Carrier 48N User Manual download pdf (Page 48)

4 to 20 mA signal. It can be connected to terminals 8

and 9 on TB202.

• Remote Static Pressure Reset Set Point — A remote

supply air temperature set point reset can be supported

when the controls expansion module is used. This input

requires a 4 to 20 mA signal. It can be connected to ter-

minals 6 and 7 on TB202. This input is shared with the

Outdoor Air IAQ signal.

• Outdoor Air IAQ Signal — If an external outdoor air

signal is being used then it can be connected to termi-

nals 6 and 7 on TB202. This input requires a 4 to 20

mA signal. This input is shared with the Remote Static

Pressure Reset signal.

• IAQ Switch Input — If an external control will be con-

trolling IAQ then it can be connected as a contact clo-

sure through terminals 12 and 13 on TB202.

• Space Humidity — A space humidity sensor can be

used to enable the dehumidification and humidifier con-

trol logic. It can be connected to terminals 3 and 4 on

TB202. This input requires a 4 to 20 mA signal.

• Humidifier Control Output — A contact closure out can

be provided to enable the operation of a field-provided

humidifier. Carrier can also support electronic interface

to other systems using the following:

— MODBUS Carrier translator (read/write, provides

CCN to MODBUS remote terminal unit [RTU] protocol

conversion)

— LonWorks Carrier translator (read/write, provides

CCN to LON FT-10A ANSI/EIA-709.1 protocol con-

version)

Constant volume and staged air volume appli-

cations

The 48/50N Series units are designed to operate in CV

and SAV™ applications. The units are shipped as operable,

stand-alone units using either a standard (mechanical or

electronic) 2-stage heat, 2-stage cool thermostat, or with

an electronic room temperature sensor. With a standard

thermostat (programmable is optional), heating and cool-

ing operation is set by space temperature. With a space

sensor, the machine will operate at default values unless

they are changed using appropriate input devices. The

space sensor monitors space temperature and may be

equipped with a timed override feature, which allows unit

operation during unoccupied periods. The space sensors

may be used in multiples of 4 or 9 to achieve space tem-

perature averaging. The use of a space sensor also allows

the unit to be turned on and off from a remote signal or it

can be programmed to use the time of day scheduling that

is built into the control.

Features with thermostat control of unit

• Two-stage heating (if installed)

• SCR electric heating if equipped with the SCR electric

heat option

• Modulating gas heating if unit is equipped with the mod-

ulating gas heat option

• Two-stage demand with fully proportional economizers

and integrated compressor capacity

• Adaptive multiple stage cooling which can provide up to

8 stages of capacity

• Control of unit using Y1, Y2, W1, W2, and G thermo-

stat or T55, T56, or T58 space sensors

• Control of the indoor fan

• Outdoor-air temperature/supply-air temperature moni-

toring with logic to lock the compressors out at low

ambient temperatures down to 32 F (-20 F with Motor-

master

control)

• Control of a condenser fan based on outdoor-air and

condensing pressures

• Control of modulating economizer to provide free cool-

ing when outdoor conditions are suitable

• Control allows for use of the economizer and the com-

pressors to maximize the use of outside air cooling to

reduce part load operating costs

• Control of the power exhaust fan VFD based on config-

urable the building pressure sensor

• Compressor time guard override (power up and mini-

mum on and off timers) to assure air return in low load

conditions

• Support of IAQ sensor

Features with sensor control of unit

There are 3 sensor options available:

• T55 sensor will monitor room temperature and provide

unoccupied override capability (1 to 4 hours).

• T56 sensor will monitor room temperature, provide

unoccupied override capability (1 to 4 hours), and pro-

vide a temperature offset of 5° F maximum.

• T58 is a CCN communicating sensor that will provide

the set point and space temperature values.

Standard features are:

• Support of remote occupied/unoccupied input to start

and stop the unit

• Two-stage economizer demand with fully proportional

economizers and integrated compressor capacity

• Adaptive cooling capacity control with up to 8 stages of

mechanical refrigeration capacity

• Variable capacity control with digital scroll compressor

option

• Occupied or unoccupied set point

• Enable heating (if installed) or cooling during unoccu-

pied periods as required to maintain space temperature

within the unoccupied set points

• Adjustment of space temperature set points of ± 5° F

when using a T56 sensor

• Support of IAQ sensor

• 365-day timeclock with backup (supports minute, hour,

and day of week, date, month, and year access). The

timeclock includes the following features:

— Daylight savings time function

— Occupancy control with 8 periods for unit operation

— Holiday table containing up to 18 holiday schedules

— Ability to initiate timed override from T55 or T56

sensors (for a timed period of 1 to 4 hours)

— Temperature compensated start to calculate early

start times before occupancy

— For units connected into a CCN network the time

clock can be integrated into the overall building ener-

gy management system and be updated remotely

Controls (cont)

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