New AutoPilot SWG & Chemical Controller System Installed - ORP Question

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lovemyazpool

lovemyazpool

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Nov 16, 2015
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Hey Everyone -

OK, so I just finished the installation and startup of our new AutoPilot SWG & Chemical Controller system. We also installed the Pentair IntelliFlo 3HP Pump. This system monitors Salt, ORP, pH, & Temp and controls the power output to a Stenner pH Acid Pump as well as an RC-52 SWG Cell (52,000 Gallon sized, my pool is 33,000 gallons).

23325674090_1c908e5f1e_c.jpg



So first, here are my current readings:

TC: .2
FC: 5.5
pH: 7.6
TA: 120
CH: 290
CYA: 40
Salt: 2900
Temp: 56F


The AutoPilot book tells me that my FC should be 1.0 - 3.0, pH should be 7.5, CYA should be between 60 to 80 and ORP should be 650. Right now, the system is telling me that my ORP is low (582), pH is slightly high (7.6) and it is running the SWG constantly to get the ORP up to 650.

What I do not understand is if my FC is 5.5, why would the system be attempting to produce more chlorine?
 
Welcome! I would work on getting the CYA up to the recommended level. And did you make a mistake by posting TC instead of CC?
 
I was afraid of this ....

You did such a great job in your rebuild thread that I was not totally following what equipment you were installing. I thought your chemical system was simply an acid pump. If you had asked for advice on equipment, I think you would have found the overwhelming reaction to an ORP-controlled chemical system to be a big NO!! You can do some searches on the TFP site with the search terms "ORP" and "chem geek" (keep the double quotes around the separate search terms) and you will get back a wealth of posts written by Richard (aka, chem geek) on the many short-comings of ORP control in residential, outdoor pools. I'm not going to list them all as you can easily find them for yourself.

Here's the summary though - ORP is not an effective method of chemical control because it is not actually measuring the FC concentration. ORP is sensitive to a whole collection of parameters including pH, TA, salt level, CYA concentration, sunlight (because UV from the the sun produces hydroxyl radicals), and on and on. So even if you can find the right control point for the ORP voltage, it will drift all over the place and be impossible to control. This is especially true for pools that use CYA in excess of 30ppm because CYA very heavily moderates the concentration of hypochlorous acid in the water and CYA will also foul the ORP probe membranes. This is why the manufacturers tell you to use such a low CYA concentration even though, in an Arizona pool with an SWG, you want to use HIGH CYA concentrations to keep the SWG from running at 100% all the time.

Here's my suggestion - forget about ORP control and just stick with duty cycle automation of the SWG. Use the ORP output only as a "monitor" but not as a control point. Try to establish, if it is possible, a relationship between measured FC (using your test kit) and what the ORP probe is outputting. That's the best you're going to be able to do. Otherwise you will be chasing ORP ghosts forever. pH can be automated with acid injection and a pH probe, that much is at least possible. But ORP control of your SWG is only going to frustrate you and, very likely, burn out the SWG cell with constant 100% on power.

Sorry, wish I had known what you were doing sooner.

Good luck,
Matt
 
Re: New AutoPilot SWG & Chemical Controller System Installed - ORP Question

JoyfulNoise said:
I was afraid of this ....

You did such a great job in your rebuild thread that I was not totally following what equipment you were installing. I thought your chemical system was simply an acid pump. If you had asked for advice on equipment, I think you would have found the overwhelming reaction to an ORP-controlled chemical system to be a big NO!! You can do some searches on the TFP site with the search terms "ORP" and "chem geek" (keep the double quotes around the separate search terms) and you will get back a wealth of posts written by Richard (aka, chem geek) on the many short-comings of ORP control in residential, outdoor pools. I'm not going to list them all as you can easily find them for yourself.

