Benefits of DC pumps

[triton_uk]

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?

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

Cheers!

 

[Breadman03]

Jumping on this one for the ride.

 

[Jeff000]

They are no safer, but everything else is true.

 

[Gorgok]

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

Could be as simple as because someone else did, then everyone else should too or they seem out of date. Or because it looks better on their ads to have "total control of pump output to precisely tune..." etc.

 

[Bui]

Why dont they deliver electricity in DC? I have so many ugly transformer hanging out from everything.

 

[Breadman03]

Why dont they deliver electricity in DC? I have so many ugly transformer hanging out from everything.

DC loses more power between the power plant and the end user.

 

[coolkidtr]

Wouldn't touch those dc pumps just yet. Wonder what the reliability is? Replacement cost? Just my two cents.

T

 

[skipro]

Wouldn't touch those dc pumps just yet. Wonder what the reliability is? Replacement cost? Just my two cents.

T

Why not? DC motors are not new so reliability shouldn't be an issue....hopefully :fun4:

 

[atreis]

Tunze controllable, Koralia controllable, VorTech are all DC pumps. Tunze also makes a controllable DC return pump... They're not new, it's just a new application. The downside is that they're more expensive.

In terms of the bullets, they're (typically) all true for the aquarium DC pumps. The only reason the safety one is true is because DC pumps for the aquarium are typically low voltage.

Power distribution: It takes MUCH larger wire to deliver the same number of amps over a distance. At long distances, the wire size required is prohibitive making line losses very high. (In other words: AC is cheaper/easier to deliver over long distances.)

Another reason for AC in the home is safety. AC of particular voltages and frequencies (e.g. 115V and 60Hz, or 220V and 50Hz) will cause muscles in the human body to spasm meaning that a person stands a chance of being thrown clear of the contact, avoiding death. With DC there is no such effect, muscles contract and grip tightly and that's it.

 

[ksed]

Before we go any further on AC DC topic. From what I was told is these pump are actually AC. They operate on true sine wave. They have a chip built in the pump which converts DC power from the supply back to AC or sine wave at the pump.

 

[dread240]

I got a 6095 tunze from the wife for christmas, and I love it. There's a few differences though that aren't mentioned on here

AC pumps have a brake feature, and are also prone to starting in reverse more common. This means cycling them fast for detritus removal or that pulsing flow to make your corals REALLY sway will shorten the life of the pump considerably.

While it is true what atreis said about the safety of ac blowing you back, the other side of the equation is the voltage behind it. My pump runs at a max of 24VDC, compared to my 120v AC going to the korallias that are already in there. Your skin acts as an insulator against voltage, and it's generally accepted that anything over 50v can overcome your skins insulation properties. DC current also only flows in one direction, it's ground to complete the source (not any path to ground like an ac pump) and considering each pump has it's own + and - leads right next to each other, chance of amperage to you is slim to none unless the cable is shorted and you stick your hand in. That's not the case with ac powered objects in the tank which can ground through you to the floor and subsequently to earth.

There's other benefits to this new pump though aside from that, but you actually get that on all the nanostream pumps now. It's the same footprint as my korallia 1400 and 750, however it's mounting options and angles are vastly superior (I used to think the korallia's gave good aiming where you want to put the flow, and I was totally wrong once I saw a tunze)

The controllability is a big point though. You simply can't make ac pumps do this type of work without some SERIOUSLY expensive hardware behind it. I priced VFD's to put on ac pumps, and it just wasn't cost effective by any means

 

[ksed]

Not all AC pumps spin in both directions. Askoll or Sicce just to list some of them spin in one direction. They are synchronous motors. They have a built in chip which allows for this to happen.

I got a 6095 tunze from the wife for christmas, and I love it. There's a few differences though that aren't mentioned on here

AC pumps have a brake feature, and are also prone to starting in reverse more common. This means cycling them fast for detritus removal or that pulsing flow to make your corals REALLY sway will shorten the life of the pump considerably.

While it is true what atreis said about the safety of ac blowing you back, the other side of the equation is the voltage behind it. My pump runs at a max of 24VDC, compared to my 120v AC going to the korallias that are already in there. Your skin acts as an insulator against voltage, and it's generally accepted that anything over 50v can overcome your skins insulation properties. DC current also only flows in one direction, it's ground to complete the source (not any path to ground like an ac pump) and considering each pump has it's own + and - leads right next to each other, chance of amperage to you is slim to none unless the cable is shorted and you stick your hand in. That's not the case with ac powered objects in the tank which can ground through you to the floor and subsequently to earth.

There's other benefits to this new pump though aside from that, but you actually get that on all the nanostream pumps now. It's the same footprint as my korallia 1400 and 750, however it's mounting options and angles are vastly superior (I used to think the korallia's gave good aiming where you want to put the flow, and I was totally wrong once I saw a tunze)

The controllability is a big point though. You simply can't make ac pumps do this type of work without some SERIOUSLY expensive hardware behind it. I priced VFD's to put on ac pumps, and it just wasn't cost effective by any means

 

[cdial]

I think a big reason is because a lot of us are building our own monitor/controllers now with microcontrollers like the arduino. I'm looking at using mini polario pumps 9V DC and just controlling them with a arduino and my own code. An arduino UNO cost $20. A motor shield to run dc motors can be found for $5. I'm already using dc dosing pumps. Easy to control the flow and easy to hook up to a microcontroller for dirt cheap. And there are SO many input sensors for the arduino. You can measure just about anything from orp, ph, salinity, EC, temp, motion, light, humidity, etc etc... Limitless possibilities for much cheaper price than buying a controller. Making your own wavemaker controller/led light controller/dosing system/top off is pretty cool.

