Hayward Aquarite SWG - Further Reading

Overview

The Hayward Aquarite consists of two units:

• Control panel and power supply, typically wall mounted
• T-Cell for chlorine generation

The T-cells come in various generating capacities. The specific T-cell being used needs to be set in the control panel for proper operation.

Aquarite T-Cells

Cell chlorine Generating Capacity

Each cell T-3, T-9, T-15 will produce a specific quantity of chlorine before it is depleted.

• T-3 = 210 pounds - 15,000 gallons
• T-9 = 385 pounds - 25,000 gallons
• T-15= 580 pounds - 40,000 gallons
• Equivalent pounds of Trichlor produced over the lifetime of the cell with properly maintained cell and water chemistry.

Which T Cell Should I Buy?

TFP recommends you get a cell at least 2X your pool water volume. Manufacturers specifications assume you will run your pump 24/7 and have the cell generating 24 hours a day. Oversizing the cell allows reduced pump runtimes, reduced SWG %, and excess chlorine generating capacity if needed.

Not all cells, that are the same size, last the same amount of time in the real world is true due to many factors, but they should come very close to making the same amount of chlorine during that time. The ones that make less chlorine are most likely acid washed and each time they are acid washed they will lose some of their lifespan. If one uses a strong mix of acid to water then they can significantly reduce the lifespan.

T-15 Cell Types

The Hayward T-Cell-15 and Hayward T-Cell-15-SWP are the same thing.

The T-Cell-15 has a 3 year warranty.

The Hayward T-Cell-15-SWP is a Swimpure branded cell, which has a 2 or 3 year warranty. You would need to verify with the seller to be sure.

The first number of the serial number is the length of warranty.

The TCELL940 is a T-15 "long life" cell with a 4 year warranty.

A T-15-W is a warranty replacement cell with a 1 year warranty. It's not designated as a retail cell. It's supposed to be used as a replacement for a cell that fails under warranty. Some places sell warranty cells as regular cells.

Determining Salinity

The AquaRite uses the performance of the cell to determine salinity. For each cell (T-3, T-5, T-9 OR T-15), Hayward knows the performance of a properly functioning cell at each temperature and salinity combination. The higher the salinity and/or water temperature, the higher the performance (chlorine output).

There is no separate salinity sensor in an AquaRite. There are six wires going to the cell, two white, two black, one red and one blue wire.

The black and white wires carry the power to the cell and are heavier gauge than the other wires. The two white wires go to the center plate. The two black wires tie together and go to the two outer plates. The red and blue wires go to the temperature sensor.

There are no other wires going into the cell to support a salinity sensor. There are 4 extra wires in the cell cord (brown, orange, yellow and green) that are not used and do not go to the cell.

Another way to tell that the AquaRite does not have a separate salinity sensor is that if the T-Cell setting does not match the cell type, the salinity will read wrong.

If the Cell is larger than the T-Cell setting, the salinity will read higher than actual. If the Cell is smaller than the T-Cell setting, the salinity will read lower than actual. One can verify this by changing the T-cell type and see the salinity change.

If there was a separate salinity sensor in the cell, the salinity would not change when the tcell type was changed.

Thermistor

How the Thermistor Works

The thermistor protects the electronics and transformer from excessive inrush current. Inrush current depends on what part of the sine wave the ac voltage is in when power is turned on.

If the voltage is zero, the inrush current can be very high and overload the electrical components. The thermistor provides a temporary resistance to control inrush current. Basically, it acts as a surge protector.

The AS32 2R025 will get up to 428 °F at its full current rating of 25 amps. However, there should not be that much current going through the thermistor while operating. It is designed to heat up while operating, so it does get hot.

Failure Modes

The thermistor is pretty much the only thing that fails in the AquaRite power box. It stays hot the entire time it's generating. However, it's only needed during the first few seconds of operation.

When the thermistor begins to fail, the voltage gets erratic. Zero volts points to a bad thermistor.

The thermistor used to limit inrush current (the "big black disc") usually blows after a power surge, typically brought on by a storm or utility glitch.

Diagnostics

Usually you can see cracks in the coating on the thermistor indicating it’s bad. Some have looked normal and couldn’t find any cracks - but they were bad. Don't bother testing them because in order to access the thermistor...everything else is removed, it wouldn’t take much longer to just replace it.

The thermistor on the SWG is a Negative Temp Coefficient (NTC) thermistor, so resistance will decrease as temp increases. The rating for the thermistor is 2 ohms at room temp (low 70’s F), which is about the reading you should get on a multimeter, give or take a little depending on temp. If it’s wayyy off, it’s bad. If it’s close, proceed.

