My AWC solution using a N.C. Solenoid

[BrettH]

Since this was a topic of discussion at the recent meeting, I thought I'd share what I finally decided to do for my AWC. I think it is fairly simple and fail safe and works in a similar manner to Joe's, but no relay box. Only issue I can determine would be the New Salt water pump failing. But even then it's not really a problem

Main Parts:
-Controller (I am using Apex)

-N.C. Solenoid plumbed off main pump return manifold with ball valve (for Old Salwater pump out) http://autotopoff.com/Solenoids/

-External pump to pump in new saltwater with Ball Valve control

-Conductivity probe (optional, not needed, but gives me peace of mind)

-John guest plumbing parts to plumb 1/4" refrigerator line to Solenoid and water pump

Cost: I only needed to buy a solenoid, so this cost me ~$30 and saved me $350 since I was considering the DOS. But this could be achieved using two digital timers to save some money. Obviously the big expense is the APEX.

The ball valves are used to match the flow rates between the Oldsalt/Newsalt pumps. At 2am, the Solenoid is activated via the Apex (under certain conditions, one being that salinty is in check, and the high and low float alrms are not activated). It pumps out 2 gallons over 14mins (I can increase/decrease the rate via the ball valve). I choose this rate becuase it is fairly granular, ~18oz/min. When the solenoid is activated the ATO is set to off. Then at ~2:15am the apex turns on the NewSaltwater pump and runs for 16 mins. That's it. For added protetcion, if the salinity is above 35ppt, then it won't add the new salt water, the ATO will kick on and add 2 gallons of fresh, which will reduce the salinty back to normal (My system is ~280 gallons). I actually set it up to slowly raise the slainity over time to compensate for skimmate wihch tends to reduce salinity over time.

Since I have both high and low sump switches these also serve as fail safes to stop my AWC. And as far as I can tell, the only issue would be the new salt water pump failing, but my salinity probe would catch that issue. And I have been using N.C. solenoids for many, many years without a single issue. And even if fails, it will most likley fail closed, so no real issue. The extra 2 gallons being added (since old salwater was not pumped out) would either raise the salinity or activate my high sump alarm and shut down the AWC completely.

Toughts?

brett

 

[dudemeister]

My initial thought is it will certainly work without a lot of harm to a large system but that margin shrinks for smaller systems. My problem lies in reliance on timed amounts. Over time tubes and lines can get clogged with stuff thus throwing off your calibration. Also the solenoid can get gunked up and fail. That said float switches can get gunked up too but if you make cleaning them part of regular maintenance they should be fine. I prefer measured amounts by float valve and am eagerly waiting for Joes solid state build on the relay.

 

[dudemeister]

Here's a side question though related- where to buy John Guest fittings in our area? Home Depot is woefully lacking. Anyone?

 

[RTMA]

I usually find the 1/2" Watts JG-type connectors pretty plentiful at Home Depot...cant wait for Lowes to open!

Brett, this shoudl work fine, my only finding is that some of our pumps may not have enough pressure to seal a solenoid. I saw that they say 0-100 psi, but I'd be worried that at low psi, it woudl leak through. Will be interested to see your project

 

[dudemeister]

I usually have to make a BRS order to get what I need. I wish there was some place locally. Is Lowes opening by us?

 

[RTMA]

Yes, on Connecticut ave, closer to Toys R Us..

 

[BrettH]

my only finding is that some of our pumps may not have enough pressure to seal a solenoid. I saw that they say 0-100 psi, but I'd be worried that at low psi, it woudl leak through. Will be interested to see your project

Joe, the solenoid is not pressure activated, it is electric. The apex turns it on and off to actuate it. That is the max pressure that it can hold back, and it is high pressure that you are worried about, not low. It is not pressure activated like the ones you see to shutdown R.O. units. And that's what makes it fail safe. It's virtually impossible for it to fail open.

My initial thought is it will certainly work without a lot of harm to a large system but that margin shrinks for smaller systems.

dudemeister, I would think you can use it for small system too because of the ability to set the flow with a ball valve (or even better with a gate valve). I am using 1/4" tubing, so it doesn't move a lot water that fast even when the ball valve is fully open. I'm only moving 18oz of water per minute, so that could even work on a 20 gallon system theoretically.

My problem lies in reliance on timed amounts. Over time tubes and lines can get clogged with stuff thus throwing off your calibration.

Yes, but the salinity probe will handle that. Also the same can be said whether you use a solenoid or the relay box---lines can get clogged in either system. And the way Joe is doing it could be slightly less accurate since he doesn't know the starting point. i.e he could have a gallon of evaporation so he will be replacing more saltwater than he took out. But again, like Joe said, dosing small amounts will not throw a tank off. And either method would be fairly reliable.

Also the solenoid can get gunked up and fail. That said float switches can get gunked up too but if you make cleaning them part of regular maintenance they should be fine. I prefer measured amounts by float valve and am eagerly waiting for Joes solid state build on the relay.

Typically float switches fail due to voltage spikes or a snail gets on it (which has never happened on either of my tanks! keeping fingers crossed now that I just said that ). Since 2002 I have had two float switches fail and I have never had a solenoid fail; not that it can't fail, it's just that they are not sitting in corrosive saltwater all day bouncing around constantly opening and closing like a float switch. My solenoid sits very comfortable out of site, just chilling out, never bothered by anything, just once a day it opens and closes. It has an easy life. And the solenoid which turns on the supply water to my R.O. unit which is controlled by a float switch in my sump might open and close 10-15x a day, but after 13 yrs, it still works. If my solenoid fails, then water doesn't get pumped into the tank.

