Overview; Resources; Background - Trane BCHC Application Manual

Overview

This guide should be used only for new systems design. It is not to aid with the remodel, retrofit,
or partial replacement of older systems. Older blower coils and heat pump systems were not
designed for the higher pressures of R-410A.
Trane's 4TTA3, 4TWA3, 4TTB3 and 4TWB3 sizes 1-1/2 through 5 ton and TTA073D and TWA120D
sizes 5 through 10 ton cooling only and heat pump products have been matched to Trane® indoor
unit models BCHC and BCVC 024 through 090. Beginning mid-2009, the TTA and TWA 6- through
20-ton product line has been designed for use only with R-410A and POE oil (check unit model
number for specific refrigerant). R-410A is a high-pressure refrigerant that requires the other
components of the system to be rated for R-410A. For compressor lubrication, the refrigerant
requires POE oil.
Trane's BCHC and BCVC 024-090 blower coil air handler products have also been redesigned for use
with the higher pressures of R-410A.
Traditionally, refrigerant piping practices were guided by four principles:
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These piping practices are similar for R-410A and POE oil. However, because of the different mass
flows and pressures, the line diameter required to carry the oil and refrigerant may not be the same
as a similar tonnage R-22 unit. Also, the allowable pressure drop may be greater for R-410A than
R-22.
Evidence accumulated over years of observation demonstrates that the lower the refrigerant
charge, the more reliably a split air-conditioning system performs. Any amount of refrigerant in
excess of the minimum design charge becomes difficult to manage. The excess refrigerant tends
to collect in areas that can interfere with proper operation and eventually shortens the service life
of the system.
To successfully minimize the system refrigerant charge, the correct line size should be used and the
line length must be kept to a minimum.

Resources

This purpose of this Application Guide is to aid the designer in applying the 4TWA, 4TTA, TTA, and
TWA R-410A products with either BCHC or BCVC blower coils. For more information about the
outdoor units, refer to the following application guides:
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Background

In a split air-conditioning system, the four major components of the refrigeration system are
connected by field-assembled refrigerant piping
evaporator to the compressor, the discharge line connects the compressor to the condenser, and
the liquid line connects the condenser to the expansion device, which is located near the
evaporator inlet. Operational problems can occur if these refrigerant lines are designed or installed
improperly.
SS-APG010C-EN
Return the oil to the compressor.
Maintain a column of liquid at the expansion valve.
Minimize the loss of capacity.
Minimize the refrigerant charge in the system.
Refrigerant Piping Systems [32-3009-03; SS-APG006-EN]
Tube Size and Component Selection for TTA and TWA Split Systems (6-20 Tons) Using
Refrigerant 410A [SS-APG008-EN]
(Figure 1). A vapor or gas line connects the
1