Circuit Diagrams
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21
Circuit Diagrams
Circuit diagram legend for the Thermo 90 ST
1. Temperature coding (temperature at water outlet):
Refer to following circuit diagram legend for further
information.
2. Vessel Fuse
3. Vessel Blower Switch
Thermo 90 ST Circuit Diagram Legend
Cable cross-sections
< 7.5 m 7.5 - 15 m
0.75 mm
2
1.0 mm
2
0.75 mm
2
1.0 mm
2
1.0 mm
2
1.5 mm
2
1.5 mm
2
2.5 mm
2
2.5 mm
2
4.0 mm
2
4.0 mm
2
6.0 mm
2
Cable Colors
bl
br
ge
gn
gr
or
rt
sw
vi
ws
Blue
Brown
Yellow
Green
Grey
Orange
Red
Black
Violet
White
Item Designation Comment
A1 Heater
A2 Control module
B1 Flame sensor
B2 Temperature sensor
B3 Temperature limiter/
Overheating guard
B4 Room thermostat
E Glow plug
F1 Fuse 20 A Flat fuse SAE J 1284
F2 Fuse 5 A Flat fuse SAE J 1284
F3 Fuse 20 A Flat fuse SAE J 1284
H1 “Heating” symbol in the display Operating indicator (in item
P2)
H2 Light max. 2 W Operating indicator (in item
S4)
H3 Symbol light Light (in item P2)
H5 Lamp, min. 1.2 W Switch-on indicator pumping
device
H6 Red LED Immediate heat button light,
ready indicator, switch-on
control (in item P2)
K3 Relay Circulating pump remote
control
K5 Relay for vehicle fan
M1 Motor Combustion air fan
M2 Motor Circulating pump
M3 Motor Vehicle fan
P2 Digital timer For programmed operation
S4 Switch ON/OFF
S5 1 or 2-pin disconnecting switch Emergency off switch,
electric or pneumatic
S7 Pumping device switch to positive
S8 Momentary-contact switch Immediate heat button
remote control
S9 Switch Heating/Circulating pump
remote control
S10 Switch Battery switch in positive
X1 12-pin plug connection to item A1
X3 12-pin plug connection to item P2
X5 Plug connector, 2-pin to Y1
X6 Plug connector, 2-pin Diagnostics
X11 12-pin plug connection To item A2 (ST 1)
X12 12-pin plug connection To item A2 (ST 2)
X13 Plug connector, 2-pin To item A2 (ST 3)
Y1 Metering pump Fuel pump for heater
Y2 Solenoid valve for pumping device
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