Honeywell T2798I2000 User Manual

APPLICATION:

This standalone micro-controller based LCD temperature
controller provides proportional plus integral (P+I) and on/off
temperature control for commercial Heating, Ventilating & Air
Conditioning System such as Hydronic Heating, Air Handling
Unit, Heat Exchanger or Condensing Tower.
This controller has a modulating analog 2 to 10Vdc or 4 to
20mA output and a 2A on/off output to realize various optional
control functions including cool/heat changeover, heat/cool
sequence control, emergency interlocking and auto-alarming
control.

Table of Contents

Application………………………………………….1
Features…………………………………………….1
Specification………………………………………..2
Dimensions, Installation & Wiring Terminals..….3
Control Operation………………………………….4
Installer SetUp……………………………………..12

FEATURES:

• PI (proportional plus integral) control action
provides accurate, stable and comfortable
temperature control.

• Compatible with series 70 direct-coupled
damper / valve actuator like ML7161,
ML7174, ML7420 / ML7421series ML7425,
ML7984 series, N20010, S10010, M7410E
series, CN7505, CN7510 / CN72 series
CN7220 & CN7234 also VC79 series etc.

• Backlit LCD to display both setting and
measured value.

• Adjustable Zero Energy Band, On/Off
Differential, Proportional Band and
Temperature Offset.

• Analog output can be forced manually to be
convenient for installation & commissioning.

• Optional 2 to 10Vdc or 4 to 20mA direct
acting and reverse acting analog output.

• Selectable internal and external temperature
sensor.

• Wide temperature control range (-20 to 110
°C by using external temperature sensor) is
suitable for extreme temperature control such
as steam and ice water.

• Watch Dog Timer: to resume the controller
from hanging condition.

• Brownout effect to avoid malfunctioning and
care on power ON and power OFF.

• Pluggable terminal block allows pre-wiring
outside of the controller.

• Compact size and slim design provide
elegant and attractive modern style
appearance.

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SPECIFICATIONS:

IMPORTANT: The specifications given in this publication
do not include normal manufacturing tolerances.
Therefore, this unit may not exactly match the listed
specifications. Also, this product is tested and calibrated
under closely controlled conditions and some minor
difference in performance can be expected if those
conditions are changed.

MODEL: T2798I2000
Control Performance: This controller provides 4 to 20mA
or 2 to 10Vdc Proportional plus Integral modulating control
and 4(2) A On/Off control.

INPUTS:

1) Analog - 1 No. (Only PT1000)

2) Digital - 1 No. (Dry Contact)
OUTPUTS:

1) Analog - 1 No.

2) Digital - 1 No.

SETPOINT RANGE:
5-50°C (internal temperature sensor)

-20-110°C (external temperature sensor)

POWER SUPPLY: AC24V ±20%, 50/60Hz,
2 VA.

ANALOG OUTPUT:
2 to 10Vdc OR
4 to 20mA.

DIGITAL OUTPUT:
2A, 24Vac

MOUNTING: Direct wall mounting
with standard electrical mounting box [type-3 module].

TERMINALS: Plug-in screw terminals
are suitable for 1.5 square mm wire.

OPERATING AMBIENT:
0-50°C, 5-80%RH.

Shipping & Storage:

-20 - 45°C, 5-95%RH
ACCURACY:
< / = +/- 0.30°C
REMOTE SENSOR: RTD
PT1000.
Maximum 15m cable length
(line resistance < 4.5Ω)

Enclosure: ABS Plastic, 2-piece. (IP30)

OPERATING PARAMETER:
See TABLE 2 for installer selections.

Parameter Selection
Zero Energy Band 1.5 or 3.0°C
On/Off Differential 0.5 to 3.0°C (0.5°C

step change)

Proportional Band 2.0 to 19.0°C (0.1°C

step change)

Offset -3.0 to 3.0°C (0.5°C

step change)

Set Point Definition Heating, Cooling,

H/C midpoint,
Heating/Alarming or
Cooling/Alarming.

