1) Understanding the Fleck NXT2 Controller

The NXT2 controller is the second-generation networkable platform developed for Fleck and Pentair valves such as the 2815, 2850, 3150, and 9500 series. It monitors flow, controls motorized valve positions, and coordinates multi-tank systems for softening or filtration. Key advantages over older models include faster processing, larger memory, a backlit LCD, and USB firmware updates.

The controller stores operational parameters such as capacity, regeneration timing, hardness, flow limits, and system network address. If these values drift or reset after power loss, the system may over-regen or deliver hard water—so knowing how to reprogram it is essential.

2) Hardware Components & Connections

All wiring is low-voltage, but keep cables dry and protected from chemical vapors. Use strain relief and label each connection before removal.

3) Display Layout & Button Functions

The NXT2 interface is menu-driven with soft keys and scroll buttons. Understanding these buttons makes navigation fast and error-free.

During normal operation, the home screen shows the time of day, current flow rate, total volume remaining, and system status (Service / Regen / Error code). If networked, the node address displays briefly on startup.

4) Specifications & Power Requirements

Always use the OEM 24 VAC transformer. Improper voltage can corrupt firmware or burn the motor driver.

5) Safety and Data Preservation Before Programming

• Disconnect power before connecting or removing any cables.
• Photograph each program menu before making changes for backup.
• Record hardness, capacity, salt dose, and meter type on a worksheet.
• If networked, label node addresses to avoid cross-communication.
• Never press REGEN while the valve is disassembled.

6) Factory Reset & Firmware Notes

Perform a factory reset only when a controller shows persistent logic errors after verifying hardware. To reset:

1. Hold SET + REGEN for 10 seconds until “Factory Reset?” appears.
2. Select YES with arrow keys → press ENTER.
3. Controller reboots to default English language and time 12:00 AM.
4. Re-enter system type, meter, capacity, and hardness immediately.

Firmware versions display briefly on startup (e.g., v2.14 2024-06). Always match firmware for networked systems to avoid communication mismatch errors.

7) Initial Startup: Language, Time, Units & First Boot

After mounting and wiring the NXT2 (see Part 1), power the controller with the OEM 24 VAC transformer. On first boot—or after a factory reset—the NXT2 walks through a short setup wizard. If yours loads to the home screen, you can access the same settings via the main menu.

Startup Wizard (typical path)

1. Language: Choose English (or preferred).
2. Units: U.S. gallons (G) or liters (L). Use gallons if your lab results are in gpg.
3. Time & Date: Set 24‑hour or 12‑hour format; verify AM/PM.
4. Timezone Offset: Optional; ensures correct regen time around DST changes.

8) Basic Programming: From Raw Water to Reliable Regeneration

Every successful NXT2 setup programs the same nine elements. Enter them in the order below to avoid circular edits and mismatched values.

8.1 Hardness

• Convert ppm (mg/L) to gpg by dividing by 17.1. Example: 240 ppm ÷ 17.1 ≈ 14 gpg.
• If iron is present and not fully removed upstream, add 3–5 gpg per 1 ppm iron as a rule‑of‑thumb “hardness equivalent.”

8.2 Capacity (Grains)

Capacity is the usable grains per tank between regenerations at your chosen salt setting. You’ll calculate this in Section 9. For now, note that a 1.5 ft³ softener at 6 lb/ft³ typically programs around 30–36 kgr. (We’ll firm that up shortly.)

8.3 Salt Dose (lbs)

Salt dose determines how fully the resin regenerates. Higher salt ⇒ more capacity but lower salt efficiency. Common setpoints are 6–8 lb/ft³ for efficiency, or up to 10 lb/ft³ for maximum run length.

8.4 Regeneration Type

• Metered Delayed: Tracks usage; regenerates at the programmed time. Best for homes and businesses with nighttime off‑peak hours.
• Metered Immediate: Regenerates immediately at exhaustion. Use when water quality cannot dip at any hour.
• Time Clock: Fixed day interval—use only if no meter or with specialty medias.

8.5 Regeneration Time

Set to 02:00 (or local off‑peak). In duplex or lead/lag networks, stagger times so multiple units don’t backwash simultaneously unless designed for it.

8.6 Day Override

Defines maximum days between regenerations regardless of flow. Typical: 7–14 days. Shorten if iron, manganese, or fouling risk exists.

