Stiebel Eltron SOL 23 Premium Utilisation Et Installation page 42

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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 pos-
sible causes if this occurs later:
The cylinder cools down over night. After the
pump has switched off, the flow and return
operate at different temperatures. At night the
collector temperature is higher than the out-
side temperature.
Reheating does not work. The boiler runs
briefly, stops and starts again. This repeats
frequently, until the cylinder has reached its
set temperature.
The cylinder cools down excessively.
The pump does not switch off.
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There is still too little insolation to heat up the en-
tire 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 inter-
changed. (The problem occurs after commission-
ing).
A pressure drop shortly after the system is filled
is quite normal, as air is still escaping from the
system. A pressure drop later on can be caused by
an air lock that has shifted. In addition, during nor-
mal 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 unpressurised or faulty. Collector damage
(leaking) and frost damage through insufficient
antifreeze content.
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 set too high.
The gravity brake does not close.
Single pipe circulation for short pipework with low
pressure drop.
There is air in the reheat heat exchanger.
The heat exchanger 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
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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 termi-
nals (see the control unit installation and operating instruc-
tions).
Is the automatic air vent valve closed?
Check the fittings, the glands on shut-off gate valves and the
threaded connections. Check the soldered joints.
Check the pre-charge pressure of the expansion vessel and
ensure the diaphragm is not leaking.
Check the vessel size. Check the antifreeze content 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.
Switch to a lower speed 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 a swarf become jammed or are there dirt
particles on the sealing surface?
Change the line routing. Never connect the solar heat
exchanger directly but draw the supply lines first in a U
downwards. The siphon assists the gravity brake. If required,
install a two-way valve that is switched simultaneously with
the pump.
Vent the reheat heat exchanger.
Compare the details supplied by the boiler manufacturer with
those supplied by the cylinder manufacturer. The problem
may be resolved 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 switch off immedi-
ately but only after it reaches its lowest speed.
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