Here's the summary though - ORP is not an effective method of chemical control because it is not actually measuring the FC concentration. ORP is sensitive to a whole collection of parameters including pH, TA, salt level, CYA concentration, sunlight (because UV from the the sun produces hydroxyl radicals), and on and on. So even if you can find the right control point for the ORP voltage, it will drift all over the place and be impossible to control. This is especially true for pools that use CYA in excess of 30ppm because CYA very heavily moderates the concentration of hypochlorous acid in the water and CYA will also foul the ORP probe membranes. This is why the manufacturers tell you to use such a low CYA concentration even though, in an Arizona pool with an SWG, you want to use HIGH CYA concentrations to keep the SWG from running at 100% all the time.

Here's my suggestion - forget about ORP control and just stick with duty cycle automation of the SWG. Use the ORP output only as a "monitor" but not as a control point. Try to establish, if it is possible, a relationship between measured FC (using your test kit) and what the ORP probe is outputting. That's the best you're going to be able to do. Otherwise you will be chasing ORP ghosts forever. pH can be automated with acid injection and a pH probe, that much is at least possible. But ORP control of your SWG is only going to frustrate you and, very likely, burn out the SWG cell with constant 100% on power.

Sorry, wish I had known what you were doing sooner.

Good luck,
Matt
Click to expand...


Hi Matt -

Thank you for the advice. I did look around here on TFP and the AutoPilot system was recommended as a good SWG system.

So basically I need to figure out a good baseline for my FC, then a good runtime for my cell (mine is sized for a 52,000 gallon pool and I am at 33,000 gallons), then program my pump runtimes to coordinate with the amount of time it takes to get my my FC level (1.0 to 3.0 correct?). Without the pump running, the cell will shut down automatically.

I can also adjust the ORP setpoint up or down as well and it would appear that I need to adjust down. I can always uses the "24 Hour Boost" option the system has to run the cell at 100% for 24 hours if I see a dip in FC.

Does this sound right..?

- - - Updated - - -

Casey said:
Welcome! I would work on getting the CYA up to the recommended level. And did you make a mistake by posting TC instead of CC?
Click to expand...

Thanks Casey - I am working on the CYA now. I will shoot for 70 and see where that leads me....
 
Re: New AutoPilot SWG & Chemical Controller System Installed - ORP Question

lovemyazpool said:
Hi Matt -

Thank you for the advice. I did look around here on TFP and the AutoPilot system was recommended as a good SWG system.

So basically I need to figure out a good baseline for my FC, then a good runtime for my cell (mine is sized for a 52,000 gallon pool and I am at 33,000 gallons), then program my pump runtimes to coordinate with the amount of time it takes to get my my FC level (1.0 to 3.0 correct?). Without the pump running, the cell will shut down automatically.

I can also adjust the ORP setpoint up or down as well and it would appear that I need to adjust down. I can always uses the "24 Hour Boost" option the system has to run the cell at 100% for 24 hours if I see a dip in FC.

Does this sound right..?
Click to expand...

Yes, AutoPilot is good. But the salt water systems typically can be run independent of any chemical control system. All the major manufacturers sell chemical dosing systems (Pentair IntelliChem, Hayward Sense and Dispense, etc), but all them sell SWG's that simply run on standard duty-cycle output (no ORP control point).

Let's just hit the basics of SWG's so we're all on the same page. Your SWG can only produce a fixed amount of chlorine gas each 24-hour period. No more, no less. For my IC-40, I think it's 1.4lbs of Cl gas per day. Not sure what yours is, but it should be listed in the manual. So, if you do the PoolMath (Effects of Adding Chemicals section), you will find that you can only add so much FC per day (assuming 100% on time for 24 hours). Again, that's the physical limit of the cell. So in reality, Boost Mode is really useless (in my opinion) because it doesn't do much for you and it runs the cell really hard. If you ever have an algae problem or a high FC loss problem, then you have to manually chlorinate with bleach because there is no way an SWG can keep up with an algae bloom and chlorinate a pool to high levels. SWG's maintain a particular FC level when the water is clean, they can not create clean water from an algae filled green swamp.