Main Sensor Remote or Internal

ACCESSORIES:

Duct Mount Remote Sensor PT1000.
DIN Class B.
Model # RSPT1000
Probe Length: 300mm
(to be ordered separately)

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1234567

8

14

135

17

135

107.5

83.5

86.5

20

DIMENSIONS:

115

60

115

M3 Self Tapping screw

INSTALLATION:

The controller can be installed in any position on a
flat surface using electrical box [Type-3 Module].
To measure room temperature by internal sensor
and choosing wall mounting method, it is
recommended to be installed 1.5m (about 5 ft.)
above the floor in the area at average temperature
conditions.
For all kinds of mounting method, the product must
be installed in an area with good air circulation.

Do not install the controller where it may be
affected by:

 Draughts or dead air spots behind doors

and in corners.

 Hot or cold air from ducts.
 Radiant heat from sun or appliances.
 Concealed pipes and chimneys

WIRING TERMINAL:

1 & 2 – Relay Output
3 – 0Vac
4 – 24Vac
5 – Digital Input
6 – 2…10Vdc OR 4…20mA analog output
7 & 8 – PT1000 Remote Sensor

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CONTROL OPERATION:

Input1 –Remote Temperature Sensor

The controller has an integral sensing device mounted internally. It is also possible to install a
remote room or duct return sensor at different locations. See wiring diagram.
Note#1: The remote sensor should be PT1000 (Refer Accessories)

Input2- Emergency Input

Input2 is to connect with an On/Off dry contact for system error or emergency interlock control. If
the contact is close, the controller will automatically close all output (or open to the maximum
position in reverse mode) and cut off the power. The controller can only be restarted manually.

Note#2: If you don’t want to use the interlock function/emergency input please use a jumper wire
to connect input2 (terminal no.5) and neutral port (Terminal no.3), see wiring diagram.

Output1-Modulating Analog Output (2 to 10Vdc or 4 to 20mA)

Output1 is modulating P+I analog 2 to 10Vdc or 4 to 20mA. It can be selected by Selector
switch. The output signal is normal mode (2 to 10Vdc or 4 to 20mA) or reverse mode (10 to
2Vdc or 20 to 4mA) selectable.

Output2- On/Off digital Output (2A, 24Vac)

Output2 is digital output with 24VAC 2A Contact rating, nominal capacity. It provides On/Off
control for electric heater, on/off valve actuator or fan etc.
Output2 can provide limitation control through pre-setting a separate temperature limitation.

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Heat / Cool Changeover of Output1

Valve Open

Temperature Increase

Valve Close

Output1 is suitable for Heat/Cool changeover (manually) control in 2pipe AHU, Zoning control or
Hydronic Heating application. Wiring connection is shown in fig.
With cooling or heating selected, the user set point (SP) will be positioned at the middle of
proportional band. The output percentage is proportional to the temperature measured and
decided by proportional band. The proportional band can be set from 2.0°C to 19.0°C. The
control logic is seen in Diagram 1.

Diagram 1:

100%

50%

0%

Wiring Diagram

Heating

sp

Cooling

Proportional band

Pt1000
sensor

24VAC

A/OD/I

8

PT1000
REMOTE SENSOR

4 - 20 mA

2 - 10 VDC

110VAC /
230VAC

1 2 3 4 5 6 7

L

24VAC

N

0VAC

E

POWER
SUPPLY

0VAC

2-10VDC /
4-20mA

Actuator
Unit

Add link between terminal No 5 & 3.
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Note: If Emergency IP [D/I] not used then

Heating + Cooling Sequence control with Zero Energy Band

Z-Band

Output 2

Valve Open

Temperature Increase

Valve Close

Output 1

This kind of control requires Zero Energy Band (Z-Band). Z-Band is pre-set. For control purpose,
the zero energy band is centered on the user set point (SP), so its value defines the effective
heating (H SP) & cooling (C SP) set points. The cooling set point (C SP) will be positioned on
the right side of Z-Band & the heating set point (H SP) on the left side of Z-Band. Z-Band can be
set as 1.5°C or 3.0°C. Any change of set point will cause both heating and cooling set points to
change in parallel. Either output1 or output2 can be used for cooling or heating control. The
control logic is seen in Diagram 2 and 3.

Diagram 2: Heating + Cooling Sequence Control.

100%

0%

50%

Heating

H SP

SP

C SP

Cooling

Diff

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