Carrier 040-420 User Manual

IMPORTANT: This publication contains controls, op-
eration and troubleshooting data for 

 and

 250, and 280 

 II chillers,

Circuits are identified as circuits A and B, and com-

pressors are identified as Al, A2, etc. in circuit A,
and 

 B2, etc. in circuit B.

Use this guide in conjunction with separate Instal-

lation Instructions booklet packaged with the 

The 

 Series standard Flotronic II chillers feature

microprocessor-based electronic controls and an electronic
expansion valve (EXV) in each refrigeration circuit.

NOTE: The 

 and 045 chillers with a 

installed brine option have thermal expansion valves (TXV)
instead of the EXV.

Unit sizes 240,270, and 300-420 are modular units which

are shipped as separate sections (modules A and B). Instal-
lation instructions specific to these units are shipped inside
the individual modules. See Table   for a listing of unit
sizes and modular combinations. For modules 

 and 

follow all general instructions as noted for unit sizes 

 For all remaining modules, follow instructions for unit

sizes 130-210.

The Flotronic II control 

cycles compressor un-

loaders and/or compressors to maintain the selected leaving

water temperature set point. It automatically positions the

EXV to maintain the specified refrigerant superheat enter-
ing the compressor cylinders. It also cycles condenser fans

on and off to maintain suitable head pressure for each cir-

cuit. Safeties are continuously monitored to prevent the unit
from operating under unsafe conditions. A scheduling func-

tion, programmed by the user, controls the unit occupied/

unoccupied schedule. The control also operates a test pro-

gram that allows the operator to check output signals and
ensure components are operable.

The 

 consists of a processor module 

a low-voltage relay module (DSIO-LV), 

  an EXV

driver module (DSIO-EXV), a 6-pack relay board, a key-
pad and display module (also called HSIO or LID), ther-
mistors, and transducers to provide  inputs to  the
microprocessor. An options module (SIO) is used to pro-

vide additional functions. This module is standard on 30GN

modules and is a field-installed accessory on the 30GT 

tronic II units. See Fig. 1.

This module contains the oper-

ating software and controls the operation of the machine. It
continuously monitors information received from the vari-
ous transducers and thermistors and communicates with the

relay modules and 

 relay board to increase or de-

crease the active stages of capacity. The processor module
also controls the EXV driver module, commanding it to open
or close each EXV in order to maintain the proper super-
heat entering the cylinders of each lead compressor. Infor-
mation is transmitted between the processor module and re-
lay module, the EXV driver module, and the keypad and
display module through a 3-wire communications bus. When
used, the options module is also connected to the commu-
nications bus.

For the Flotronic II chillers, the processor monitors sys-

tem pressure by means of 6 transducers, 3 in each lead com-
pressor. Compressor suction pressure, discharge pressure,
and oil pressure are sensed. If the processor senses high
discharge pressure or low suction pressure, it immediately

shuts down all compressors in the affected circuit. During
operation, if low oil pressure is sensed for longer than one

minute, all compressors in the affected circuit are shut down.

At start-up, the coil pressure signal is ignored for 2 min-
utes. If shutdown occurs due to any of these pressure faults,
the circuit is locked out and the appropriate fault code is
displayed.

 This module closes

contacts to energize compressor unloaders and/or compres-
sors. It also senses the status of the safeties for all compres-
sors and transmits this information to the processor.

 This mod-

ule receives signals from the processor and operates the elec-
tronic expansion valves.

This module allows the use of 

tronic II features such as dual set point, remote reset, de-

mand limit, hot gas bypass, and accessory unloaders. The

options module also 

 for reset and demand limit to be

activated from a remote 4-20 

 signal. The options mod-

ule is installed at the factory on 040-210 and modular 240-
420 units. It is a field-installed accessory for 225, 250 and
280 units.

This device consists of a keypad with 6 func-

tion keys, 5 operative keys, 12 numeric keys, and an al-
phanumeric g-character LCD. Key usage is explained in
Accessing Functions and Subfunctions section  on  page 28.

Control of the chiller is defined by

the position of the LOCAL/ENABLE-STOP-CCN switch.
This is a 3-position manual switch that allows the chiller to
be put under the control of its own Flotronic   controls,
manually stopped, or put under the control of a Carrier Corn-
fort Network (CCN), Switch allows unit operation as shown

   

in Table 2.

2