Need to add liquid chlorine when using SmarterSpa SWG?

[DrNinjaman]

The sensor on this thing is not so good, I think. Or it's not well-calibrated to the adjustment range. Or I can't test while it's running? Zeropoint of 15 resulted in it turning on at 1.2 as I previously mentioned. Running for three hours then raised the free chlorine by 2 to 3.2ppm plus the dichlor I added, so that run time seems pretty good if I can get it to turn on at 2ppm or above. As you folks suggested, I increased the zeropoint, I think to 20, maybe 25 but I went too high I guess, because the next time I checked, the free chlorine was at 13 ppm with the cell still operating. Keep in mind, the zeropoint range of adjustment is 0-60. Anyway, I set it back down to 17, and waited for the chlorine levels to fall. We used it last night. FC before we soaked: 6.0ppm.
FC this morning, after we soaked, 1.4ppm and the cell was still off. So 17 is still too low. Bumped zeropoint to 18. Will wait and see.

 

[DrNinjaman]

Seriously, this thing is goofy. Do I need to keep the water temp constant for it to work consistently? Is that what's messing up the sensor? It ran earlier today when I boosted it and brought the FC up to 3.2. I have now adjusted the zeropoint and power by one, to 18 and 5 correspondingly. I also turned the heater up to use it tonight, so the temp stayed above 95 degrees. We didn't use it after all, but when I went back out to turn the lights off, the cell was running, less than 4 hours after I measured 3.2 ppm FC.
17 wasn't active at 1.4 ppm, but 18 turns on at over three? That's not a lot of granularity. I'm not loving this so far.

 

[DrNinjaman]

Well, it turned on again, way too early. I noticed it was running just now and checked the FC. 9.0. When the zeropoint was set to 17, it didn't turn on even at 1.4 FC, now it won't turn off. I think there is something amiss with the sensor. I emailed ControlOmatic, we'll see what they say.
On thing I am wondering about is the salt concentration. It's right on the edge of the "high" range, to the point that it says it's high when it starts generating chlorine and shifts to normal after it's done. It was flicking back and forth between the blue and green light tonight as I watched. The concentration measures at 2200ppm, which is higher than what the manual says it should need, but it's supposed to let me know if it's too high. I've drained and refilled a bit already, but it's a pain to get everything balanced again after I do that, and it's getting pretty cold to be screwing around with the hose.
I just don't get why the sensor is acting so weird.

 

[duganderson]

The instructions for the smarter spa have you adjust the zero point so the cell turns on at 0 ppm FC.

I thought that was what the instructions were saying too initially, but I would not set it to turn on at 0 PPM FC. In communicating with the SmarterSpa owner via email, he suggested that it's fine to set it at higher levels too.

Regarding the sensor, I think the owner says the sensor is most accurate when the water is not moving. In my experience, it does seem to jump around when I"m using it or the jets are on. I've, however, also noticed that the sensor seems reliable to turn on at the same set point when I check that with Taylor FC test.

The only time I've noticed that the sensor seems wrong is when the chlorine demand is too high. Since the SmarterSpa won't turn on for 3 hours or more after it ran last, the FC can get lower than the set point if the chlorine demand brings the FC down below the set point in less than 3 hours. Therefore, if I notice the sensor says the FC is less than the set point that I have a problem or have a high chlorine demand.

Please keep us updated what you learn about the sensor and the salt/levels and FC production.

 

[DrNinjaman]

I thought that was what the instructions were saying too initially, but I would not set it to turn on at 0 PPM FC. In communicating with the SmarterSpa owner via email, he suggested that it's fine to set it at higher levels too.

Regarding the sensor, I think the owner says the sensor is most accurate when the water is not moving. In my experience, it does seem to jump around when I"m using it or the jets are on. I've, however, also noticed that the sensor seems reliable to turn on at the same set point when I check that with Taylor FC test.

The only time I've noticed that the sensor seems wrong is when the chlorine demand is too high. Since the SmarterSpa won't turn on for 3 hours or more after it ran last, the FC can get lower than the set point if the chlorine demand brings the FC down below the set point in less than 3 hours. Therefore, if I notice the sensor says the FC is less than the set point that I have a problem or have a high chlorine demand.

Please keep us updated what you learn about the sensor and the salt/levels and FC production.

duganderson,
Do you vary the water temperature with yours? It's getting mighty cold out around here, so we've been reducing the water temperature during the week to around 78-80degrees to keep the power draw manageable. Through further reading on the site here, it seems that the sensor involved is known as an ORP sensor. They don't explicitly measure free chlorine, like the test kit, they measure Oxidation-Reduction Potential. This stands in for free chlorine levels in practice, since that is usually the main oxidizer present in the water, but they are apparently very sensitve to a lot of different variables. pH is the main one. As the pH changes, the percentage of active hydrochlorous acid changes as well, and that's the species that the sensor primarily reacts to. So pH, CYA, temperature, non-chlorine shock, dissolved metals of various kinds, hydrogen gas, all these things can affect the performance of the sensor. However, if you can keep most of that stuff steady over time, these sensors can work okay, particularly for maintaining a setpoint. I think that my problem is primarily the changing temperature, as I've been keeping the other stuff pretty constant. I'm going to need to figure out if lower temperature makes it more sensitive or less, and set it up to run when it needs to for the most sensitive range. Then I'm going to have to manually boost it when it needs to run for the other temps. This is not my favorite. It is easier than measuring some bleach, but only just. In the summer I should be able to get it to run steadily for a while, as I can leave it hot all the time, but regardless, this is far from a "set it and forget it" automated system. It seems I have considerable more reading to do about the foibles of these sensors before I can get this nailed down.