The next test is, while holding the two leads of the multimeter on the legs of the thermistor, apply a heat source (hair dryer, heat gun, etc.) for a few moments. The resistance reading should begin to drop as the heat source is applied. If not, it’s bad.

A thermistor hack is to put a binder clip on it. It holds it together and acts like a heat sync. If the binder clip test makes it work, then you know your thermistor has done gone bad. You can leave the binder clip on mine while you waited for a new thermistor to arrive.

Thermistor Replacement

Thermistor is a AS32 2R025.

The part cost is $2.50 and the repair takes about 15 min. You can cut the legs of the old one and solder the new one to them at a 90 degree angle standing away from the board. It's easier to do and allows for better cooling.

Screw Terminal for Thermistor

One member used a screw terminal (Digi-Key part# ED2561-ND) to mount the thermistor on. This should enable replacing the thermistor in the future without having to solder. The original thermistor is AS32 2R025 which has a wider lead wire footprint but the available replacement on hand is SL32 2R025. The latter has a high failure rate due to overheating compare to the AS32. If your PCB footprint can accommodate both types, then you will be far better off using the AS32.

Detailed directions with pictures can be found in this thread

Upgraded Thermistor

The exact cold resistance value of that part is not super critical but don’t go under 2 Ohms or over 5 Ohms. The steady state current rating (SSI) should be at least 20A. For a direct replacement, I recommend a SL32 2R025 or 4R023 over the currently shipping 5R020. They have higher failure energy ratings. That said, a combination of devices mounted off-board can yield much improved robustness and ease of replacement (read on).

When I bought my Aquarite in 2004, it came with an SL32 2R025 NTC Thermistor (548J fail threshold, 2 Ohms cold resistance). A few years later, when I replaced my main board (fried to a crisp by a lightning surge) the manufacturer had switched to SL32 5R020 NTC thermistors (lower 300J fail threshold but 5 Ohms cold resistance). I assume the 5R020 is still what is being shipped in current models. That new board eventually suffered a blown NTC Thermistor too and I had to replace it. I could have just installed the same part but decided it was time to improve things a little. An easy, but marginal, robustness improvement could have been had by using an SL32 4R023 NTC Thermistor (448J fail threshold over the 5R020's 300J). However, I decided to go the extreme route for my setup and did a Parallel/Series combo of SL32 2R025 devices mounted on terminal blocks for roughly 4x the original surge energy and heat dissipation ability, AND easy replacement (see pics and Ametherm SL32 series NTC Thermistor specs table). Ironically, I have not had to replace them since, so it was well worth the effort. Note that the parallel/Series combo is not perfect and can fail at lower than 4x the surge energy due to the 4 devices not equally sharing said surge BUT, it has been going strong ever since I installed it so practically speaking, it does indeed provide significantly increased robustness vs the single device.

Tips

• To protect the thermistor you can try running at the low end of the salt range. This will help keep the amps down. Shading wouldn't hurt either.
• The thermistor carries 24 volts dc.
• Anytime you shut off the box, you should allow at least a minute or more for the limiter to cool down before starting it back up. The limiter only provides protection if it's cool.<refhttps://www.troublefreepool.com/threads/aqua-rite-should-current-limiter-get-very-hot.66309/post-564344</ref>
• Desoldering these Ametherm devices from the Aquarite main PCB is not an easy task for the inexperienced or ill-equipped. The PCB pads are large and heavily peppered with vias giving them a lot of thermal inertia. It is easy to damage the PCB or device mounting holes while attempting to remove the NTC Thermistors. If you don't have the experience or tools, ask a friend who does.

Burnt T-Cell Connector Plug

The plug is a Molex 76650-0078 plug

Extend AquaRite T-Cell Cable

First, is there any way the box can be relocated? This would remedy the problem in the easiest way with regard to warranty.

This thread describes how an extension cord was constructed.

Even though a 10-position connector is being used, the T-Cell only uses 6 of the 10 pins. There are two Black and two White wires that appear to supply the voltage to the T-Cell from the AquaRite controller. Looks like they're distributing the current across the two paths since the T-15 cells can draw over 6 AMPS. The Red and Blue wires are presumably carrying data (Water Temperature, Instant salt level, etc) back and forth between the controller and T-Cell.

Here are the Pin-outs to be used with the Molex 0469931011 mating plug:

• BLACK 1 -> PIN 1
• BLACK 2 -> PIN 2
• WHITE 1 -> PIN 6
• WHITE 2 -> PIN 7
• RED -> PIN 8
• BLUE -> PIN 10

The PIN numbers on the Molex connectors can be tricky so watch out.