ļ 2002 by ELTRA GmbH Germany ā January 2002 ā Service Manual OH 900 / ON 900 / ONH 2000
1.10-1
1.10
1.10
The message "No Water Flow" appears on the display
The message "No Water Flow" appears on the display, if the water flow detector on the
board ON21 cannot recognise the flow ( detector wheel not rotating ).
The pump can be checked for operation, by removing the screw in the middle of its front
plate. This way one can see whether the pump shaft is rotating or not.
Is the
water in the
wheel case very
dark so that the wheel
almost can not
be sheen
?
Clean the optical
element from dust
by using a soft
brush
Air
in tubes
?
Pump
operating
?
Water
detector wheel
running
?
no
If necessary,
change pump
Check the
wiring from
pump to mains
switch for
continuity
see 4.2
Check water
tubes for bends
Check if water
is clean
yes
If necessary,
change pump
yesno
no
N O W A T E R F L O W
220VAC
pump voltage
present
?
yes
no
Displace air
see 2.6
operational
manual
yes
The pump
is jammed,
release it,
see 1.10
Change the water, see
operation manual 1.7
yes
P 1 P 2 P 3
TP8
TP7
TP6
TP5
TP4
TP3
TP9
J 1
TP2
TP1
TP10
no
yesno
About
13-15VDC on
TP6+TP9
of ON21
?
About
6-12VDC on
TP12+TP9
of ON21
?
yes
no
no
yes
Replace ON21
Try spacing
photo cells of
the water flow
detector
Replace ON21
About
13-15VDC on
TP14+TP9
of ON21
?
Check the wiring between
ON21 and electronic unit,
see 1.13 and 4.2
Change the electronic
drivers, see 1.20
1-10
See 1.13
furnace
temperature
too high
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