Error Code 90 - Rheem RTG2-42 Troubleshooting Manual

5. If the unit does not operate on initial installation or after replacement of the PCB, then the
circuit board requires programming with the fuel type and altitude chip.
WARNING: When replacing High Altitude Connector, turn off the electric power to water heater.
Pull out the power cord to
disconnect electricity.
Reconnect power cord.
Was the proper
high altitude
fuel type
connector
installed?
Yes
When the
power turns on,
does the Error
Code 82 still
display?
Install & adjust the proper Program chip according to the instruction. A different Program
chip is required for every 3,280 feet. The Program chip is not interchangeable between Indoor
and Outdoor models or type of gas. Check the number on the High Altitude Connector.

Error Code 90

Explanation: Blocked Flue. The venting system has failed the pre-purge test. At a minimum
check the following:
1. Ensure maximum vertical vent length and elbows do not exceed allowable limits.
2. Ensure maximum horizontal vent length and elbows do not exceed allowable limits.
3. Check heat exchanger flapper valve at vent connection of water heater moves freely.
4. Is the entire vent structure clear and clean of any obstructions?
5. Remove all obstructions. Check the vent termination on the outside of the building and
the flapper valve at the top of the heat exchanger
6. You may rule out the venting by temporarily disconnecting the vent structure from the
water heater. If this fixes the problem, then the issue lies in the venting. If this does not
fix the problem, then the issue lies in the blower motor or printed circuit board.
No
Install or adjust the high altitude fuel
type chip/dip switch settings
No The water heater seems to be normal.
Try to operate again.
Yes
Replace the Printed Circuit Board and program chip
62
SVC 810 Tankless Troubleshooting Manual