Rinnai Q85SN Installation & Service Instructions Manual page 66

16.1.5
66
Block 67
check the sensors
NTC 1 and NTC 2
a temperature difference has been detected
between the supply and return sensor whilst
the burner is not in operation. After the
average T has disappeared, the block will
disappear.
check the supply and return sensor for the
resistance value and replace the defective
sensor
check the installation for any external heat
source and rectify this