Carrier 50PG03-07 Specifications download pdf (Page 30)

Performance Adjustment section on page 39. See Table 18 for

accessory electric heat static pressme.

Cooling -- To start unit, turn on main power supply. Set

system selector switch tit COOL position and fan switch tit

AUTO position. Adjust therlnostat to a setting below room

temperatme. Compressor sttuts on closure of contactoc

Check unit charge. Refer to Refrigerant Charge section on

page 40.

Reset thermostat at a position above room temperature.

Compressor will shut off.

TO SHUT OFF UNIT -- Set system selector switch at OFF

position. Resetting thermostat at a position above room tem-

perature shuts unit off temporarily until space temperature ex-

ceeds thermostat setting. Units me equipped with Cycle-

LOC TM protection device. Unit shuts down on any safety trip

and remains off; an indicator light on the thermostat comes on.

Check reason for safety trip.

Complessor restart is accomplished by manual reset at the

thermostat by turning the selector switch to OFF position and

then ON position.

Heating (If Accessory Heater is Installed) -- To

st_ut unit, turn on main power supply.

Set thermostat at HEAT position and a setting above room

temperature, and set fan at AUTO position.

First stage of thermostat energizes the fi_st-stage electric

heater elements; second stage energizes second-stage electric

heater elements. Check heating effects fit air supply grille(s).

if accessory electric heaters do not energize, reset limit

switch (located on evaporator-fan scroll) by pressing button lo-

cated between termimds on the switch.

TO SHUT OFF UNIT -- Set system selector switch at OFF

position. Resetting heating selector lever below room tempera-

ture temporarily shuts unit off until space temperature ftdls be-

low thermostat setting.

Safety Relief- A soft solder joint in the suction line

fit the loss-of-charge/low-pressure switch fitting provides

pressure relief under abnormal temperature and pressure

conditions.

Ventilation (Continuous Fan) -- Set fan and system

selector switches fit ON and OFF positions, respectively.

Evaporator fan operates continuously to provide constant air

circulation.

Operating Sequence

COOLING. UNITS WITHOUT ECONOMIZER -- When

thermostat calls for cooling, terminals G and YI me energized.

The indoor-fan contactor (lFC) and compressor contactor me

energized and indoor-fan motol: compressor, and outdoor fan

stm'ts. The outdoor-fan motor runs continuously while unit is

cooling.

HEATING. UNITS WITHOUT ECONOMIZER -- Upon a

request for heating from the space thermostat, terminal Wl will

be energized with 24 v. The lFC and heater contactor no. 1

(HCI) are energized.

COOLING. UNITS WITH ECONOMISER IV -- When free

cooling is not available, the compressors will be controlled by

the zone thermostat. When free cooling is available, the

outdoor-air damper is modulated by the EconoMiSer IV con-

trol to provide 50 to 55 F mixed-air temperature into the zone.

As the mixed-air temperature fluctuates above 55 or below

50 H the dampers will be modulated (open or close) to bring

the mixed-air temperature back within control.

If the load is high and Y2 is energized, then the that stage of

mechanical cooling will be used to supplement the free cooling

provided by the economizer If mechanical cooling is utilized

with free cooling, the outdoor-air &_mper will maintain its

current position at the time the compressor is started. If the

increase in cooling capacity causes the mixed-air temperature

to drop below 45 F. then the outdoor-air dmnper position

will be decreased to the minimum position. If the mixed-air

temperature continues to fall, the outdoor-air (ktmper will

close. Control returns to normal once the mixed air temperature

rises above 48 E

If optional power exhaust is instfdled, as the outdoor-air

damper opens and closes, the power exhaust fans will be

energized and deenergized if the position goes above or below

the power exhaust set point. When the exhaust fan is required

to be on, the LED on the control will be energized.

If field-installed accessory CO2 sensors are connected to the

EconoMiSer IV control, a demand controlled ventilation strate-

gy will begin to operate. As the CO2 level in the zone increases

above the CO2 set point, the minimum position of the damper

will be increased proportionally from the minimum damper

position to the maximum demand ventilation damper position.

As the CO2 level decreases because of the increase in fresh air,

the outdoor-air damper will be proportionally closed.

If there is no G signal then the control will drive the &tmper

to the fully closed position.

The control is also equipped with an occupied/unoccupied

input. If the input is closed, then the damper will be driven to

the minimum position when G is energized. If the input is open

then the damper will remain in the lully closed position unless

there is a demand for free cooling of DCV ventihnion.

On the initial power to the EconoMiSer IV control, it will

take the damper up to 21/2 minutes before it begins to position

itself. Any change in damper position will take up to 30 sec-

onds to initiate. Damper movement from full closed to full

open (or vice vel_a) will take between 11/2to 21/2 minutes.

If free cooling can be used as determined from the appropri-

ate changeover command (switch. dq bulb, enthalpy curve,

differential dry bulb, or differential enthalpy), then the control

will modulate the dampers open to maintain the mixed air

temperature set point at 50 to 55 E

If there is a further demand for cooling (cooling second

stage -- Y2 is energized), then the control will bring on

compressor stage 1 to maintain the mixed air temperature set

point. The EconoMiSer IV &tmper will be open at maximum

position. EconoMiSer IV operation is limited to a single

complessoE

HEATING. UNITS WITH ECONOMISER IV -- When the

room temperature calls for heat, the heating controls rueenelgized

as described in the Heating, Units Without Economizer section.

The IFM is energized and the EconoMiSer IV dalnper modulates

to the minimum position. When the thermostat is satisfied, the

dalnper modulates closed.

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Carrier 50PG03-07 Specifications Page 30

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