Check Temperature Switch; Testing The Differential Pressure Switch; Test The Continuity Of The Differential Pressure Switch At Negative Pressure - Bosch Condens 7000 F Installation And Maintenance Instructions For The Contractor

Check temperature switch

15 Check temperature switch
If service code 6A 578 is continuously displayed ( Fig. 63), the
temperature switch on the burner must be checked as follows:
Fig. 63 Display of service code 6A 578 (example of display using
MX25)
▶ Pull plug off temperature switch.
▶ Measure electrical resistance across the contacts of the temperature
switch ( Fig. 64).
If the value measured is < 1 Ohm (or signal tone, depending on
measuring device), the temperature switch is ok.
If no value, or a resistance of > 1 Ohm, is displayed ( Fig. 65)
contact the plant customer service to arrange a return and replace
the burner.
Fig. 64 Measure the electrical resistance across the contacts of the
temperature switch (temperature switch ok)
Fig. 65 Measure the electrical resistance across the contacts of the
temperature switch (temperature switch not ok)
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> 1
OFF 1000
1000
200 200
20 20
2 2
200m 200m
2 2
200m 200m
20m 20m
10A 10A
2m 2m
200 200
20m
2M 200
200K 20K 1K
0010014359-001
0L
OFF 1000
1000
200 200
20 20
2 2
200m 200m
2 2
200m 200m
20m 20m
10A 10A
2m 2m
200 200
20m
2M 200
200K 20K 1K
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16

Testing the differential pressure switch

If the service code 8L 534 is continuously displayed, the differential
pressure switch (Fig. 34, page 32) must be tested as follows to make
sure it is working correctly:
16.1 Test the continuity of the differential pressure switch
at negative pressure.
The differential pressure switch is closed during operation. The contacts
are closed.
The fan must be switched on in order to simulate an operating condition
with negative pressure.
▶ Put the control unit on standby ( Technical documentation of
control unit).
▶ Pull off plug (PWM signal) [1] at fan. The fan runs.
Fig. 66 Pull off plug (PWM signal) at fan (boiler rating 200-300 kW)
[1] PWM signal plug, boiler rating 200-300 kW
Fig. 67 Pull off plug (PWM signal) at fan (boiler rating 75-100 kW)
[1] PWM signal plug, boiler rating 75-100 kW
Condens 7000 F – 6720871560 (2019/11)
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