Carrier 38AD - Thermostatic Expansion Valve Installation; Suction Piping and TXV Bulb Location; Unit Safety Relief System; Wiring and Electrical Data Overview

Fig. 9 — Recommended Filter-Drier(s)
and Sight Glass Locations
Table 5 — Filter-Drier Replacement Parts and Data
UNIT
FILTER-DRIER
Part No.
Qty
Conn.
Size ;
Replacement
Part No.
Core
Qty
38AD024
KH43LE1 23
1
% :
Same 0
38AD028 |
KH43LE121 2
s /»
Same
0
38AD034 j
KH43LE 121
2 %
Same
0
38AD044 j
KH49EA030
1
X
KH29EZ050*
2
38AB054 !
KH49EA120
1
l 1 /*
KH29EZ050*
2
38AB064 |
KH49EA120
1
i l / 8
KH29EZ050*
2
38AB084
KH49EA040
1
iv»
KH29EZ050*
3
* Replaceable cores only
Install field-supplied thermostatic expansion
valve in liquid line ahead of each evaporator
section. For two-step cooling, the solenoids used
must be wired to be opened by control from a
two-step thermostat
For example: two solenoids may be used with
three TXV’s — one of the solenoids serving a liquid
line feeding two of the TXV’s. When three
solenoids are used with three TXV’s, two of the
solenoids must be tied in parallel with the thermo¬
stat to serve the one liquid line feeding the two
TXV’s. The third solenoid operates independently
for the other step of cooling.
Suction Piping at Evaporator and TXV Bulb
Location
The purpose of these recommendations is to
achieve good mixing of the refrigerant leaving the
evaporator suction header for proper sensing by
the TXV bulb.
1. A minimum of two 90° elbows must be
installed upstream of the expansion valve bulb
location.
2. The thermal bulb must be strapped to a vertical
riser following the second elbow of item 1. This
riser must be at least 15 pipe diameters high
and the bulb should be fastened 10 pipe
diameters above the preceding elbow.
3. S i ze the suction line from near evaporator thru
the 15 diameter long riser for high velocity.
Enter the suction pipe sizing charts in Carrier
System Design Manual at corrected design tons
(each evaporator split) and 80 feet equivalent
length (for 2° loss). Choose the smaller size
pipe, when reading falls between two sizes on
chart. Since the selection of suction piping
recommended for high velocity is approxi¬
mately 20 ft equivalent length, this sizing
method will result in about 0.5° friction loss
for that section. If a 2° loss is allowed for the
entire suction line, this leaves 1.5° tor the
balance of suction line and should be sized on
that basis. This high-velocity sizing should be
adequate for oil return up the 15 diameter long
riser. It should be checked.
If an oil return connection at the bottom of the
suction header is supplied with an evaporator, this
connection must be teed in ahead of first mixing
elbow (Fig. 8). When the compressor is below the
evaporator, the riser at the evaporator does not
have to extend as high as the top level. After the
15 diameter riser has been provided, the suction
may elbow down immediately.
Safety Relief — A fusible plug is located on unit
liquid line before liquid valve.
WIRING AND ELECTRICAL DATA
Power Supply — Electrical characteristics of avail¬
able power supply must agree with unit nameplate
rating. Supply voltage must be within tolerances
shown in Table 6. Phase unbalance must not
exceed 2%. Operation of unit on improper supply
voltage or with excessive phase unbalance con¬
stitutes abuse and is not covered by Carrier
Warranty.
Power Wiring — All power wiring must comply
with applicable local and national codes. Install a
field-supplied branch circuit disconnect switch of a
type that can be locked “Off’ or “Open.” Run
power wires from the disconnect switch thru the
power opening (H on Fig. 1) on unit and connect
to terminal block just inside the opening. On
38AB084, there are two terminal blocks (on
208-volt and 230-volt units only). Each is limited
to 350 MCM maximum wire size (see Table 7).
These units are provided with two power openings
to accommodate two conduit runs.
For access to power opening and terminal
blocks on 38AD044, unlatch the two latches on
the outer hinged door and swing open outer door.
Remove screws on barrier panel and remove barrier
to expose wiring.
5