Pentair IntelliChlor Plus and LT

The IntelliChlor Plus and IntelliChlor LT are Pentair's current salt cells, the line that replaced the original IntelliChlor. There are five sizes, from the LT15 for a 15,000-gallon pool to the PLUS60 for 60,000 gallons. Each cell carries its own controller, with a small display and buttons, on top of the cell body.

Pentair designed them to go where its older cells were. They fit the same unions, plug into the same PC100 power center, and talk to the same Pentair automation.

Which size

• LT15 — 15,000 gallons, 0.65 lb of chlorine a day, on its own power pack or a PC100
• LT25 — 30,000 gallons, 0.9 lb a day, PC100
• PLUS30 — 30,000 gallons, 1.1 lb a day, PC100
• PLUS40 — 40,000 gallons, 1.4 lb a day, PC100
• PLUS60 — 60,000 gallons, 2.0 lb a day, PC100

The volumes and chlorine figures are from the manual, and the chlorine is at 100% output around the clock. Pentair's product page calls the LT25 the "25K" cell, while its manual gives it the same 30,000 gallons as the PLUS30.

The cell's output setting is a percentage of pump run time. At 80%, it makes chlorine for 80% of the time the pump runs and rests for the other 20%. A bigger cell on a normal pool simply runs at a lower percentage.

Fitting one where an old cell was

• PLUS40 and PLUS60 are the same length as the original IntelliChlor and drop into its plumbing.
• LT15, LT25 and PLUS30 are the length of Pentair's iChlor, shorter than an IntelliChlor. Each comes with a retrofit adapter, 523101, to bridge the gap in plumbing cut for the longer cell.
• The thread size and unions are the same across the IntelliChlor, iChlor, Plus and LT, per Pentair's FAQ.
• Every model plugs into a PC100 with the same connector as the older cells.
• The LT15 can also run on its own power pack, 523753, which plugs into a 110 V GFCI outlet. Never connect it to an older IntelliChlor or iChlor power pack: Pentair says that permanently damages the cell's electronics.

Installing it

The manual wants a qualified professional to install it, and several of its rules decide whether the cell works at all.

• Wire the power center or pack to the load side of the pump timer, switch, relay or automation, so the cell only gets power when the pump runs. Wired wrong, it can make chlorine gas with no water moving.
• At least 5 feet from the pool wall, and at least 3 feet past the heater outlet. The cell goes after the filter and heater.
• Chlorine or bromine feeders go after the cell. Upstream, they permanently damage it.
• On a pool and spa, put the cell before the pool/spa return valve.
• Vertical is best, with water flowing upward through the cell and the power cord pointing down. The manual says a vertical cell with the flow going the other way voids the warranty. Horizontal, the control panel faces up.
• 12 to 18 inches of straight pipe into the inlet, for the flow sensor.
• At least 25 GPM through the cell. Above 80 GPM, plumb it in a bypass loop with a flow control valve.
• Check that the crosshair is in the cell inlet, seat the union o-rings, and don't overtighten the unions.
• Mount the power supply on a wall within 15 feet of the cell.
• Indoor pools need ventilation for the hydrogen the cell gives off.

On a new pool, run a spacer cell until the plumbing is flushed and the water balanced. The manual wants the pool filled for at least a month with salt stable at 3,600 ppm before the cell runs, and new plaster left to cure for a month before any salt goes in.

Salt

Pentair's ideal is 3,600 ppm, with a range of 2,600 to 4,500. The display shows ADD SALT below 3,000, and the cell shuts off below 2,600. Above 4,500 it shows HI SALT; drain some water and refill to bring it down. Pentair warns that above 6,000 ppm, equipment corrodes faster and pool surfaces can discolor.

• Use at least 99.8% pure sodium chloride, ideally evaporated, granulated and food quality, with no iodine or additives.
• Not rock salt, not salt with anti-caking agents, and never calcium chloride, sodium bromide or potassium chloride.
• Pour it around the edge of the pool, never into the skimmer, brush the floor, and give it 24 hours to dissolve.
• Check the reading with a separate test as well as the cell's display.

