Can I keep resetting Rheem code 14?

No. Code 14 is an overheat safety. Resetting it without fixing the cause risks damaging the heat exchanger.

Rheem Tankless Code 14 (Overheat): Causes and What to Do

Code 14 is a safety shutdown. The heat exchanger reached a temperature high enough to trip the overheat protection, and the unit stopped firing.

Treat it seriously. The code is a sign that something is making the heater run hotter than it was designed to.

Never bypass an overheat safety device. It is there to prevent damage and fire.

What you can check

Clear the vent terminal outside of any blockage.
Make sure nothing is stored against the heater.
Check the maintenance history. A unit that has not been descaled in years, especially on hard water, is a strong candidate for scale.

Common causes

Scale in the heat exchanger

Scale creates hot spots because heat cannot pass into the water. Annual descaling prevents it.

Airflow and venting

Blocked vents, dust inside the unit or a failing fan can make combustion run hot.

Gas and combustion settings

Incorrect gas type, a bad conversion or gas pressure out of range can overfire the burner.

What a technician will do

Expect gas pressure checks, an inspection of the heat exchanger for damage or discoloration, a test of the safety circuit and usually a descale. Depending on the damage, the heat exchanger may need to be replaced.

Other Rheem codes

Code	Meaning
00	Continuous combustion for more than one hour
03	Communication failure between units, remote or manifold controller
05	Improper combustion detected by the flame rod (warning)
10	Air supply or exhaust blockage (hard lockout)
11	Ignition failure
12	Flame failure
13	Poor combustion detected by the flame rod (indoor units)
14	Overheat safety tripped
15	Heat exchanger or hot water temperature too high (boiling safety)
16	Outlet water temperature above the set point (over temperature warning)
21	Air intake filter switch fault (earlier models)
24	Remote control buttons held too long, or operational switch fault
29	Condensate not draining (condensing models) or heat exchanger temperature too low
31	Inlet water temperature sensor (thermistor) fault
32	Heat exchanger thermistor fault
33	Outlet (outgoing water) thermistor fault
34	Ambient or combustion air temperature sensor fault
35	Improper thermistor connection
51	Gas valve fault: flame detected after shutdown (current) / gas inlet solenoid valve fault (earlier)
52	Modulating gas valve (PGFR) fault
61	Blower (combustion fan) motor fault
65	Water volume control valve fault
66	Water bypass valve fault
71	Gas inlet solenoid valve fault
72	Flame rod fault: flame sensed before ignition
76	Remote control communication fault
79	Blower (fan) motor current fault
80	Gas cut-off failure: flame detected after the unit turned off
82	Control board program chip fault (current) / gas type data failure (earlier)
90	Vent blockage detected before ignition
92	Neutralizer needs replacing soon (warning, condensing models)
93	Neutralizer must be replaced; unit will not operate (condensing models)
1L	Lime (scale) buildup detected in the heat exchanger
99	Vent blockage detected after shutdown / blocked flue (hard lockout)
P1	Not enough water flow to fire the burner (warning)

Rheem tankless code 14: overheating, causes and fixes