Checking The Plate Heat Exchanger; Checking The Flue Gas Temperature Sensor - Viessmann Vitodens 200-W Installation And Service Instructions For Contractors

Troubleshooting
Repair
(cont.)

Checking the plate heat exchanger

A
EDC
B
F G H K
Fig. 50
Heating return
F
Cold water
G
Heating flow
H
DHW
K

Checking the flue gas temperature sensor

The flue gas temperature sensor locks out the boiler
when the permissible flue gas temperature is excee-
ded. Reset the interlock after the flue system has
cooled down by pressing reset button R.
A
Fig. 51
86
01. Shut off and drain the boiler on the heating water
and DHW sides.
02. Release the side closures and pivot the control
unit forward.
03. Disconnect leads from comfort sensor
04. Remove the retaining clip and siphon
05. Remove thermal insulation
06. Undo screws D and remove plate heat
exchanger through the front.
E
Note
During disassembly and once removed, small
amounts of water may escape from the plate heat
exchanger.
07. Check the connections on the DHW side for scal-
ing, and if required clean or replace the plate heat
exchanger.
08. Check the connections on the heating water side
for contamination, and if required clean or replace
the plate heat exchanger.
09. Install in reverse order using new gaskets.
10. Danger
Escaping gas leads to a risk of explosion.
Check all gas equipment for tightness.
20
10
8
6
4
2
1
0.8
0.6
0.4
10 30 50 70 90 110
Temperature in °C
Fig. 52 Sensor type: NTC 10 k
1. Pull leads from flue gas temperature sensor
2. Check the sensor resistance and compare it with
the curve.
3. Replace the sensor in the case of severe deviation.
.
A
.
B
.
C
Ω
.
A