Elta T210 Specifications download pdf (Page 4)

Variable Air Volume (VAV) Features — The 48/

50AK,AY units are designed to operate in VAV applications. As

standard, the units include a supply fan VFD to control the sup-

ply cfm and duct pressure. The units are designed to control the

leaving-air temperature in cooling to configurable set points.

The control, depending on the selected options and accessories,

will operate in one of three primary modes which are heating,

ventilating and cooling. Initiation of these modes is configurable

from the return air temperature sensor, which is factory sup-

plied, or from a space temperature sensor.

Some special features on VAV applications are:

• Provide cooling control to a supply air temperature in both

occupied and unoccupied modes.

• Supports morning warm-up heating mode which is used

when changing from unoccupied to occupied mode.

• Supports an optional space temperature sensor for mode

control and supply air temperature reset.

• Interface with DAV (Digital Air Volume) control systems

through linkage.

• Support of static pressure reset when used with DAV

systems.

• If space sensor is equipped with an override feature, the

sensor will allow operation during the unoccupied period

for a fixed length of time (1 to 4 hours).

• Control of two stages of heat to maintain return-air

temperature.

• Multiple stage gas heating controlled to a supply air temper-

ature set point if equipped with the staged gas heat option

for use in supply air tempering.

• Base unit control supports a Heat Interlock Relay (field

supplied) to signal the VAV terminal devices to operate at

minimum required airflow for the heaters during heating

operation.

• Controls the operation of the supply fan VFD to maintain a

configurable supply duct static pressure set point. VFD is

configured and controlled directly by the ComfortLink™

Controls. It also can be configured to operate from a third

party control system.

• Cooling capacity control of up to 6 stages plus economizer.

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

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

clock includes or enables the following features:

— Daylight savings time function.

— Occupancy control with 8 periods for unit operation.

— Holiday table containing up to 9 holiday schedules when

programmed from the Scrolling Marquee and up to

30 holiday schedules when programmed from CCN.

— Ability to initiate timed override from T-55 or T-56 sen-

sors (for a timed period of 1 to 4 hours).

— Temperature compensated start to calculate early start

times before occupancy.

— Pre-occupancy purge cycle.

— For units connected into a CCN network, the timeclock

can be integrated into the overall building Energy Man-

agement System and be updated remotely.

MAJOR SYSTEM COMPONENTS

General —

The 48/50A series package rooftop units with

electric cooling and with gas heating (48A units) or electric

cooling and electric heating (50A Units) contain the

ComfortLink electronic control system that monitors all opera-

tions of the rooftop. The control system is composed of several

components as listed below. See Fig. 1-7 for typical control and

power component schematics. Figures 8 and 9 show the layout

of the control box, unit, and thermistor and transducer locations.

Factory-Installed Components

MAIN BASE BOARD (MBB) — See Fig 10. The MBB is

the center of the ComfortLink control system. The MBB con-

tains the major portion of the operating software and controls

the operation of the unit. The MBB has 22 inputs and 11 out-

puts. See Table 2 for the inputs and output assignments. The

MBB also continuously monitors additional data from the

optional ECB1, ECB2, SCB, and CEM boards through the

LEN communications port. The MBB also interfaces with the

Carrier Comfort Network through the CCN communications

port. The board is located in the main control box.

ECONOMIZER BOARD (ECB1) — The ECB1 controls the

economizer actuator and the power exhaust fans. The ECB1

operates the economizer motor using a digital communication

signal that also provides status and diagnostics for the econo-

mizer motor. See Fig. 11. The ECB1 also controls the operation

of the power exhaust motors and provides up to 6 stages of dig-

itally sequenced power exhaust either based on the economizer

motor position or the building pressure. The board has 4 inputs

and 6 outputs. Details can be found in Table 3. The ECB1

board is located in an auxiliary box located at the end of the

unit behind the filter access door. The board also contains

a second LEN port than can be used with the accessory

Navigator display.

VAV BOARD (ECB2) — The VAV board (which is the same

hardware as the ECB1) is used to control the supply fan on

VAV units. See Fig. 11. It sends a 4 to 20 mA signal to the VFD

based on a supply duct pressure sensor connected to the board.

The board also accepts a signal from another pressure sensor

that monitors building pressure and controls the operation of

the optional modulating power exhaust motors. The board will

also be used on CV units with the optional building pressure

control feature and modulating power exhaust. This board is

also used to control a digitally controlled hot gas bypass sole-

noid with an integral orifice for use in low load applications.

This board is located in the auxiliary control box. Input and

output assignments are summarized in Table 4.

STAGED GAS HEAT BOARD (SCB) — When optional

staged gas heat is used on CV and VAV units, the SCB board is

installed and controls operation of the gas valves. See Fig. 12.

The SCB also provides additional sensors for monitoring of the

supply-air temperature. This board is located in the gas heat

section of the unit. The inputs and outputs are summarized in

Table 5.

CONTROL EXPANSION MODULE (CEM) — The optional

CEM is used to provide inputs for demand limiting, remote set

point and other optional inputs typically need for Energy

Management Systems. See Fig. 13. These inputs can be inter-

faced through the CCN communications. It is located in the

main control box. The inputs and outputs are summarized in

Table 6.

INTEGRATED GAS CONTROL (IGC) — One IGC is pro-

vided with each bank of gas heat exchangers (2 used on the size

020-050 units and 3 on the size 060 unit). The IGC controls the

direct spark ignition system and monitors the rollout switch,

limit switches, and induced-draft motor Hall Effect switch. The

IGC is equipped with an LED (light-emitting diode) for diag-

nostics. See Table 7.

COMPRESSOR PROTECTION BOARD (CS) — This board

monitors the status of the compressor by sensing the current

flow to the compressors and then provides digital status signal

to the MBB.

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Elta T210 Specifications Page 4

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