Noritz · Tankless water heater

F76 Multi-system communication error

Low severity Noritz EZNoritz NRCRNoritz CDVNoritz NRC/NRCP

What the control is telling you

Communication error between two quick-connected units.

Applies to: All Noritz residential tankless with quick connect (EZ, NRCR, NCC199CDV, NRC/NRCP)

Likely causes

More than one remote control connected on a quick-connect pair
Units are not the same model
Quick connect cord problem

Test and repair steps

Connect only one remote controller when two units are quick connected.
Make sure both units are the same model (required to quick connect).
Check the quick connect cord and connectors.

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

EZ111DVEZ71DVEZ98DVN-0841MCN-0841MC-DVN-0842MCN-0842MC-DVNCC199CDVNRC111-DVNRC111-SVNRCR111DVNRCR92DV

Other codes on the same units

65 Main water control servo abnormality
66 Bypass water control servo abnormality
73 Circuit board setting abnormality
90 Combustion abnormality
91 Gas conversion not done correctly
901 Combustion abnormality (sub-code of 90)
902 Combustion abnormality (sub-code of 90)
C1# Descaling reminder (C11-C19)

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.

Open the app

Source: Noritz EZ/NRCR/CDV Level 2 Maintenance & Troubleshooting (Premix R2 V2), 73 & F76 error codes, p.15; Noritz Residential Level 2 Maintenance & Troubleshooting (NRC/NRCP and older, R2 V1), 73 & F76 error codes, p.9. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

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.