Danfoss Maneurop NTZ Series Application Guidelines

Application guidelines
20 FRCC.PC.002.A4.22
System design recommendations
Suction accumulator
Liquid line solenoid valve
& pump-down
Crankcase heater
A suction accumulator oers considerable
protection against refrigerant oodback both at
start-up and during operation or after the defrost
operation. This device also helps protect against
o-cycle migration by providing additional
internal free volume to the low pressure side of
the system.
The suction accumulator must be selected in
accordance with the accumulator manufacturer
recommendations. As a general rule, Danfoss
Commercial Compressors recommends to size
the accumulator for at least 50% of the total
system charge. Tests however must be conducted
to determine the optimal size.
In refrigeration applications, the Liquid Line Sole-
noid Valve (LLSV) is highly recommended. During
the o-cycle, the LLSV isolates the liquid charge
in the condensor side, thus preventing refriger-
ant transfer or excessive migration of refrigerant
into the compressor. Furthermore, when using
LLSV in conjunction with the pump-down cycle
(especially in low-temperature applications), the
quantity of refrigerant in the low-pressure side of
the system will be reduced.
A pump-down cycle design is required when
evaporators are tted with electric defrost
heaters.
A crankcase heater protects against the o-cycle
migration of refrigerant and proves eective if
oil temperature is maintained 18°F above the
saturated LP temperature of the refrigerant. Tests
must thereby be conducted to ensure that the
appropriate oil temperature is maintained under
all ambient conditions. A PTC crankcase heater is
required with all Maneurop®‚ NTZ compressors.
PTC crankcase heaters are self-regulating.
Under extreme conditions such as low ambient
temperature at 5°F or lower a belt type crankcase
heater could be used in addition to the PTC heat-
er, although this is not a preferred solution for 1
and 2 cylinder compressors. The belt crankcase
heater must be positioned on the compressor
shell as close as possible to the oil sump to
ensure good heat transfer to the oil. The below il-
lustrated mounting positions are recommended:
Belt crankcase heaters are not self-regulating.
Control must be applied to energise the belt
heater once the compressor has been stopped
and then to de-energise it while the compressor
is running. The belt heater must be energised
12hours before restarting the compressor follow-
ing an extended down period.
If the crankcase heater is not able to maintain the
oil temperature at 18°F above the saturated LP
temperature of the refrigerant during o cycles
or if repetitive oodback is present a the Liquid
Line Solenoid Valve (LLSV) + pump-down cycle is
required, possibly in conjunction with a suction
accumulator.
Models: NTZ048 - NTZ068 - NTZ096 - NTZ108 - NTZ136 Models: NTZ215 - NTZ271

Danfoss Maneurop NTZ Series Specifications

General

Brand	Danfoss
Model	Maneurop NTZ Series
Category	Air Compressor
Language	English