 

[Mdragger88]

After reading what dug said above I am wondering how much of your issue is timing (based on the 3 hr situation) Orp can be fickle as well.. keeping low cya (under 30) should avoid some of the issues from that though.
I like the control i get from my manually adjusted unit. Adding an external mechanical timer is plenty of automation for me. It allows me to just press a button for more fc if I don’t want to manually dose without messing up my daily automatic settings. Vacations are also a breeze.

 

[duganderson]

DrNingaman...Thanks for the update.

I keep my temp pretty steady (100-103) and my tub typically gets used 6-7 days a week.

One thing to check.....I'm curious how much money you save on electricity turning it down during the week. I know it takes a lot of energy to raise the temperature a lot. You could start a new post about that OR see if folks chime in here. If you have a newer tub and good cover, some spa stores have warranties that your electricity bill won't go up more than $40 a month or so or they will pay your extra electricity.

 

[DrNinjaman]

It saves significant money. My electric bill looked like a staircase for September and October until I started turning it down. More than double the consumption compared with last year. Our electric bill typically falls in the fall as the AC stops being needed, but not this year. Rate of heat loss is directly proportional to the delta T between the hot and the cold temperatures. So maintaining a higher temperature will always require running the heater more frequently. While I do need to run the heater intensely in order to raise the water up to 102 when we use it, I am not holding it there for 24 hours per day. That is the real killer. The duration. The tub is well insulated, though the salesman discouraged me from buying the Arctic weight cover, saying it would be too difficult for the kids and wife to open. There are many things I would like to have done differently when we bought this thing, and that is one of them. We do really enjoy it, I just don't appreciate the lousy advice I got at the pool store. What I'd really like is one of these: The Covana Hot Tub Cover but they don't make the Oasis for a tub as large as ours and the one that does fit our tub doesn't offer the same R-value for the top and would require putting the stairs on the wrong side of the tub. It does take a fairly long time for the water to drop all the way down to 78-80, so it's not leaking out that fast, but it definitely makes a difference.

Do you have your tub enclosed in something that would break the wind? Ours is currently just sitting on a fresh concrete slab next to the house, so it is pretty exposed. A wind break might help lower the energy bills. I'm planning on putting up a small fence next year for privacy and for this. Also, I did notice there is a spot around the skirt where there is a healthy gap between the tub shell and the skirt. I think I'm going to hit that with a little Great Stuff to seal it up.

 

[duganderson]

Thanks for sharing about the electrical bill and the cover recommendation. To be honest, I have not compared my electrical bills. I do however, have a wind shield on the three sides. The tub is about 3 feet from the house. There is a fence on the other two sides. One side is about 3 feet from the tub and the other side is about 8 feet from the tub.

 

[DrNinjaman]

Okay, so, more reading and observations. One: there was green corrosion on the copper sensor electrode, which would seem a likely culprit for my premature triggering issues . It seems I will need to be more attentive to keeping the sensor clean. Like, clean it every time I rinse the filters. Gonna need to get more muiriatic acid and a bucket with a lid.
Also, not mentioned in the manual, do not leave the cell out of the water, ever. That is pretty bad for the sensor apparently. Accelerates corrosion.
I'm going to check on whether CSI matters for the sensor's fouling rate. I'm usually around -.25, so if closer to zero helps, I'll make the necessary adjustments.
Finally, a bit of bad news, these sensors apparently have a typical service life of about two years max. And since this one is built into the cell, you now have two potential sources of cell failure. Which means I'm going to run it hard and put it away wet, adding chlorine manually isn't going to preserve anything as far as cell life. I suppose when the sensor dies I could still run it manually by just taking it out of the tub.
What a terrible product design. When the sensor fails, the failure mode is "continuous chlorine production". Awesome.
It also seems that while water temp does affect ORP measurements, the effect is pretty minor over the 20 degree range I'm working with.

