another ORP - FC question

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fredpamm

0
May 14, 2017
31
FRANKFORT, il
I have a SWG (Intellichlor) pool (10,000 gallon)which also has an Intellichem (Acid tank only). I can never seem to get the ORP right. My pool guy just left and said that my FC was above 5 (which I knew because of the chlorine smell in my clothes. My intellichem has the following readings:
PH 7.70 set at 7.4(pool guy reading 7.4 confirmed by pool store)
ORP 582 set at 700
Calcium Hardness 300
alkalinity 110
CYA 70

So I have read everything on ORP and Chlorine and it seems that you can't correlate the two. So how do I get the chlorine down to 4? I've removed the probes and have cleaned them with Dawn so they are clean. The probe bowl is on the sunny side of the house so I have aluminum foil covering the probe bowl as recommended my Pentair so the sun doesn't affect the readings. I have the PH tweaked down as far as I can.

So what can I do?
 
Last edited:
Fred,

Sadly, we have found that you are not alone.. We do not recommend using the ORP system at all..

That said, you cannot have a CYA of over 30, if you are trying to use an ORP probe..

If I bought a pool that had an ORP system, I would shut it off and save myself the trouble. I have three saltwater pools, that have been running using the TFP pool care process... In the combined 20 years of operation, I have never had a "chlorine smell", nor have I ever had algae...

I like the idea that I am the one in charge of my pool, and that I do not have to rely on some "system" to keep my chemicals in range.

Thanks,

Jim R.
 
Fred,

I am not sure, but let me do a little research and see what I can find out.

It might make sense to find a local Pentair guy who can evaluate your whole system.

Let's see if we can get some more of our members to chime in...

Calling @bdavis466 ... Do you have any input on the operation of the IntelliChem and SWCG??

Thanks,

Jim R.
 
I would disconnect the IntelliChem and disconnect the cable from the SWG to the Inettlichem and connect it directly into whichever Pentair automation box you have.

it would be easier giving you specifics if you create your signature .
 
Fred,

So how does your home pool work with just the IntelliChlor and no IntelliChem, compared to the seasonal house with the IntelliChem?

What is the main reason for the IntelliChem, if you have a pool guy?

Thanks,

Jim R.
 
Intellichlor without intellichem just plugs into the intellitouch and is controlled though the inside control panel. The Intellichlor with intellichem is controlled by intellichem. The reason I have the intellichem is that I am not at this house for most of the year so I want to make sure the chemicals are balanced and that I can use screen logic to see what the readings are remotely.
 
Get the WaterGuru to get remote readings of your FC and pH. Although it will not make adjustments for you if the water chemisrty gets off. But it will give you notice.
 
Fred,

In theory, it sounds like that perfect way to maintain a "remote" pool. Unfortunately, we have found it tends to not work well in real life.. :(

For salt cells in particular, you are caught in between a rock and a hard place. The ORP won't give accurate data if the CYA is more than 30. And with a CYA of only 30, the salt cell will have a hard time generating the amount of chlorine you need as the sun will just consume your FC.

It is pretty easy to tell people to take care of their own pool, but not sure how to respond when the pool is at a vacation home that is not being used most of the time.

I guess since you already have the equipment, I would try reducing the CYA to less than 30 and see how the system worked.. It will work or it won't.. If it works for you, then great.. If not, I'd probably have the pool guy manually use the equipment to maintain the chemicals when you are not there.

Thanks,

Jim R.
 

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I feel Fred's pain.

I have the same setup. The only semblance of success I'm seeing in having the system work closed loop based on ORP, is to set the intellichem to dose ORP by time, not to setpoint.

For my pool, if the intellichlor is left on 100% of the time, it will drive ORP down so far (about -150mv delta) it will stay on basically forever, burn through acid at about a gallon/24 hours, and never reach ORP setpoint. Its does eventually bottom at some number in the low 500s but never rises and so the FC goes off the chart, rising about 7ppm in 24 hours. After manually turning off the intellichlor by lowering the ORP setpoint, ORP will rise almost immediately and continue to rise over the next couple of days into the high 700s or low 800s usually. Then it will slowly drop proportionally to the FC all while cycling up and down due to the sun. I wish I had a schematic for the probe circuitry in the intellichem. I'd love to know what kind of isolation (if its isolated), amplification, and filtering are on the probe input. Whats the response time constant?

Some say this is due to hydrogen gas production and then off-gas, which I'm sure is at least partly to mostly right, based on months of experiments and reading papers, even with a gold tip probe which Sensorex and others recommend for salt water. (Is there a way to "getter" or remove the hydrogen gas in the flow cell?) I think for my pool's installation (which is not exactly per the manual for intellichem) and based on a few articles and posts I've read, a component of the negative offset might also be electrical current in the pool water but I haven't tested/proven that yet. I've looked for errors in grounding and bonding creating ground loops but nothing obvious has popped out at me. You can see noise (about 1mv) in the ORP when the cell is energized though.

So far by experimentation, I've determined that by setting the intellichem to dose intellichlor for 45 minutes on and 15 minutes off, I can keep the system from entering a permanent on runaway condition. The ORP still drops, BUT it rises over time so it eventually will reach setpoint and turn off. This is highly dependent on the on/off ratio and I don't know how stable it will be as we heat up here into summer. I may have to trim it.

I wish the intellichem would allow the cell to be turned on to a percentage value. It seems it only bangs the cell on or off at 100%. I'm pretty sure if I could tone it down enough to stay below the critical "hydrogen limit" the system would be more workable.

Confounding me a bit is my CYA is 50 and so I get a big swing in ORP just from the sun during the lengthening clear days in Arizona. I'd like to see what happens when CYA drops to about 30. I'm hoping that will happen during the summer under the intense sun. I so far am unwilling to drain the pool to test this.

If you want to experiment, I highly recommend you keep intellichem in charge of the pH. It works fantastic for that and a stable pH removes a HUGE variable in ORP level. If my pH also moved around a lot it would be impossible to develop any sort of work around.

I'm an engineer and this bothers me no end. Especially since there are anecdotes and videos from professional pool people out of Hawaii using intellichem all over with salt cells. I can't see these folks running around all the time manually adjusting ORP set points all the time. Is it something about the water in the southwest? Mineral content? I know folks will recommend we just abandon ORP control, but I'm not there yet.
 
Scotts,

Thanks for the feedback.. It is pretty much what others have said, one way or the other..

I have three saltwater pools and I spend about an hour a week taking care of all three of them.. This includes cleaning the skimmer baskets, cleaning and running the robot, brushing the steps, testing the chemicals, etc, etc..

You make me jealous that I don't have an IntelliChem to make my life easier... :poke:

Thanks,

Jim R.
 
Thant's funny for sure, Jim.

Even with the troubles I still only visit the pool once a week to clean the skimmer basket, see if the acid tank needs a fill, and check chemistry. I can still turn the cell on and off from home by moving the ORP setpoint and I'm getting really good at interpolating FC levels from the last known good measurement. I know when ORP, without the cell on, starts to drop more rapidly I'm at about 3-4ppm FC.

Let's see what happens this summer.
 
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