 

[joshPensacola]

i bought a small DC pump to run off of car batteries in the event of a long period with no electricity. i live in a hurricane zone and fairly close to the beach. if we go a few days or weeks without power i will hopefully be able to keep some oxygen in my tank.

 

[Dashiki]

Before we go any further on AC DC topic. From what I was told is these pump are actually AC. They operate on true sine wave. They have a chip built in the pump which converts DC power from the supply back to AC or sine wave at the pump.

So they go from ac-dc-ac(sine wave)

I dont think that is reasonable. If they are looking to get the "true sine wave it would be more cost effective to create the wave and keep it ac.

 

[madean]

I don't see why someone would use ac to convert it to dc then back to ac to use in a pump. If its an ac pump they will utilize the ac out of the wall. If they need a different voltage then is supplied then they use a transformer to step up or down the voltage. A simple way to convert ac to dc is a bridge rectifier which simply allows alternating current to flow in one direction through the use of four diodes. One of the main reasons why we don't produce electricity in dc and use it in dc is because you can't use a transformer to step up or down the voltage. So if a power plant wanted to generate enough power to supply current for a city the operating voltage would need to be the same from the power plant to the power lines and to the consumer. Lets say its 120 volts dc is what the consumer desires. And one customer desires 10 amps of current at any particular time. Now lets multiply that by 1,000,000 customers. That's 10,000,000 amps that are needed to be supplied at that particular dc power plant. Your typical house circuit has a max rating of 20, 25, maybe 30 amps depending on wire size. 14, 12, 10 awg. So can you imagine the wire size needed to carry 10,000,000 amps. Imagine the equipment needed to support 10,000,000 amps. The breakers needed, the switch gear needed would be monstrous. Dc can't be stepped up or down. Lets say the power plant generated and transmitted at 13,000 Vic (13 kv), then each house would need to have equipment that used 13 kv, our microwaves, dishwashers, refrigerators, fish tanks ect would need to operate on 13 kv.
On the flip side we as a country, for the most part, generate in ac at a certain voltage. Lets say its 13kv to 35kv. A step up transformer then transforms the voltage up to 235 kv. The power is then sent all over the country. A general rule of thumb for transformers is power in equals power out (minus some minor losses from the transformer- excitation current, hysteresis, and eddy currents). So lets say a small power plant produces 50 megawatts of power. I will try and keep this simple for most to follow. Assuming power factor is perfect (usually not the case) but for this example to prove a point it is. Lets say said power plant produces 50 megawatts at 21kv. That's roughly 2380 amps produced. The company would need to have equipement to handle that amperage. Which is feasible. They then have a transformer that steps up the voltage to 230kv on the output side. So power in equals power out. Volts x amps in = volts x amps out with a transformer with 0 losses. Remember easy math here. So 21 kv x 2380 amps = 230 kv x ?amps. Which roughly 218 amps. So the output side is 230kv line that has 218 amps on it. The size wire is considerably smaller then its dc equivalent. Which in my opinion is also a considerably cheaper system to install and operate. Ac is so much more versatile. And it's rather easy to convert to dc. It's harder to convert dc to ac.

As far as it being safer, I think that's a false claim if your comparing similar voltages. Yeah 12v dc is considerably safer than 120 v ac. Dc pumps can have less losses than ac which translates to a higher power factor which means its more efficient. 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. Which equals more power used, less efficient. So I would agree for the most part that those statements are pretty accurate. Soft start features are good for the pump if used correctly. Lets say a dc pump has 6 speed settings. If you start the pump at a low setting and cycle it up to max speed then you are using the soft start feature. If you require the pump to utilize the max pump speed and output on start up then what's the difference compared to a regular ac water pump we currently use? So it can improve pump life if used correctly. Hope this diatribe helped

 

[barjam]

They are no safer, but everything else is true.

How are they not safer? 12/24vdc leak nothing happens. 120vac leak and bad things happened.

I accidentally shorted 12v 1200 mah in the tank for 24 hours before I noticed and nothing happened.

 

[mussel and hate]

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.

How are they not safer? 12/24vdc leak nothing happens. 120vac leak and bad things happened.

I accidentally shorted 12v 1200 mah in the tank for 24 hours before I noticed and nothing happened.

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.

 

[barjam]

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.

And the pumps in the hobby I am aware of are all low voltage 12/24. Are there bigger voltages too?

 

[barjam]

Before we go any further on AC DC topic. From what I was told is these pump are actually AC. They operate on true sine wave. They have a chip built in the pump which converts DC power from the supply back to AC or sine wave at the pump.

Where did you read this from? If so then they aren't dc pumps are they?

My understanding is they are all basically brushless dc motors that work by turning them on/off thousands of times a second. The ratio of on to off in a given time period dictates the motor's speed.

This is how brushless motors in RC vehicles work anyhow.