Carrier 40VMC, 40VMF, 40VML, 40VMH, 40VMR Installation And Operating Instructions Manual

40VM Series Indoor Fan Coils

VRF (Variable Refrigerant Flow) System

24V Interface Accessory

Installation and Operating Instructions

Part Number 40VM900008

SAFETY CONSIDERATIONS

Read and follow manufacturer instructions carefully.
Follow all local electrical codes during installation. All wiring
must conform to local and national electrical codes. Improper
wiring or installation may damage thermostat.

Understand the signal words — DANGER, WARNING,
and CAUTION. DANGER identifies the most serious hazards,
which will result in severe personal injury or death.
WARNING signifies hazards that could result in personal
injury or death. CAUTION is used to identify unsafe practices,
which would result in minor personal injury or product and
property damage.

Recognize safety information. This is the safety-alert
symbol ( ). When this symbol is displayed on the unit and in
instructions or manuals, be alert to the potential for personal
injury. Installing, starting up, and servicing equipment can be
hazardous due to system pressure, electrical components, and
equipment location.

GENERAL

The 24V Interface for the VRF (Variable Refrigerant Flow)
system is a device that enables the use of a conventional
24VAC thermostat with indoor units. The Interface receives
24VAC signals for Cool, Heat, and Fan; translates these
commands to the system's communication protocol; and sends
the commands to indoor unit over the HA / HB communication
bus.

The 24V Interface accessory is available for use with the
VRF (variable refrigerant flow) system indoor units listed in
Table 1.

Table 1 — 24V Interface Accessory Usage

UNIT SIZES

40VMC Compact Cassette 007,009,012,015

40VMF 4-Way Cassette

40VMH High Static Ducted 024,030,036,048, 054, 072, 096
40VML Low Static Ducted 007, 009, 012, 015, 018, 024

40VMM Medium Static Ducted

40VMR Floor Console ­Recessed

40VMU Under Ceiling/Floor 012,018,024,030,036,048
40VMV Vertical AHU 018,024,030,036,048, 054
40VMW High Wall 007,009,012,015,018, 024, 030

009,012,015,018,024,030,036,
048

007,009,012,015,018,024, 030,
036, 048

007, 009, 012, 015, 018, 024

WIRING REQUIREMENTS

24V Interface shall be configured for use with a conventional
24VAC thermostat with outputs for Fan, Heat, and Cool.

1. Wiring for Fan, Heat, and Cool signals from
Thermostat to interface should be performed with 18
AWG thermostat wire.

2. Terminals on 24V interface support 24VAC (+

10%)

signal only.

3. Communication wiring from 24V Interface to Indoor
Unit (HA/HB) should be 20-16 AWG, stranded, shielded
control wire.

INSTALLATION

To install the 24V Interface:

1. Turn off all power to the indoor unit; turn off all power to
field-supplied 24VAC transformer serving the thermostat.

WARNING

Electrical shock can cause personal injury and death.
Before installing thermostat, shut off all power to this
equipment during installation. There may be more than one
power disconnect. Tag all disconnect locations to alert
others not to restore power until work is completed.

2. If an existing thermostat is being replaced:

a. Remove existing thermostat from wall or unit.

b. Disconnect wires from existing thermostat. Do not

allow wires to fall back into the wall or unit.

c. Discard or recycle old thermostat.

CAUTION

Failure to follow this caution may result in equipment
damage or improper operation.

Improper wiring or installation may damage the
thermostat. Check to make sure wiring sequence is correct
at both ends before proceeding with installation or turning
on unit.

3. Select an appropriate location to install the 24V
Interface—for example, inside a 4”x4” junction box.
Coordinate with local electrical codes.

4. Connect HA HB terminals of 24V Interface to the HA
HB terminal of the indoor unit control board using
stranded, shielded control wiring.

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.

Catalog No. 17-40VM900008-01 Printed in USA Form 40VM-7SI Pg 1 02-17 Replaces: New

NOTE: The thermostat and 24VAC power are field provided.

5. Connect COOL, HEAT, FAN, and COMMON terminals

COOL

HEAT

FAN

COM

1-7/8

SW1

1

2

HA

HB

1-1/4

1-1/4

Thermostat

24V Interface

Indoor Unit

Y W G C

Cool Heat Fan Com

HA HB

HA HB

CN2

CN1

R

Shielded Pair

of 24V Interface to Cool, Heat, Fan, and Common of
the thermostat using 18 AWG thermostat wire.

6. Using SW1 dip switches on 24V Interface, select IDU
fan speed operation when thermostat calls for fan:

Table 2 — SW1 Fan Speed Selection

00 selects low fan speed

01 selects medium fan speed

10 selects high fan speed

11 selects auto fan speed

7. Configure the third-party thermostat per manufacturer’s
instructions. If third-party thermostat has adjustable
time delays among Fan, Heat, or Cool; disable them (i.e.

fan delays for gas furnace warm-up). Fan signal shall
start/stop simultaneously with any call for Heat or Cool.

NOTES:

1. The 24V Interface can only connect one thermostat and
an indoor unit.

2. COOL/HEAT/FAN inputs can only receive 24VAC signal
with common (“C”/”COM”) wire.

3. The 24V Interface relies upon both the thermostat and
the indoor unit’s thermistors in order to monitor room
temperature. The thermostat’s sensor is used to set the
room temperature. The indoor unit thermistor is used
when calculating cooling and heating rate of change.

4. When cooling signal is enabled, the IDU operates in
cooling mode. When heating signal is enabled, the IDU
operates in heating mode.

5. The Fan signal is used only for the operation of IDU in
Fan mode when there is no call for heating or cooling.

6. While using 24V Interface, fan speed can only be set by
the 24V Interface dip switches.

7. 24V Interface is not recommended for systems using a
Central Controller.

8. The indoor unit will limit the temperature range set
point based on the indoor unit’s specifications.

9. The 24V Interface does not support Carrier VRF ERV
Interface.

10. The 24V Interface is for indoor use only.

24 VAC

Fig. 1 — Wiring diagram

2-7/8

© Carrier Corporation 2017

Catalog No. 17-40VM900008-01 Printed in USA Form 40VM-7SI Pg 2 02-17 Replaces: New

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.

Fig. 2—Dimensional Drawing