Danfoss DHP-AL Installation And Service Instructions Manual page 44

Cause
7. The operating pressure switch
does not open.
8. The high pressure pressure
switch opens too soon.
9. External system shunt that
closes on time setting.
10. Incorrectly facing non-return
valve with too high opening pres-
sure.
11. Large pressure drop in the
heating system.
12. Overfilled refrigerant circuit.
13. Blocked condenser on the
water side.
14. Blocked condenser on the
refrigerant side.
44
Troubleshooting
• Incorrect pressure switch installed. Same or
higher break pressure than high pressure pressure
switch. See marking.
• Pressure switch fault, opens at a higher pressure
than indicated (mark pressure). Check using the
manometer apparatus.
• Defective pressure switch, never opens.
• Incorrect pressure switch installed. As low or
lower break pressure than operating pressure
switch. See marking.
• Pressure switch fault, opens at a lower pressure
than indicated (mark pressure). Check using the
manometer apparatus.
• Defective pressure switch, always open.
Check for shunts or valves in the system, which are
timer-controlled, that close down the entire or too
large a part of the heating system.
• Check the system's direction of flow and that the
non-return valve is turned the correct way.
• Check that the heat pump's external available
pressure exceeds the non-return valve's opening
pressure.
• Dirt in the heating system.
• Closed or partially closed thermostats/valves in
the heating system.
• Under dimensioned pipe system. Check that the
HP's external available pressure exceeds the sys-
tem pressure drop.
Using manometer apparatus and thermometer,
check that the unit's overheating is correct for the
specific refrigerant.
Then check in the same way that the unit's cool-
ing is correct. See separate instructions for cooling
techniques.
If there is no strainer in the heating system, there
is a risk of dirt sticking in the condenser and block-
ing it. Unfortunately there is no easy way of check-
ing if the condenser is blocked.
You can carry out a test by allowing the compres-
sor and circulation pumps to remain in operation
and after a while, check that the delivery pipe
becomes hot and that the circulation pumps work
(for circ.pumps with a venting screw, unscrew it
and feel if the pump rotor rotates using a screw-
driver).
Then read the temperature on both connection
pipes to the condenser:
If the temperature difference is <3°C, the condens-
er is probably blocked.
If the temperature difference is 3-13°C, it is prob-
ably not blocked.
If the temperature difference is >13°C, the con-
denser is probably blocked.
Using manometer apparatus and thermometer,
check that the unit's overheating is correct for the
specific refrigerant.
Then check in the same way that the unit's cool-
ing is correct. See separate instructions for cooling
techniques.
VMBME102
Remedy
If the operating pressure switch does not
open, replace it.
If the high pressure pressure switch opens too
soon or is always open, replace it.
Always ensure that there is a sufficiently large
water volume for the heat pump to work
against, i.e. for the heat to give off its heat to.
If the non-return valve is facing the wrong way,
turn it.
If the non-return valve has too great an open-
ing pressure, replace it.
If necessary, clean/flush the heating system.
Open closed thermostats/valves.
If there is not sufficient pressure equipment,
the heating system can be adjusted according
to the system solution for large pressure drop.
If cooling is not at the correct level compared
with the specific refrigerant and is too high,
there is too much refrigerant. Follow the cor-
rect procedure (depending on type of refrig-
erant) to add the correct amount of refrigerant.
If there appears to be a leak in the refrigerant
circuit, carry out leak tracing and any neces-
sary corrective action.
If the condenser is thought to be blocked, try
flushing it. If this does not work, it must be
replaced
If the condenser is thought to be blocked by
oil for example, try blowing nitrogen through
it to release the oil. If this does not work, it
must be replaced