ORP Probe Failing; Current in the Water; Bonding Issue?

[VAPoolboy788]

Commercial Pool Keeps blowing ORP Probes!

Suspect: Current in the water

History: Commercial pool in Norfolk, VA. Apartment Complex, built 11/20014, Concrete. Pool on second floor equipment on first floor. Equipped with HCC200 system, (2) Aquarite salt generators w/ T-15 cells, Triton II Commercial Sand Filter, Whisperflo Pump, (1) Universal Color Logic (White), 17,500 Gallons, (3) Deck jets, (6) hand rails (S/S)
Management has never been able to maintain proper chlorine level w/ automation ORP levels vary hour to hour, day to day.
The pool has first been replaced with new probes, they read in the 350 mV range with 3.5 ppm Cl with DPD test
Replaced the HCC2000 system still has the same problem
Replaced probes again, same problem
Hayward has authorized and provided these products
I have been disconnected from this issue until today, and installed a CAT4000 to replace system
Same problem low ORP and good Cl levels, but system locks out and stops producing chlorine
Removed ORP probe and installed new probe but instead of installing in sample well, placed in bucket of pool water.
Removed from the circulation system, probe is reading more accurate mV at 600
pH probe is accurate both in bucket test and in sample well

Hypothesis: This is not developed by myself, but by speaking with Pat with CAT controllers who is the developer of the system. The only possible issue is there is an electrical current in the circulation system that is damaging the probes. The problem is almost instantaneous and the ORP probe is destroyed

What I am asking: I need an electrician that understands the equipotential bonding grid and can explain why and how to find the break in ground with the best resolve to the problem. I have considered running a bonding wire #8 from the panel ground to the pool equipment in the equipment room but dont want to keep damaging ORP Probes, they are not cheap. There is nothing within 5' or 10' of pool that could contribute to this problem I am at a loss.

Very open to ideas and thoughts. I need to readdress issue by 8/17/15. Thanks in Advance

 

[chem geek]

See ORP Control. The problem is related to your use of saltwater chlorine generators. What is the location of your ORP system? If your generator, which outputs hydrogen gas bubbles, goes out a return too close to a skimmer or gutter returning water back to your equipment pad where your ORP is located, then you may be getting hydrogen gas bubbles that will mess up your ORP readings.

Why don't you try your ORP system with the SWG turned off for an extended period of time. Say you only run it during the day -- then try the ORP system in the morning where the pump is running but you have the SWG system turned off. Does it work? If so then it is related to the SWG system. Could be the hydrogen gas bubbles if the ORP system doesn't fail the instant that the SWG is turned on.

You say that this may be an electrical bonding problem and that the ORP is destroyed, but are you sure about that? With the ORP system measuring low in the pool, take it out and measure a bucket of chlorinated water with reasonably high FC level, say 5 or 10 ppm with no CYA. What happens then? If it measures OK, then the ORP is not actually destroyed, but rather temporarily disabled.

By the way, this is one of several reasons why we do not recommend ORP controllers, at least not for residential pools. For commercial/public pools they are OK using a setpoint, but ultimately relying on the separately measured FC and CYA levels. Then again, it seems like there's an issue with SWG systems and ORP controllers that needs to be figured out.

 

[lembi]

I agree with chem geek that this is not a problem with the probe, and i also think that it's not a problem with the electrical bonding or an external current in the water. The measurement amplifiers are galvanically isolated, so that a current in the water shouldn't have any effect on the probe and the reading.
You can check the probe - like chem geek said - with a bucket of fresh water and a FC level of 3..5 ppm (no CYA). This should result in an ORP Level above 800mV.

It's more a problem with the water itself or better with the SWG, generating something else than chlorine only. We are discovering same problems in several pools (not in all). And in no case the probe or the system itself is the reason for the low ORP reading.

Maybe you can switch off the SWG for several days and try dosing CH or liquid chlorine for this time. I think that this will result in normal ORP readings -> so it should be the running SWG causing the problems (but not due to the fact that it is bringing a voltage into the water).



Independently of that... it can be also just a problem with a too low production rate and a too high bather load (even if you reach "normal" FC Levels). We have here, for example, no problems with pools using an "oversized" SWG, where the runtime of the SWG is usually rather short (i.e. SWG for 30-40.000 gallon-pool used for a 6.500 gallon pool). But if you have a high CYA level the runtime will always be longer to raise ORP back to the desired level (I'm from Germany, we normally don't use any CYA here - No CYA results in a faster reaction of the ORP on chlorine dosing)

Have you checked the salinity of the water? How long is the daily runtime of the SWG? 24/7 because of low ORP reading?

>>Pool on second floor
So it's indoor? Or is it outside on the roof?


