Actions
7
We reserve the right to make technical modifications
Buderus Ltd. • http://www.buderus-domestic.co.uk
Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006
49
box 110
z
Use a digital contact-type thermometer to measure the
temperature in the vicinity of the corresponding sensor.
z
Compare the resistance readings with the values listed in
box 111.
z
Replace the corresponding sensor if the reading fluctuates
by more than 10% with respect to the reference value (e.g.
infinitely high resistance in the event of a line break or
resistance of 0
Ω
in the case of a short circuit).
z
Reinsert the plug.
z
Refit the casing and place the boiler into operation,
box 111
box 112 Check the flow, safety and DHW temperature
sensors – cables
H
DANGER OF FATAL ACCIDENT
due to electric shock
A
CAUTION!
To prevent damage, do not insert the measuring
electrodes of the multimeter too far into the holes of the
plug-and-socket connection.
z
Take the boiler out of service and tip the DBA control panel
forwards, see box 43, 44, 47 or 63.
z
Loosen the six screws and remove the rear section,
z
Pull out the plugs of the flow NTC sensor and safety
sensor, see box 105.
Resistance readings (approximate values) for the sensor
Temperature
in °C
Resistance in
Ω
Temperature
in °C
Resistance in
Ω
0
29,490
5
23, 462
55
3,271
10
18,787
60
2, 760
15
15,136
65
2, 339
20
12, 268
70
1, 990
25
10,000
75
1, 700
30
8,197
80
1,458
35
6,754
85
1,255
40
5,594
90
1,084
45
4, 656
95
940
50
3 ,893
100
817
box 113
Key to terms:
1) Flow NTC sensor
2) Safety sensor
z
Set multimeter to “measure resistance”.
z
Check the cables of the flow NTC sensor and safety
sensor for breaks. The electrical resistance measured at
each individual wire must be approximately 0
Ω
.
z
Check the cables of the flow NTC sensor and safety
sensor for internal short circuits. The level of electrical
resistance, measured between two wires, must be
infinitely high.
z
Measure the electrical resistance of the flow NTC sensor
and check the earth (ground) connection of the safety
sensor. This must be infinitely high.
13
JP3
12
11 10
1)
2)
