Danfoss VZH Series - General Overview; Scope; Benefits

Application guidelines
75FRCC.PC.023.A7.22
Manifold compressors
General overview
Scope
Benets
A second reason for manifolding of Variable
speed compressor and xed speed compressor
is improved part load eciency. In the variable
speed+xed speed parallel installation, the
system can run either only Variable speed
compressor at lower load or both Variable speed
and xed speed compressors at higher load with
xed speed compressor operating at 100% load.
Therefore the higher part load eciency can be
achieved. Conventional xed speed compressor
unloading methods and manifolding of xed
speed compressors impose a serious penalty for
part load eciency, mainly at low load operation.
Third, the capacity of hybrid manifolding system
can be widely regulated ex. 10% to 100%.
The continuous capacity regulation allows for
accurate temperature control and comfort indoor
environment.
The application guideline describes the operating
characteristics, design features and application
requirements for hybrid manifolding of the
Danfoss SH xed speed compressor and VZH
Variable speed compressor in air conditioning
and heat pump applications.
To ensure proper parallel installation and running
conditions, the following recommendations must
be followed:
• It is essential to respect all instructions given
in these guidelines, the instruction leaet
delivered with each compressor and the
Application Guidelines for single compressors.
• For additional system components related to
specic application requirements, the supplier
recommendations must always be respected.
A parallel compressor installation refers to a
system of interconnected compressors with a
common suction line and common discharge
line. The technique of mounting compressors
in parallel is also called manifolding. The hybrid
manifolding in this application guideline refers
to manifolding of Danfoss Variable speed
compressor (VZH) and xed speed compressor
(SH), which has several benets.
The main reason is reduced operating cost
through greater control of capacity and power
consumption. This is achieved by both staggering
compressor switch-on sequences and regulating
speed of Variable speed compressor that allow
the parallel system to continuously match its
power with the capacity needed.
Capacity
Compressor n°1
VZH 25-100 Rps
Compressor n°1
VZH 25-100 Rps
Compressor n°2
xed speed SH