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Old 08/31/2019, 10:02 PM   #1
FortyFour
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Question Using solenoid for RODI

Hoping someone can chime in here. I have a 55g drum that I use to store RODI water. It takes about 6 or 7 hours to fill and I want to use a combination of float and solenoid valves to prevent overflow and waste. A float valve will prevent overflow, but I also want to set up a solenoid valve so that the water will shut off if I forget to turn it off or get pulled away for some reason.

Does anyone have instructions on how to use a solenoid valve to accomplish this? I have an extra float switch laying around. Or would I be able to put the solenoid on timer?


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Old 09/01/2019, 06:40 AM   #2
mcgyvr
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Use the float switch to energize a relays coil..Switch the solenoid on/off with the relays contact.
Should be a diagram floating around somewhere..


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Old 09/04/2019, 03:55 PM   #3
discussmith
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The solenoid should either have 2 wires hanging out of it or 2 terminals to connect power. Your float switch should have the same. Either 2 wires hanging or 2 terminals. One wire should go in and out of the float switch to the solenoid. The other wire from the solenoid goes directly to your power source. The float switch contacts should be closed allowing power through when the water is low and should open and stop power when the water reaches the high level. You should use a low voltage solenoid for safety and power it with a transformer. Lawn sprinkler solenoids are fairly cheap and work well if you are using house tap water. They run on low voltage and do not require high wattage. They will run on any float switch. They don’t work if you are pumping the water with an aquarium type pump. Not enough pressure to open the solenoid diaphragm.


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Old 09/07/2019, 12:27 PM   #4
FortyFour
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Very helpful, thank you both.


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Old 09/09/2019, 11:46 PM   #5
FortyFour
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My BRS RODI unit came with an auto shut off valve, so the solenoid wasn’t needed. The shut off valve is activated once the float valve cuts off flow.


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Old 09/10/2019, 07:52 AM   #6
CuzzA
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Quote:
Originally Posted by FortyFour View Post
My BRS RODI unit came with an auto shut off valve, so the solenoid wasn’t needed. The shut off valve is activated once the float valve cuts off flow.
Although an RODI auto shut off is good, it is not optimal for continuously filling a reservoir. The setup you describe keeps the reservoir full all the time, which is nice, but the constant cycling of your RODI unit will have a negative effect on your DI due to TDS creep. You may not have this issue if your water source is more pure.

Generally speaking the best way to fill a reservoir is to flush the RO membrane and then do a long fill on the reservoir. Setting the flushing aside, to achieve this we utilize two techniques to fill reservoirs. Either a timer or dual float switches hooked to a controller or relay.

The easiest method is a simple countdown timer switch commonly available for around $10. Turn the dial to the time it takes to fill the reservoir and it will energize the solenoid until the time runs out and then cut power to the solenoid and close the solenoid. The downside is this method requires you to turn the unit on as there's little automation.

Next would be two float switches programmed to a controller to fill the reservoir when the low switch is activated and cut off the solenoid when the high switch is activated.

Finally, the most involved setup would be two float switches installed like the previous method, but wired to a relay, acting in a similar fashion as a controller would. I say more involved simply because you have to wire everything up correctly.

The benefit, aside from the TDS creep, is you now have fail safes in the event the mechanical float valve fails by breaking or debris or growth inhibits the valve to fully close. I personally would not rely solely on a mechanical valve.


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Old 09/10/2019, 10:17 AM   #7
mcgyvr
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Quote:
Originally Posted by FortyFour View Post
if I forget to turn it off or get pulled away for some reason.
Quote:
Originally Posted by CuzzA View Post
The setup you describe keeps the reservoir full all the time,
I don't believe they are describing a system that keeps it full..
Seems they are manually turning the water on when they think it needs to be refilled..


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Old 09/10/2019, 06:10 PM   #8
FortyFour
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Thanks guys. As I have it today, I am not over relying on the valve. The valve will keep me safe if I have to step away for any minimal amount of time, as I’m doing large batches as a time to minimize TDS creep and prolong the media.

This is the exact feedback I am looking for though. While I don’t see myself running the RODI continuously, I’ll eventually add the solenoid for redundancy.


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