Maritime Geothermal TF-45, Installation And Service Manual

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1-Jul-2017 Page 55 001223MAN-05
HYDRONIC OPERATION TROUBLESHOOTING
Fault Possible Cause Verification Recommended Action
High Discharge
Pressure
Aquastat set too high. Verify aquastat setting. Lower aquastat setting to recom-
mended value of 115°F (46°C).
Low or no Indoor loop flow. Delta T across the Indoor Loop ports
should be 8-12°F (3-6°C), or compare
pressure drop to the tables for the unit.
Verify pump is working and sized
correctly. Check for restrictions in
the circuit, e.g. valve partially closed.
TXV adjusted too far closed. Verify superheat. It should be between
8-12°F (3-6°C). Superheat will be high if
TXV is closed too far.
Adjust TXV to obtain 8-12°F (3-6°C)
superheat.
TXV stuck almost closed or
partially blocked by foreign
object.
Adjusting the TXV does not affect the
superheat or the suction pressure.
Adjust the TXV all the way in and out
a few times to loosen it. Replace
TXV if this does not work.
Filter-dryer plugged Feel each end of the filter-dryer: it
should be the same temperature. If
there is a temperature difference then it
is plugged. Also causes low suction
pressure.
Replace filter-dryer.
Unit is overcharged.
(Only possible if unit has
been serviced in the field and
incorrectly charged.)
High sub-cooling, low delta T across air
coil.
Remove 1/2lb of refrigerant at a time
and verify that the discharge pres-
sure reduces.
Faulty 4-way (condenser
select) valve or actuator.
Verify actuator rotates 90 degrees over
~80 seconds when unit is switched from
air heating to hydronic heating modes.
Replace valve or actuator if faulty.
Low Suction
Pressure
Low or no outdoor liquid flow. Delta T across the Outdoor Loop ports
should be between 5-7°F (3-4°C), or
compare pressure drop to the tables for
the unit.
Determine the cause of the flow re-
striction and correct it.
Verify pumps are working and sized
correctly for ground loop systems.
Verify well pump and water valve are
working for ground water systems.
Entering liquid temperature
too cold.
Measure the entering liquid temperature.
Most likely caused by undersized ground
loop.
Increase the size of the ground loop.
Dirty or fouled coaxial heat
exchanger (more likely for
open loop, unlikely for ground
loop)
Disconnect the water lines and check
the inside of the pipes for scale deposits.
Backflush the coaxial exchanger with
a calcium-removing cleaning solution.
Indoor loop entering liquid
temperature too cold
Measure temperature. Should be above
60°F (15°C).
Restrict Indoor liquid flow temporarily
until buffer tank comes up to temper-
ature.