Minimum Run Time; Shut-Off Sound; Supply Frequency And Voltage; Oil Level - Emerson Copeland Scroll ZR24KRE Application Manuallines

NOTE: For pressure control setting, never set the low-pressure limiter to shut off outside of
the operating envelope. To prevent the compressor from running into problems during such
faults as loss of charge or partial blockage, the low-pressure limiter shall not be set lower
than the minimum suction pressure allowed by the operating envelope.

Minimum run time

5.13
Emerson recommends a maximum of 10 starts per hour. There is no minimum off time because
scroll compressors start unloaded, even if the system has unbalanced pressures. The most critical
consideration is the minimum run time required to return oil to the compressor after start-up. To
establish the minimum run time, a sample compressor equipped with an external oil sight glass is
available from Emerson. The minimum on time becomes the time required for oil lost during
compressor start-up to return to the compressor sump and to restore a minimal oil level that will
ensure oil pick-up through the crankshaft. Cycling the compressor for a shorter period than this, for
instance to maintain very tight temperature control, will result in progressive loss of oil and damage
to the compressor.

Shut-off sound

5.14
Scroll compressors incorporate a device that minimizes reverse rotation. The residual momentary
reversal of the scrolls at shut off will cause a clicking sound, but it is entirely normal and has no effect
on compressor durability.

Supply frequency and voltage

5.15
There is no general release of standard Copeland Scroll compressors for use with variable speed
AC drives. A number of considerations must be taken into account when applying Scroll compressors
with variable speed, including system design, inverter selection, and operating envelopes at various
conditions. Only frequencies from 50 to 60 Hz are acceptable. Operation outside this frequency range
is possible but should not be done without specific Application Engineering review. The voltage must
vary proportionally to the frequency.
If the inverter can only deliver a maximum voltage of 400 V, the amps will increase when the speed
is above 50 Hz, and this may give rise to nuisance tripping if operation is near the maximum power
limit and/or compressor discharge temperature limit.
The last digit of the model motor code indicates which frequency and voltage must be applied – see
Chapter 2.2 "Nomenclature".
Range
380 - 420 V / 3 ph / 50 Hz
460 V / 3 ph / 60 Hz
Table 6: Electrical code for motors

Oil level

5.16
The oil level should be maintained at mid-point of the sight glass.
Some systems may contain higher than normal refrigerant charges. Systems with large coils, low
ambient condenser flooding, or systems with multiple heat exchangers are among some system
configurations that may require additional lubricant.
During the system development phase, adequate oil return from the system to the compressor should
be evaluated and qualified. For this purpose, a sample compressor for lab testing, equipped with an
external oil sight tube, is available from Emerson.
If an oil regulator is being used the oil level should be set within the top half of the oil regulator sight
glass.
AGL_AC_ST_ZRKRE_E_Rev01
Code
D
25