2002 by ELTRA GmbH Germany – January 2002 – Service Manual OH 900 / ON 900 / ONH 2000
2.15-2
All the jumpers of J2 are set by the manufacturer.
However, adjustments are possible if necessary; for example if the furnace and the water
inside the barrel feels too hot.
Water temperature threshold adjustment
Remove the jumper from A1-A2 and install it on B1-B2
Connect multimeter between TP7 and TP9 ( GND ). Range 20 VDC.
Turn P1 counter-clockwise for lower water temperature threshold.
Turn clockwise for higher temperature threshold.
The correct temperature is approximately 40°C in th e barrel.
The voltage on TP7 for fixed temperature is about 6.1 VDC.
Note: The higher the voltage on TP7, the lower the water temperature threshold.
Furnace temperature threshold adjustments:
Analyse with a power of 8 KW ( setting = 800 ) without the tap water connected till the
message "temperature too high" appears on the display. This error message should
appear once the temperature of the furnace has reached about 70°C.
The furnace cools down very fast, after the tap water is connected.
If the error message doesn´t appear at about 70°C, then:
remove the jumper from A3-A4 and install it on B3-B4,
connect a multimeter between TP5 and TP9 ( GND ). Range 20 VDC
The voltage on TP5 for fixed temperature threshold is about 4.7 VDC.
Turn P2 counter-clockwise, for the error message to appear at lower furnace
temperature. Turn clockwise, for the error message to appear at higher furnace
temperature.
Note: The lower the voltage on TP5, the higher the furnace temperature at which
the error message „temperature too high“ appears.
Detailed explanation :
The board ON 21 contains three circuits.
One of the circuits senses the cooling water temperature. The sensor is attached to the
T-piece of the water hose. If the water temperature exceeds the threshold value,
a solenoid valve will be energised, in order to pass tap water through the coil of the
primary water flow in the tank. If the water temperature of the secundary water flow
( through the furnace ) exceeds a certain level, or if the water temperature sensor is
broken, the analyser gives a warning on the screen for too high water temperature.
At the same time the furnace power will be switched off, see also 1.11.
B3
B2
B1
B4
B5
B6
Adjus t ab l e
w a ter t emp.
Adjusta b l e
f u r n a c e t emp .
Adjusta b l e
w a ter f lo w
d e t ect i on
J 2
A5
A6
A1
A2
A3
A4
F ix e d f u rn a c e
t e m pera tu re
P1
P2
P3
A B
F ix e d
d e t ect ion
w a ter f lo w
F ix e d wa t er
te m p er atur e
0 2 - 1 7 - 1 b
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