Alex

 

[VAPoolboy788]

Pool is outdoor in a courtyard above the parking garage. Pool equipment in the parking garage. Apartments built up aboave and around the pool. Salinity is 3200, and the salt systems work just fine if I take the flow switches off the automation sytem. Automation locks out because ORP is too low. Our company has 35 years experience building pools and all modern pools are equipped with salt. Never had an issue like this.

 

[VAPoolboy788]

Pool is only 17,500 Gallons with (2) T-15 Cells. The SWG's are not the problem because the problem starts before they are introduced to the system. Immediately after installing a brand new system or probes the ORP reads approx 320-350 (in the testing wells). I have put brand new PRO-25-Au probes into a cup of the same pool water and they read 625-635 mV. Will hold as long as I dont put them into the circulated water. Once they are introduced to circulated water they fail and never read right again.

 

[JoyfulNoise]

Two questions -

1. Possible chemical contaminant in the water? Have you and your company had control of the pool chemistry? Do your water test parameters all look normal?

2. Can you hire an electrician that specializes in detecting stray voltages? You said the pool is built on top of a parking structure. Any apartment I ever lived in with a dedicated parking garage always had all of their electrical/mechanical rooms in the garage. I wonder if something in that garage is causing a problem.


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[Bama Rambler]

I'd like to know if the probes are actually damaged or if they're just reading wrong when in in the pool.

If they are being damaged then I agree that you need someone well versed in stray voltages and also a full chem panel ran.

 

[JoyfulNoise]

I'd like to know if the probes are actually damaged or if they're just reading wrong when in in the pool.

If they are being damaged then I agree that you need someone well versed in stray voltages and also a full chem panel ran.

I think the OP answered that - if they go into the pool water they are irreversibly changed.

Immediately after installing a brand new system or probes the ORP reads approx 320-350 (in the testing wells). I have put brand new PRO-25-Au probes into a cup of the same pool water and they read 625-635 mV. Will hold as long as I dont put them into the circulated water. Once they are introduced to circulated water they fail and never read right again.

Sent from my iPhone using Tapatalk

 

[lembi]

So if you remove the probes from the testing wells an put them back into the bucket they still only read 325mV?
Have you tried to clean them? ... Put them in a glass of water with at least 10% chlorine for about 30 minutes and then try to measure the bucket again.

What kind of metal components are used in the pool and in the piping? ... Feeders, Adapters... anything made of brass (for example)? in lower quality then 316L stainless steel? Or different types of metals? Are these parts electrically connected to the ground?

 

[Balex]

I agree with chem geek that this is not a problem with the probe, and i also think that it's not a problem with the electrical bonding or an external current in the water. The measurement amplifiers are galvanically isolated, so that a current in the water shouldn't have any effect on the probe and the reading.
You can check the probe - like chem geek said - with a bucket of fresh water and a FC level of 3..5 ppm (no CYA). This should result in an ORP Level above 800mV.

It's more a problem with the water itself or better with the SWG, generating something else than chlorine only. We are discovering same problems in several pools (not in all). And in no case the probe or the system itself is the reason for the low ORP reading.

Maybe you can switch off the SWG for several days and try dosing CH or liquid chlorine for this time. I think that this will result in normal ORP readings -> so it should be the running SWG causing the problems (but not due to the fact that it is bringing a voltage into the water).



Independently of that... it can be also just a problem with a too low production rate and a too high bather load (even if you reach "normal" FC Levels). We have here, for example, no problems with pools using an "oversized" SWG, where the runtime of the SWG is usually rather short (i.e. SWG for 30-40.000 gallon-pool used for a 6.500 gallon pool). But if you have a high CYA level the runtime will always be longer to raise ORP back to the desired level (I'm from Germany, we normally don't use any CYA here - No CYA results in a faster reaction of the ORP on chlorine dosing)

Have you checked the salinity of the water? How long is the daily runtime of the SWG? 24/7 because of low ORP reading?

>>Pool on second floor
So it's indoor? Or is it outside on the roof?


Alex

Thank You Thank You Thank You.
My ORP sensor readings were dropping like a rock whenever I turned my system on. I partly drained the pool to reduce CYA levels, I replaced the ORP sensor, I replaced the SWG electrode, I tore out my hair, and then I found this forum. With the help of he information here, I realized that if I unplugged the SWG, the ORP returned to normal and stayed here even when the system was running. I was on the verge of converting to a chlorine pool, when I took one last at my setup and discovered the copper ground wire on the SWG had come loose. Reattached the ground wire and Voila, system is back to working perfectly.

 

[Spa Owner]

Just a cautious word to the wise...ORP and SWG do not play nice.

Sometimes they work. Sometimes they don't.

Then to make life really interesting sometimes the working ones decide not to work. Fortunately the not working ones usually don't start working so that's one blessing.

The original train of thought is it was an earth related issue. It isn't on testing multiple sites.

I personally suspect formation of free radicals with the stray electron but why in some and not others I don't understand and to date have not researched to get a better idea.