Maritime Geothermal EMWT-65-HACW-P-1T, Installation And Service Manual

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01 MAR 2012 Page 27 000662MAN-03
OPERATION TROUBLESHOOTING - HEATING MODE
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)
TXV closed too far. Verify superheat. It should be be-
tween 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 for-
eign object. Adjusting the TXV does not affect
the superheat or the suction pres-
sure.
Adjust the TXV all the way in and out a
few times to loosen it. Replace TXV if
this does not work.
Filter-drier plugged
Feel each end of the filter- drier, it
should be the same temperature. If
there is a temperature difference
then it is plugged. Also causes low
suction pressure. Replace filter-drier.
Unit is overcharged.
(Only possible if unit has
been opened 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
pressure reduces.
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
restriction and correct it.
Verify pumps are working and
sized correctly for ground loop sys-
tems.
Verify well pump and water valve is
working for ground water systems.
Entering liquid tempera-
ture too cold. Measure the entering liquid temper-
ature. Most likely caused by under-
sized ground loop. Increase the size of the ground
loop.
Dirty or fouled coaxial
heat exchanger.
(typically for ground water,
unlikely for ground loop) Disconnect the water lines and
check the inside of the pipes for
scale deposits. Have a qualified service technician
backflush the coaxial exchanger.
Indoor Loop entering liq-
uid temperature too cold Measure temperature. Should be
above 60°F (15°C). Restrict Indoor liquid flow tempo-
rarily until buffer tank comes up to
temperature.
TXV stuck almost closed
or partially blocked by for-
eign object. Adjusting the TXV does not affect
the superheat or the suction pres-
sure. TXV may be frosting up. Adjust the TXV all the way in and out a
few times to loosen it. Replace TXV if
this does not work.
Low refrigerant charge. Entering liquid temperature, flow
and entering air temperature are
good but suction is low. Check
static refrigeration pressure of the
unit for a very low value. Locate the leak and repair it.
Spray nine, a sniffer and dye are
common methods of locating a
leak.
Faulty compressor, not
pumping. Pressures change only slightly from
static values when compressor is
started. Replace compressor.
Low or no flow in heat ex-
changer to buffer tank
circuit. Check that isolation flanges and
any ball valves are open. Verify
115VAC to pump. Check gauges
for pressure drop. Ensure flow path is unrestricted.
Replace pump if faulty.