Bard CMA-38 Betriebsanleitung

Page 1 of 8

The CMA-38 is a ﬁeld-installable low ambient fan

speed control for 460V motors. The CMA-38 460V

head pressure control helps maintain the correct

condensing temperature/pressure, which results in a

constant head pressure. By adjusting the condenser

fan speed, the CMA-38 controls the airﬂow through

the condenser. A single desired temperature/pressure

setpoint adjustment will result in precise condensing

temperatures and stable head pressures.

The CMA-38 kit is for use with Bard models W24AB-C

wall-mount air conditioners.

The

CMA-38

kit consists of:

• 7960-847 Installation Instructions

• 902-2069 Fan Speed Control Box

• 910-2058 Outdoor Temperature Switch Assembly

• 8408-048 Freeze Protect Thermostat

• 5810-006 Flare Tee

• 1012-066 3/4" Screw (1)

• 8607-017 Terminal Block

• 1012-085 1/2" Self-Tapping Screws (5)

• 7950-004 Nylon Wire Ties (6)

• 7961-312-0338 CMA-38 Unit I.D. Label

Field-supplied tools needed:

• Personal protection equipment, including gloves

and safety glasses

• 5/16" nut driver

• 1/2" wrench (service port), 11/16" wrench (LAC

control) and 3/4" wrench (LAC assembly)

• Side cut pliers (for cable tie removal)

• Flat head screwdriver

• Small flat head screwdriver for securing wire in

terminal blocks

Bard Manufacturing Company, Inc.

Bryan, Ohio 43506

www.bardhvac.com

Manual: 7960-847B

Supersedes: 7960-847A

Date: 12-9-19

CMA-38 Low Ambient 460V Fan Speed Control

SUPPLEMENTAL INSTRUCTIONS

Sharp metallic edges.

Take care and wear appropriate protective

devices to avoid accidental contact with

sharp edges.

Failure to do so can result in personal

injury.

!CAUTION

Exposed moving parts.

Disconnect all electrical power before

servicing.

Failure to do so can result in severe injury

or amputation.

!WARNING

Electrical shock hazard.

Disconnect the remote electric power

supply or supplies before servicing.

Failure to do so can result in serious injury

or death.

!WARNING

FIGURE 1

MIS-4078

CONTROL

BOX

4'' 12.5"

Manual 7960-847B

Page 2 of 8

Installation

1. Disconnect all power to the unit. Remove control

panel inner and outer covers, upper front panel and

both right-side and left-side condenser inlet grilles.

2. Mount the fan speed control box as shown in

Figure 1 using the three self-tapping screws.

The dimensions for mounting the control box are

provided in Figure 1.

3. Remove service cap and attach the pressure

transducer and ﬂare tee to the liquid line as shown

in Figure 2; re-install the service cap on the end of

the service tee. Check for leaks.

Attach the plug from the fan speed control box to the

pressure switch as shown in Figure 2.

5. Install outdoor temperature switch assembly to the

fan shroud and route wires through the bushing

and up to the control panel as shown in Figure 3

on page 4. This switch defeats Balanced Climate

airﬂow when the temperature falls below 50°F to

help prevent evaporator freeze up. Refer to the

unit installation manual for more information on

Balanced Climate operation.

6. Install freeze protect thermostat to the evaporator

coil as shown in Figure 4 on page 5. Route the

wires down through the copper bushing and into the

control panel with the blower motor wires.

7. Run all wires from the low ambient control

(LAC) box (except the ones going to the pressure

transducer) up through the bushing in the bottom

of the unit control box as shown in Figure 5 on

Manual 7960-847B

Page 3 of 8

FIGURE 2

MIS-3880

REINSTALL CAP

REMOVE CAP AND INSTALL

PRESSURE TRANSDUCER

TEE TO SERVICE PORT.

BOX

PLUG WITH

WIRES TO CONTROL

LIQUID LINE

RE-INSTALL CAP

page 6. Disconnect the black fan wire running

from the T2 terminal of the compressor contactor.

Install terminal block (as shown in Figure 5) and

reconnect the black fan wire to one side of the

terminal block. Run the black/red wire from LAC

to the terminal block so that it is connected to the

fan motor wire. Run the black wire from LAC to the

T2 terminal of the compressor contactor. Run the

black/white wire from LAC to the C terminal on the

24V transformer. Run the red/white wire from LAC

to the R (hot) terminal on the transformer. Run

the yellow wire from LAC to the T3 terminal of the

compressor contactor.

