Grundfos Geo-Flo Universal Pump Controller Installation, Operating And Maintenance Manual page 20

18 | Installation, Operating, and Maintenance Manual
Additional Troubleshooting (continued)
Problem
Controller will not energize the
UPS26-99.
Sporadic flow rate display on con-
troller.
Controller displays "PROTECTED"
and will not respond to button
inputs.
Controller will not respond to but-
ton inputs when trying to change
flow rate, ΔT, etc.
Controller displays
"1 PUMP RUNNING" or
"2 PUMPS RUNNING,"
but heat pump is off.
Pump continually overshoots and
undershoots set point in ΔT mode
(i.e. pump ramps up and nearly
stops).
Possible Cause
No 208-230V input power at L2/
N2 IN.
No 208-230V output power at L1/
N1 OUT.
UP26-99 not required to meet the
demand (set point for flow or ΔT).
Bad relay on controller PCB.
Grundfos VFS Sensor/ Senor tube
mounted incorrectly.
Plumbing disturbance in front of
entrance to flow tube.
Air in loop.
Sensor dirty or defective.
Controller Lockout mode has been
set to SCREEN.
Controller Lockout mode has been
set to PARAM.
Controller may be connected
directly to thermostat. In some
cases, backfeed voltage could
cause pump(s) to run.
Small pump speed changes result
in large ΔT swings at low flow
rates.
Rev. 05JUL2016
Solution
Correct input/output wiring.
To check UPS26-99 operation,
increase the demand (i.e. required
flow rate) incrementally and moni-
tor the display. When the pump
is at or near its maximum perfor-
mance level the power will read
about 230W. A higher demand will
result in the relay energizing L1/N1
OUT terminals (UPS26-99) and/or
a "FLOW SETPOINT" warning.
Replace controller.
Check direction of flow arrow on
sensor tube body and re-plumb if
necessary.
Re-plumb to remove disturbance.
Flush loop.
Remove sensor and clear debris.
Replace sensor if necessary.
Change Lockout mode to None or
Parameter. See Lockout Setup sec-
tion for more information.
Change Lockout mode to None.
See Lockout Setup section for
more information.
Wire controller as shown on pageS
5 & 6 with isolation between ACC
and Y2.
Increase MIN % to prevent pump
from stopping.