PART-SVN237B-EN 5
General Information
Initial production RTAE Chillers include 1
st
Gen GP4 Screw
Compressors with legacy motors (Phase Motion), external
inductors between the drive and compressor, and (on
some units) smaller AFD3 frames compared to second
generation chillers. While 2
nd
Gen GP4 Screw
Compressors include an updated motor (Regal Beloit), no
external inductors, and (on some units) larger AFD3
frames.
Table 1. GP4 classic compressor
Description 1
st
Gen GP4 Classic Compressor 2
nd
Gen GP4 Classic Compressor
Motor Phase Motion Regal Beloit
External Inductor Yes No
AFD3 Frame Size Smaller on some units Larger on Some units
With Trane's conversion to the GP4 Variable VI ratio
(VarVI) compressor architecture, in the event of a
compressor failure it is not possible to replace 1
st
or 2
nd
Gen GP4 Classic Compressors with the new GP4 VarVi
model. Thus, a service model GP4 VarVi Compressor was
developed for replacement of both 1
st
and 2
nd
Gen GP4
Classic Compressors. This service model compressor
performs similarly as a classic GP4 compressor due to the
following adaptations:
• Locked VI assembly to 'high VI' configuration (same as
GP4 Class
i
c).
•2
nd
generation motor (Regal Beloit instead of Phase
Motion).
• Removal of external inductors (if installed).
Replacement of a 2
nd
Gen GP4 Classic Compressor
requires replacement of the compressor motor terminal
box but no other adaptations to unit electrical wiring or
AFD3 programming. Replacement of the 1
st
Gen GP4
Classic Compressor requires extra steps to replicate
similar unit operation. This document outlines extra
retrofit conversion steps in event of a failure of a 1
st
Gen
GP4 Classic Compressor on an RTAE Chiller:
• Replacement of 1
st
Gen GP4 Classic Compressor to
GP4 Locked VarVI Service Compressor.
• Removal of external inductors.
• Re-programming of AFD3 (including special RLA
values for
some models).
• Addition of common mode chokes.
• Replacement of the compress
or motor
terminal box.
Note: Some units will lose a small portion of top end
op
erational capacity due to the difference in motor
performance and the size of the originally installed
AFD3 on the 1
st
Gen RTAE unit. The reduction of
top end capacity is small, and noted later in this
document.
Figure 1. Replacement of 1
st
or 2
nd
Gen GP4 classic
compressor to VarVi service compressor on
RTAE
1
st
Gen
GP4 Comp
2
nd
Gen
GP4 Comp
New Terminal Box
A new cartridge heater
is required
GP4 VarVi
Service Comp
New Terminal Box
Remove inductor
AFD3 re-programming
Add chokes
A new cartridge heater
is required
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