SWC high salt when solar turned on

[mas985]

Just wondering if anyone else has had this problem.

When the solar is turned off and then back on, I get a high salt warning. After I reset the SWC, the salt level is fine (3200 ppm). I don't get another warning unless the solar is turned off and then back on again. The warning is fairly repeatable and I can watch the salt level rise on the controller when the solar is first turned on.

I suspect that the panels do not fully drain while the pump is on because of the pressure on the one-way valves. Salinity in the 20 ft vertical pipes up the house probably rises to the top over time making some of the water a higher salt ppm.

This is not a huge problem but the Aqualogic controller has a 100 minute cycle which means I lose chlorination during that cycle. Unfortunately, the controller does not turn the cell off for a delay when the panels are turned on. For changing the spa/pool valves, it does delay the cell.

Thanks

[Poolsean]

It has to do with the water temperature and the amps/volts through the cell.
The Aquarite salt display is not a true salinity meter reading. It's an assumption based upon the cell amps and volts, which should be fine as long as the cell is clean and not worn out, and the water temperature stays consistent.
In your case, the increased water temperature from the solar panels tricks the unit into thinking the salt is higher due to the warm/hot water temperature. Don't worry though, the same thing happens with a gas heater. It corrects itself once the water temperature balances out, which you're finding out occurs during the 100 minute cycle.

[PatL34]

Just wondering if anyone else has had this problem.

When the solar is turned off and then back on, I get a high salt warning. After I reset the SWC, the salt level is fine (3200 ppm). I don't get another warning unless the solar is turned off and then back on again. The warning is fairly repeatable and I can watch the salt level rise on the controller when the solar is first turned on.
When the solar is turned on, the solar panels have to be refilled with pool water. What you are seeing is a combination of water and air, and the poor old salt sensor is being thrown for a loop seeing water and air. Don't ask me what it is trying to measure at this stage. The next time you turn on the panels, put your hand on the cell, and check to see if you feel vibration. That is the mixture of air and water going through the cell, and will continue until all the air is removed. The PoolPilot sees this as low flow and shuts off the power to the cell, otherwise you can have a mixture of hydrogen being generated from the cell mixed with oxygen from the air, and the chances of having an expolsion are pretty good.

I suspect that the panels do not fully drain while the pump is on because of the pressure on the one-way valves. Salinity in the 20 ft vertical pipes up the house probably rises to the top over time making some of the water a higher salt ppm.
I do not think the salinity is a factor here, because of what I said above, but I may be wrong on this.

This is not a huge problem but the Aqualogic controller has a 100 minute cycle which means I lose chlorination during that cycle. Unfortunately, the controller does not turn the cell off for a delay when the panels are turned on. For changing the spa/pool valves, it does delay the cell.
With the PoolPilot I do not seem to have this problem, but Poolsean may be able to clear this up. No matter when the PoolPilot is shut off, it remembers what part of the cycle it is in and continues from there. Again Poolsean will have to clarify this.

Thanks

Hope this helps.

Pat

PS. Sean just beat me too it. He appears to know the competition better than I, but I take nothing back from what I have said.

[mas985]

Thanks Sean,

I didn't think about the temperature causing the problem. I know the conductivity of water goes up with temperature but I thought it was less than 10% change over 100 degrees. Perhaps they are using the temperature in the salt ppm calculation and that is where the error arises from.

Pat,

Mine has a flow switch as well but always seem to indicate a flow so there must be enough water with the air to keep the switch closed or the air rushing by it is sufficient.

One more thing, when I watch the salt level, it does not seem to rise until after the air is purged from the panels.

[waterbear]

I am sure it is the temperature as Poolsean said. I have an Aqualogic PS-8 and it controls my pool and spa separately. I know the salt concentration in both is the same (I run the spillover when adjusting chemicals and check salt levels in each with both chemical tests and a handheld and calibrated salt meter) but my spa constantly show a higher salt concentration than my pool on the Aqualogic control panel (usually about 200ppm higher). The only difference is my pool is at 82 deg and the spa at 104!

[PatL34]

Mark,

You mention that there is sufficient flow with the pool water/air mixture to keep the flow switch on. If this is correct than you have the potential to create a hydrogen/air mixture which could be explosive. I am not kidding. Any system of this sort has to have that protection to shut off regardless of who made it. Hydrogen can be very unpredictable in the presence of oxygen. In other words been there, seen it happen. You just do not fool around with hydrogen in the presence of anybody.

Pat

[Poolsean]

Pat,

I'm very certain that mas' high salt problem is due to the increased water temperature. I've seen it over and over again. There is no increased concentration of salt in the solar panel when it is off. It's the increased temperature.
Solar panels should not drain down when the pump shuts off, therefore there should not be a period of air cycling through the system to cause the hydrogen/oxygen condition you're cautioning about. This is mostly a problem when there is a failed flow switch and the cell is saturated in water, but not for intermittent air pockets passing through the cell.

[PatL34]

Sean,

The feeling I get is that the PoolPilot protects and recovers from a water/air mixture better than the Autologic by virtue of the low salt reading and low flow reading, delaying the power to the cell until things are normal. That's what I am trying to get at.

Pat

[mas985]

There are really two conditions when this happens.

1) When the pump first turns on in the morning, 11am, there is air in the solar panels and the flow switch does turn off as the air pass through the cell so that does seem to work ok. Given that there is no water in the panels, at least that I know of, the only explaination for the high salt in this condition is that the water is very hot going through the cell. I will verify this later when I heat up my spa to see how much the salt reading changes.

2) After the panels have been on for a while and then turned off due to a cloud or wind and then turned on again later, there is very little if no air in the system so that is why I did not see the no flow indicator or I think I might have missed it. High salt comes on in this condition as well.

I was thinking at first of condition #2, so that is why I thought that the salinity was changing in the panel. However, condition #1 would not happen if it was just the salinity, unless water or salt was left in the panel. That is probably unlikely.

Therefore, as Sean orginally pointed out, temperature is probably the culprit. I am still looking for a good reference relating temperature, salinity and conductivity.

[mas985]

Well, a very interesting development. I did a couple of experiments and got the following results.

Put the spa on solar starting at about 90 degress and a salt level of 3200. Ran the cell temp up to 105 degrees but the salt level did not change at all, still 3200. The controller must do some compensation for temperature.

Next, I turned the valves to spa spillover without solar and waited 10 minutes for the panels to really heat up. Turned them on and I saw the temperature, salt level and amps all rise together until the temp hit 108 and salt hit 3700 and the warning came on. I immediately reset the cell and there is a 15 sec delay before coming on again. When it came on, the temp was still 108 but the salt level was down at 3200. I watched as the temp lowered but the salt level did not change.

I repeated the above again but after 20 min and got a slightly different result. The temp did not rise as quickly but the salt level did. It hit 3700 ppm when the temp was only 92 degrees. This makes me think it is a salinity issue and not temperature.

If temperature is causing the problem, it may be that the controller cannot compensate fast enough for a fast rise in temperature or even display it correctly.