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Thread: RO/DI Controller

  1. #1
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    RO/DI Controller

    As a future project, I am contemplating building a RO/Di controller using an Apex Jr.

    Currently, I have a 10 gallon ATO built-in to my DT cabinet. My RO/Di unit is in the garage about 50-ft away. They two are connected via 50-ft of 3/8" tubing. Each Sunday morning, I go manually turn on my RO/DI master valve, flush valve and RO waste (TDS Creep). After 10 seconds I close the flush valve and when my TDS out of the RO hits 7 ppm, I close the RO waste...takes about 2-3 minutes. I then go back to my cabinet and open the fill valve. The ATO has a 1/4" float valve to prevent overfilling. In about 2 hours, this is done, I flush the RO again and then shut everything down and then open a waste valve to drain the line in the attic. I then do this again the next Sunday.

    The plan: I have a 2 conductor wire that runs from the RO/DI to the tank. I would install a relay at the tank EB8 #8 outlet to close the 2 conductor wire. At the RO/DI, I would install an Apex Jr, PM1 w/BoB and three 1-Link Modules. On the Bob via PM1, I would have two (2) call for water switches, 1 from the DT and the other from the salt water mixing station (future). Either of these would then trigger a sequence of events:
    1. Solenoid A: Open Master Solenoid for duration of call, max 2 hours + 3 minutes
    2. Solenoid B: Open Flush Valve for 20 seconds initially and then every 60 minutes and at final
    3. Solenoid C: Open RO TDS Creep Waste Line for 3 minutes
    4. Solenoid D: Open ATO Fill line for duration of call, max 2 hours
    5. Solenoid E: Open ATO Waste Valve


    If possible, i would love to wire in a TDS switch into the Bob, to automate Solenoid C based on a TDS target instead of a timed event, but I have not gotten that far into this yet. If I can figure this out, then I can also wire in TDS alarm switches for when DI #1 is exhausted or when the RO fails to achieve 95% reduction.

    I would also have Solenoid F & G for the future line into the salt mixing station (fill and waste). This will be a 65 gallon tank so the run duration would be longer.

    The future salt mixing station will also be its own Apex Jr setup as it is another 60-ft away from the garage away from the tank. This station will also receive a weekly call for saltwater from the tank (another 10 gallon reservoir I manually fill now) and will use the PMUP. It will feature an Apex Jr, PM2 w/Bob, Temp & Conductivity and a 1-Link Module. Once the tank is empty, I would have it call for RO/DI, begin the fill sequence and, set a latch so it no longer responds to calls for salt water and notifies me via alarm that a new batch of salt water is required. Hardware would include a mixing pump and a transfer & waste pump (Pmup). I don't need temp control as temperatures here are relatively moderate and water from this tank would not be used immediately; it will sit in a reservoir in my cabinet prior to use. I currently auto change 2 liters of water daily.

    On a side note, the reason for the two waste valves is I am using 3/8" tubing in my attic to transfer water and I do not want the lines to hold water when it is not needed. I also run these tubes is a 1/2" tubing as a sleeve to prevent condensation in the attic from drawing rodents to the lines.

    Any thoughts? This project will be next year, so plenty of time to plan and revise.

    --Edit--
    The DT call for RO/DI water and Salt Water will be restricted by DoW statements for Sundays only. This way if a dosing pump is stuck on, it will be limited in supply to 10 gallons a week. This has been more than adequate so far. Both Reservoirs will have low and high float switches for alarms and also have 1/4" float valves in case the high floats fail to shut off the fill sequence..

  2. #2
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    Why not just run long aquabus cables and run the whole thing off one apex (as long as you keep the total aquabus length below 250ft)? Would be cheaper and easier to synchronize than multiple apex jrs.

    You might be an engineer if...You have no life and can prove it mathematically.

  3. #3
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    I did give that some serious thought. Just decided I did not want one controller doing it all. I would need 60 to 75-ft of cable to get from the DT to the garage and then another 75-ft to get from the garage to the shed out back for the salt mixing. Now I have already hit 150-ft. Plus I already have 6 EB's and 5 modules on the main unit and that makes the dashboard a beast. And then I am still going to add an FMM and a PM1 pretty soon.