With those limitations in mind, you should try to manually control your SWG and pump run times using your Taylor test kit as your direct measurement of FC and just forget about ORP for the moment. Also, you can't mix the recommended levels in the SWG owners manual with TFP's recommendations, they are not compatible. So if you use 70ppm CYA, then you need to follow the TFP guidelines for the correct FC/CYA ratio. Typically what's printed in all pool equipment user manuals is just the standard boilerplate industry guidelines which are, in many cases, incorrect or not effective.

Once you get your pool under control, then you can start looking at the ORP signal to see if you can find a correlation; you should still maintain operational control over the SWG output and only use the ORP signal as readout, not a control point. Finding a correlation will be very tricky and it is the thing that most people find very frustrating about ORP control. The voltage output tends to just randomly wander all over the place with no correlation to the actual chemical levels in the pool. I forget the thread name, but someone posted graphs of the various chemical levels they were measuring with ORP voltage, water temps and time of day. While all the actual chemistry values stayed relatively within their respective set points, the ORP graph of voltage versus time looked completely random. There was literally no correlation between ORP and any of the important chemistry levels. The only correlation you could see in the data was that the ORP voltage would go up and down with daylight and nighttime because of the UV exposure. No other parameter (FC, pH, TA, water temp) was having any effect on the ORP output.

Good luck,
Matt
 
OK, after adding stabilizer (liquid) and salt yesterday, here are my new readings:

CC: 0
FC: 7.6
pH: 7.6
TA: 120
CH: 290
CYA: 70
Salt: 3100
Temp: 56F
ORP: 685


I currently have my pump running at a very low power setting 24*7 which means the Autopilot system will generate chlorine 24*7 if it thinks it needs it. There is a way to shut off ORP measurements and put the system into sanitizer mode only which based on what Matt (JoyfulNoise) was saying sounds like the best way for me to move forward right now.

It looks like my pH has stabilized. I have set the system to 7.5 and the acid pump does run a very little bit every few minutes. According to the Total Control system manual, that pump only puts out something like a maximum of 2 gallons per day and that it only adds acid very, very slowly to manage the pH. There is an acid boost feature, but I figured I would let the system do its own thing and make sure it can get the pH where it needs to be and keep it there.

I currently have the salt test strips which seem to indicate that I need more salt, I am going to get the Taylor regents for the salt test today (as well as have NSP run a salt test for me (I know, I know, pool store tests suck!) and see if they all match and adjust my salt from there.

I will test FC/CC again tonight and see where it is at again since I just added the stabilizer yesterday.
 
If you SWG is happy (no low salt alarms), then leave the salt alone until you get the Taylor drops. It is way too easy to over salt a pool and you are not going to hurt anything if you wait a few days to get a proper test kit. I used both strips and the Taylor drops and the K-1766 is way more accurate than the strips are.
 
JoyfulNoise said:
If you SWG is happy (no low salt alarms), then leave the salt alone until you get the Taylor drops. It is way too easy to over salt a pool and you are not going to hurt anything if you wait a few days to get a proper test kit. I used both strips and the Taylor drops and the K-1766 is way more accurate than the strips are.
Click to expand...

Ordered the salt test regents today, in the mean time I have switched off the ORP system and have gone to a Purifier setting (in %) only. Once I determine how long I want my pump to run, I will start working on the purifier settings to keep my FC around 3.0!
 

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lovemyazpool said:
Ordered the salt test regents today, in the mean time I have switched off the ORP system and have gone to a Purifier setting (in %) only. Once I determine how long I want my pump to run, I will start working on the purifier settings to keep my FC around 3.0!
Click to expand...

You don't want to target the minimum FC level, you want to target the TARGET level. The minimum FC level is a "floor" value, a number you should never go below - your avatar looks like a pilot so I'll say it like this, the minimum FC value of 3ppm is your STALL SPEED. Don't go there! You want your FC up around 5ppm when the pumps shutoff for the day and the SWG is no longer running.

