tankslave
New member
I've been trying to figure out how to do an auto water change with my AC3 without having disastrous results. I currently have two float switches in the sump, which the AC3 reads, and adds RODI accordingly, using the MaxChange command. (second float switch is a redundant backup) Incorporating a auto waterchange has a few potential problems:
1). What happens when saltwater reservoir runs out? This is where a lot of problems occur. Since the pump-out pump will keep going, the autotopoff will begin replacing back with RODI! System needs to know when reservoir is empty and stop the pump-out pump.
2). How do you compensate for imbalanced pump-in/pump-out pumps. Even with peristaltic dosing pumps, I wouldnt trust the life of my tank to whether nor not those two pumps work in perfect harmony.
My solution (Idea at this point):
Utilize two modes. Say, 90% of the time the system will be in autotopoff mode (switches control RODI solenoid). 10% of the time will be auto water change mode. This means the autotopoff will be off, and the float switches will be used to make sure the water exchange in/out will be ballanced. (this requires that you use "ghost" output/timers on the AC3. Since you cant do nested IF statements, you assign a Variable to a nonexistent output, set timers for that output, and then use that variable in other "IF VAR=ON, then..." type statements)
Assuming your normal topoff mode leaves your sump level where it should, you could do something like this:
Make a variable "VAR" = ON for the times of day when you want your auto water changer to come on:
If Time>20:00 THEN VAR=ON
If Time>21:00 THNE VAR=OFF
Say our autotopoff is controlled by solenoid "H20", you turn this OFF during the water change, so that saltwater that's pumpted out isnt replaced by freshwater:
If VAR=ON THEN H2O=OFF
Then start your autowater change program. Call OUT your pump out pump and PIN your pump in pump. Your float switch is SW1 and it is ON, when in the LOW position.
If VAR=ON, THEN OUT=ON
If VAR=ON, THEN PIN=ON
If SW1=ON THEN OUT=OFF
Now, you wont pump out any more water than you pump in, using only one float switch as a feedback. This, however, wont prevent more water being pumped in than is pumped out. You could prevent this case, by handicapping your input pump (physically restrict the flow with a valve) so that you know it will always pump less water than your output pump. When the float switch goes LOW, the controller will stop the output pump, and wait for the input pump to "catch up". This also wont prevent a flooded sump, if your output pump fails or gets clogged. You need a second switch to do that.
If you do use a second switch to turn the input OFF if the level gets too high, dont think you dont still need to handicap your input pump. If your input is faster than the output, you'll be able to add the difference in volume between the switches in saltwater each time the system comes on (assuming your sump level was, like mine, at the bottom switch when the auto water changer program started).
Point is: You want your be sure that your autowater change system leaves your sump level exactly in the same spot that your auto topoff system does, or your salinity will drift over time. A single swtich has a smaller hysterisis than two, and its easier to design a system to compensate for how much faster one pump is than to compensate for which pump is faster.
Again, I havnt tried this yet, but I think I am going to, once I get some dosing pumps that can pump water all the way to the drain pipes. Thinking I might try using two Reef Filler pumps for this.
1). What happens when saltwater reservoir runs out? This is where a lot of problems occur. Since the pump-out pump will keep going, the autotopoff will begin replacing back with RODI! System needs to know when reservoir is empty and stop the pump-out pump.
2). How do you compensate for imbalanced pump-in/pump-out pumps. Even with peristaltic dosing pumps, I wouldnt trust the life of my tank to whether nor not those two pumps work in perfect harmony.
My solution (Idea at this point):
Utilize two modes. Say, 90% of the time the system will be in autotopoff mode (switches control RODI solenoid). 10% of the time will be auto water change mode. This means the autotopoff will be off, and the float switches will be used to make sure the water exchange in/out will be ballanced. (this requires that you use "ghost" output/timers on the AC3. Since you cant do nested IF statements, you assign a Variable to a nonexistent output, set timers for that output, and then use that variable in other "IF VAR=ON, then..." type statements)
Assuming your normal topoff mode leaves your sump level where it should, you could do something like this:
Make a variable "VAR" = ON for the times of day when you want your auto water changer to come on:
If Time>20:00 THEN VAR=ON
If Time>21:00 THNE VAR=OFF
Say our autotopoff is controlled by solenoid "H20", you turn this OFF during the water change, so that saltwater that's pumpted out isnt replaced by freshwater:
If VAR=ON THEN H2O=OFF
Then start your autowater change program. Call OUT your pump out pump and PIN your pump in pump. Your float switch is SW1 and it is ON, when in the LOW position.
If VAR=ON, THEN OUT=ON
If VAR=ON, THEN PIN=ON
If SW1=ON THEN OUT=OFF
Now, you wont pump out any more water than you pump in, using only one float switch as a feedback. This, however, wont prevent more water being pumped in than is pumped out. You could prevent this case, by handicapping your input pump (physically restrict the flow with a valve) so that you know it will always pump less water than your output pump. When the float switch goes LOW, the controller will stop the output pump, and wait for the input pump to "catch up". This also wont prevent a flooded sump, if your output pump fails or gets clogged. You need a second switch to do that.
If you do use a second switch to turn the input OFF if the level gets too high, dont think you dont still need to handicap your input pump. If your input is faster than the output, you'll be able to add the difference in volume between the switches in saltwater each time the system comes on (assuming your sump level was, like mine, at the bottom switch when the auto water changer program started).
Point is: You want your be sure that your autowater change system leaves your sump level exactly in the same spot that your auto topoff system does, or your salinity will drift over time. A single swtich has a smaller hysterisis than two, and its easier to design a system to compensate for how much faster one pump is than to compensate for which pump is faster.
Again, I havnt tried this yet, but I think I am going to, once I get some dosing pumps that can pump water all the way to the drain pipes. Thinking I might try using two Reef Filler pumps for this.
