Stenner and ORP probe setup questions and thoughts

[miwitte]

So I converted to the BBB method the end of last year and I wanted to get some automation for the chlorine. I got a Stenner 45mp5 for injection. I was planning on sending to liquid chlorine into my old tab feeder to inject the chlorine. I know most people figure out how much the pool uses per day then calculate the stenner output and put a timer to inject the right qty of chlorine per day.

I was thinking of doing a step further and incorporate a ORP probe and controller into the mix. I got one off eBay and it will switch 120V depending on the ORP voltage. All I need to do is calibrate the voltage to what my chlorine level needs are and if it drops, it turns on the outlet and hence the stenner to inject chlorine.

Since this is a feedback loop, the problem is the slow amount of time from injection of liquid chlorine until it registers enough to move the ORP voltage to shut off the stenner which could lead to injecting too much chlorine. I was thinking of adding a On/OFF mechanical timer to fix the lag. So if the ORP turns on the outlet and then the timer will get voltage and go on for say 15,30,45 minutes and power the Stenner to inject. I will set the off for say 30,45,60 minutes, whatever I find it takes the ORP to sense the increase and shut the outlet off. I think once this on/off is close I can set the timer to the on/off that works.

My injection point would be my old chlorinator, drill a hole in top and put tube in and since there is water flowing into the chlorinator and getting sucked in this seems like a ideal place for injection. For the ORP probe I was thinking of doing it at the suction side of the pump so its seeing the skimmers and main drain combined so should be a good average of what's really in the pool from a chlorine level.

Anyone that has done something like this I would appreciate input, or if I am off base or crazy to try and make this work. I think if I can get this close it will be a great way to keep the levels pretty consistent throughout the day and night.

 

[jblizzle]

Just a heads up that we generally do not recommend the use of ORP sensors. The recommended CYA levels tend to interfere with the ORP sensors and you get erratic behavior.

I also would not recommend injecting the bleach into the old chlorinator, just seems like a potentially dangerous idea. Why not remove it completely and just inject directly into the plumbing?

 

[JoyfulNoise]

You've identified some problems early-on like lag time so good for you. One other problem you will have to solve (which none of the major equipment manufacturers have so far) is how to use an ORP probe in a high CYA environment. Stabilizer drops the level of hypochlorous acid (HOCl is the oxidant that ORP needs to measure accurately) to very low parts-per-billion levels. CYA also fouls the ORP sensors membranes which forces the user to do frequent manual cleanings (toothbrush and toothpaste is recommended by some manufacturers). As well, the ORP voltage is not only sensitive to [HOCl] but also to pH, TA, UV light induced hydroxyl radicals, temperature, etc, etc. Because the ORP voltage is affected by all of these inputs AND because the HOCl contribution to the signal is so low, you get a very, very low signal-to-noise ratio with lots of environmentally induced drift.

If you look at commercial units (like the IntelliChem system by Pentair), you will see that they recommend stabilizer levels far lower than we recommend here. While that boosts the HOCl contribution to the signal, it also increases chlorine loss to UV light greatly which means the system will demand more chlorine injection to make up for it. This is often seen in the commercial systems as they require low CYA levels and then, because chlorine loss is so high, the ORP controller forces the SWG output to run excessively which ultimately shortens the useful life of the SWG cell.

Let us know how it goes and if you've found any good work-arounds to the above issues.

 

[miwitte]

so looking at the ORP output over the last seveal weeks, alas I don't think this will work. It looked like a really good idea, however I am not seeing much drift from say 1PPM to 7 PPM. when researching this it appeared that ORP was directly proportional to mv found a bunch of charts so this looked real promising. Looks like ill put it on ebay where I got it from

Now the next question is where do I inject? My thought was to drill a hole in the old puck style chlorinator, since it is fairly full of water and has the tube that suck chlorinated water in anyway. Someone suggested thats unsafe not really sure why could you explain?. For future owners? I will never put pucks in there again and no one will as long as I own the house.

My plan was to drill and tap into the old chlorinator cover pretty good meat. I can get some kind of fitting threaded in. If I move from house, I remove everything and plug and its back to a regular puck style chlorinator. This seems the easiest way to me not sure why its unsafe if only I am maintaining pool. I would certainly put it back if I left.

