Error Code 16; Error Code 21 (Indoor Models Only) - Rheem RTG2-42 Troubleshooting Manual

Error Code 16

Explanation: Outlet water temperature is to hot. The outlet water temperature is above set point
on the remote control. The unit cannot resolve the issue with the cold-water by-pass function.
Display maintenance information line [5y] Hot Water
Outlet Thermistor temperature.
Does the
maintenance
information
indicate the hot
water outlet temp?
Yes
The water heater appears to be normal. Attempt
to operate again. Check the water flow servo –
especially the cold water bypass solenoid for
operation. Check for blockage in the cold water
bypass piping.

Error Code 21 (Indoor Models Only)

Explanation: Air intake filter switch does not work. The air intake filter switch ensures the front
cover is attached and the inlet filter screen is in place and clean. Air intake switch and Error
Code 21 has been removed from second generation 4.2, 5.3 and all Direct Vent (DV) models. At
a minimum check the following:
1. Make sure air filter door is properly seated and clean.
2. Make sure front panel is properly installed with all four retaining screws.
3. Press the air intake switch when operating the unit without the front cover installed.
Is the Air Filter
switch OK?
Yes
Replace the Printed Circuit Board
No
Is the resistance
to the hot outlet
thermistor OK?
Yes
No
Replace Air Filter Switch Assy
Press filter switch down. Measure the voltage and resistance of
connector O between both white wires:
Voltage = less than 1 VDC
Resistance = 1 ohm
53
SVC 810 Tankless Troubleshooting Manual
No
Measure the resistance of
connector R between Black#3
and Red#4 wires: 4k - 10 k ohms
Replace Printed Circuit
Board.
Replace Hot Water
Outlet Thermistor.