8.7 Flow Meter Type & Pulses/Gallon

Pick the exact meter profile. An incorrect pulses/gal value causes early or late regenerations.

• Locate the meter model/label; reference its pulse factor (e.g., 1, 2, 10 pulses/gal).
• Confirm arrow orientation matches service flow. If reversed, counts fall or read zero.
• Perform a bucket test: Run 5 gallons and verify the NXT2 counted within ±5 %.

8.8 Service Flow Limit (SFR)

SFR protects water quality at peak demand by preventing flow beyond what the tank and resin can handle. If your application has rare high spikes (large tubs, irrigation), set a sensible limit (e.g., 10–12 gpm for a 1.5 ft³ residential bed) or leave off if not needed.

9) Cycle Times: Backwash, Brine Draw, Rinse & Refill

Cycle durations depend on valve size, bed depth, fouling risk, and injector size. Start with conservative defaults, then fine‑tune based on water tests and performance.

Record the BLFC value (e.g., 0.25 gpm). Since ~3 lbs of salt dissolve per gallon of water, Refill minutes × BLFC × 3 ≈ salt lbs.

10) Capacity & Salt Math (Step‑By‑Step)

This is where your NXT2 programming pays off. We’ll compute a right‑sized capacity and salt setting based on real usage and resin volume.

10.1 Convert Hardness to gpg

• gpg = ppm (mg/L) ÷ 17.1
• Add iron equivalence if upstream iron is present and not fully removed: + 3–5 gpg per 1 ppm iron.

10.2 Estimate Daily Gallons

• Residential rule: 60–75 gallons per person per day (total cold+hot).
• Example: 4 people × 65 gpd = 260 gpd.

10.3 Daily Grains to Remove

Daily grains = Daily gallons × Hardness (gpg).
Example: 260 gal × 14 gpg ≈ 3,640 grains/day.

10.4 Choose a Salt Dose (lbs per ft³)

Typical efficiency targets (approximate per ft³ of resin; varies by resin and injector):

• 6 lb/ft³ → ~20–24 kgr/ft³
• 8 lb/ft³ → ~24–27 kgr/ft³
• 10 lb/ft³ → ~28–30 kgr/ft³

Use manufacturer curves if available. The values above are practical planning numbers for most modern softening resins.

10.5 Calculate Usable Capacity

10.6 Convert BLFC to Refill Minutes

Refill water (gal) × 3 ≈ salt lbs. So with BLFC 0.25 gpm and a 9 lb salt target:

1. Salt lbs ÷ 3 = brine water gallons → 9 ÷ 3 = 3 gal
2. Minutes = gallons ÷ BLFC → 3 ÷ 0.25 = 12 minutes refill

10.7 Pick a Day Override

Start at 7–10 days for typical homes. Shorten if iron present or if you see taste/hardness drift before capacity is used.

11) Ready‑To‑Use Programming Templates

Use these as starting points. Always confirm with your resin specs, meter type, and BLFC value.

12) Verify Operation (Commissioning Tests)

Before leaving the installation, prove each stage works:

1. Meter Check: Run 5 gallons; confirm display counts within ±5 %.
2. Manual Regen: Hold REGEN to start. Observe: service → backwash → brine draw → fast rinse → refill. Listen for motor and watch outlet for flow changes.
3. Brine Draw: During BD, verify brine level drops in tank. If not, check injector, brine line, air check, and seals.
4. Hardness Test: Measure hardness at a fixture after return to service. It should read near zero immediately after regen.

13) Common Pitfalls (and Quick Fixes)

• AM/PM error: Regen starts during the day. Set 24‑hour time or verify AM/PM.
• Wrong meter profile: Premature or late regenerations. Select the correct meter and pulses/gal; perform a bucket test.
• Capacity too high: Hardness bleed before regen. Reduce programmed capacity 5–10 % or increase salt dose.
• Refill mismatch: Salt not dissolving fully or too salty water after regen. Check BLFC and recalc refill minutes.
• Forgot Day Override: Long idle periods lead to channeling. Set 7–14 days.

14) Advanced Programming: Duplex, Alternating, Lead/Lag & Parallel

The power of the NXT2 platform shows up when you coordinate multiple tanks. This section explains the major architectures and the exact parameters to review so your system stays synchronized through power cycles and peak‑flow events.

