Autopilot Digital Random Salt Cravings

[EnoughToBeDangerous]

Every now and then my autopilot digital starts blinking that darn red light and demanding 40, or 80 or 107 lbs of salt, but when I test the water with a taylor kit I bought to help with this situation, the salt ppm is good. I don't really want to pay for and dump hundreds of excess lbs of salt into my pool, or have it be in my pool. Sometimes I have a pool company tend my pool in the summer, and I tried explaining this to them, but they don't trust me or my test kit and just want to do whatever the autopilot says. What's the deal? I adjusted the calibration on the autopilot to match the taylor kit last year. Do I need to recalibrate this more often than that?

Edit: Actually theres another detail that my be important here. I recently added a heat pump unit. The heat pump heats the water before the salt generator, the the SWG thinks the water is warmer than it really is when the pool is heating. I'm not sure what to do about this, or if it could be related to the salt cravings. Any advice appreciated!

Thanks!

 

[JamesW]

 

[EnoughToBeDangerous]

Thanks. No muriatic acid on site, I use dry acid when I need it, which is not often. Any reason not to use vinegar?

 

[JamesW]

Vinegar might work.

 

[EnoughToBeDangerous]

Thanks, I'll give it a shot this weekend. Any comment on the heat pump temperature distoration issue with the autopilot?

 

[JamesW]

The salinity is temperature compensated, so it should not make too much difference.

 

[EnoughToBeDangerous]

Well won't it overchlorinate on days when we heat the pool? The water passing the sensor could be 5-10 degrees warmer than the pool depending on how fast the pump is running. I thought, did we make a mistake? But I don't think you want the SWG before the heat pump, that would put a lot of wear and tear on the heat exchanger. Perhaps the sensor should be before the heatpump with the generator after, but that does not seem easy to implement.

 

[JamesW]

The production should not be too much different.

You have to adjust the production as needed based on testing.

There are a variety of factors that affect the amount of chlorine needed.

So, test daily and adjust as needed.

 

[EnoughToBeDangerous]

6 hours in the vinegar seemed to do the trick, now reading 3000ppm. Chlorine is at 2.5ppm without the heater on so I guess if I run the heater with the temp reading 10 degrees higher than it should, it might bost the chlorine a bit. Hopefully I can find setting where the overshoot doesn't get me over 5ppm. Probably excess wear on the cell also. Does 10 degrees make a big differnce in how much chlorine gets produced?

 

[JamesW]

Does 10 degrees make a big differnce in how much chlorine gets produced?

Some. You can check the amps to get a sense of how much difference there is.

For example, if the amps go from 6 to 7, the cell is making 1.17 times as much chlorine.

 

[amwillg]

With the autopilot, the set percentage (time on per hour) actually increases as the temp increases. This is easily seen on the screen.
As an example, I heated my pool from 70 to 90 a week ago and the set percentage went from ~35% to something like 70%. As the pool cooled back down over the next week, the percentage dropped accordingly back to the 30% range.

You are right, the cell is supposed to be after the heater and autopilot's manifold includes cell and sensor. I've noticed the same thing with the pool heat coming out of the heater 10+degrees hotter than the pool and the sensor saying "your pool temp is 100?! MAX CHLORINATION!!!" Luckily, when the set temp is reached, this isn't an issue any more. Is this fooling of the sensor during active gas heating going to superchlorinate the pool? Probably not. Heating with a heat pump is more gradual and the change in temp after the heater is probably less extreme, so I'd think the change in chlorinator % run time would be smaller than I saw with mine.

Make sure you use a pool company that is used to SWGs. These sensors are not perfect and can need some tending to. Blindly following readings of a sensor like that can cause big trouble. An extra 100lb of salt in the pool? Probably not a massive issue, but they'll still bill you for an unnecessary addition.

 

[EnoughToBeDangerous]

Thanks AmwillG. I see your point, if the heater reaches the setpoint, it will stop running. I have a new aquacal variable speed pump, it tends to run a very long cycle, but maybe it will be less when the whether warms up. The temperature difference also depends on how fast the pump is running. If the heat pump runs for 24-48 hrs, I guess it will just chlorinate the pool a little more. Might be a little confusing when trying to get the chemistry properly balanced.

 

[Heavenlytunes]

@amwillg Don't crucified me for this but I haven't tested my water. Is it normal for AUTOPILOT Digital Nano. To increase the purifier percentage by itself? I have it set up at 50% but water temperature has reached 80 degrees. Salt 3200 and 90% purifier.
I haven't adjusted it

 

[amwillg]

I haven't checked the Nano, but my larger Autopilot DIG-220 absolutely does that, so it wouldn't surprise me

 

[EnoughToBeDangerous]

It will increase when the water temperature goes up.