Buderus 500 - 28/C Servicing Manual page 26

6 Diagnosis
box 23
Replace the servomotor of the internal 3-way valve, see box 190.
step 30
Check the power supply cable of the internal 3-way valve, see box 191.
step 31
Is the power supply cable of the internal 3-way valve in good condition?
step 32
Replace the cable loom (or the affected part thereof).
step 33
Check the movement of the servomotor of the Buderus 24V AC external 3-way valve, see box 211.
step 34
Does the servomotor of the Buderus 24V AC external 3-way valve operate correctly?
step 35
Check to ensure that the the Buderus 24V AC external 3-way valve has been fitted correctly,
step 36
see box 227.
Has the Buderus 24V AC external 3-way valve been fitted correctly?
step 37
Install the Buderus 24V AC external 3-way valve correctly, see box 227.
step 38
Check to ensure that the Buderus 24V AC external 3-way valve is actuated correctly,
step 39
see box 212 and box 228.
Does the Buderus 24V AC external 3-way valve actuate correctly?
step 40
Replace the servomotor of the Buderus 24V AC external 3-way valve, see box 217.
step 41
Check the wiring of the Buderus 24V AC external 3-way valve, see box 220.
step 42
Is the wiring of the Buderus 24V AC external 3-way valve in correct condition?
step 43
Replace the wiring of the Buderus 24V AC external 3-way valve.
step 44
Check the drive mechanism of the Buderus 24V AC external 3-way valve, see box 221.
step 45
Is the drive mechanism of the Buderus 24V AC external 3-way valve working correctly?
step 46
Replace the internal components of the Buderus 24V AC external 3-way valve, see box 224.
step 47
Check the wiring of the Buderus 24V AC external 3-way valve between the connection box or moving plug-
step 48
and-socket connection and the DBA control panel as per box 287.
box 24
On combi boiler supply: hot water available, but no heating operation.
On system boiler supply: no heating operation.
Hot water may be available, but no heating operation.
Check to ensure that the power supply cable to the RTH converter/Junction box has been installed correctly,
step 1
see box 285.
Is the 230V connection to the RTH converter/Junction box fitted correctly?
step 2
Correctly attach the switch live to terminal 1 and Neutral to terminal 2 on the 230V connector, see box 285.
step 3
Disconnect black leads from terminals 1 & 2 on the back of the DBA and test for continuity between the two
step 4
leads.
No continuity check S/L and N connections are made correctly and that there is 230v between the two.
Replace RTH converter/Junction box.
Continuity reconnect the cables to terminals 1 & 2 and check the connections between the terminals and
the DBA.
Is the volt free connection to the RTH converter/Junction box fitted correctly?
step 5
Check to ensure that the connections of the external control unit are attached to terminal 1 and 2 of the
step 6
connection block, indicated by a clock inside a rectangle, see box 286 and box 285 (item 3).
We reserve the right to make technical modifications
26 Servicing manual Gas condensing boiler Buderus 500-24/S, 500-24/C and 500-28/C • Issued 02/2006
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Buderus Ltd. • http://www.buderus-domestic.co.uk
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