current pump?

 

[BeanAnimal]

You are mistaken BeanAniaml, there was no voltage amplitude specified in the comparison, merely type AC vs DC. Go back and check.

I would be happy to re-evaluate:

In general - In our hobby AC return pumps operate at 120VAC and DC return pumps at 36VDC or less. The benefits of "DC Pumps" pointed earlier in the thread where made in exactly that context (120VAC vs 24VDC pumps). You chose to counter those points by changing that context but NOT explicitly pointing out what it was changed to. You were countered based on the context of the conversation. I am not sure where the argument is.

 

[BeanAnimal]

When will the new prototype be available. Do you think they will have an improved faceplate that fits the current pump?

I am not sure when it will ship, I was just told that it would be hopefully soon. I am also not sure if the new volute will fit the old pump body, but that is a great question.

 

[Kawi9_cf]

I sure hope it does, Hopefully they will send me one if it does. When I talked to RLSS they told me they intentionally made the existing volute so that only the output will accept the pvc fittings. I dont believe that at all...