MCC EM-1 - EnviroMATE Controller (Single Zone); Controller Operation; Evaporator Fan Operation

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2.8.2 Variable Speed Control Operation

With Power to the ignition circuit breaker and

battery circuit breakers ( see Figure 5-6) the fan speed

switch is brought to the desired speed position to

start the system. Bringing the fan speed switch to the

desired speed position closes the fan speed switch

contacts to supply power to the input terminal of the

thermostat and through the terminal board terminal

TB-1 to energize t he high speed relay (HSR) and

optional hour meter. Energizing HSR closes a set of

normally open contacts to supply power to the

electronic speed contro l.

Poweralsoflowsthroughthefanspeedswitch

potentiometer to provide a signal through TB-9 to

the electronic speed control ADJ terminal. With this

signal present, the electronic speed control will

provide power to energize the evaporator blower at

the desired speed.

With the thermostat calling for cooling, power flows

from the thermostat output terminal, through

TB-10, the Freeze-up thermostat and low pressure

switch (optional location) to TB-3.

From TB-3, power flows to energize the condenser

relay (CR). Energizing CR closes it's normally open

contacts to provide power from the battery circuit

breaker through TB-4 to start the condenser fans

(CM).

Power also flows from TB-4 through the low

pressure switch (LP - optional location), high

pressure switch (HP) and TB-5 to energize the clutch

relay (CLR). Energizing CLR closes it's normally

open contacts to provide power from the battery

circuit breaker thro ugh TB-6 and energize the clutch.

Energizing the clutch starts the compressor.

2.8.3 Total Control - Gen 5 Operation

With Power to the battery circuit breakers (see

Figure 5-7) the Total Control Key Pad ON button is

pressed to start the system. The microprocessor will

perform a voltage check (10 seconds) and then

proceed to the start-up sequence. With voltage

within the specified range, the microprocessor will

provide power from the CFM+ terminal to energize

the condenser relay (CR). Energizing CR closes it's

normally open contacts to supply power from the

battery circuit breaker through terminal board

terminal TB-1 to start the condenser fan motors.

Two seconds after starting the condenser fans, the

microprocessor will provide power from the CL

terminal through TB-3, the low pressure switch (LP -

optional location) and high pressure switch (HP) to

energize the clutch. Energizing the clutch starts the

compressor.

Two seconds after starting the compressor, the

microprocessor will provide power from terminal

EFM+ to en ergize the high speed relay (HSR).

Energizing HSR closes a set of normally open

contacts to supply power through TB-4 to the

electronic speed cont rol. At th e same time, the

microprocessor will provide power from terminal

BPV+ to energize th e pulse width modulation relay

(PWM). Energizing PWM closes a set of normally

open contacts to allow regulated voltage from

microprocessor terminal BPV- , through TB-5 to the

electronic speed contro l adjustment (ADJ) terminal.

The voltage output will begin at the lowest setting

andthenrampuptothevoltagerequiredin

accordance with the speed selection made at the

TotalControlKeyPad.

If at any time during operation the circuit from

microprocessor t erminal BPT+ back to terminal

BPT- is opened by the freeze-up thermostat or low

pressure switch (LP - optional location) the

compressor clutch will be de-energized. Once the

circuit is re-established, the clutch will be

re-energized after a one minute delay.

When th e system is installed as a tie-in system, power

is supplied by the vehicle controls to the

microprocessor ignition terminal (NEIM) when

operation of the compressor is required by the

in-dash defroster. With power to the NEIM

terminal, the compressor clutch is energized.

2.8.4 Total Control - Gen 4 Operation