Remote ATO refill pump, voltage drop

[bishoptf]

@Sral @theatrus sorry to always tag you guys but I am wanting to work on a way to refill my ATO container, I upgraded to a 10g tank and its working fine, I have one float in it to light and send me an email when it gets to around 5g but what I'd like to do is use that float to kick off a fill job, and instead of having another float to turn it off just set a long timer to let it fill back up and turn off at the next check. But my question is around voltage drop, I'm pretty conservative and try to think about fail safes since murphy loves to muck around in automation etc..My plan is to have a tiny 12v pump that is located about 60ft away, vs controlling it via a kasa tplink outlet that is closer. I looked at the voltage drop calculators and since my pump is pretty small I think its doable but wanted to get some input. Here are the specs for the pump 12v, 350ma and I am thinking of using 20ga wire about 60ft, according to my calculations I would end up about 11.6v at the pump or about 3-5% drop depending on wire gauge.

Here is the pump if anyone is interested, it will push water that I have tested at least 8ft high, not overly fast but for what I need it to do I think it will work, but I have more testing to do -

 

[paragrouper]

Typically they will have an input voltage tolerance stated, but in this case it is not stated on the Amazon webpage. Below is a link to the manufacturers ”contact us” page and I would suggest you shoot them a query.

 

[bishoptf]

Typically they will have an input voltage tolerance stated, but in this case it is not stated on the Amazon webpage. Below is a link to the manufacturers ”contact us” page and I would suggest you shoot them a query.

Yeah it's seems to be a pretty generic pump, you will see the same pump from a lot of different vendors, but no real specs but my guess is since its low amperage I can get away with long runs with minimal drop if I go bigger gauge wire, I could run 18ga and that gets me even less drop.

 

[Sral]

I'm always happy to contribute, even if it's just chaos ^^

So if I understand correctly:
- you want to refill your 10g ATO container regularly when it reaches 5g
- your refill pump is located 60ft/18m away

You will likely experience a drop in pump performance from several things:
- voltage drop on the 60ft/18m cable
- pipe resistance in the 60ft/18m if pipe
- height pressure from any kind of height differences between the water level in the container that your pump sits in and the height of the outlet feeding your ATO container

Voltage drop:
I have calculated the performance of my 12V DC brushed peristaltic pumps here. Brushless motors operate very similar, they "simply" replace the mechanic commutation of the coil current through brushes with an electronic control through an IC, if I'm not mistaken. I would therefore expect that the performance to be very similar to my calculation:
- You have a stall voltage around 1-3V
- Every bit of voltage above that stall voltage increases maximum rotor frequency and therefore, maximum pump speed.
- a voltage drop of 3-5% will result in maybe 4-6% reduction in pump speed, but it will likely still work. Should even work if you reduce the voltage to 10V, just slower.

Pipe resistance:
pipe length creates "resistance" very much like cable length for electrical resistance. The longer the pipe, the lower the flow and the larger the pipe diameter, the larger the flow. The pump will likely try to account for this reduced flow by drawing more current, which will partially compensate this with the downside of a larger current draw.

Spoiler: EMF details

(The mechanics here is that the motor speed and current is limited by the internally induced back EMF currents from the rotating magnetic parts. If the water flows slower, the rotor rotates slower and therefore creates less back EMF, which allows more current to flow).

Height difference:
The pump is specified for up to about 10ft/3m max. This means maximum pump power occurs for height differences of 0m, pumping downhill will compensate your pipe resistance. The more you approach 3m height difference, the gradually less flow you will get from your pump.

You can increase this though by using one pump on each end, which should partially compensate all of the above. It should increase maximum height difference, partially compensate pipe resistance, getting flow closer to nominal, as well as help the pump on the long cable.

You will likely have to simply test how fast the pumps run in your case.

