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

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:
Attachment 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.

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

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

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

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".

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

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

Got a link for a 1/4" valve? I'm currently using this one (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.

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