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Salt System For Spa


graysilm
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I have been considering a salt system for my spa. Obviously my main concerns are about corrosion. One thing I do not understand is how quickly do they make chlorine? If I have a light bather load during the week, and a heavy bather load during the weekends is it easy to adjust these systems to compensate up or down for chlorine demand? And how quickly do they respond? Does anyone have any experience with the saltron mini?

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Chlormaker SWCG's use 1800 - 2500ppm. This is by most standards quite low, infact it's not unusual for a non salt spa (Chlorine /Bromine) to reach that salt level simply by adding bleach over 6-8 months. Corosion is only a problem for metal components and that being said is only a problem if the components are made from low quality stainless. A common area of corosion problems is metal trim around jets. Many spas, like mine, have plastic trim. Quality spas, from reputable manufacturers usually don't have any problems even if the trims are metal but I certainly can't vouch for low end spas from questionable dealers.

As for how long they take, SWCG's generate chlorine immediately once activated. Chlormakers work on a 3hr cycle. The ON time during the cycle is dependent on the level set. In your case, you would set a low power level when the spa is not in use. You can leave the unit on low and use "BOOST" mode when you use the spa. Boost mode generates chlorine instantly and continues production for an extended time (Depending upon the set level) before returning to normal operation.

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The ControlOMatic TechniChlor, and ChlorMaker products makes up to 30 grams of chlorine per day if run 24 hours. Their MiniChlor makes up to 15 grams of chlorine per day while their MegaChlor makes up to 100 grams of chlorine per day.

30 grams of chlorine is enough to handle around 3-1/3rd person-hours of soaking so one person-hour of soaking would get handled by the system if it were to run for 7.2 hours. Boost Mode runs the unit for 4 times longer than the normal power level. The unit runs in 3-hour increments where the power level indicates the percentage of on time during that interval (power level 10 = 100%). In the extreme case where you soaked infrequently, you might set a lower power level to keep a background chlorine level of 2 ppm FC so that this is what you started with your next soak. If you don't have an ozonator, then the 24-hour chlorine loss would be around 25% or 0.5 ppm FC which in 350 gallons is 0.66 grams of chlorine. I think this is lower than what the unit can produce unless the level scale is non-linear. Spanky, do you know how the power level correlates to on-time? If the lowest setting were 3 grams of chlorine in 24-hours then that is 2.3 ppm FC so 4 times this would be 9 ppm FC which would handle 1.3 person-hours of soaking.

Given how chlorine loss in between soaks is normally a percentage loss, it would make sense for the power level to be a power scale rather than linear. If I started with a base output at level 1 of 0.2 grams of chlorine, then if this increases by 65% for each setting then I get to 30 grams at power level 10. If I started with a base output at level 1 of 0.5 grams of chlorine, then if this increases by 50% for each setting then I get to around 30 grams at power level 10. I'll bet that may be what they do. An output of 0.5 grams of chlorine in 24-hours would have the unit run for 3 minutes out of each 3 hour interval.

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Chem Geek; I don't know if there are any Control-O-Matic reps are on this fourm, I'm sure they could shed more light on the subject. I would presume that the cell output would be constant as the power supply is designed to maintain a steady, controlled current to the cell. The "Power Level" alters the "On Time" within the 3hr cycle so yes I'd presume that the daily output would be linear with 10 producing 30g down to 1 @ 3g. The trick is to balance the cell output to the natural demand of te spa then use boost to deal with bather demand. I have mine set to 5 with the ozone on 50% (on every half hr) The reason for this is 2 fold, The ozone helps with bather demand and also helps moderate the FC when the spa isn't in use. Just like the pool, you have to find the optimum output level as SWCG's can take FC levels to surprisingly high levels. My Hayward took my pool up to 12ppm before I got it dialed in. My tub seems stable at 4ppm with using every other day with "Boost Mode" but I do have to regularly monitor the FC. If we don't use the tub for more than 3 days, the FC begins to climb.

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Well if you can only go down to 3 grams per 24 hours, then in a 350 gallon spa that would be 2.25 ppm FC which is quite a lot in between bather load. With an ozonator that may create a 50% or higher 24-hour chlorine demand, then that would mean going from roughly 4 to 2 ppm so the 2 ppm from the generator would make sense though would maintain a rather high chlorine level of 4 ppm. Without an ozonator, the chlorine demand might be 25% or lower and that would mean a steady state of 8 ppm to have 25% loss be 2 ppm. So this just doesn't seem right. I'll bet that scale for on-time isn't linear and is instead geometric so that each 1 level increase has the on-time increase by 50%. That would make the most sense. Level 5 would then be 3 ppm FC which sounds about right with the ozonator on so much (probably creating nearly 75% 24-hour chlorine demand) and a stable 4 ppm FC level where the boost mode would be 4 times higher at 12 ppm FC.

Of course, I could be wrong and in fact the 30 gram per 24 hour units would be hard to dial down to a 2 ppm FC background in a 350 gallon spa with no ozonator. However, if level 5 were linear, then that would be 15 grams per 24 hours and would be 11.3 ppm FC in a 350 gallon spa which seems high even with an ozonator and bather load.

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I just checked my owners manual. The "ON" times for each power level are as follows;

L1; 2min/cycle, L2: 7.5min/cycle, L3: 15min/cycle, L4: 30min, L5: 45min, L6: 60min, L7: 90min, L8: 120min, L9: 150min and L10 180min

So I stand corrected, the output is "Graduated" and not linear

At level 5 the cell will be generating for 360mins per 24 hr period so by your calculations that would translate to about 5.5ppm. Don't forget that this is based on 100% efficiency. Since the cell generates gas bubbles, we dont know how much chlorine escapes out of the water. There is an obvious chlorine odor when you first open the cover. This, now that I think about it, is another good reason to use the Ozone. Im sure theres one hell of a science project happening in the airspace between the water and the cover as Ozone is reacting with Chlorine.

All I know for certain is that my 1320L spa maintains 3.0-4.5ppm FC with a bather load of 2 adults 20-40 min 3-4 times /week using a Chlormaker IL set to Level 5 + Ozone @ 50% (DEL MCD-50) and "Conservative" use of Boost Mode.

I think the most important point here is to remember that SWCG's are very efficient at generating chlorine and if not set correctly, can easily raise the FC of a 350gal spa to rather high levels. I understand that this is the main reason there are limited choices available in the spa market as its difficult to make a cell with such low output. Pool units are very similar, but have substantially higher chlorine output. I was amazed at how quickly my Hayward system raised my pool to almost "Shock" level

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Thanks for letting us know about the time for the level settings. So the bather load of say 2 adults 30 min 3.5 times per week would normally require around 32 grams of chlorine per week to oxidize the bather waste. Level 5 for 45 minutes every 3 hours is 25% so 7.5 grams of chlorine per day so 52.5 grams per week. That's interesting because I would have thought that your ozonator would be handling far more of the bather waste so that the needed chlorine would be roughly cut in half or 16 grams for the week plus some amount to maintain a background chlorine level. Are you sure your ozonator is working?

In pools, most saltwater chlorine generators are woefully undersized and the scenario of getting the FC too high usually only occurs when the water is cold and there is little sunlight so during the fall-to-winter transition before the SWG shuts off (usually around 50ºF).

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