3.5.4
Hot-water
Table 19.
Problem – Temperature and/or quantity
Cause
Troubleshooting
Remedy
1. Defective 3-way valve motor.
Check the function of the reversing valve
by test running it manually.
If the motor is defective, replace it.
2. Jammed reversing valve.
The valve is not secure and releases
hot water to the radiators during hot
water production.
Detach the motor and test closing and
opening the valve by turning the shaft by
hand.
If it jams, replace with a new one.
3. Air in TWS coil or water outer jacket.
During hot water production:
•
Listen for air.
•
Check the temperature difference
between supply and return line.
Bleed the system.
A Large temperature difference can indi-
cate air in the system.
4. Start temperature set too high for
hot water production.
Check that the start temperature is cor-
rectly set. Should not be set above the
factory set value.
•
If the start value is set too high,
reduce it to the factory set value.
5. Sensor fault, hot water sensor.
Hot water production is started by the
hot water sensor.
Check what the hot water sensor (the
start sensor) shows. Is it a plausible/actual
value?
Measure the resistance of the sensor,
check against the ohm table in Measure-
ment points, Page 11.
If the sensor is defective, replace it.
6. Large drain flow (>12 l/min).
Check how many litres of hot water
(approx. 40°C) per minute drains from the
tap.
Use a clock and bucket to measure the
drain flow.
If the drain water flow is greater than 12
l/min, stratification in the water heater is
affected, which reduces the hot water
capacity.
Suggested corrective actions:
•
Install a pressure reduction valve on
the incoming cold water pipe.
•
Change to a mixer with lower flow.
•
Adjust the drain flow on the exist-
ing mixer, do not open the tap fully.
7. Water heater too small in relation to
requirement.
How large is the requirement and what is
the capacity of the heater?
Replace with a larger heater or supple-
ment with an extra heater.
E.g. supplement with an DWH or an
electric heater.
8. The operating pressure switch opens
too soon (at too low a pressure).
Hot water production ends when the
operating pressure switch opens.
Check the break pressure using manome-
ter apparatus.
If the pressure switch opens at the incor-
rect pressure, replace it.
The replacement pressure switch can be
installed on the service output (Schrader
valve).
Service instructions VMGFJ102 – 23
