Danfoss VLZ065, Инструкции по применению

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Manage off cycle migration
Requirement
System evaluation
Off -cycle refrigerant migration happens:
• when the compressor is located at the coldest
part of the installation, refrigerant vapor
condenses in the compressor.
• or directly in liquid-phase by gravity or pressure
difference.
When the compressor restarts, the refrigerant
diluted in the oil, or stored in evaporator,
generates poor lubrication conditions, and may
reduce bearings lifetime. In extreme situations,
this leads to liquid slugging that can damage the
compressor scroll set.
· Compressor can tolerate occasional flooded
start, but it should remain exceptional situation
and unit design must prevent that this situation
from happening at each start.
· Right after start, liquid refrigerant must not flow
massively to compressor.
· The protective measures must be taken to limit
risk of liquid slugging and extreme dilution at
start.
R
VLZ is designed for split system application.
The External Non-Return Valve is mandatory to
use.
Ensure tightness between condenser & evaporator when system is OFF
• Thermostatic expansion Valve (TXV), Liquid Line Solenoid Valve LLSV** strongly recommended
• Electronic expansion valve (EXV) must close when system stops including in power shut down
situation
Since each installation is unique, refrigerant charge may vary
• Belt type heater*
• Liquid Line Solenoid Valve**+ pump-down cycle***
• External Non-Return Valve
*Crankcase heater
The belt crankcase heaters are designed to
protect the compressor against off-cycle
migration of refrigerant.
Additional heater power or thermal insulation
might be needed in case of ambient temperature
below -5°C (23°F) and a wind speed above
5m/second (16.4 feet/second).
The heater must be turned on whenever all the
compressors are off.
Crankcase heater accessories are available from
Danfoss (see section “Accessories”). **Liquid line solenoid valve (LLSV)
A LLSV is used to isolate the liquid charge
on the condenser side, thereby preventing
against charge transfer to the compressor
during off -cycles. The quantity of refrigerant
on the low-pressure side of the system can be
further reduced by using a pump-down cycle in
association with the LLSV.
***Pump-down cycle
By decreasing pressure in the sump, pump down:
• Evacuates refrigerant from oi.l
• Set the sump saturating pressure much
lower than ambiance temperature and due
to that, avoid refrigerant condensation in the
compressor.
For more details on pump-down cycle see
section “Control Logic”.
Optimum
location area
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AB444226142054en-000101