Various - Viessmann SCU 123 Manual

SCU 123
6.1

Various:

Pump is overheated, but no heat transfer from the
collector to the tank, flow and return have the same tem-
perature; perhaps also air / gas bubbles in the lines.
Air in the system?
no yes
Is the collector circuit
blocked at the dirt trap?
yes
Pump starts up very late
Switch-on temperature
difference ∆Ton to large?
no yes
Non-ideal position of the coll-
ector sensor (e.g. flatscrew
sensor instead of sensor in
sensor wells)?
yes
Air in the system; in crease
the system pressure to at
least static primary pres-
sure plus 7. 25 psi (0.5 bar);
if necessary continue to
increase pressure; switch
the pump off and on for a
short time.
Clean the dirt trap
Change ∆Ton and ∆Toff
correspondingly.
Activate tube collector
function if necessary.
o.k.
Pump starts for a short moment, switches off, switches
on again, etc.
Temperature difference
at the controller too
small?
no yes
Wrong position of collec-
tor sensors?
no
yes
Plausibility control of
the option tube coll-
ector special function
The temperature difference between tank and collector
increases enormously during operation; the collector cir-
cuit cannot dissipate the heat.
Collector circuit pump
defective?
no yes
Heat exchanger calcified?
no yes
Heat exchanger blocked?
no yes
Heat exchanger too
small?
yes
Change ∆Ton and ∆Toff
correspondingly. Problem
solved?
no
yes
o.k.
Mount the collector sen-
sor at solar flow (warmest
collector output); use sen-
sor well of the respective
collector.
Check / replace it
Decalcify it
Clean it
Replace with correctly
sized one.
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