Specifications

46 – Service VMBMH302
Break pressure pressure switches
Refrigerant Pressostat Break pressure
R407C Low pressure pressostat 0.08 MPa
Operating pressure switch A 2.65 MPa
Operating pressure switch B 2.85 MPa
High pressure pressostat 3.10 MPa
15.4 Operational problems
 
The tables in the following section apply to all types of heat pump and collector solutions. This means that cer-
tain information does not apply to DHP-AX.
The tables have the most probable and most common causes of the problem listed first. When troubleshoot-
ing the cause of a problem start with the first cause and go down the list. There may be more than one way of
troubleshooting a cause where the most probable is given first.
15.4.1 Alarm
Problem – Alarm LP (low pressure pressure switch)
Cause Troubleshooting Remedy
1. Blocked strainer on the brine
circuit.
Check that the strainer is not blocked. Clean the strainer if necessary.
2. Air in the brine circuit. Listen for air in the heat pump and brine
circuit.
Bleed the brine circuit according to the
installation instructions.
3. Closed taps, main tap or filler
cock on the brine circuit.
Check that the shut-off cock/any other
taps are open.
Open closed taps.
4. The circulation pump for the
brine circuit is defective or has
jammed.
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.
The circulation pump may have jammed,
if so, open the bleed screw and try to
release the paddle wheel using a screw-
driver for example.
Open closed valves or taps.
Check, and, if necessary, clean the strai-
ner.
If necessary, bleed the heating system
according to the installation instructions
5. Cable break or loose cable to
low pressure pressure switch.
• 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, dis-
connect the cables from the pressure
switch and circuit board.
If a cable has come loose, connect it.
If there is a cable break, replace the cable.
6. Low pressure pressure switch
opens too soon.
• 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.
If the low pressure pressure switch opens
too soon or is always open, replace it.
7. Incorrect type of anti-freeze,
must be in accordance with
instructions.
Check that the correct type of anti-freeze
is used.
If the incorrect type of anti-freeze is used,
the entire system must be drained and
refilled with a new mixture.