 

[Mdragger88]

Very interesting about the sensor- good idea in theory but a little arduous in practice. When the whole thing goes u can decide if that’s the system for u or if u want to try a manually controlled one. I really love my swg’s & automation to an extent but I also am leary of things that claim to sense my needs - like automatic braking for example.
On the electricity ️ topic - our utility bill increased about $15/month after getting the spa (it’s 110v) - the increase is year round as i added a pool w/ 1.5hp pump a few months later after getting the spa. I leave mine set to 105 or 106 except in the summer or else it takes too long to heat up. In the summer i lower to 102-103 or else it will overheat as the ambient temp and the sun beating down on the cover raise the temp. I guess it really doesn’t work too hard to maintain in the summer so my power bill isn’t affected too much by running both pool & spa vs just spa in the winter. I keep my pool open from early April to at least Halloween. We use the spa pretty much every day and sometimes twice a day in the cooler temps so I don’t like turning it down unless I’m on vacation.

 

[duganderson]

Bummer........where did you get the information the "these sensors apparently have a typical service life of about two years max." Hopefully, that's not always true.

 

[DrNinjaman]

Bummer........where did you get the information the "these sensors apparently have a typical service life of about two years max." Hopefully, that's not always true.

Well that was in a discussion of ORP sensors for pool automation, not this one in particular. This one may be more robust, I don't actually know. Typical ORP sensors use two wires, either platinum or gold, and a silver-silver chloride, so they"re a little different, as this is gold and copper, but the fact remains that this cell now has two potential sources of failure rather than just the plates. Incidentally the dang swg was running again tonight, with the FC at 11ppm and the zeropoint at 14. I may have to unplug it until I get a chance to give it a proper cleaning. It's great that the cell isn't easily detachable from the controller. So I have to clean it outside in the cold. Yay. I turned the power level down to three and the zeropoint to 13. We'll see how that goes. If I lower the power level all the way, it would run for 30 minutes every 3 hours even if it triggers immediately. That would be 3.42 hrs per day. That would be about 2.5ppm chlorine increase per day. That's probably still too much in the winter, but would probably be okay in the summer.

 

[duganderson]

Thanks for the response. I'm thinking there sensor is more durable. I've read reviews of folks having them for 3-4 years with no problems.

 

[DrNinjaman]

Thanks for the response. I'm thinking there sensor is more durable. I've read reviews of folks having them for 3-4 years with no problems.

Oh one other thing, I got a response from Scott at ControlOmatic and he mentioned these sensors are usually installed in a flow stream with some glass beads to bump around and keep them clean. So it would seem having it in front of a jet should be fine. I don't, but it doesn't seem like that would make anything worse.

 

[Dirrby]

Have they offered a replacement yet? You are going above and beyond the average consumer to get it working properly and are still having issues. I would hope they work with you on this one to make it right. It's obviously not working as advertised.

 

[DrNinjaman]

Have they offered a replacement yet? You are going above and beyond the average consumer to get it working properly and are still having issues. I would hope they work with you on this one to make it right. It's obviously not working as advertised.

Ha, they barely respond to my emails.

 

[Mdragger88]

Ha, they barely respond to my emails.

That’s disheartening

 

[DrNinjaman]

Okay, so after a bit more digging and thinking on it, I think the reason the sensor is acting weird is mostly because of the temperature drop when I lower the water temp during the week.
The sensor is basically a chemical battery, right? It senses current in the electrodes due to electrical activity between the chemicals in the water and the reactive electrode. The electrical activity generated is very small, mVs, but the level of activity is related to the concentration of oxidizer in the solution. That's how it measures the chlorine. However, it is also due to the temperature. And obviously, as with most chemical reactions, the activity slows as the temperature falls. I said before that I didn't think 20 degrees was enough to mess it up too much, but I have changed my mind. The reason that it kept triggering was because the temperature kept falling, which appeared to the sensor like the FC was falling. With the weather as it is, it takes several days for the temperature in the tub to drop all the way to 78 degrees. So I'd readjust the zeropoint and the temp would go lower and it would turn back on, even though the FC was actually high. Zeropoint of 13 seems to be numb enough to keep it from turning on at high FC when the water is as cold as it gets. I'm going to keep it like that and raise the power level to run for a good long time when it does run to raise the chlorine up to around 5, in case it falls too low for a time.
This is another corner that this system cuts though. A thermocouple is just about the simplest and most robust sensor that exists and this thing could then compensate for the water temperature so this wouldn't happen. Instead I get a system that is overactive at temperatures where pathogens grow slower anyway. Awesome. This means that at normal temperatures, it will let the FC go really low, but for the winter I think that'll be fine. I'll boost it after we use it, which should compensate for our demand and keep it high enough until the dropping temp makes it sensitive enough to turn on.
What really chaps me though is that this system is significantly more expensive than the timed open loop system, yet it doesn't have the programmable timer available in that system. Nor does it have a means to disable the sensor if it fails. I'd have to get like a light timer or something similar, plug the power supply into it, and just turn the whole thing off.
All that said, the water looks and feels great. I really like this better than the fricking Frog system this thing came with. That used to get all foamy and cloudy. If I could just get the controls tweaked and reliable, I'd be all set.

 

[DrNinjaman]

Oh, I did get a response regarding the sensor life. 2-4 years was what Scott at Controlomatic said. And yeah, if it fails, it will just run all the time. I'll need to unplug the whole system to control it.