 

[bishoptf]

I'm always happy to contribute, even if it's just chaos ^^

So if I understand correctly:
- you want to refill your 10g ATO container regularly when it reaches 5g
- your refill pump is located 60ft/18m away

You will likely experience a drop in pump performance from several things:
- voltage drop on the 60ft/18m cable
- pipe resistance in the 60ft/18m if pipe
- height pressure from any kind of height differences between the water level in the container that your pump sits in and the height of the outlet feeding your ATO container

Voltage drop:
I have calculated the performance of my 12V DC brushed peristaltic pumps here. Brushless motors operate very similar, they "simply" replace the mechanic commutation of the coil current through brushes with an electronic control through an IC, if I'm not mistaken. I would therefore expect that the performance to be very similar to my calculation:
- You have a stall voltage around 1-3V
- Every bit of voltage above that stall voltage increases maximum rotor frequency and therefore, maximum pump speed.
- a voltage drop of 3-5% will result in maybe 4-6% reduction in pump speed, but it will likely still work. Should even work if you reduce the voltage to 10V, just slower.

Pipe resistance:
pipe length creates "resistance" very much like cable length for electrical resistance. The longer the pipe, the lower the flow and the larger the pipe diameter, the larger the flow. The pump will likely try to account for this reduced flow by drawing more current, which will partially compensate this with the downside of a larger current draw.

Spoiler: EMF details

(The mechanics here is that the motor speed and current is limited by the internally induced back EMF currents from the rotating magnetic parts. If the water flows slower, the rotor rotates slower and therefore creates less back EMF, which allows more current to flow).

Height difference:
The pump is specified for up to about 10ft/3m max. This means maximum pump power occurs for height differences of 0m, pumping downhill will compensate your pipe resistance. The more you approach 3m height difference, the gradually less flow you will get from your pump.

You can increase this though by using one pump on each end, which should partially compensate all of the above. It should increase maximum height difference, partially compensate pipe resistance, getting flow closer to nominal, as well as help the pump on the long cable.

You will likely have to simply test how fast the pumps run in your case.

Yeah thats one of the big questions is the resistance of the pipe, I now have a long section of pipe and will do some testing to see how well it works, I'm ok with slow which will take a long run time but I'm ok with that since it will only run maybe 1 every 2 weeks or so...so I am concern about ciurrent draw and I could measure that but if the pump is rated at 350ma is that something I should really be concerned about?

Fun Fun...

 

[bishoptf]

So I have been lazy and not tested the pipe resistance function, I purchased a 100ft of 1/4" rodi tubing and while I think my distance is less than 60ft I just did a test for the 100ft pipe looped up an over an 8 feet height and here are the numbers.

500ml less than 2min so I rounded up to 2min, 1l then would be 4min so a gallon at 3.8l would be approx 15min. Thats at 100ft of tubing, so maybe at 60ft it's a little quicker and that is with a short run of power for the pump and not long distance power, I assume running the pump for longer length of time should not be an issue, correct?

 

[Sral]

So I have been lazy and not tested the pipe resistance function, I purchased a 100ft of 1/4" rodi tubing and while I think my distance is less than 60ft I just did a test for the 100ft pipe looped up an over an 8 feet height and here are the numbers.

500ml less than 2min so I rounded up to 2min, 1l then would be 4min so a gallon at 3.8l would be approx 15min. Thats at 100ft of tubing, so maybe at 60ft it's a little quicker and that is with a short run of power for the pump and not long distance power, I assume running the pump for longer length of time should not be an issue, correct?

Interesting. Nominally the pump has about 1 gallon/minute
A pump height of 8ft for maximum of 10ft should in my guesstimate drop this to about 2/10, meaning 1 gallon/5 minutes
Adding the 100ft of piping drops this, according to your measurement, to 1 gallon/15 minute, so about another 1/3

If one uses an internal resistance analogy for the pump like one does for electrical power sources, one could guesstimate this to rise to about 1 gallon/10 minutes for half the pipe length. If you run two parallel pipes you might get a further increase to about 1 gallon/6.7 minutes.

About the safety of running the pump longer:
difficult to say. If the pump is inside the water for cooling, it's probably a lot safer. I would try to measure the current draw though. That shouldn't exceed 350mA in my mind, although I have no real experience in this regard and this is just my paranoid precaution speaking.
You could also see if adding another pump on the opposing end changes the current draw and pump speed.

 

[bishoptf]

Interesting. Nominally the pump has about 1 gallon/minute
A pump height of 8ft for maximum of 10ft should in my guesstimate drop this to about 2/10, meaning 1 gallon/5 minutes
Adding the 100ft of piping drops this, according to your measurement, to 1 gallon/15 minute, so about another 1/3

If one uses an internal resistance analogy for the pump like one does for electrical power sources, one could guesstimate this to rise to about 1 gallon/10 minutes for half the pipe length. If you run two parallel pipes you might get a further increase to about 1 gallon/6.7 minutes.

