Error Code 24; Error Code 29 - Rheem 874W27NF Service Manual

Fault Finding Test 16
SW1
Ensure the min/max
buttons are not depressed.

Error Code 24

Malfunction of Operational Switch. At a minimum check the following:
1 Verify unit is electrically earthed. Do not use a 2 prong electrical adapter on the power
cord.
2 Check for presence of return circulation pump in the system. Any water flowing through
the unit prior to turning unit ON may cause error code 24.
Error Code 24
Is the Min or Max button
depressed?
TEST 16
NO
Replace the control PCB.

Error Code 29

Heat exchanger outlet temperature is too low.
Error Code 29
Measure the hot water outlet
temperature
Display maintenance information
„5y‟ on remote control
Does the measured hot water
temperature match that
indicated by 5y?
YES
Check heat exchanger for
blockage/restriction (possible
scale build-up). Ensure air inlet is
clear and free of debris
TM061 Rheem 27 Water Star Service Instructions – Issued: 11/10
REV A Issued 08/13
This document is stored and maintained electronically by
ON
DIP1
OFF
1 2 3 4
ON
DIP2
OFF
1 2 3 4
SW2 SW3
Is the resistance of the heat
exchanger thermistor normal?
Is the resistance of the hot
NO outlet thermistor normal?
Service. All printed copies not bearing this statement in RED are deemed "uncontrolled"
Test 16
Are any cables/components inadvertently
depressing the Min or Max buttons on PCB?
YES
YES
NO
TEST 15
YES
NO
TEST 15
Release the Min/Max button.
Replace PCB
Replace heat exchanger
thermistor
Replace hot outlet thermistor
Check the burner pressure and
adjust if necessary.
Refer to section on burner
pressure adjustment
35