The cell checks salinity when it powers up and every 2 hours after that, and the display always shows the most recent reading.

Setting the output

Pentair's target is 2 to 4 ppm free chlorine. Below 2, raise the output; above 4, lower it. After any change, wait 24 hours before testing.

• Test at the right moment and place. The manual has you press Boost so the test catches the cell making chlorine, and take samples near a return and 18 inches deep away from it. The return sample should read higher.
• Boost runs the cell at 100% for the next 24 hours of cell operation. The countdown pauses whenever the cell isn't making chlorine. Hold the button to cancel.
• At start-up, shock the pool with a bought shock treatment, then wait for free chlorine to fall back to 2 to 4 before running the cell.
• Connected to Pentair automation, the cell's own buttons stop working and the output is set from the automation.
• SmartSense flow detection watches an IntelliFlo pump over RS-485. It needs a PC100, not the LT15 power pack, and doesn't work when automation is connected.
• SmartSense pool cover detection needs the 523216 board in the PC100. When the cover closes, output defaults to 0%; you can still raise it, up to a maximum of 50%.

Chemistry the manual rules out

• Never adjust pH with dry acid (sodium bisulfate). Pentair says its by-products build up and damage the cell. Use muriatic acid.
• Never use trichlor or dichlor with the cell, and don't use bromide products.
• Cyanuric acid: 0 to 50 ppm outdoors where local rules allow, and none indoors. The original IntelliChlor manual gave 30 to 50. This site's salt guidance argues for more on a salt pool; Pentair's written figure is the one above.

Maintenance

Weekly: pH at 7.4 to 7.6, alkalinity 80 to 120 ppm, free chlorine 2 to 4.

Monthly: salt, a pool store water test, cyanuric acid, calcium hardness at 200 to 400 ppm, metals, total dissolved solids, and the saturation index, which Pentair wants between -0.3 and +0.3.

Every two months: take the cell out and look at the blades.

1. Turn off the pump, automation and cell at the breaker, and disconnect the cell from its power supply.
2. Close the suction and return lines, and open the filter's air relief until the pressure is gone.
3. Take the cell out and spray both ends with a garden hose on its jet setting.
4. No pressure washer, and no screwdriver or brush. Either can damage the blade coating.
5. A little scale is normal. Heavy scale means an acid clean.

Never separate the two halves of the cell body. Pentair says opening it voids the warranty.

The cell also runs an automatic cleaning cycle to slow scale, and Pentair's FAQ says the polarity reverses every 3 hours.

Acid cleaning, and a misprint

Every cell comes with an acid wash stand. It threads onto the cell's inlet, so the acid goes inside the cell and the outside stays dry.

1. Power off, and wait at least 60 seconds for stored charge to drain.
2. Pry off the retaining clip and lift the controller straight up off the cell. Rocking it side to side can damage the terminals.
3. Wearing rubber gloves and eye protection, somewhere well ventilated, mix 4 parts water to 1 part muriatic acid, pouring the acid into the water.
4. Thread the stand on, set it level, and pour the solution into the cell until the blades are covered. Never submerge the whole cell.
5. Let it foam until it stops, no longer than 30 minutes, then rinse the cell thoroughly. No foaming means the blades probably didn't need it.
6. Repeat if scale is still visible, then refit the controller and the cell.

The misprint. Pentair's table, in the manual and the kit sheet alike, gives 800 mL of water and 200 mL of acid for the LT15, LT25 and PLUS30, and 1.4 L of water and 350 mL of acid for the PLUS40 and PLUS60. Those are 4 to 1. The US figures printed beside them are 0.8 quart of water with 27 ounces of acid, and 1.5 quarts with 47 ounces. 27 fluid ounces is about 800 mL, more acid than water. Go by the ratio or the metric volumes, not the ounces.

