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frequently. Repeated short cycling of this nature can result in a low oil situation and consequent
damage to the compressor.
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.
5.13 Minimum run time
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.
5.14 Shut-off sound
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.
5.15 Supply frequency and voltage
There is no general release for the fixed-speed horizontal scroll compressor models YRH*KTE/KTG
for use with variable-speed AC drives. Only frequencies from 50 to 60 Hz are acceptable.
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.
Variable-speed horizontal scroll compressor models YRHV*KTE/KTG can be applied in the
frequency band, as shown in section 4.6 "Inverter operation".
The last digit of the model motor code indicates which supply frequency and voltage must be applied
– see section 2.3 "Nomenclature".
50 Hz
380-420 V – 3 ph
-
Table 6: Electrical motor codes for YRH(V)*KTE/KTG compressors
5.16 Oil level
There is no oil sight glass on YRH(V)*KTE/KTG compressors. Consequently, it is difficult to get an
indication about the actual oil level in the compressor during operation.
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. A sufficient oil level must be present in the
compressor at all times to ensure compressor reliability.
AGL_AC_ST_YRH_EN_Rev01
60 Hz
Code
460 V – 3 ph
D
380 V – 3 ph
7
23
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