Operational Problems - Alarm - Danfoss DHP-AL Installation And Service Instructions Manual

14.3 Operational problems – Alarm
Problem – Alarm LP (low pressure pressure switch)
Cause
1. Blocked strainer on the brine
circuit.
2. Air in the brine circuit.
3. Closed taps, main tap or filler
cock on the brine circuit.
4. The circulation pump for the
brine circuit is defective or has
jammed.
5. Cable break or loose cable to
low pressure pressure switch.
6. Low pressure pressure switch
opens too
soon.
7. Incorrect type of anti-freeze,
must be in accordance with
instructions.
8. Incorrect mix of anti-freeze, the
concentration must be in accord-
ance with instructions.
9. Short active collector, e.g. short
or dry bore hole, short surface soil
collector.
10. Collector too long, pressure
drop too great.
11. Expansion valve defective or
incorrectly set.
12. Lack of refrigerant, not enough
refrigerant in the system.
42
Troubleshooting
Check that the strainer is not blocked.
Listen for air in the heat pump and brine circuit.
Check that the shut-off cock/any other taps are
open.
Check:
• That the circulation pump spins.
• That the shut-off valves are open.
• That the strainer is not blocked.
• That no air is in the heating system.
• Check that both cables are connected on the
pressure switch.
• Using the buzzer, check that there are no cable
breaks. In order to do this, disconnect the cables
from the pressure switch and circuit board.
• Incorrect pressure switch installed. Higher break
pressure than intended. See marking.
• Pressure switch fault, opens at a higher pressure
than indicated (mark pressure). Check using the
manometer apparatus.
• Defective pressure switch, always open.
Check that the correct type of anti-freeze is used.
Check the freezing point of the mix using a refrac-
tometer.
• Check the length of the collector that is being
used and compare with the collector length in the
dimensioning documentation.
• In addition, check that the collector is not sus-
pended "in free air" if boreholes are used.
Check the length of the collector that is being used
and that it is connected in parallel (not connected
in series) if more than 1 coil is being used.
Using manometer apparatus and thermometer
check what the overheating reading of the unit is.
Also check that bulb and capillary tube are undam-
aged and that the bulb is correctly installed.
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
Clean the strainer if necessary.
Bleed the brine circuit according to the
installation instructions.
Open closed taps.
The circulation pump may have jammed, if so,
open the bleed screw and try to release the
paddle wheel using a screwdriver for example.
Open closed valves or taps.
Check, and, if necessary, clean the strainer.
If necessary, bleed the heating system accord-
ing to the installation instructions
If a cable has come loose, connect it.
If there is a cable break, replace the cable.
If the low pressure pressure switch opens too
soon or is always open, replace it.
If the incorrect type of anti-freeze is used, the
entire system must be drained and refilled
with a new mixture.
If the mixture is not in accordance with the
instructions, it must be remixed in an external
container. This is because the fluids do not mix
with each other well if one is filled directly into
the system.
If the active collector is too short, the heat
pump cannot receive enough energy from the
heat source , which results in it requiring an
addition to cover the energy requirement.
If a longer collector is being used than recom-
mended for the specific heat pump, it must be
divided on several parallel connected coils.
If the overheating reading does not corre-
spond with the instructions for the specific
refrigerant, adjust the expansion valve until
the correct value is obtained. See separate
instructions for cooling techniques.
If overheating cannot be adjusted with the
expansion valve or if the capillary tube/bulb is
damaged, replace it.
If cooling is not at the correct level compared
with the specific refrigerant and is too low,
there is insufficient refrigerant in the unit.
Follow the correct procedure (depending on
type of refrigerant) 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.