About the safety of running the pump longer:
difficult to say. If the pump is inside the water for cooling, it's probably a lot safer. I would try to measure the current draw though. That shouldn't exceed 350mA in my mind, although I have no real experience in this regard and this is just my paranoid precaution speaking.
You could also see if adding another pump on the opposing end changes the current draw and pump speed.

In fact I did test a shorter run when I started just to see if it could pump 8ft head height and I did get 1g for 5min timing. I am running the pump submersed in my rodi container so it sould stay cool for sure thats not a problem. Checking current draw is a little more involved since I do not have a clamp on meter but I have a killiwatt and can see what the draw is and calculate the draw based on wattage used. I do have a meter and I could run in through but its more involved for sure, so looks like I need to do more testing...

 

[bishoptf]

I could go with a bigger pump, something like this but a much higher amp draw, I really do not care about speed but maybe I will keep looking - pump

 

[bishoptf]

I think I am going to go with this pump way stronger than I need but with the resistance drop in voltage I think it will do fine, supposedly has a voltage range of 6v-15v, I calculate the voltage drop for 12v over 60ft for 1.2a using 16ga wire to be .72v or 11.28v or if I go with 14ga wire it would be .45v drop or 1.55v...I think this will work, pump seems to be pretty strong pump with 15ft of head and read some comments that it may do even better than that.

Off to find some in wall 14ga wiring...

 

[Sral]

12W of pump power sounds a bit like an overkill in my mind. Just take care that your power Supply is big enough, if you also run ReefPi of it. How are you planning on powering it ?

 

[bishoptf]

12W of pump power sounds a bit like an overkill in my mind. Just take care that your power Supply is big enough, if you also run ReefPi of it. How are you planning on powering it ?

Yeah I was looking for something smaller which I have but what I have is a lot smaller. Would be nice to find something in between but with all the resistance with the tubing the head height is pretty large. I have lots of choices for 12v power supply, i have some 1.5a 12 supplies, which is what I was using for the smaller pumps but probably not big enough for this pump. I will have this tied to reef-pi ato function so the float will trigger an outlet that has a 120v to 12v brick on it, I know you stated that the amperage draw may go up, so is a 2a supply big enough, I will measure things once I get things on hand but I have lots of transformers to choose from.

 

[Lbrdsoxfan]

I use a variation as a actual ATO top off pump that works off my apex 24v supply. My biggest worry would be the distance your trying to pump, the head numbers are misleading as hell.

Watching this thread.

 

[Sral]

I use a variation as a actual ATO top off pump that works off my apex 24v supply. My biggest worry would be the distance your trying to pump, the head numbers are misleading as hell.

Watching this thread.

Interestingly enough, @Tom Bishop has tested the pump performance for a pure 8ft pump height (as mentioned above) and it works out pretty nicely to 2/10 of nominal flow, exactly what one would expect if the pump really has a 10ft pump head.

The 100ft of 1/4" rodi piping dropped this further to 1/3 of 2/10, e.g. 2/30 of nominal flow.

 

[bishoptf]

Update, well that was almost 2 fun days of pulling wire, getting old not so much fun...Lets go back over the details

pump (specs stated on Amazon)
Rated voltage: 12V
Working voltage 6-15V
Rated current: 1.2A
Maximum head: 5 m
Maximum flow: 600L/H

After running the cable (14awg) and tubing (1/4" RODI tubing) distance is 50ft.

Actual measurements, using a 12v 2.5a ac/dc power supply:

Short Cable no head height (killawatt readings):
.22a, 120v, 17.4w, measured dc voltage 12.17v

50ft length tubing and cable (killawatt readings):
.13a, 120v, 10w, measured dc voltage 12.17v ( I was expecting this to be lower)

Kind of scratching my head since I thought the amperage would be higher over the longer cable distance but according to the killawatt it was lower. I did not measure the gpm with no head but the pump seemed really strong, not sure it would do 600l/hour but it does move some water.

Here is what I measured for water volume, approximately 1g about 8min, and that is through 1/4" tubing.

Thoughts comments???