Secure wires running on the outdoor section of the

unit using the supplied nylon wire ties as shown

in Figure 1). Be sure that there is no way that the

wires can come in contact with the fan blades or

any sharp edges.

9. Check wiring and control knob settings. See Figure

5 (page 6) and Figure 6 (page 7) for wiring and

suggested setpoints.

10. Find the purple wire not connected to anything that

is tucked in the cable duct (see Figure 5). Pull it

out and connect it to the LAC terminal block on

the terminal that is separate from the LAC control

wires. Connect the end of the outdoor temperature

switch that has the insulated quick connect to the

terminal block beside the purple wire. Connect the

other end of the outdoor temperature switch to the

Y terminal on the phase monitor. (Refer to Figure 7

on page 8 or the unit wiring diagram).

11. Connect the freeze protect thermostat wires in line

with the “Y” input signal to the compressor control

module (CCM). Refer to the unit wiring diagram.

For 1-phase units, connect the end with the 1/4”

quick connect to Y terminal on the CCM, and the

other end with the 1/4” tab to the yellow/white wire

coming from the low voltage terminal strip.

For 3-phase units, connect the wire end with

the 1/4” quick connect to “Y out” on the phase

monitor, and the other end with the 1/4” tab to the

yellow/black wire going to the CCM.

12. Apply “This unit is equipped with CMA-38 control

module” label to the inside of the inner control

panel cover above the wiring diagrams.

11/16" WRENCH

3/4" WRENCH

1/2" WRENCH

FIGURE 3

RUN WIRES THROUGH THE BUSHING

UP TO THE CONTROL PANEL

SCREW

PART #1012-085

OUTDOOR TEMP

SWITCH

PART #910-2058

MIS-4053

Manual 7960-847B

Page 4 of 8

13. Replace all panels, grilles and covers. This

completes the installation.

14. Check proper operation of the unit by energizing

the compressor in cooling mode. The condenser fan

motor should start and ramp up speed as system

pressure increases.

Sequence of Operation

Upon initiation, the CMA-38 will apply full voltage to

the fan motor for the time period selected with the Hard

Start knob (see Figure 6). Hard start time is adjustable

from 0.1 to 5 seconds. The hard start ensures correct

rotation of the condenser fan, even in windy conditions.

After a hard start, the control reads the temperature/

pressure sensor and the fan speed is adjusted until the

input temperature/pressure matches the setpoint.

The CMA-38 enables the user to set and adjust the

pressure to be maintained by the control. The setpoint

pressure is adjustable from 35-465 psig.

FIGURE 4

MIS-4054

USE ONE OF THE MIDDLE

HEADER STUBS TO ATTACH

THE FREEZE STAT TO THE

EVAPORATOR COIL

FREEZE STAT WIRES

RUN DOWN COPPER

THROUGH THE GROMMET

AND INTO THE CONTROL

PANEL WITH THE BLOWER

MOTOR WIRES

Manual 7960-847B

Page 5 of 8

FIGURE 5

MIS-4074

MOTOR

FROM FAN

MODULATING

LOW AMBIENT BOX MIS-4074

TRANSFORMER

COMPRESSOR

CONTACTOR

TERMINAL BLOCK

CABLE DUCT

Manual 7960-847B

Page 6 of 8

FIGURE 6

MIS-3881 A

Black/Red

Yellow

Black

top 2 pins

(N.O. Setting)

position

Set to"MIN"

position

Set to"MIN"

position

Set to"315"

RED

BLACK

BLACK/WHITE BLUE

Set jumperto

TO PRESSURE

TRANSDUCER

RED/WHITE

Manual 7960-847B

Page 7 of 8

FIGURE 7

Manual 7960-847B

Page 8 of 8

LPC

ALR

HPC

MINUTES

1012 1345678911

Phase Monitor

L2 L3

Yout C

MIS-4052 B

PHASE

Black

Fan Motor

Purple W24 Units

Switch

Temp

(Behind Low Voltage Block)

12 Pin Plug

Blue on

UNITS

3 PHASE

Low Ambient

W24 Units

MONITOR

Outdoor

Contactor

Compressor

Terminal

Block #2

Control

Module

Compressor

Brown onBlack

Black

Yellow

UNITS

Control

Outdoor

1 PHASE

NOTE:

CONNECT YELLOW WIRE FROM

OUTDOOR TEMP SENSOR TO

"Y" TERMINAL ON THE COMPRESSOR

CONTROL MODULE FOR 1-PHASE UNITS,

OR THE "Y" TERMINAL ON THE PHASE

MONITOR FOR 3 PHASE UNITS.

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