Oh, and another point, it's winter. Your FC demand is going to be very low because algae really doesn't grow much below 60F. There is no bather load in your pool and so your oxidation load is low too. So it should be very easy to get your FC up to 5ppm and hold there with very little pump run time and a low % output on the SWG. In fact, when the water gets cold enough, your SWG doesn't run. Cold water cutoff is typically around 56-58F. So you do not need to run your pump 24X7. You're wasting electricity. At this point, you run your pump long enough to get the level of pool cleanliness you like and that's it. Try to run your pump during the times of the day when you get maximum sun exposure on the pool in case it warms up enough for the SWG to run. As we approach spring and summer, you'll be increasing your pump run times and SWG output to maintain 5ppm.
 
In my case, I also noticed that my ORP reading was coming up low (~~570) even when the FC was around 6. After opening up the ORP sensor, cleaning it with a little toothpaste / toothbrush and putting it back, it started showing ORP as around 720.

Before cleaning the ORP sensor, I noticed that a bunch of bubbles were sticking to the sensor bulb. These may have skewed the sensor's readings... but now, I clean the sensor every week or so.. and I am extremely happy with the setup.

I ALWAYS check FC periodically and my ORP seems to be perfectly in line with the FC amounts.. Shows ~~700+ when FC levels are around 3-4 .. and if it drops below 2, ORP readings also come down to 640, thereby starting the chlorinator automatically.

I am no chem expert, but I have noticed that the key to all this is that the pH level must be between 7.5 and 7.6. Anything outside this also skews the ORP values. So, my stenner is maintaining 7.5, FC 3~5 and ORP values are around 730~740.

------
This is a good read http://www.sbcontrol.com/orpuse.pdf
 
Re: New AutoPilot SWG & Chemical Controller System Installed - ORP Question

JoyfulNoise said:
You don't want to target the minimum FC level, you want to target the TARGET level. The minimum FC level is a "floor" value, a number you should never go below - your avatar looks like a pilot so I'll say it like this, the minimum FC value of 3ppm is your STALL SPEED. Don't go there! You want your FC up around 5ppm when the pumps shutoff for the day and the SWG is no longer running.

Oh, and another point, it's winter. Your FC demand is going to be very low because algae really doesn't grow much below 60F. There is no bather load in your pool and so your oxidation load is low too. So it should be very easy to get your FC up to 5ppm and hold there with very little pump run time and a low % output on the SWG. In fact, when the water gets cold enough, your SWG doesn't run. Cold water cutoff is typically around 56-58F. So you do not need to run your pump 24X7. You're wasting electricity. At this point, you run your pump long enough to get the level of pool cleanliness you like and that's it. Try to run your pump during the times of the day when you get maximum sun exposure on the pool in case it warms up enough for the SWG to run. As we approach spring and summer, you'll be increasing your pump run time and SWG output to maintain 5ppm.
Click to expand...


Understood...thanks! I'll reprogram the pump for midlevel daytime operation and start with 4 to 6 hours and see how that makes it look and go from there. Right now I have the ORP shutoff so I will wait for the FC level to drop to 4ppm, and set that as my ORP 'floor' and see how it works from there.

- - - Updated - - -

trbvm said:
In my case, I also noticed that my ORP reading was coming up low (~~570) even when the FC was around 6. After opening up the ORP sensor, cleaning it with a little toothpaste / toothbrush and putting it back, it started showing ORP as around 720.
Click to expand...

My system is brand new so I don't think it needs to be cleaned as of yet. I will check for bubbles however! Thanks for the link.
 
This is one area where even the manufacturers are forthcoming in the need for regular maintenance of ORP (and pH) probes. See the Hayward Sense and Dispense manual:

Probe Maintenance
The probes must be clean and free from oil, chemical deposits and contamination to function properly. After saturation in pool or spa water, the probes may need to be cleaned on a weekly or monthly basis depending on bather load and other pool specific characteristics. Slow response, increased need to calibrate pH, and inconsis- tent readings are indications that the probes are in need of cleaning.
Click to expand...

or the Pentair IntelliChem Water Chemistry Controller manual:

Sensor Maintenance
The Flow Cell sensors must be clean and free from oil, chemical deposits and contamination to function properly. After saturation in pool or spa water, the sensors may need to be cleaned on a weekly or monthly basis depending on bather load and other pool speci c characteristics. Slow response, increased need to calibrate pH, and inconsistent readings are indications that the probes are in need of cleaning.
Click to expand...