 

[Sral]

Update, well that was almost 2 fun days of pulling wire, getting old not so much fun...Lets go back over the details

pump (specs stated on Amazon)
Rated voltage: 12V
Working voltage 6-15V
Rated current: 1.2A
Maximum head: 5 m
Maximum flow: 600L/H

After running the cable (14awg) and tubing (1/4" RODI tubing) distance is 50ft.

Actual measurements, using a 12v 2.5a ac/dc power supply:

Short Cable no head height (killawatt readings):
.22a, 120v, 17.4w, measured dc voltage 12.17v

50ft length tubing and cable (killawatt readings):
.13a, 120v, 10w, measured dc voltage 12.17v ( I was expecting this to be lower)

Kind of scratching my head since I thought the amperage would be higher over the longer cable distance but according to the killawatt it was lower. I did not measure the gpm with no head but the pump seemed really strong, not sure it would do 600l/hour but it does move some water.

Here is what I measured for water volume, approximately 1g about 8min, and that is through 1/4" tubing.

Thoughts comments???

Sounds like almost the same performance as the smaller pump if it goes through 50ft instead of the full 100ft. Curious.

The voltage sounds strange though. Where and how did you measure that ?

 

[bishoptf]

Sounds like almost the same performance as the smaller pump if it goes through 50ft instead of the full 100ft. Curious.

The voltage sounds strange though. Where and how did you measure that ?

The killawatt readings are 120v readings so there is some conversion that one needs to do in order to get the DC amperage and thats ballpark only since I do not know the efficiency of the transformer. I used this calculator to get approx DC numbers - dc-calc according to this calc it was using more amperage on the short cable vs the long cable which doesnt sound right but the numbers are what I recorded from the KillaWatt:

To get the DC voltage I just measured the voltage at the end of the 50ft cable, nothing attached, I assumed going through 50ft of cable there would be a small voltage drop I did not see any drop.

 

[Sral]

The killawatt readings are 120v readings so there is some conversion that one needs to do in order to get the DC amperage and thats ballpark only since I do not know the efficiency of the transformer. I used this calculator to get approx DC numbers - dc-calc according to this calc it was using more amperage on the short cable vs the long cable which doesnt sound right but the numbers are what I recorded from the KillaWatt:

To get the DC voltage I just measured the voltage at the end of the 50ft cable, nothing attached, I assumed going through 50ft of cable there would be a small voltage drop I did not see any drop.

Yeah, the amperage is curious. I would not have expected the long cable and pipe to draw that much less current as well. Might be in part the measurement though, I would have gone for a multimeter after the ac/dc converter to do this.

To measure the voltage drop you need to have a load. Without a load there is no current and therefore no voltage drop. That’s why you needed to specify the load current in the calculator.

 

[bishoptf]

Yeah, the amperage is curious. I would not have expected the long cable and pipe to draw that much less current as well. Might be in part the measurement though, I would have gone for a multimeter after the ac/dc converter to do this.

To measure the voltage drop you need to have a load. Without a load there is no current and therefore no voltage drop. That’s why you needed to specify the load current in the calculator.

Yeah I don't disagree but I just dont have an clamp on meter and running amps through my multimeter is a hassle and always afraid I am going to smoke it. Taking voltage reading with a load is another one that I will have to think about I can get a reading.

Sounds like almost the same performance as the smaller pump if it goes through 50ft instead of the full 100ft. Curious.

The voltage sounds strange though. Where and how did you measure that ?

Performance is much better on the larger pump (it's still pretty small), basically I was getting 1g/8min on the smaller pump with just 8ft head height maybe 10ft of 1/4" tubing, thats the same performance I am seeing with the larger pump going through 50ft of pipe. The smaller pump going through 100ft of tubing (before I really knew the distance) was taking approximately 1g/15min so almost 50% longer.

Will think about how to take better measurements but the Killawatt is seeing what is flowing through the meter although its ac voltage.

 

[bishoptf]

So I made a pigtail jumper and got a voltage reading the power supply puts out without load 12.17v, measuring with the load at the end of the cable I was seeing 11.55v so I think that is a good reading, looks like my MM will support 10a of current so I can use the pigtail to do that also, my only problem is my alligator clips are pretty thin wire and trying to figure out something better to measure current.

Update, took the amp measurement using my normal alligator pigtails, .723a

Now I should repeat with a normal length cable, will try to do that this afternoon.