19
Solenoid drop control wiring: Control the power to the
liquid line solenoid through a Solenoid Valve Relay (SVR)
in all units. Use part number H N61PC005 (field--supplied,
installed). 38AUZ unit requires one or two SVR; 38AUD
unit requires two relays.
A unit with two liquid line solenoid valves also requires a
separate control power transformer for the liquid solenoid
valve loads. Select TRAN3 transformer part number
according to unit power supply.
Model Qty
LSV
Relay SVR
Q t y --- Pa r t N b r
TRAN3
Primary V:Part Nbr
38AUZ 1 1 --- HN61PC005 N/R
2 2 --- HN61PC005 208/230V:HT01BD202
460V : HT01BD702
575V : HT01BD902
38AUDA,B 2 2 --- HN61PC005
38AUDC 2 1 --- HN61PC005* N/R #
LSV: Liquid Solenoid Valve
SVR: Solen oid Valve Relay
N/R: Not Required
N/R #: Not Required / Factory Installed
* : I n st a l l a s S V R --- 2 ( S V R --- 1 i s f a c t o r y --- i n s t a l l e d)
Mount the SVR (and transformer TRAN3 when used) in
unit control box. Connect per wiring schemati c label on
unit or per Fig. 30 (38AUZ) or Fig. 31 (38AUD). On
38AUDC, disconnect the RED wire at LVTB--A1 and
reconnect on SVR terminal 4.
Note: TRAN3 and SVR--1 are provided with the HGBP
factory installed option for 38AUDC16 and 38AUDC25
units.
Evaporator Capacity Control Liquid Line Solenoid
Val ve : Many older unit designs included automatic
capacity controls that sensed changes in suction pressure
and could increase or decrease compressor capacity
automatically as the evaporator load changed. Control
systems were used on these units that had the thermostat’s
second stage contacts control a capacity control liquid line
solenoid valve to open or shutoff a portion of the
evapora tor surface without any direct connection to the
compressor circuit.
This form of system capacity staging control is not
possible with 38AU models. If this installation is a retrofit
for a unit that included automatic pressure--operated
unloading, check the existing thermostat and liquid
solenoid valve. When found, convert the evaporator
second stage solenoid control into a drop--solenoid
control. Use the two SVR relays and transformer as
required on 38AUD models (above); wire the SVRs and
transforme r per two solenoid valve systems as shown in
Figs. 19 and 31.
Selecting an Accumulator –
Becaus e all 38AU models use scro ll compr es s or s , an
accumulator is not req uir ed . If an accumulato r is to be
added, check the accumulator manufactu r er’s literature
carefully for indicatio n of its suitab ility for us e with
R--410A; look for minimum working pressure of 420 psig
(2896 kPa). Select the accumulator first on the basis of its
cataloged minimum capacity (tons ) to ensu r e oil return fro m
the accumulator, then on tube size or hold ing capacity.
Make Piping Connections —
Piping c onnections at the 38AU unit are ball valves with
stub tube extensions. Do not open the unit service valves
until all int erconnecting tube brazing has been completed.
The stub tube connections include
1
/
4
-in SAE serv ice fittings
with Schrader valve cores (see Fig. 12). Before making any
brazed connections to the unit service valves, remove both
Schrader valve caps and cores and save for re-installation.
Con nect a source for nitr og en to one of these service fittings
during tube brazing to prevent the formation of copper
oxides inside the tubes at brazed joints.
Factory
High-Flow
ccess Port
Service Valve
with Stem Cap
Field Service
Access Port
(Schrader core)
Sweat
Connection
C10203
Fig. 12 -- Typical Piping Connection Assembly
When conne cting the field tubing to the 38AU se rvice
valves, wrap the valves i n wet rags t o prevent overheating.
Pressure-test all joints from outdoor unit connecti ons over
to the evaporator coil, using nitrogen as pressure and with
soap-and-bubbles.
When pressure-testing is completed, remove the nitrogen
source at the outdoor unit service valves and re-install the
two Schrader valve cores. Torque the cores to 2-3 in-lbs
(23-34 N-cm).
Evacuation/Dehydration —
Evacuate and dehydrate the connected refrigeration
system(s) (excluding the 38AU unit) to 500 microns using
a two-stage vacuum pump attached to the service ports
outside the 38AU service valves, following description in
GTAC II, Module 4, System Dehydration.
UNIT OPERATION AND SAFETY HAZARD
Failure to foll ow this warning could cause personal
injury, death and/or equipment damage.
Puron
R
(R--410A) refrigerant systems operate at
higher pressure than standard R--22 systems. Do not
use R--22 service equipment or compone nts on Puron
refrigerant equipment.
!
WARNING
This unit is designed for use with Puron (R--410A)
refrigerant. Do not use any other refrigerant in this
system.
Puron (R--410A) refrigerant is provided in pink (rose)
colored cylinders. These cylinders are available with and
38AU
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