11
7. Fault finding
Before starting work on the pump, make sure that the electricity supply has been switched off and that it cannot be
accidentally switched on.
Fault Possible cause Remedy
1. The pump fails to start. a) The electricity supply is switched off. Switch on the electricity supply.
b) The fuses are blown. Replace the blown fuses. If the new ones blow too,
the electric installation should be checked.
c) The built-in thermal protection has switched
off the motor.
The thermal protection resets automatically within
1 to 2 hours.
d) Isolating valves are closed. Open the isolating valves.
e) Strainers are blocked. Close the service isolating gate valves, clean the
strainers and re-open the service isolating gate valves.
f) Pump installed with non-vertical discharge
ports (flow switches).
The pump must be installed with vertical discharge ports
(flow switches).
g) Insufficient water flow, below 0.5 l/min. Increase the water flow to at least 0.5 l/min.
2. The flow from the
shower drops.
a) Blocked strainers. Clean the pump strainers.
3. The pump runs
continuously.
a) A tap or outlet is open. Ensure that there are no leaks and that all taps and
appliances are closed.
b) Air in the system. Vent the system.
c) The float in the flow switch is stuck in the
up (on) position.
Make sure that the flow switch can operate correctly and
there is no debris in the flow switch.
d) Flow switch or reed switch faulty or
incorrectly set.
Adjust or replace as appropriate.
4. The pump pulses. a) The use of other taps in the house may
cause the pump to start momentarily.
Ensure that taps or other outlets are not causing water
hammer. A low-pressure non-return valve can be fitted
on the outlet pipework from the pump.
Contact your installer.
5. Unstable water
temperature/noisy
pump.
a) Air entering the pump, most commonly from
the hot-water cylinder.
Fit a Surrey flange and study the pipework layout.
There should be no high points where air can collect.
b) Too high water temperature. Reduce hot-water temperature. The maximum
recommended hot-water temperature setting is 60 ºC
(140 ºF).
c) Debris caught in the impeller casing. Remove debris.
6. Noisy pump. a) Vibration through pump mounting surface. Mount the pump on a concrete slab to reduce noise.
7. Hose connection
leaking.
a) Hose connection loose. On STC, STR, SSR, STL and SSL pumps, ensure that
the hose washers and strainer washers are fitted.
Ensure that the plastic nuts on the hoses are tight.
On STP and SSP pumps, ensure that the hose
connection is fully inserted to a minimum depth of
33 mm.
Grundfos.bk Page 11 Thursday, April 22, 2010 10:28 AM
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