• Check current draw and voltage levels on the
mains. The values for the compressor electri-
cal motor can be directly displayed on the fre-
quency converter control panel.
• The optimum compressor suction superheat is
around 6K.
• Eventual reverse rotation can be detected by
following phenomena; the excessive noise,
no pressure differential between suction and
discharge, and line warming rather than imme-
diate cooling. A service technician should be
present at initial start-up to verify that wiring
from drive to compressor is properly phased
and that the compressor is rotating in the cor-
rect direction.
• Note that a 300 seconds period is necessary be-
tween 2 starts, a shorter period will be not al-
lowed by the drive. The minimum running time
is 12s for each start.
11 – Check with running compressor
Check current draw and voltage. Measure-
ment of amps and volts during running condi-
tions must be taken at other points in the power
supply, not in the compressor electrical box.
• Check suction superheat to reduce risk of slug-
ging.
• Observe the oil level at start and during opera-
tion to confirm that the oil level remains vis-
ible. Excess foaming in oil sight glass indicates
refrigerant on the sump.
• Monitor the oil sight glass for 1 hour after sys-
tem equilibrium to ensure proper oil return to
the compressor. This oil check has to be done
over the speed range to guarantee:
- a good oil return at low speed with minimum
gas velocity.
- a good oil management at high speed with
maximum oil carry over.
• Respect the operating limits.
• Check all tubes for abnormal vibration. Move-
ments in excess of 1.5 mm / 0.06 inch require
corrective measures such as tube brackets.
• When needed, additional refrigerant in liquid
phase may be added in the low-pressure side
as far as possible from the compressor. The
compressor must be operating during this pro-
cess.
• Do not overcharge the system.
• Never release refrigerant to atmosphere.
• Before leaving the installation site, carry out
a general installation inspection regarding
cleanliness, noise and leak detection.
• Record type and amount of refrigerant charge
as well as operating conditions as a reference
for future inspections.
• Compressor failure to build up pressure: Check
all bypass valves in the system to ensure that
none of these has been opened. Also check
that all solenoid valves are in their proper posi-
tion.
• Abnormal running noise: Ensure the absence
of any liquid flood-back to the compressor by
means of measuring the return gas superheat
and compressor sump temperature. The sump
should be at least 6K above the saturated suc-
tion temperature under steady-state operating
conditions.
• The high-pressure switch trips out: Check con-
denser operations (condenser cleanliness, fan
operation, water flow and water pressure valve,
water filter, etc.). If all these are OK, the problem
may be due to either refrigerant overcharging
or the presence of a noncondensable (e.g. air,
moisture) in the circuit.
• The low-pressure switch trips out: Check evap-
orator operations (coil cleanliness, fan opera-
tions, water flow, water filter, etc.), liquid refrig-
erant flow and pressure drops (solenoid valve,
filter dryer, expansion valve, etc.), refrigerant
charge.
• Low refrigerant charge: The correct refrigerant
charge is given by the liquid sight glass indica-
tion, the condenser delta T in relation to the
refrigerant pressure tables (pressure-tempera-
ture), the superheat and the sub-cooling, etc.
(if additional charge is deemed necessary, refer
to section 8).
• Compressor short cycling: The number of cy-
cles shall never exceed 6 starts per hour.
12 – Maintenance
Internal pressure and surface temperature are
dangerous and may cause permanent injury. Main-
tenance operators and installers require appropri-
ate skills and tools. Tubing temperature may exceed
100°C / 212°F and can cause severe burns.
Ensure that periodic service inspections to
ensure system reliability and as required by local
regulations are performed.
To prevent system related compressor problems,
following periodic maintenance is recommend-
ed:
• Verify that safety devices are operational and
properly set.
• Ensure that the system is leak tight.
• Check the compressor current draw by reading
one of the parameters via Modbus.
• Confirm that the system is operating in a way
consistent with previous maintenance records
and ambient conditions.
• Check that all electrical connections are still ad-
equately fastened.
• Keep the compressor clean and verify the ab-
sence of rust and oxidation on the compressor
shell, tubes and electrical connections.
• Acid / moisture content in system and oil
should be checked regularly.
13 - Warranty
Always transmit the model number and serial
number with any claim filed regarding this prod-
uct.
Use the fault memory of the frequency con-
verter to recover the fault descriptions before
initializing the system and even before shutting
off the power.
Variable speed drive model and serial number
must also be transmitted with the claim.
The product warranty may be void in following
cases:
• Absence of nameplate.
• External modifications; in particular, drilling,
welding, broken feet and shock marks.
• Compressor opened or returned unsealed.
• Rust, water or leak detection dye inside the
compressor.
• Use of a refrigerant or lubricant not approved
by Danfoss.
• Any deviation from recommended instructions
pertaining to installation, application or main-
tenance.
• Use in mobile applications.
• Use in explosive atmospheric environment.
• No model number or serial number transmit-
ted with the warranty claim.
14 – Disposal
Danfoss recommends that compressors
and compressor oil should be recycled
by a suitable company at its site.
Danfoss A/S
6430 Nordborg
Denmark
4 | © Danfoss | DCS (CC) | 2017.07
8510286P01B - FRCC.PI.039.A3.02
Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Danfoss reserves the right to alter its products without notice. This
also applies to products already on order provided that such alterations can be made without subsequential changes being necessary in specifications already agreed. All trade-
marks in this material are property of the respective companies. Danfoss and the Danfoss logotype are trademarks of Danfoss A/S. All rights reserved.