What the display tells you

• WAITING FOR FLOW: under 25 GPM. Clean the filter, pump basket and skimmers, raise the pump speed, and check for air in the plumbing. After that, look for a flow switch paddle loose from the sensor module, or a damaged switch.
• ADD SALT / LOW SALT: under 3,000 / under 2,600 ppm. If LOW SALT persists after adding salt, Pentair replaces the sensor module.
• HI SALT: over 4,500 ppm. Drain and refill.
• LOW TEMP: the water is below 52°F. See below.
• CHK CELL / INSPECT: the blades need cleaning. Pentair's FAQ says a CHK CELL that is still there after an acid clean means the blades are worn out.
• OVERLOAD: debris touching the blades, or scale. Clean them.
• SENS ERR: a bad connection between sensor module and controller, or a failed sensor module.
• Low chlorine with no message: output too low, pump not running long enough, a heavy load from rain, leaves or swimmers, nitrates, phosphates or metals, dirty blades, or low stabilizer. For a temporary drop, Pentair suggests 24 hours of Boost, then shock if it's still low.

Cold weather and winter

The cell shuts off below 52°F, give or take 3°F, and shows LOW TEMP until the water warms. Use another form of chlorine until it does. Pentair's FAQ adds a LOW TEMP warning below 60°F, before the shutoff, which the manual doesn't mention.

Against freezing, Pentair gives two options: run the pump continuously, or drain the plumbing and replace the cell with a spacer cell. That's 523102 for the LT15, LT25 and PLUS30, and 520588 for the PLUS40 and PLUS60.

Replacing a part

• Sensor module: power off, wait 60 seconds, and lift the controller off. Remove the six T20 screws, fit the new o-ring and module, and tighten the two side screws first, then zig-zag. Coat the three connections with the kit's dielectric grease and refit the controller. The new module picks up the cell's history automatically.
• Controller: a new controller shows SPARE and pairs itself. One that shows RESET HMI was used on another cell and has to be reset first: hold INFO and BOOST for 10 seconds at SYS OFF / SENS ERR, then cycle the power.
• Cell, when the blades are worn: fit the new cell assembly, reset the old controller the same way before it goes on, and pick the model at SET TYPE.

Warranty and where to buy

The warranty runs on years or hours, whichever comes first. The Plus gets 3 years or 10,000 hours, the LT 2 years or 6,000. The cell keeps a run-time meter, under INFO, of the hours it has spent making chlorine. Those terms need the cell bought from a pool store, builder or service company and professionally installed.

Bought online, including Pentair's EC- numbers, it's one year parts only with no labor. The EC versions Pentair lists are 523735-EC (PLUS40), 523747-EC (LT25) and 523744-EC (LT15 with power pack).

Where Pentair's documents disagree, or are unclear

• LT25 pool size. The product page calls it the 25K cell. The manual rates it for 30,000 gallons.
• Sensor module screw torque. The manual gives 15 inch-pounds. Pentair's FAQ gives 18 to 20.
• Maximum flow. The manual says the cell takes 25 to 105 GPM and needs a bypass loop above 80. The FAQ calls 80 GPM the maximum.
• The cold warning. The FAQ shows a LOW TEMP warning below 60°F before the 52°F shutoff. The manual only lists LOW TEMP at 52°F.
• Acid volumes. The ounce figures don't match the 4 to 1 ratio or the metric volumes beside them, in both the manual and the kit sheet.
• Spacer cell 523102. The parts list gives it to the LT15, LT25 and PLUS30. The winterizing section says "LT15/30 and PLUS30".
• Cyanuric acid. The manual's chemistry table and troubleshooting say to add stabilizer when it's low. Pentair's FAQ lists both low and high cyanuric acid as causes of low chlorine.
• Page references. The troubleshooting chart twice sends you to Cell Disassembly on page 27; it's on page 25.
• A dimension. The drawings label the same 7.2-inch measurement 183 mm on the smaller cells and 193 mm on the larger ones.
• The retrofit adapter. The manual calls it a retrofit adapter and, a line later, a spacer adapter. Its English parts table numbers it 523101, the number retailers carry; the French table in the same manual gives 523099.