Programming Steps (Any Multi‑Tank Mode)

1. Set unique node addresses (e.g., 1, 2, 3...). Power units one at a time to avoid duplicate auto‑addressing.
2. Select System Type: ALT (Alternating), PAR (Parallel), or Lead/Lag (if shown on your firmware).
3. Choose meter strategy: Each tank’s own meter or one shared header meter. Program pulses/gal correctly.
4. Define capacity/salt per tank (from Part 2 math). Don’t cut corners—mismatched capacities cause asynchronous regens.
5. Stagger regens with a delay so two units don’t backwash simultaneously unless your plumbing is sized for it.
6. Set return priorities: Which tank becomes lead after power loss, manual regen, or simultaneous return to service.

15) Networking the NXT2: Bus Wiring, Topology & Addressing

The NXT2 network is a low‑voltage bus designed for robust communication between controllers. Wiring rules are simple—follow them and you’ll avoid intermittent “ghost” faults.

Shared vs Individual Meters

• Shared header meter: Simplifies plumbing; all nodes read the same pulses. Ensure the same pulses/gal on each controller.
• Per‑tank meters: Higher fidelity and redundancy. Program each controller with its own pulses/gal factor.

16) Coordination Logic: Assist Thresholds, Regen Stagger & Priorities

Coordination logic prevents hard‑water breakthrough during peak demand and keeps the plant quiet overnight.

• Assist Threshold (Lead/Lag): Set the gpm at which the lag tank joins service. Start around 8–12 gpm for 1.5–2.0 ft³ beds.
• Regen Stagger: Offset start times by 10–30 minutes to avoid simultaneous backwash unless plumbing supports it.
• Return Priority: Choose which tank returns to lead after a power cycle or dual regen event.
• Lockout Windows: Some firmware supports “No‑Regen” windows (e.g., 7am–9pm); use in retail or hospitality venues.

17) Error Code Reference: Meanings & Fast Fixes

Exact wording varies by firmware, but the underlying causes are consistent. Use this table as a field cheat‑sheet and escalate to full mechanical inspection if errors persist.

When in doubt, perform a manual regen and watch each stage. The sound and flow pattern reveal valve or plumbing issues faster than menus do.

18) Advanced Cycle Tuning: Bed Expansion, Backwash Rates & Media Care

Cycle times are half the story—the other half is flow rate. Ensure your backwash delivers enough gpm to expand the bed without channeling.

• Bed Expansion (softening resin): Target ~30–50% expansion during backwash. Check valve size and distributor for required gpm.
• Iron/Manganese: Add 2–5 minutes to backwash and fast rinse, and shorten day override to reduce fouling.
• Low‑yield wells: If your pump can’t sustain the backwash flow, split cycles (two shorter backwashes) or resize media.
• Injector Sizing: Choose injector size recommended for your valve and bed volume to ensure proper brine draw rate.

19) External I/O & Integration: Remote Start, Inhibit & Alarm Relays

Many NXT2 installations tie into building systems. Use low‑voltage dry contacts per your wiring diagram and observe polarity where specified.

• Remote Start: Trigger a regeneration from a PLC/BMS at a scheduled time (e.g., after hours).
• Regeneration Inhibit: Block regen during business hours, then allow at night.
• Alarm Relay: Signal BMS when a controller posts a critical error or salt is low.
• Flow/Leak Inputs: Some sites add leak detectors that force bypass or lockout if tripped.

Label every cable at both ends. Future techs will thank you—and you’ll avoid mis‑wiring during board swaps.

20) Data Logging, Firmware & Documentation

Small habits prevent big outages. Keep a simple log and you’ll solve 80% of issues in minutes.

• ✔ Firmware version & date (record after each update)
• ✔ Node addresses & roles (lead/lag/parallel)
• ✔ Meter type & pulses/gal (shared vs per‑tank)
• ✔ Capacity, salt dose, day override
• ✔ Cycle times (BW/BD/FR/RF) and BLFC gpm
• ✔ Last three hardness readings (post‑service)
• ✔ Any error messages and resolutions

21) Case Profiles: Real‑World Multi‑Tank Setups

22) Troubleshooting Trees: Diagnose → Fix → Verify

Use these symptom‑based trees in the field. Each ends with a verification step so you leave the site confident.

