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M-AI-VT-001-EN Rev.C.1
Refrigerant Piping Design
Motor and Drive Module
Cooling Requirements
NOTE
Sub-cooled liquid must be fed to the motor and drive module cooling port of the compressor.
It must be solid liquid with a minimum of 6° F (3.5°C) sub cooled at the connection point to the motor and drive
module cooling port of the compressor.
NOTE
Filter dryer, sight glass and service valve must be fitted in the motor and drive module’s cooling liquid line.
To ensure sub-cooled liquid, it is important
that the condenser is fitted with a sub-cooler
(integrated or separate).
It is essential that compressor motor and
cooling is available immediately at start up.
Recommended minimum pipe size is 13 mm
(1/2") for all models. A full flow filter/drier, a
liquid sight glass, and a service valve must be
installed adjacent to each compressor.
Motor-cooling liquid should be fed from the
common liquid line before the main liquid line
solenoid valve.
Motor and drive cooling return lines should be
no smaller than the stated minimums in table
16. In multiple compressor installations where
manifolding of return lines is used, care should
be taken to maintain the equivalent area of the
sum of the minimum pipe sizes. Pressure drop in
these lines should be minimized by using direct
runs of pipe and short radius fittings whenever
possible.
This section provides basic guidelines and
requirements for the design and manufacture of
R134a systems equipped with VTT compressors.
Refer to the applicable VTT technical manual
for applications, operating, installation and
commissioning instructions.
Design of the system control should not be
based on pump down cycle; due to the surge
characteristics of centrifugal compressors, the
system cannot be pumped down.
In humid environments, the compressor’s bell
housing should be insulated; a bell housing cover
thermal insulator is available as an accessory.
NOTE
The compressor internal safety control settings are designed to provide protection for the compressor only.
Designers MUST provide SYSTEM protection within their control design. DTC will not be responsible for system
protection other than the compressor.
System Piping and Design