Direct answer: For North Star NSC31 and NSC42 equipment matching the January 2026 manuals, use SELECT to reach present time, hardness and recharge time, then the arrow buttons to enter verified values. Hardness is entered in grains per gallon, with the manual’s compensation for measured ferrous iron when applicable. NSC42 also has a documented NaCl/KCl salt-type setting; the reviewed NSC31 manual does not show that step. Record the existing settings before changing them, and do not use a factory reset as a routine hard-water fix.
Publisher boundary: Water System Guide is an independent research publisher, not North Star support. This guide summarizes owner controls in manuals 7393624 and 7393632, both Rev. H dated January 7, 2026, reviewed October 7, 2026. It does not apply every menu to older boards, NST models, hybrid systems, filters or salt-free conditioners.
Identify the equipment and control
Photograph the equipment label and faceplate. The reviewed manuals show model codes n31P for NSC31 and n42P for NSC42, but a code from a different board or older manual requires its own matching instructions. Do not reprogram a replacement board merely because its code differs from an illustration here; have the supplier match the full model and controller revision.
For these editions, NSC31 has a TANK LIGHT button, while NSC42 has a WATER USE button. That is a useful visual distinction alongside the model label. Our NSC31 vs NSC42 comparison explains the separate capacity and flow ratings.
Sources: NSC31 manual, pages 3 and 12, and NSC42 manual, pages 3 and 12.
Gather values before entering the menu
Keep a short settings record:
| Item | What belongs in the record |
|---|---|
| Equipment | Full model, serial number, controller photo and manual revision |
| Untreated hardness | Test result, units, method, date and sampling point |
| Iron, if present | Measured concentration and identified type; not a guess from staining |
| Current settings | Present time, hardness number, recharge time and salt level |
| NSC42 salt type | Actual regenerant and displayed NaCl or KCl setting |
| Optional settings | Existing efficiency, clean, maximum-day and 97% values, plus installer explanation |
Use the home water testing guide if the test or sample location is unclear. A hardness result reported in mg/L or ppm as calcium carbonate is not the same number as grains per gallon; the hardness calculator helps with that unit conversion. The manual’s factory hardness value of 25 is a default, not a measurement of your home.
Both manuals direct adding 5 to the hardness number for each 1 ppm of ferrous, clear-water iron when the softener is being used to reduce that iron. Their example is 20 gpg hardness plus 2 ppm iron: 20 + (2 × 5) = 30. This programming compensation is not permission to treat every type or concentration of iron. Page 5 distinguishes ferrous iron from types the softener does not remove; have the treatment plan and test results verified before compensating.
Sources: NSC31 manual, pages 5 and 13, and NSC42 manual, pages 5 and 13.
Set present time, hardness and recharge time
Use these basic controls only with the matching faceplate and manual. A short SELECT press navigates the ordinary setting screens; holding it enters other functions.
- Reach PRESENT TIME with SELECT. Use UP or DOWN to set the current time, checking AM/PM or the selected clock format. Press SELECT to continue.
- At HARDNESS, enter the verified grains-per-gallon value, including the supported iron compensation if applicable. Press SELECT to continue.
- At RECHARGE TIME, choose a low-use start time. The default is 2:00 AM, and the manuals describe one-hour adjustments with the arrows. Check AM/PM, then press SELECT.
- NSC31 returns to normal time display. On NSC42, continue through SALT TYPE before returning to normal operation.
Recharge time selects the usual start time, not a command to regenerate every day. The controller determines frequency from its programmed inputs and metered use. The manuals also say water drawn during recharge bypasses softening, so choose a time that fits the household rather than copying another home’s schedule.
NSC42 salt type: keep this model difference intact
Page 13 of the NSC42 manual provides a NaCl/KCl screen. NaCl is the default for sodium-chloride softener salt. If using potassium chloride, the manual directs selecting KCl; this changes cycle timing for its different dissolving behavior. Select the actual salt type with the arrows, then press SELECT to finish.
The NSC31 basic programming sequence in its reviewed manual has no equivalent salt-type screen. Do not invent one or assume NSC42’s instruction settles potassium-chloride operation for every North Star unit. Confirm the exact model, controller and regenerant instructions with support if considering a change.
Source: NSC42 manual, page 13; compare NSC31 manual, page 13.
Salt monitor, extra recharge and power interruptions
The salt-level monitor is an estimate to remind you to refill, not a salt-dose setting or a sensor that proves brine draw. Page 14 directs leveling the salt, reading the 0–8 scale on the brinewell and using SET SALT LEVEL to match the bars. Update it after adding salt; different salts can affect its accuracy.
For an extra recharge on these controls, a short RECHARGE press schedules the next preset start time; another short press cancels it before it begins. Holding RECHARGE for three seconds starts an immediate cycle. The manuals describe about two hours for that recharge, with a preceding cleaning stage if enabled. Add salt first if the supply ran empty, and avoid drawing water during recovery. Repeated manual cycles do not diagnose an unresolved fault.
After a power interruption, page 17 says the controller retains settings and keeps time for several hours. Reset present time if it flashes after power returns; do not erase all settings simply because the clock needs correction. A cycle interrupted by the outage resumes when power returns.
Sources: NSC31 manual, pages 14 and 17, and NSC42 manual, pages 14 and 17.
Optional settings need a documented reason
Efficiency, Clean, maximum days between regenerations, the 97% feature and rinse times affect different behavior. The manuals describe the 97% option as permitting regeneration at any time when its threshold is reached; a maximum-day setting instead imposes a calendar limit. Neither is a universal fix for hard water.
Optional-menu order and Clean-time ranges differ between the two manuals. Record the existing settings and ask the installer to explain changes using the exact model’s pages 15–16. Do not shorten rinses to save water or activate several options as an experiment. Follow the manual’s installation-specific efficiency instructions, including its California note where applicable, rather than assuming factory defaults suit every installation.
If the symptom is measured hard water, poor brine behavior or an error, use the not-softening guide to collect evidence. Changing hardness or resetting the board cannot establish that the valve, meter or brine path is sound.
Sources and review scope
- North Star NSC22/NSC31 manual 7393624, Rev. H January 7, 2026. Manufacturer primary source; pages 3, 5 and 12–17, including the controller diagram, reviewed October 7, 2026.
- North Star NSC42 manual 7393632, Rev. H January 7, 2026. Manufacturer primary source; the same subject sections and its distinct salt-type menu reviewed October 7, 2026. Service diagnostics and board replacement are outside this owner-settings summary.
Frequently asked questions
What hardness number should I enter on a North Star softener?
Use measured untreated hardness in grains per gallon, with the matched manual’s compensation for measured ferrous iron when applicable. The default value of 25 is not a household test result; verify the units and treatment plan before changing it.
Do NSC31 and NSC42 have the same salt-type menu?
The reviewed NSC42 manual includes a NaCl/KCl salt-type screen; the reviewed NSC31 manual does not. Match the actual model and controller before using potassium-chloride instructions or transferring menu steps.
Does setting recharge time to 2:00 AM make it regenerate daily?
No. Recharge time is the usual start time. Demand operation and the configured options determine when a recharge is needed; a maximum-day option or the 97% feature can alter that behavior.
Should I factory-reset the controller after a power outage?
The manuals say other settings are retained and the clock keeps time for several hours. Correct present time if it flashes after power returns. A factory reset is not the ordinary clock-correction procedure and should not be used as a trial repair.