Viessmann SCU 123 Manual page 14

SCU 123
Heat exchanger temperature limitation
Heat exchanger antifreeze function
Evacuated tube collector function
O TC:
Evacuated tube collector
function
Adjustment range: OFF / ON
Factory setting: OFF
TCST:
Evacuated tube collector func-
tion
starting time
Adjustment range:
00:00 ... 23:00
in steps of 00:15
Factory setting: 07:00
TCEN:
Evacuated tubecollector function
ending time
Adjustment range:
00:30 ... 23:30
in steps of 00:15
Factory setting: 19:00
TCRU:
Evacuated tube collector function
runtime
Adjustment range: 30 ... 500 s
in steps of 5 s
Factory setting: 30 s
TCIN:
Evacuated tube collector function
standstill interval
Adjustment range: 5 ... 30 min
in steps of 1 min
Factory setting: 30 min
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The primary loop heat exchanger temperature limitation is
set to 212°F [100°C] to protect the system against over-
heating.
The antifreeze function of the heat exchanger activates R2
(100%) if the heat exchanger temperature falls below 40°F
[5°C].
This function helps overcome the disadvantages caused by
the non-ideal sensor position with some tube collectors.
This function operates within an adjusted time frame (be-
ginning at TCST and ending at TCEN). It activates the
collector loop pump for an adjustable runtime (TCRU)
between adjustable standstill intervals (TCIN) in order
to compensate for the delayed temperature measurement.
If the runtime TCRU is set to more than ten seconds, the
pump will be run at 100 % for the first ten seconds of the
runtime. For the remaining runtime, the pump will be run
at the adjusted minimum speed n1MN.
If the collector sensor is defective or the collector is blo-
cked, this function is suppressed or switched off.