Solenoid cycles on CO2 to reactor: how often is too often?

[Delphinus]

When I ran a reactor about a decade ago, I set it up to run without a CO2 controller. It took a lot of trial and error, but eventually I got things to settle on about a 6.7 pH in the reactor with a steady-ish bubble rate (that I generally had to adjust on a daily basis, which got annoying over time).

Fast forward to today. I've been running a reactor again, and liking the results (yay SPS growth!). I run the CO2 solenoid on the Apex controller and I've set the control to turn on at 6.7 and turn off at 6.5 (hopefully so so settle on 6.6 as the "average" pH in the reactor). I've then tried dialing down the CO2 feed to as slow as I can muster whilst still being strong enough to be steady, yet fast enough still that I can see the pH in the reactor decrease when the solenoid is on.

As with the natural tendency when you have a controller that can chart things over time though (ok maybe I mean, when "I" have a controller, STOP JUDGING ME), I started looking to how many times the solenoid is kicking on and off, and it's about 60 cycles per day.

Here's a chart of the last hour, for example:
15667

You can see that when the reactor output hits 6.7, the CO2 turns on and runs for about 5 minutes. This is enough take the reactor to just above 6.5, then the CO2 turns off and it takes between 15 to 20 minutes for the pH to slowly creep back up to 6.7.

This works out to close to 60 on/off cycles per day. Is there any risk of overusing the solenoid at this kind of rate? Should I endeavour to slow down the CO2 flowrate even further ... or maybe slow down the reactor effluent rate? The reactor itself is an old Wendell-made unit using a John Guest valve for flow control, which doesn't lend itself well to really fine adjustments.

[brotherd]

I think you are fine given your current demand. Ultimately your tank/systems alk test will dictate any changes you need to make right.

[brotherd]

Sorry, to answer the question, 60 cycles a day is nothing. An hour, yes that could be problematic. Hth.

[SoloSK71]

Most 'hobby grade' solenoids in most hobbies at STP have a mean life expectancy of 10,000,000 cycles.

Even discounting that by an order of magnitude, you should not see reliable chance of failure in your tank's life span at 60 cycles per day.

Using the electronic method as opposed to physical, the coils usually have 10,000 hours MTBF, and assuming the cycle time is 2 seconds (I am guessing here) then you are 120 seconds a day (2 minutes) or 12.167 hours a year. Again, statistically, not much chance of failure in your tank's life span.

Having said that, the failure curve for these items is heavily weighted to the left, so take what I said with a grain of salt. You should still have no problem at all with that duty cycle.

Charles

[brotherd]

Most 'hobby grade' solenoids in most hobbies at STP have a mean life expectancy of 10,000,000 cycles.

Even discounting that by an order of magnitude, you should not see reliable chance of failure in your tank's life span at 60 cycles per day.

Using the electronic method as opposed to physical, the coils usually have 10,000 hours MTBF, and assuming the cycle time is 2 seconds (I am guessing here) then you are 120 seconds a day (2 minutes) or 12.167 hours a year. Again, statistically, not much chance of failure in your tank's life span.

Having said that, the failure curve for these items is heavily weighted to the left, so take what I said with a grain of salt. You should still have no problem at all with that duty cycle.

Charles
What he said

[Delphinus]

Thanks for the info, very helpful.

The solenoid itself is already a replacement, or rather, a rebuild based on a solenoid I bought off ebay because the original froze on (it was a decade old). I had hoped I could unfreeze the original but I couldn't (and it turns out you can't lube these? So I guess when they're done, they're done). Between that and the number of options of feed pumps I've gone through (tried a peristaltic pump but the gears wore out after a couple months), then some other pumps that eventually weakened ... etc ... I feel that "eventual failure of parts" is a sort of given in this hobby.

Just wanted to be sure I wasn't in the territory of "Wow! That's a really burdensome way to dial in your reactor, there's an obvious better way that you're overlooking".

[maron6977]

I personally think it's too much . If it's cycles that much - just turned down you bubble count !
Right now , I don't think mine has cycled in days .
Also , when first set up (& didn't know anything) found solenoid shut off but was still bubbling (slowly) .
So just to cover problems - turn your bubble count down . As far as I've read , should only cycle 2-3 times a day

[maron6977]

Oh Ya . Also they make 1/4" needle valves , work way better - been there, done that .

[Delphinus]

Got a link for a 1/4" valve? I'm currently using this one (http://www.jlaquatics.com/needle-valve-for-co2-regulator.html) (which seems to have good customer feedback, but is 1/8" not 1/4")

I have the thing currently barely open. If I close it any further I don't get consistent gas flow into the reactor. I've tried lowering the regulator output pressure so that I could open the valve more, but again I get weird effects when I do that. Ie., either the bubble rate stops altogether, or the reactor effluent stops .. stuff like that.

