HVACopediaNavien · Tankless water heater
Preheat icon Recirculation schedule / preheat icon
What the display is showing
The preheating icon turns on during a reservation (timer) schedule and the Reservation area flashes. During recirculation started with Preheat & Timer the icon flashes continuously. Timer steps are 30 minutes; up to 3 schedules.
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
- MA.00 Cascade main unit confirmed
- MAIN Remote asks for main/sub setting
- Main/Sub Cascade main or sub unit indicator
- Master unit icon Master unit (cascade) indicator
- R&D information menu R&D information menu (Power off, key sequence)
- Recirculation mode display Recirculation mode display
- Recirculation/Space Heating Recirculation / space heating indicator
- Remote LED Remote controller LED colour
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Source: Navien NPE-A2/S2 Installation Manual, 4.9-4.10, p.68-69; Navien NPN-U/NPN-E Installation Manual, 4.8-4.9, p.55-56. 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.