Intellichem, ORP and FC level question (low ORP, but high FC)

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S

shermanator

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Jun 17, 2011
4
Hi All,

I have a 16k gunite pool and last season I installed an Easytouch, IntelliChem with Intellichlor. The intellichem runs the intellichlor based on ORP and I have a pump/container for muriatic acid.

As things are setup, I pretty much always have high FC levels. In the 10-15 ppm range and I'd like to keep the pool much closer to 5 ppm max. But the ORP levels look good or even on the low side (so clearly the ORP readings are low and triggering the intellichlor to come on too often). Right now the FC is 15 ppm and ORP is 635.

Two questions:

1) My CYA is high (60 ppm), is that the cause of the artificially low ORP levels? Should I keep it closer to 30 ppm? What other issues can contribute to artificially low readings on the ORP meter? My other readings are: Salt = 3400, pH = 7.4, Alk = 85, Hardness = 370.

2) If it's not just high CYA doing this, should I lower the set point for turning on the intellichlor? It's set at whatever the default setting is.

Thank you!!!
 
Welcome to TFP!

We don't recommend the use of ORP based control for a residential pool. Standard percentage based control is more than sufficient and does not have the additional expenses, additional maintenance, shorter SWG cell lifetime, and frequent problems that ORP based control has.

If using ORP: CYA of 60 is too high for ORP based control. 50 is about the limit, and even that is marginal. You need to adjust your ORP target to get the desired FC level. Expect wide variations in FC level, as a couple of things you have no control over will change the ORP reading in ways that do not relate to FC levels.

Separately, I recommend a PH target of 7.6 or 7.7. That will make your TA a bit more stable.
 
Thanks Jason!

I will try to switch the intellichlor control away from the intellichem and go the percentage route. I know my CYA is way too high, will the SWG work OK for now with that CYA? I'm going to drain the pool at the beginning of next season to acid wash, and bring in a truck of clean water so I will be able to fix all the levels then. But I'm on a well and I'd do more damage by re-filling the whole thing with well water.

I guess my questions is: if I move to percentage control, will the high CYA be OK for this season? Or should I plan on draining and refilling now?

And I think my intellichem is set to 7.6, but for some reason it usually sits at 7.4.

Thanks again for the help! Funny that I joined TFP 3 years ago, but finally made a post. =)
 
Your CYA is too high for ORP control (target 30 to 40), but it is too low for percentage control (target 70 to 80). For percentage control CYA at 60 will be fine for the moment.

So, you are fine for the moment, but should raise CYA a little after switching to percentage control.
 
JasonLion said:
Your CYA is too high for ORP control (target 30 to 40), but it is too low for percentage control (target 70 to 80). For percentage control CYA at 60 will be fine for the moment.
Click to expand...

I understand that if you want to use ORP to control you SWG, you need to keep the CYA under 50. I used to use ORP to control the SWG, but I encountered some of the issues that you have brought up in other threads. I'm now using %. But, I still like to check the ORP level. If I raise my CYA to the 70-80 range, will that cause my ORP sensor to give incorrect results?
 
Higher CYA level won't make the ORP readings "incorrect" but it will reduce the influence of chlorine on ORP. When CYA is very low, adding 2 ppm of chlorine raises ORP dramatically. When CYA is high adding 2 ppm of chlorine still raises ORP, but not by nearly as much. Meanwhile some of the other things that affect ORP remain just as effective as they were before, making it more difficult to distinguish the effect of chlorine from the effects of other things which change ORP readings.
 
Okay, I have my intellichem now set to use percentage and I'll stick with that this season (maybe next year with all new water, I'll venture to trying ORP control again).

I set it to 25%, just kind of randomly. I figure that is a low starting point (?), but since my FC is currently 15 ppm, I need to get it lower for now. Is there any ballpark formula for what percent I should use as the initial value? I'll check FC daily and adjust, but just curious where most people start (I didn't have the IC40 before the intellichem, so I don't have a feel for how to use percentage control). Pool is 16k gal, I have an IC40 and I run the pumps (and thus SWG) 12 hours a day.

I also looked into setting the intellichem to pH 7.7, but it only goes up to 7.6, unfortunately.

I wish I would have read up on the intellichem more before buying it. I thought the ORP control was going to be such a nice feature. At least the pH control seems to work fine.
 
Normally you start at 50% and see where that gets you, and then adjust as needed. In practice it doesn't much matter where you start.

There is a way to do a bunch of math and get a better starting point, but it is complex and error prone. And besides, you always need to switch to trying it out and adjusting as needed in the end anyway, so it is conceptually simpler to just do that right from the start.
 
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