Cause
Troubleshooting
Remedy
5. Sensor fault, hot water
sensor.
Hot water production is star-
ted 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 Measurement points .
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 mi-
nute drains from the tap.Use a clock and bucket to meas-
ure the drain flow.
If the drain water flow is greater than 12 l/
min, stratification in the water heater is af-
fected, which reduces the hot water capaci-
ty.
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 existing
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 supplement
with an extra heater.
E.g. supplement with an DWH 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 pres-
sure switch opens.
Check the break pressure using manometer apparatus.
If the pressure switch opens at the incorrect
pressure, replace it.
The replacement pressure switch can be in-
stalled on the service output (Schrader
valve).
9. Insufficient exchange sur-
face to transfer the heat
pump’s output to the heat-
er.(Only applies to heat
pumps with a separate heat-
er.)
Is the exchange surface too small?
Can the heater cope with the heat pump’s output?
Replace with a heater with a larger ex-
change surface.
10. Heat loss in the hot wa-
ter pipe.
Open the hot water tap, read off the temperature on the
outgoing hot water pipe from the heat pump and the tem-
perature of the hot water. The temperature difference
measured between the heat pump and hot water indicates
the temperature loss.
Examples of temperature loss causes:
▪
Long water pipes.
▪
Uninsulated hot water pipes.
▪
Hot water pipes routed through cold areas.
Other causes that can affect the hot water temperature:
▪
Is a mixer valve installed in the system? Temperature
set too low on the mixer valve? Leaking mixer valve?
▪
Water tap fault? Leaking thermostat mixer?
▪
VVC loss.
If any problems occur during troubleshoot-
ing as per the points, carry out corrective
actions.
To quickly check that the heat pump’s hot
water production works as it should, drain
the hot water so that the heat pump starts
to produce the hot water. When done, read
off the temperature on the top sensor and
on the start sensor. The top sensor should
show a temperature of around 50 - 55°C
and the start sensor around 45 - 48°C. If, af-
ter completed hot water production, these
temperatures are obtained, this means that
you have the correct temperature and vol-
ume of hot water in the water heater.
Service Instructions
DHP-AQ
Danfoss Heating Solutions
VMGFJ202
23
