Bryant 548J User Manual

Page 5

460, 575-v Units

208/230-v Units

C09263

Fig. 7 -- EMC Unit Wiring

ECM Motor – The direct--drive motor is an X13

Electronically Commutated motor (ECM). An ECM

contains electronic circuitry to convert single--phase line

AC voltage into a 3--phase DC voltage to power the motor

circuit. The motor circuit is a DC brushless design with a

permanent magnet rotor. On the X13 design, the

electronic circuitry is integral to the motor assembly and

cannot be serviced or replaced separately.

208/230--v units use a 230--v motor. 460--v units use a

230--v motor with a stepdown transformer (mounted on

the end of the fan housing, see Fig. 5). 575--v units use a

460--v motor with an autotransformer. Motor power

voltage is connected to motor terminals L and N (see

Fig. 6 and Fig. 7); ground is connected at terminal G.

The motor power voltage is ALWAYS present; it is not

switched off by a motor contactor.

Motor operation is initiated by the presence of a 24--v

control signal to one of the five motor communications

terminals. When the 24--v signal is removed, the motor

will stop. The motor control signal is switched by the

defrost board’s IFO output.

Evaluating motor speed – The X13 ECM is a constant

torque motor design. The motor speed is adjusted by the

motor control circuitry to maintain the programmed shaft

torque. Consequently there is no specific speed value

assigned to each control tap setting. At the Position 5 tap,

the motor speed is approximately 1050 RPM (17.5 r/s) but

it will vary depending on fan wheel loading.

Selecting speed tap – The five communications terminals

are each programmed to provide a different motor torque

output. See Table 1. Factory default tap selection is

Position 1 for lowest torque/speed operation.

Table 1 – 548J Standard Static Motor Tap Programing

(percent of full--load torque)

Unit Size

Tap 1

Tap 2

Tap 3

Tap 4

Tap 5

100

Factory Default: Tap 1 (VIO)

To select another speed:

1. Disconnect main power to the unit.
2. Remove the motor signal lead (VIO) at the motor

communications terminal.

3. Reconnect the motor signal lead to the desired speed

terminal.

4. Connect main power to the unit.

Motor “rocking” on start--up – When the motor first starts,

the rotor (and attached wheel) will “rock” back and forth

as the motor tests for rotational direction. Once the correct

rotation direction is determined by the motor circuitry, the

motor will ramp up to specified speed. The “rocking” is a

normal operating characteristic of ECM motors.

Troubleshooting the ECM motor – Troubleshooting the

X13 ECM requires a voltmeter.

1. Disconnect main power to the unit.
2. Remove the motor power plug (including the control

BRN lead) and VIO control signal lead at the motor

terminals.

3. Restore main unit power.
4. Check for proper line voltage at motor power leads

BLK (from L terminal) and YEL (from N terminal).

548J