Bosch HP270-2 Technical Manual page 44

Code E04 – Warning Code (self reset when press OK * and T top < 75ºC)
Temperature in storage tank higher than 80ºC (Detected by the hot water NTC in the top of the tank)
* Note: appliance will work if a start condition is reached, however error must be acknowledge by the user.
The Top NTC sensor is
measuring a wrong
temperature value
Replace wiring
Ensure set point in solar
control is maximum 70ºC
Ensure máx inlet
temperature is < 70ºC
Ensure set point in boiler
is in maximum 70ºC
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Unplug the NTC connection wire
and measure the NTC electrical
resistance [R] (Ω)
[R] Ω = Current Temp.
No
(ºC) ?
Yes
Yes
Appliance connected with
a solar thermal system?
No
HP tank installed as back
Yes
up and receiving pre-
heated water?
No
Appliance connected with
Yes
a boiler system?
6-720-821-364 SM HP270 – 250 - 200 2016/12 en
Refer to table with values
in Service Manual