I guess I will also need a check valve where did you guys get yours?

Also from a 5 or 10 gallon chlorine tank what did folks use don't want to by a $100 tank. The good news is I have a crawl space door right next to the pool equipment, that seems like a very good place for the chlorine tank, pump and timer.. The is also power under there for the HVAC so that's covered.

Thoughts anyone doing injecting into their old chlorinator? Warnings and why?

Again appreciate everything this place is awesome my pool is best its ever been just need to automate the chlorine and I am golden.

 

[miwitte]

so what I have seen with the ORP probe is that for readings of FC 6-1 the probe is reading 690-680 very inconsistent. I have see ORP probe MV charts and show variance of 75 mv or more with a ph of 7.5 so surprised mine is not reacting as such.

 

[jay jay]

My injection point would be my old chlorinator, drill a hole in top and put tube in and since there is water flowing into the chlorinator and getting sucked in this seems like a ideal place for injection.

Hello everybody. Mostly a lurker here, but I did try this last year.

Converted to the BBB method last year and tried chlorine injection. Was previously using pucks. Since this was a trial, I wanted a temporary hookup. My thoughts were the same as yours, except I screwed a 1/4" plastic compression fitting, in place of the drain plug at the bottom of the chlorinator. Ran some PVC flex tubing from that fitting to a peristaltic pump and set the chlorinator to max flow. The peristaltic pump runs at a slow 6 rpm, so I was not concerned about too high of a concentration.

This worked great all last season. The injection pump was interlocked with the main pump, so that there was never a chlorinator full of just liquid chlorine. The main pump also ran for hours after the chlorine injection timer shut off. This also flushed the chlorinator.

For a trial, I say give it a shot. If it works, then install a real injection fitting.

 

[trbvm]

I, personally, am a big proponent of ORP... for the last year, I have had great success in tuning my SWG to run just enough to maintain a constant 5 FC. From what I am seeing, keeping pH constant and lower CYA is the key. I have pH set at 7.5 (stenner) and CYA around 50. On hind sight, I probably should have kept my CYA to around 30.

 

[jblizzle]

I, personally, am a big proponent of ORP... for the last year, I have had great success in tuning my SWG to run just enough to maintain a constant 5 FC. From what I am seeing, keeping pH constant and lower CYA is the key. I have pH set at 7.5 (stenner) and CYA around 50. On hind sight, I probably should have kept my CYA to around 30.

Keeping a lower CYA means your SWG has to work more to maintain a FC level since more is lost to the sun. This means that your SWG cell will not last as long.

So, if you are willing to trade sooner cell replacement for the convenience, then I suppose it would work fine.

 

[trbvm]

Yup, @jblizzle, you are right. The SWG has to work more. I have the cover on most of the day. So, it works out OK.
Without a cover, maybe find a nice spot where the CYA/FC is balanced.


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[JoyfulNoise]

Yup, @jblizzle, you are right. The SWG has to work more. I have the cover on most of the day. So, it works out OK.
Without a cover, maybe find a nice spot where the CYA/FC is balanced.


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Please let us know how this works out for you. If you have any data you can share on SWG % output and pump runtimes required to keep your FC at 5ppm with ORP control that would be great. Since you cover your pool for most of the day, that eliminates a huge variable in ORP control, namely UV photolysis of hypochlorite. It also helps keep your pH in check by limiting the amount of CO2 outgassing. Paired with your pH control, that allows your water chemistry to remain fairly stable which is hugely important for ORP to work. Lowering your CYA to 30ppm should be entirely possible since your pool is covered.

 

[trbvm]

I didnt set the percentage on the SWG. I am not sure I'd there is a way to set the percentage, since my interface doesn't have that option.

My pump runs for 3 hours on "high" at night. I also run it on "low" from 2 pm to 6 pm mainly to keep water circulating in the probes and keep them cool. SWG doesn't run during my "low" run times since the flow switch trips.
So, with 3 hours of running the pump (and SWG) everything is in balance for now.
I may have to increase the pump times next month onwards, once the AZ heat kicks in with full force.


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