Function
4
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
15
step 22
Is the current CH flow temperature lower than 7 °C (frost protection)?
Yes:
→
step
62
No:
→
step
23
step 23
The pump is run for 10 seconds in order to prevent it from seizing up.
step 24
Have 10 seconds elapsed?
Yes:
→
step
18
No:
→
step
25
step 25
Is the plate heat exchanger triggered and/or is the temperature in the external storage-type water heater at least
5 °C below the temperature set at the DBA control panel?
Yes:
→
step
28
No:
→
step
26
step 26
Is there a current heat requirement from the (room) temperature controller?
Yes:
→
step
46
No:
→
step
27
step 27
Is the current CH flow temperature lower than 7 °C (frost protection)?
Yes:
→
step
62
No:
→
step
24
step 28
The symbol “
H
" or “
I
" for hot water mode on the DBA control panel display lights up.
step 29
C [0c]
The fan runs at 49 % of capacity.
The 3-way valve turns to the hot water setting for two seconds.
The glow ignitor is activated for two seconds.
step 30
C [0l]
Ignition phase: The gas valve is opened. The glow ignitor is activated for one second, followed by
alternating half-second periods of inactivity and activity until five seconds have elapsed.
step 31
Does the ionisation current exceed 1.4 µA (microamperes) within 5 seconds?
Yes:
→
step
32
No:
→
step
72
step 32
C [=h]
The boiler is in hot water mode. If there has been a power cut: The startup load on the boiler is 49%
for the first 13 seconds for the purposes of flow monitoring. It is then increased or decreased accordingly. The
symbol ”
G
“ lights up.
step 33
Is the temperature in the plate heat exchanger higher than the temperature entered via the DBA control panel? Yes:
→
step
39
No:
→
step
34
step 34
Is the CH flow temperature 46 °C higher than the preset DHW temperature and/or higher than 93 °C?
Yes:
→
step
35
No:
→
step
32
step 35
C [0y]
The gas valve is closed and the burner is shut down.
step 36
The symbol ”
G
“ goes out.
step 37
The fan stops after 30 seconds.
step 38
Is the CH flow temperature lower than the preset DHW temperature plus 35°C?
Yes:
→
step
29
No:
→
step
38
step 39
The gas valve is closed and the burner is shut down.
step 40
The symbol
G
goes out.
step 41
Start of pump over-run time via the cylinder.
Start of pre purge phase (10 seconds).
step 42
The fan stops.
step 43
C [0h]
The pump stops.
step 44
The 3-way valve turns to the heating mode setting for two seconds.
The symbol “
H
" or “
I
" goes out.
step 45
Is there a current heat requirement from the (room) temperature controller?
Yes:
→
step
46
No:
→
step
19
step 46
The symbol
K
lights up.
step 47
C [0c]
The fan runs at 49 % of capacity. The pump is started up.
The glow ignitor is activated for seven seconds.
step 48
C [0l]
Ignition phase: The gas valve is opened.
box 15
Boiler Functions
