HVACopediaNavien · Tankless water heater
MAIN Remote asks for main/sub setting
What the display is showing
Shown on a remote controller during multi-remote setup. A controller showing MAIN needs its mode set: press Down to switch to SUB, then OK. After setup, pressing OK and Lock together for 2 seconds shows MAIN on one remote and SUB on the other.
Applies to: NPE-A2/S2 and NPN-U/NPN-E remote controller
Settings for these units
Installation clearances (indoor / outdoor) · Navien NPE-2
| Side | Indoor | Outdoor |
|---|---|---|
| Top | 9 in. (229 mm) | 36 in. (900 mm) |
| Back | 0.5 in. (13 mm) | 0.5 in. (13 mm) |
| Front | 4 in. (100 mm) | 24 in. (600 mm) |
| Sides | 3 in. (76 mm) | 3 in. (76 mm) |
| Bottom | 12 in. (300 mm) | 12 in. (300 mm) |
Vent clearance to combustibles is 0 in.
Outdoor: use the Navien Outdoor Vent Kit; keep 3 ft from an eave to the top of the vent terminals; mild climates only.
Water quality limits and flushing schedule · Navien NPE-2
| Hardness | grains/gal (mg/L) | Treatment | Flush frequency |
|---|---|---|---|
| Soft | 0-4 (0-60) | None | None |
| Moderately hard | 4-7 (61-120) | None required | Once a year |
| Hard | 7-9 (121-160) | Softener or Navien PeakFlow recommended | Once a year |
| Very hard | 9-12 (161-200) | Softener or PeakFlow highly recommended | Residential once a year; commercial twice a year |
| Extremely hard | >12 (200) | Softener or PeakFlow required | - |
Other max levels: hardness 200 mg/L, chloride 250, copper 1.0, iron 0.3, manganese 0.05, sulfate 250, TDS 500, zinc 5, chlorine 4 mg/L; aluminum 0.05-0.2 mg/L; pH 6.5-8.5.
Flushing is advised when no treatment device is installed; use white vinegar or a tankless descaler.
- Installation clearances (indoor / outdoor) · Navien NPN
Models that show this code
14 models in Navien NPE-2, Navien NPN
Other codes on the same units
- Hot water recirculation icon Hot water recirculation indicator
- Hot water set temperature Hot water temperature setting display
- ID 1. Allocated! Cascade sub unit ID assigned
- MA.00 Cascade main unit confirmed
- Main/Sub Cascade main or sub unit indicator
- Master unit icon Master unit (cascade) indicator
- Preheat icon Recirculation schedule / preheat icon
- R&D information menu R&D information menu (Power off, key sequence)
Save it for the next call
Star this code in the HVACopedia app and keep the whole library on your phone for jobs with no signal.
Source: Navien NPE-A2/S2 Installation Manual, 4.6.1-4.6.2, p.65-66; Navien NPN-U/NPN-E Installation Manual, 4.5.1-4.5.2, p.52-53. Summarized in our own words; check the original manual for your model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.