Operating Conditions; Application Envelopes; Short Cycle Timer Function - Danfoss VZH Series Application Manuallines

Application guidelines

Application envelopes

Short cycle timer function

Operating conditions

The operating envelopes for VZH scroll
compressors are given in the figures below,
where the condensing and evaporating
temperatures represent the range for steady
state operation. Under transient conditions, such
as start-up and defrost, the compressor may
operate outside this envelope for short periods.
The figures below show the operating envelopes
for VZH compressors with refrigerants R410A.
Due to bearing loads and scroll stability,there
will be speed restrictions on the envelops. The
operating limits serve to define the envelope
within which reliable operations of the
compressor are guaranteed:
• Maximum discharge gas temperature: +135°C.
160
150
140
130
120
110
100
90
80
70
60
-15 -5
High PR
For 380V power input, permitted highest condensing temperature will decrease accordingly:
-High PR: 25-100rps, condensing temperature from 60C to 56C; 30-90rps, condensing temperature from 68C to 65C.
-Low PR: 25-100 rps, condensing temperature from 60C to 56C; 30-90 rps, condensing temperature from 63C to 62C.
Short cycle control is directly provided by the
CDS303 frequency converter, when parameter
28.0x is enabled.
The function is factory set to enabled, with
minimum running time 12 seconds and interval
between starts 300 seconds.
Short cycle settings are accessible in parameter
28.0x list, in the "compressor functions" menu.
• Minimum suction superheat should be above
5K and minimum sump superheat should be
above 10K due to the risk of liquid flood back.
• Attention to suction line insulation to reduce
usefulness superheat.
• Minimum and maximum evaporating and
condensing temperatures as per the operating
envelopes
• VZH drive could only protect compressor from
over current. Customers need to have high
pressure, low pressure sensor and discharge
temperature thermostat to fully protect the
envelop. Since out of map running will threaten
the reliability of compressor, customers must
qualify map protection under all extreme
conditions.
VZH operating map (SH 6 K)
25-100 rps
5 15 25
Evaporating temperature (°F)
Low PR Note: red and blue lled area are limited to 30-90 rps
When fully controlled from an external main
controller it is recommended to limit to 12 the
number of start / stop per hour.
Please note to ensure compressor is well
lubricated, it is required to keep VZH compressor
running at least 3 minutes each time after start.
Single compressors
30-90 rps
35 45 55
FRCC.PC.023.A7.22
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