STIEBEL ELTRON HPG-I 04 S Premium - Noise When Bypassing the Change-Over Valve; Water Leakage at the Motor of the Changeover Valve (MA12); Blocking the DHC Stages if the Volume Flow Is too Low; Internal Brine Pressure Switch (BP18)

Repair instructions
HPG-I 04-06-08-12-15 S-CS-DS-DCS
Premium
TQR
Page 39 from 48
D0000095883-c
In cooling mode, incorrect circulation at the changeover valve (MA12) can cause the DHW storage tank to
cool down, the system frequently interrupts cooling mode and recharges the DHW storage tank.
Insufficient cooling and higher energy costs are the result. Check the function of the multifunction group.
15.3.4 Noises when bypassing the change-over valve
If there is no PWM signal at the internal circulation pump, the pump runs constantly at 100%, the
automatic speed reduction before switching over is ineffective. Faulty plug connections, interruptions in
the lines, a pump defect or a fault in the MFG electronics are possible causes.
If the operating mode changes from heating/cooling to hot water or from hot water to heating/cooling,
the following sequence is active:
• Compressor is switched off
• Buffer charging pump/hot water charging pump is switched off
• Switching valve on the MFG moves to the defined position
• Source pump, buffer charging pump/hot water charging pump is switched on
• Compressor is switched on
The switchover takes about 6 minutes, there is no indication in the display.
If the operating mode changes from the standstill of the heat pump, there is no pump standstill while the
valve moves to the new position.
15.3.5 Water leakage at the motor of the changeover valve (MA12)
In connection with deposits on the motor shaft of the changeover valve, heating water may escape. If a
defect occurs here, the water quality in the heating circuit must be checked.
15.3.6 Blocking the DHC stages if the volume flow is too low
If the measured volume flow is less than 5l/min, the electric heating element (E1) in the multifunctional
assembly (AA07) is blocked and emergency operation is not possible.
The blocking can be triggered by the following causes:
• Control or voltage supply of circulating pump (MA10) faulty
• Circulation pump (MA10) blocked/defective
• Volume flow sensor (BF01 / BT07) defective or wiring faulty
15.4 Internal brine pressure switch (BP18)
The brine pressure switch is connected to the AA02 board; if the contact is open, an error message is
triggered.
Brine pressure switch
(BP18)
AA02 (X11.8 terminal 1/3)
Pressure sensor
(BP13)
Control unit display (AA06)
open
< 0.5 bar
3-0007
closed
> 1.0 bar
No message