Both manuals also say to "Always test water chemistry with a quality manual test kit." The idea is that these systems may be used for short-term process control if you regularly maintain them by cleaning and comparing against a known good test kit or standard. This is why they make some sense in commercial/public higher bather-load pools where responsiveness needs to be fairly fast and where state pool codes already require manual testing multiple times per day. In a residential pool, relying on these finicky electronic sensors is riskier mostly because people think they are "set and forget" when they are not. Even so, a more expensive but more reliable amperometric sensor (such as from Halogen Systems) would be better if cost was not a consideration.
 
trbvm said:
In my case, I also noticed that my ORP reading was coming up low (~~570) even when the FC was around 6. After opening up the ORP sensor, cleaning it with a little toothpaste / toothbrush and putting it back, it started showing ORP as around 720.

Before cleaning the ORP sensor, I noticed that a bunch of bubbles were sticking to the sensor bulb. These may have skewed the sensor's readings... but now, I clean the sensor every week or so.. and I am extremely happy with the setup.

I ALWAYS check FC periodically and my ORP seems to be perfectly in line with the FC amounts.. Shows ~~700+ when FC levels are around 3-4 .. and if it drops below 2, ORP readings also come down to 640, thereby starting the chlorinator automatically.

I am no chem expert, but I have noticed that the key to all this is that the pH level must be between 7.5 and 7.6. Anything outside this also skews the ORP values. So, my stenner is maintaining 7.5, FC 3~5 and ORP values are around 730~740.

------
This is a good read http://www.sbcontrol.com/orpuse.pdf
Click to expand...

I'm curious, what CYA level are you using with your system?


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
 
OK, it seems like the system is settling in some more. I still have ORP mode on my autopilot shut off and I have the Purifier set at 0% since my FC is at 6.6 today (down from 7.6 a few days ago).

Here are my current readings:


CC: 0
FC: 6.6
pH: 7.5
TA: 120
CYA: 85
CH: 320
Salt: 3100
Temp: 53F
ORP: 633


So other than my FC being a little high (shooting for TFP recommended 4 to 6 (shooting for 5), it looks like my TA is a little high and other than that, it seems ok. My plan is to allow the FC to fall to the 5 mark and then check the ORP value on my system and set that as my target for the SWG, then turn ORP back on and allow it to maintain the ORP that matches my FC of 5 and see if it will actually keep the FC where I want it. If not, I can always go back to Purifier mode and play with the power settings and %s.

I am running my VF pump right now for about 12 hours at night at about 40gpm to get a turn over. My water is crystal clear right now and I could run the pump a lot less I imagine, but until I see how long I need to run it for my FC, I won't really know what to target so I figured I would just set it for 12 hours on a low setting and adjust it from there once I start using the SWG to manage my FC.
 
Sounds like a good plan.

Your TA is definitely on the high side for an Arizona pool. High TA can lead to a fast pH rise when sources of aeration are present. You probably won't experience high acid demand in the winter months but I would bet that you'll need to get your TA down as the warmer weather kicks in. Your acid pump likely will not be able to help you lower the TA much because it will have flow rate/volume limits. That's ok because you really just want your acid pump to maintain a pH not really to make large adjustments in water parameters. So keep an eye on your acid use and don't be surprised if your pH rises.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
 
It's the only way to lower TA. You need to do the process separate from your acid injection system as you need to add a good deal of acid and then let it come back up. So you need to disable the acid pump or set the pH setpoint to something like 7.8 so it doesn't add acid.

Problem is that it's cold right now so the process will be really SLOW.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
 

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