26
Installation and maintenance instructions auroSTEP plus 0020077748_FT1
8.3
Checking the expansion relief valve
H
Danger!
Risk of being scalded by hot water!
The blow-off line for the expansion relief valve
mounted on the customer side must remain
permanently open.
• Check the function of the expansion relief valve by
venting it.
• Replace the expansion relief valve if no water escapes
when venting it or if the valve does not close properly.
8.4
Changing the solar fluid
The solar fluid must be changed every three years.
a
Caution!
Vaillant only assumes liability for the function
of the solar energy system if it is filled with
Vaillant solar fluid (Part Nos. 302363,
302498). The filling volume is about 12 l.
Draining the solar fluid
1
4
3
2
Fig. 8.3 Draining the solar fluid
• Switch off the solar energy system by interrupting the
power supply.
• Open the two screw couplings (
1
) and (
4
) between the
2 in 1 solar copper pipe P and the short coper pipes on
the solar cylinder unit (this can result in possibly hot
solar fluid escaping).
• Connect a hose (
3
) (approx. 1.5 m long) to the lower
filling connection (
2
).
• Pass the end of the hose into a suitable collection
container with a volume of at least 10 l.
• Open the valve on the lower filling connection (
2
).
• Completely drain the solar fluid.
• Close the valve on the lower filling connection.
• Remove the hose from the lower filling connection.
Filling the solar fluid
h
Note!
When filling with new solar fluid, establish a
blow-off line from the solar expansion relief
valve to the collecting container.
3
2
4
1
Fig. 8.4 Filling the solar fluid
• Open the valve on the upper filling connection (
2
).
• Connect a hose (
3
) to the upper filling connection and
plug a funnel (
4
) into the other end of the hose.
• Hold the funnel approx. 0.5 m
above the filling con-
nection.
h
Note!
The hose must be absolutely free of kinks and
goosenecks.
8 Maintenance
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