ERROR CODE
CAUSE
ACTION
ER1
Full sweep value less than 90% of
commissioned value. This is likely due to
debris inside of the valve.
Service internals of mixing valve and clean or
replace parts. See page 34 for complete
service instructions
ERPR
Inlet pressure differential greater than 10% Investigate cause of pressure differential
ERT3OS
Outlet temperature probe disconnected
from controller, not properly installed to
controller, or broken.
Check wired connection to controller and
confirm proper configuration (see page 28 for
wiring diagram). Replace probe if broken
ERT1OS
Inlet hot water temperature probe
disconnected from controller, not properly
installed to controller, or broken.
Check wired connection to controller and
confirm proper configuration (see page 28 for
wiring diagram). Replace probe if broken
ERT3+
Outlet temperature greater than 5°F above
set point
Investigate cause
ERT1+
Inlet hot water temperature is above 185°F
Investigate cause of hot water temperature
being too high. Check hot water source
ERT1-
Inlet hot water temperature is below set
point and is too cold
Investigate cause of hot water temperature
being too low. Check hot water source
ERT3-
Outlet temperature greater than 5°F below
set point
Investigate cause
ERT4OS
Return water temperature probe
disconnected from controller, not properly
installed to controller, or broken.
Check wired connection to controller and
confirm proper configuration (see page 28 for
wiring diagram). Replace probe if broken
ERT2OS
Inlet cold water temperature probe
disconnected from controller, not properly
installed to controller, or broken.
Check wired connection to controller and
confirm proper configuration (see page 28 for
wiring diagram). Replace probe if broken
ERT4+
Return water temperature greater than set
point temperature
Investigate cause
ERT4-
Return water temperature more than 20°F
below set point temperature
Investigate cause
ERT2+
Cold water temperature greater than set
point temperature
Investigate cause
24
Nucleus Digitally Controlled Mixing Valve Error Codes
Error codes are displayed on LCD screen once TTML has been exceeded. Errors must be manually cleared
by pressing ENTER when TTL time has elapsed and the error condition has not been corrected. Error codes
below are listed in order of importance to valve and system performance.
