Mammoth V-Cube - Manual (Page 17)

Refrigerant.Systems
Compressors
Scroll-type compressors are the most common type of
compressor used by Venmar CES. Other types of compres-
sors are available upon request, if required. Maintenance
and service on compressors must be completed by a li-
censed service mechanic. Provincial or state regulations
frequently require such qualifications for compressor main-
tenance. If a compressor cycles, leaks or has any defects,
contact Venmar CES as soon as possible.
Water Cooled Condensers
Shell.and.Tube.Condensers
Most integrated water cooled units contain shell and
tube condensers. Periodically, water tubes should be
mechanically cleaned to ensure optimum condenser ef-
ficiency. Frequency of cleaning will depend on individual
water conditions, so a suitable cleaning schedule should
be arranged based on experience and knowledge of the
building or local water supply loop. Cleaning brushes are
available from most refrigeration supply outlets. For better
results, always remove both heads before cleaning water
tubes.
Note that head gaskets do not require renewing at every
maintenance operation. However, if the head gasket is
physically disfigured or deteriorated in any way, the system
will require new gaskets in order to retain the water-tight
seal required for correct system operation.
Evaporator Section
The direct expansion coil is constructed of seamless cop-
per tubing expanded into full collared aluminum fins. The
tubes are arranged for a counter flow circuit and stag-
gered to provide maximum heat transfer. A pressure type
distributor with hot gas inlet port and a heavy duty copper
suction header are included. Additional refrigerant circuit
components include thermostatic expansion valves with
external equalizer and hot gas bypass valves on the full
face of the leaving side of the direct expansion coil (HGBP
option is removed when optional digital scroll compressors
are utilized).
Components of a Direct Expansion (Dx)
System
The evaporator is that part of the low pressure side of the
refrigerant system in which the liquid refrigerant boils or
evaporates, absorbing heat as it changes into a vapor.
Thermostatic Expansion Valve
The thermostatic expansion valve (TXV) is a precision de-
vice designed to meter the flow of refrigerant into the
evaporator, thereby preventing the return of liquid refrig-
erant to the compressor. By being responsive to the tem-
perature of the refrigerant gas leaving the evaporator and
the pressure in the evaporator, the thermostatic expansion
valve can control the refrigerant gas leaving the evapora-
tor at a predetermined superheat. Three forces that gov-
ern the operation of the TXV are:
1. The pressure created by the remote bulb and power
assembly (P1).
2. The evaporator pressure (P2).
3. The equivalent pressure of the superheat spring (P3).
!
WARNING
Many of the following steps need to be performed with
the unit powered off and locked out. Disconnect the
main power switch to the unit before performing service
and maintenance procedures.
Distributor
Liquid line
Hot gas bypass line
Suction line
Expansion valve
Check valve on remote condensing
application (optional)
Evaporator coil
Figure 11: Direct expansion (Dx) coil
Bulb clamp
Remote clamp
Diaphram
External
equilizer
port
P
1
P
2
P
3
Figure 12: Thermostatic expansion valve (TXV)
VCES-V-CUBE-IOM-1A 17