  4. #4
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    I have contemplated a similar project. What I have been told is the problem is the valve that will touch water after the DI. I am told that valves that can stand up to the RODI will be hundreds of dollars. Not sure if that is true or not but in contacting a few vendors I was either told their valve was not rated for RODI use or I didn't get any answer. This leads me to believe there is something there but I don't claim to have all of that information. Anxiously looking forward to your plans!

  5. #5
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    Quote Originally Posted by Muttley000 View Post
    I have contemplated a similar project. What I have been told is the problem is the valve that will touch water after the DI. I am told that valves that can stand up to the RODI will be hundreds of dollars. Not sure if that is true or not but in contacting a few vendors I was either told their valve was not rated for RODI use or I didn't get any answer. This leads me to believe there is something there but I don't claim to have all of that information. Anxiously looking forward to your plans!
    I have not gotten to that level of detail yet but I am not really seeing the issue. My house water pressure is generally 60 psi and well within the range of most 1/4" valves. I don't see a pressure rating on the Apex 1/4" but it is rated for RO/DI systems. AutoTopoff dot com also sells 120vac 1/4" solenoid valves that would be duty rated if there was a concern; their's only $25 but does not include the relays.

    Aside from that, if the concern is contamination of DI water, I have full confidence the Apex valve will have that issue resolved. If not, I can always discharge the first "plug" of water. Considering I also store my DI water in bladder tanks to help prime my fill line and always have DI water on hand for testing purposes, I don't see the 1/4" valve exposure being an issue. Plus, I can always put the valves between the RO and the DI if it turns out to be an issue. The DI will filter on demand and I run two units in series.

    I think the biggest issue is the overall concern regarding a direct connect between an RO/DI and your tank via a 1/4" valve. If this valve fails open, you will fail your tank very quickly!!! However, this is not what I am doing. I am direct connecting a RO/DI system to my ATO reservoir. The ATO reservoir is and will remain connected to the system via a 50 ml/min pump. I have seven layers of fail safes built in for this to prevent an overfill disaster. These failsafes are handled by the Apex on my display tank.


    1. 10 gallon reservoir limits the amount of RO/DI that can be dosed to my tank to only 10 gallons a week...I ONLY fill this on Sundays. This is 9% of my system volume and results in my salinity dropping from 36 ppt to 32 ppt (53.0 um/cm to 48.1 um/cm). Bad, but survivable.
    2. 50 ml/min fill pump prolongs the "Stuck On" time required to crash the tank. If stuck on, it would take 757 minutes (12 hours) to empty the reservoir into my tank - more than sufficient time to "acclimate my tank from 36 ppt to 32 ppt.
    3. My dose pump is controlled via Apex on a OSC statement, that is programed to only provide 4 liters per day. I use a high float switch to override the statement off. If the high float switch failed but the dose pump did not, then I still only put in 4 liters per day.
    4. I have an additional high float for "sump overflow" that will shut off both the RO/DI dose pump and the EB4 that controls all my dose pumps and sound the alarm, send the emails, etc. As a fail safe for all my systems, I have my EB4 units plugged into a master EB8. This gives me a redundant fail safe on dose pumps and/or heaters stuck due to outlet failure.
    5. I now have conductivity monitoring and will be setting an dose pump off and alarm statement based on conductivity. I have not done so yet because I am still determining what my normal range of variation is. Looks like I will be setting it around 51.50 but will let it run a few more days.
    6. My sump volume is big enough to carry my normal water level, plus pump off plus 10 gallons of ATO pumped into the sump.
    7. I have an ALD with 3 sensors in the sump cabinet and one on the floor underneath as a final Alarm.


    So I think I have the overfill issue covered

  6. #6
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    I believe the fear was the longevity of the valve itself, but again I don't have all the information. I appreciate the thought you are putting into this,mseveral ideas I will use on mine!

  7. #7
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    Quote Originally Posted by Muttley000 View Post
    I believe the fear was the longevity of the valve itself, but again I don't have all the information. I appreciate the thought you are putting into this,mseveral ideas I will use on mine!
    Ah, ok. I have not looked too much into that one yet but I have seen the complaint.

    I know the one on AutoTopOff dot com runs hot but several people have confirmed it can run open for hours...gets hot, but does not fail. I recall someone measured upper 90's on a thermal scanner. Perhaps fitting an aluminum heatsink would help. I would think Neptune resolved the issue since their solenoid appears to require far less power to operate. I guess I need to ask around on that issue.

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