HVACopediaNoritz · Tankless water heater
MM31 Maintenance monitor 31 - outlet water temperature
What the display is showing
Shows the temperature of water leaving the heater. If it equals the set temperature the problem is probably in the plumbing or fixtures. Useful with code 90 and with complaints of lukewarm or fluctuating water.
Applies to: EZ, NRCR, CDV, NRC/NRCP
What to do
- Open the maintenance monitor (display window, remote or EZ Start Plus app).
- Select the MM number.
- Read the value, compare with set temperature and expected behaviour.
Settings for these units
Indoor clearances (required and recommended) · Noritz NRCR
| Location | Required | Recommended (service) |
|---|---|---|
| Top | 12 in. (300 mm) | 3 in. (76 mm) above and below exhaust |
| Front | 4 in. (100 mm) | 24 in. (610 mm) |
| Sides | 3 in. (76 mm) | 8 in. (203 mm) |
Required clearances apply to both combustible and non-combustible materials.
Recommended space is for service and quick access to gas and water shut-offs.
Operation panel menu settings and defaults · Noritz EZ, Noritz NRCR
| Setting | Options | Default |
|---|---|---|
| Max Set Temperature (power off) | 100-140 F in 5 F steps; 37-48 C, 50-60 C | 120 F / 50 C |
| Recirc ON/OFF | ON / OFF | OFF |
| Recirc Mode | Always OFF, Always ON, Manual Timer, Auto Learning (NRCR) | Always OFF |
| Vacation Mode | Active / Inactive | Inactive |
| Flow Meter Alarm | 10-60 gal (5 gal steps), 70-100 gal (10 gal steps), OFF | Alarm OFF |
| Drain Water (power off) | Start / Cancel | Cancel |
| Scale Flushing (power off) | Start / Cancel | Cancel |
| Audible Alarm | ON / OFF | ON |
| Screen Lock | Active / Inactive (4-digit password) | Inactive |
| Units (first 10 min after power-up, power off) | [F/gal/ft] or [C/L/m] | [F/gal/ft] |
| Power Saving Dis. / Backlight | ON-OFF / Power Save ON-OFF | ON / Power Save ON |
| Brightness / Contrast / Touch Sound | Bright-Normal-Dim-Dark / -15 to +15 / ON-OFF | Normal / Standard / ON |
Setting 125 F (55 C) or higher needs Max Set Temperature raised first; the panel warns about scald risk.
Default Settings resets everything in Settings except Screen Lock (hold OK about 5 s).
- Water quality limits · Noritz EZ, Noritz NRCR
Models that show this code
12 models in Noritz EZ, Noritz NRCR, Noritz CDV, Noritz NRC/NRCP
Other codes on the same units
- C1# Descaling reminder (C11-C19)
- F76 Multi-system communication error
- MM14 Maintenance monitor 14 - flow rate
- MM30 Maintenance monitor 30 - inlet water temperature
- MM32 Maintenance monitor 32 - heat exchanger water temperature
- MM49 Maintenance monitor 49 - fan speed
- MM86 Maintenance monitor 86 - recirculation mode
- BURNER ON indicator Remote burner-on indicator
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Source: Noritz EZ/NRCR/CDV Level 2 (Premix R2 V2), Maintenance Monitors, p.18-21; Noritz Residential Level 2 (NRC/NRCP and older, R2 V1), Maintenance Monitors, p.12-14. 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.