Stiebel Eltron SOL 27 BASIC Utilisation Et Installation page 33

The pump starts and switches itself off again
shortly afterwards. This repeats a few times
until the system runs correctly. The same hap-
pens in the evening.
The pressure gauge indicates a drop in pres-
sure.
The pump runs noisily.
The system runs noisily. This is normal in the
first few days after filling. There are two possi-
ble causes if this occurs later:
The cylinder cools down over night. After the
pump has stopped, the flow and return operate
at different temperatures. At night the collector
temperature is higher than the outside tem-
perature.
Reheating does not work. The boiler runs for a
short while, stops and starts again. This repe-
ats frequently, until the cylinder has reached
its set temperature.
The cylinder cools down excessively.
The pump does not switch off.
There is still too little insolation to heat up the ent-
ire pipework.
The flow rate is too high (the pump is set too high). Reduce the output stage of the pump.
The switching temperature differential of the con-
troller is set too low.
The pipework is not fully insulated.
The cylinder and collector sensors are interchan-
ged. (The problem occurs after commissioning).
A pressure drop shortly after the system is filled is
quite normal, as air is still escaping from the sys-
tem. A pressure drop later on can be caused by an
air lock that has shifted. In addition during normal
operation, the pressure fluctuates by 0.02-0.03 MPa
depending on the system temperature. If the
pressure drops continuously, the system is leaking
somewhere.
Fluid loss as a result of opening the safety
valve, because the expansion vessel is not large
enough,or it is depressurised or faulty. Collector
damage (leaking) and frost damage through insuf-
ficient frost protection.
Air in the pump.
Inadequate system pressure.
The system pressure is too low. The pump draws in
air via the air vent valve.
The pump rate is too high.
The gravity brake does not close.
Single pipe circulation for short pipework with low
pressure drop.
There is air in the reheat indirect coil.
The indirect coil surface area is too small.
The insulation is faulty or incorrectly fitted.
Incorrect setting of the control unit for reheating.
DHW circulation runs too frequently and/or at night. Check the switching times and the interval operation.
Sensor faulty or incorrectly positioned.
The control unit is faulty.
Check for faults again when there is strong insolation.
Increase the switching temperature differential on the con-
troller.
Insulate all pipes.
Connect the temperature sensors to the correct sensor
terminals (see the control unit installation and operating in-
structions).
Is the automatic air vent valve closed?
Check the threaded fittings, glands on shut-off valves and
threaded connections. Check the soldered joints.
Check the pre-charge pressure of the expension vessel and
ensure the diaphragm is not leaking.
Check the vessel size. Check the antifreeze level and the
pH value.
Vent the pump.
Increase the system pressure.
Check whether the selected expansion vessel is large enough.
Check the pre-charge pressure of the expansion vessel. In-
crease the system pressure.
Change to a lower pump rate and check the flow rate at the
flow meter with balancing valve.
Check the position of the adjusting screw. Check the gravity
brake for leaks. Has swarf become jammed or are there dirt
particles on the sealing surface?
Change the line routing. Never connect the solar heat ex-
changer directly but draw the supply lines first in a U dow-
nwards. The siphon assists the gravity brake. If required,
install a two-way valve that is switched simultaneously with
the pump.
Vent the reheat indirect coil.
Compare the details supplied by the boiler manufacturer and
those of the cylinder manufacturer. The problem may be re-
solved by selecting a higher flow temperature at the boiler.
Check whether the insulation is intact. Insulate the cylinder
connections.
Check the setting on the boiler control unit.
Check the sensor position, installation and curves.
Note: The variable speed pump does not stop immediately
but only after it reaches its lowest speed.