23) Preventive Maintenance & Service Rhythm

Most NXT2 issues vanish with simple, regular care. Adopt this rhythm and log changes.

24) Recommended Spares Kit (Technician / Facility)

Carry these parts for fast restorations and fewer callbacks:

• OEM 24 VAC transformer
• NXT2 controller module (pre‑flashed if possible)
• Valve motor & harness
• Common injectors & screens for your valve model
• BLFC assemblies (0.125 & 0.25 gpm)
• Seal & spacer kit; piston assembly
• Brine float/air check assembly
• Turbine meter + cable
• O‑rings assortment; push‑fit collets
• Shielded network patch cords

25) Programming Cheat‑Sheets & Cycle Timing Reference

26) Commissioning & Service Log (Copy/Paste Template)

Site/Customer: ________________________   Date: __________
Valve Model: _________   Resin ft³: _____   BLFC: ______ gpm
Controller FW: ________   Node(s): _______  System: ALT / PAR / Lead-Lag

PROGRAM VALUES
  Time/Date: _________ (24h? Y/N)  Regen Time: ______
  Hardness (gpg): _____  Capacity (gr): ______  Salt (lbs): ______
  Day Override: ____   Meter Type: __________  Pulses/gal: ____
  SFR Limit (if used): ____ gpm

CYCLE TIMES
  BW: ____ min  BD/SR: ____ min  FR: ____ min  RF: ____ min

TESTS
  Bucket Test 5 gal: _______ counts  (±5%? Y/N)
  Post‑service hardness: ______ gpg
  Brine draw observed? Y/N   Refill rate ok? Y/N

NOTES / PARTS REPLACED:
  _______________________________________________________
Tech Sign: __________________________
      

27) Extended FAQ: NXT2 Programming & Field Issues

Q1. NXT vs NXT2 vs SXT — what’s the difference?

SXT is stand‑alone (single tank). NXT adds networking. NXT2 is the newer, faster platform with better display, memory, and multi‑tank coordination.

Q2. Which regen type should I choose?

Metered Delayed for most sites (regen at 02:00). Use Metered Immediate when quality can’t dip at any hour. Time Clock only for specialty media or no meter.

Q3. How do I set refill minutes correctly?

Use BLFC math: Minutes = (Salt lbs ÷ 3) ÷ BLFC gpm. Example: 9 lbs, BLFC 0.25 → 9 ÷ 3 = 3 gal → 3 ÷ 0.25 = 12 minutes.

Q4. My site has iron. What changes?

Add 3–5 gpg “hardness equivalent” per 1 ppm iron, shorten day override, extend backwash/fast rinse by a few minutes, and consider upstream iron filtration or resin cleaner.

Q5. Can I copy settings from one controller to another?

If your firmware supports export/import, yes. Otherwise, photo each menu and duplicate carefully. Ensure node addresses are unique on networked systems.

Q6. We changed the meter—what now?

Set the correct meter type & pulses/gal, then perform a 5‑gal bucket test. Re‑check assist thresholds and capacity sync on multi‑tank systems.

Q7. After a power outage, roles changed. Normal?

Yes—unless you set Return Priority. Program which tank should be lead after power events to keep behavior predictable.

Q8. We get hardness creep before the regen day.

Reduce capacity 5–10% or increase salt dose; verify meter accuracy and brine draw performance; check usage spikes vs SFR limit.

Q9. Can I lock menus from user tampering?

Yes. Many builds support a menu lock or PIN (check firmware). At minimum, enable a basic lockout key combo to prevent accidental edits.

Q10. Should duplex tanks backwash together?

Generally no—stagger start times by 10–30 min unless plumbing and drain sizing support simultaneous cycles.

Q11. Is resin mixing okay?

Use manufacturer‑approved resin types for your application. Mixing fine/standard mesh changes backwash requirements; re‑size times and rates if you do.

Q12. What TDS or hardness should I see after regen?

Hardness should be ~0 gpg immediately post‑service; TDS depends on feed. Rising post‑service hardness indicates programming, brine, or resin issues.

Q13. When do I replace the controller vs repair wiring?

If power, transformer, and peripherals test good but logic faults persist across resets, replace the NXT2 module. Keep one spare for critical sites.

28) Quick Links & Next Steps