I have been running my method for about week now and all is well so far. I have also been measuring the amount of water on both side daily, and it is very accurate so far. I am fairly happy with the system, but ask me in a year from now....:beer:

 

[BrettH]

Here's a side question though related- where to buy John Guest fittings in our area? Home Depot is woefully lacking. Anyone?

The Homedepot here in Stratford just off exit 33 I-95 has a decent amount of fittings. The only thing that I have needed to order online are check valves.

Now when it comes to sched 40 fittings, that's a whole 'nother story....

By the way, the new saltwater feed line has a check valve just in case it over fills my sump which could then create a siphon.

 

[dudemeister]

In regards to the accuracy, perhaps a routine could be written into the Apex so that it only runs immediately following an ATO cycle. That would eliminate the mismatch.

I'm liking the though of the solenoid for control on a gravity fed solution. I suppose for the truly paranoid you could put 2 of them on the same line running off the same outlet that way if one fails, the other is there to back the other up.

Maybe both in conjunction that way if the float fails the timed refill will cut off after a certain time?

Just thinking out loud.

 

[BrettH]

In regards to the accuracy, perhaps a routine could be written into the Apex so that it only runs immediately following an ATO cycle. That would eliminate the mismatch.

I tried going down this path and doing exactly that! I spent almost a month trying to write code for the Apex. I was thinking the same way you are now, just use a float switch to control the starting and stopping points, easier said than done. I got close, but there were issues. I even modeled the APEX on/off statements in excel to try and get the logic to work. Then finally I came to my senses, poured a bourbon and accepted defeat. Code was just too complex and I wasted too many brain cells that could have been better used for beer, bourbon or scotch...

I was going to get the DOS until I realized that Joe was right, not that big of a deal if it is off a little. I think my system will most likely only be off a couple cups of water (and so far it has dead on)...hell, I probably use that much water every time I melt the fish food with tank water.

 

[RTMA]

Joe, the solenoid is not pressure activated, it is electric. The apex turns it on and off to actuate it. That is the max pressure that it can hold back, and it is high pressure that you are worried about, not low. It is not pressure activated like the ones you see to shutdown R.O. units. And that's what makes it fail safe. It's virtually impossible for it to fail open.

Ok that is awesome then. Is it plastic or stainless? Looking forward to seeing how this comes out!

 

[BrettH]

Joe, it is plastic. But you can get a stainless steel one. I have been running electric solenoids since 2002, one on the feed line of my R.O. and the other on my CaRax CO2 tank, neither have given me any problem-- Fingers crossed!

In terms of failure of the solenoid, I think that electrical would fail before anything else and therefore it would not open. But if for some reason it failed Open, then only New Salt water would be pumped in without removing the old saltwater. But I have two ways to prevent this from being a problem:

1) The high sump alarm would shut down the new salt pump after four gallons of new water.

2) Salinty would start to rise, which would also shut off the new salt pump and only allow the ATO to run until the salinity fell back into range.

 

[BrettH]

Apex code

Apex code

In case anyone is interested, here is the Apex code....It will certainly put you to sleep!

ATO CODE
Fallback OFF
Set ON
If Outlet HighSumpAlrm = ON Then OFF (Virtual Outlet)
If Sw1 OPEN Then OFF -->>Sw1 controls ATO Solenoid
If Outlet Leak_Detect = ON Then OFF (Virtual Outlet)
If Outlet Leak_Tank = ON Then OFF (Virtual Outlet)
If Outlet OldSalt = ON Then OFF
If Outlet NewSalt = ON Then OFF
If Condx8 < 31.0 Then OFF (Salinity probe)
Defer 010:00 Then ON

-->> Sw1 actuates the Solenoid on my R.O. Unit for ATO

OldSalt (This open and closes the solenoid which is plumbed off a manifold that is connected to my main pump)
Fallback OFF
Set ON
If Time 03:20 to 03:05 Then OFF (This statement might confuse everyone)
If Outlet HighSumpAlrm = ON Then OFF (Virtual Outlet)
If Outlet Leak_Detect = ON Then OFF (Virtual Outlet)
If Outlet Leak_Tank = ON Then OFF (Virtual Outlet)
If Outlet Dolphin_Pump = OFF Then OFF
If Condx8 < 32.0 Then OFF

NewSalt
Fallback OFF
Set ON
If Time 03:35 to 03:20 Then OFF
If Outlet NewSaltFlag = OFF Then OFF (Virtual Outlet)
If Outlet HighSumpAlrm = ON Then OFF (Virtual Outlet)
If Outlet Leak_Detect = ON Then OFF (Virtual Outlet)
If Outlet Leak_Tank = ON Then OFF (Virtual Outlet)
If Outlet OldSalt = ON Then OFF
If Condx8 > 35.0 Then OFF

"NewSaltFlag" is a "virtual" outlet that insures old water has been pumped out before starting to pump New Water in.

NewSaltFlag
Fallback OFF
If Sw1 OPEN Then OFF
If Sw1 CLOSED Then ON
Defer 002:00 Then OFF

NewSaltFlag would also catch a float switch failure and would hold NewSaltFlag = "OFF" which would therefore prevent new salt from being added

Another comment about my salinity settings. I have never had a probe calibrate exactly to the S.G. And I have done all sorts of temperature checks/compensations and re-calibrations etc. Bottom line with the salinity probe is that you are looking for relative changes. The salinity of my tank is currently 35ppt, but my probe is reading 34ppt. I read so many post that people obsess over getting their probe dead nuts on, but the reality is that it is ok to be off because you are looking for relative changes over time. In my case, I know 34ppt = 35ppt.