I'm all for using less CO2 though so if the answer involves moving to a different needle valve I would consider that.

[Delphinus]

Also are you using a 1/4" regulator or do you use an adaptor to the 1/4" needle valve?

[shiftline]

You made me double check mine. I had the same battle a few weeks ago. I kept slowly tweaking the bubble count until it was stable. Now may solenoid has been on for 5 days! I keep mine between 6.7-6.9
https://uploads.tapatalk-cdn.com/20170201/f3eeddae97119415b43750b338d6e2f2.jpg


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[maron6977]

Got a link for a 1/4" valve? I'm currently using this one (http://www.jlaquatics.com/needle-valve-for-co2-regulator.html) (which seems to have good customer feedback, but is 1/8" not 1/4")

I have the thing currently barely open. If I close it any further I don't get consistent gas flow into the reactor. I've tried lowering the regulator output pressure so that I could open the valve more, but again I get weird effects when I do that. Ie., either the bubble rate stops altogether, or the reactor effluent stops .. stuff like that.

I'm all for using less CO2 though so if the answer involves moving to a different needle valve I would consider that.

Sorry , I should have been more clear.
I use a Milwaukee reg & solenoid w/bubble counter . Glycerin in bubble counter . 1/4" needle valve for effluent. I have a Geo 612 reactor & run at a PH of 6.5.
Also just added a second chamber , so effluent runs thru vertex reactor body filled with media & overflows into sump - trying to raise tank ph , seems to work.

[Delphinus]

Ah ok, that makes more sense, thanks!

I started off with a Milwaukee regulator/solenoid/needle valve/bubble counter combo but it's now been modded enough to be its own beast. Both the needle valve and the solenoid are swapped out now. I was able to unscrew the bubble counter from the needlevalve and I use a 1/8" hose barb from an old wooden airstone as the input, and it's just mounted to my wall next to the reactor.

I've been playing around with CO2 flowrate since yesterday and I'm getting closer to steady state but still not really there. The bubble rate isn't a nice steady rate, it goes more in bursts and then has a few seconds of nothing, which I think is probably from the check valve, so that's probably OK. Over a long enough period of time the bubble rate is still consistent. My challenge now is that it really doesn't take much of an adjustment (like, seriously, a small touch of the valve) to go from "the CO2 is too fast and thus the solenoid cycles off and on too much" to "the CO2 is too slow and the despite the solenoid being on the pH is just climbing higher and higher away from the desired set point".

I'm not quite sure how I can make this better. I guess one option is lower the regulator pressure and hope this gives me a bigger sweet spot for adjustments; and another is drill the reactor and get the pH probe inside the reactor chamber itself (right now the reactor effluent empties into a little capsule that the probe sits in - so the pH measurement is actually quite slow to react to whatever is happening inside the reactor).

The more I think about it the less I like not having the probe inside the reactor, so that's probably the next thing to fix..

[Delphinus]

What psi do folks tend to have on the regulator second stage?

[maron6977]

I'll double check but I think 18PSI

[sphelps]

I tend to have the opposite thinking, I'd rather it cycle more often than stay on for long periods of time. IME these solenoids typically fail off since they are NC and when left on for long periods they produce a far amount of heat. So seems to me having it stay on for longer periods is more likely to create a failure, especially one with it left open. I use to run my bubbles fairly fast for this reason, the valve would only kick on for 30 seconds or so before shutting off and then would stay off for longer periods until the pH recovered. While this did mean the reactor pH would drop a bit more than you guys are seeing it still maintained near perfect levels in the display.

I also seem to recall setting my target pH lower, closer to 6.4 as suggested by the media, which allows for a slower effluent and more efficient use of the C02.

[Delphinus]

That's interesting, thanks, I'll check the temperature of the solenoid when I'm home from work.

Mine seems to be settling out at 6.5 now although I was sort of hoping to target 6.6. If you ran fine at 6.4 then maybe I'll leave it as-is for now until I have a more substantial calcium draw (all I have are frags so far).

Here's a chart of the last 12 hours or so:
15672

You can see that overnight I still had the bubble rate too fast and the solenoid cycled off/on until I checked in the morning. I did a *very slight* decrease to the CO2 flowrate at 8am (literally, I wasn't even sure if I had moved the knob) was all it took to keep the solenoid to stay on, except that the controller kicked it off when it hit 6.55 (the previous off setpoint). So I lowered the off point to 6.5 to see where it would settle and it seems to have coincidentally completely settled on 6.5 so the solenoid hasn't turned off yet.

I wasn't sure if I was going to try slowing the CO2 again to see if it would settle at closer to 6.6 or if I should lower the off point to 6.45 (I'm a little worried that if it settles right on the borderline then it might switch the CO2 off and then it will go all the way back up to 6.7 before it turns on again ... although you can see by the "up curves" that it doesn't take very long to raise the pH).