Bosch EC Series - Page 43

Troubleshooting
Compressor Troubleshooting
Problem Mode Check Then Possible Cause Action
No compressor
operation
Cooling
Is the Fault LED
blinking one (1)
time on
1
st
stage UPM
ONLY?
Is the Fault LED
blinki
ng three (3)
times on the 1
st
&
2
nd
stage UPMs?
If Yes, Circuit 1 is
affect
ed.
If Yes, Circuit 2 is
affect
ed.
High-pressure fault—No or low
water f
low.
• Check the water valves and/
or pum
ps for proper
operation.
• Check for water coil
block
age.
High-pressure fault—High
water t
emperature.
Check water temperature—Is it in
range?
High-pressure fault—Fouled or
scaled
water coil.
Check for proper flow rate and
water
temperature, and a rise in
water-side temperature in
cooling mode.
Heating
Is the Fault LED
blinking one (1)
time on the
1
st
stage UPM
ONLY?
If Yes, Circuit 1 is
affected.
High-pressure fault—No or low
air flow.
Check the fan motor for proper
operation.
Check the air filter.
Is the Fault LED
blinking three (3)
times on the 1
st
&
2
nd
stage UPMs?
If Yes, Circuit 2 is
affected.
Inspect the air coil for dirt/
debris.
Check duct work—Are the
dampers closed or blocked?
Cooling
Is the Fault LED
blinki
ng two (2)
times on the
1
st
stage UPM
ONLY?
If Yes, Circuit 1 is
affect
ed.
Low-pressure fault—No or low
air flow.
Check the fan motor for proper
operat
ion.
Check the air filter.
Inspect the air coil for dirt/
d
ebris
.
Check ductwork—Are the
damper
s closed or blocked?
Is the Fault LED
blinki
ng four (4)
times on the 1
st
&
2
nd
stage UPMs?
If Yes, Circuit 2 is
affect
ed.
Low-pressure fault—Low
refrigerant.
Check the refrigerant pressure
with a gauge set.
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EC Series Heat Pumps — 8733841499 (2024/05)