Cooling operation – tekmar 369 Zone Control Installation User Manual

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Adjust

Zone 2

Com

1-2

Hi Stage

Lo Stage

Section B1

General Cooling

Section B2

Cooling Enable

Section B3

Cooling Control

Adjust

Zone

20 21

Com tN1

tN1

22 23

Indr

Item

View

°F

UnOcc

Cycle Length

Lo Stage

Hi Stage

Lo Stage

Hi Stage

Lo Stage

Hi Stage

Off

Section A3: Two Stage Heating

TWO STAGE HEATING

In cases where a one stage heating system can not provide sufficient heat, a second stage of heat from an
additional heating terminal can be provided to supplement the first stage. A two stage heating system
therefore has one RTU or indoor sensor controlling two output relays: a

Lo stage relay and a Hi stage relay.

If an RTU is used to control a two stage heating zone, the RTU must be connected to an even

tN1 terminal

(i.e.

tN1 2, tN1 4 or tN1 6), and TWO must be selected through the STG NUM adjustment in the Zone Adjust

menu of the control. If an indoor sensor is used to control a two stage heating zone, the sensor must be
connected to an

Indr terminal (i.e. Indr 2, Indr 4 or Indr 6), and TWO must be selected through the STG NUM

adjustment in the Zone Adjust menu of the control. The odd numbered zone relay becomes the Lo Stage
and the even numbered zone relay becomes the Hi Stage.

Example: An RTU connected between Com
and

tN1 2 terminals (20 and 22) is used to

control the output relays

Zn 1 and Zn 2.

Relay

Zn 1 is the Lo stage output relay and

relay

Zn 2 is the Hi stage output relay.

PID Staging Logic

The temperature within each two stage zone is controlled by varying the
on time of the output relays over a cycle length. During light loads, the
369 cycles the

Lo Stage relay on and off. As the load increases, the Lo

stage relay on time increases until it reaches the maximum of the cycle
length. The

Hi stage relay is then turned on and its on time is increased

as the load increases. When the heating load decreases again, the on
time of the

Hi stage relay is reduced until the Hi stage relay is turned off

completely. The control then starts to reduce the on time of the

stage relay.

Section B: Cooling Operation

Section B1: General Cooling

GENERAL COOLING

The Zone Control 369 is capable of operating a single cooling group to provide either cooling enable (ENBL)
or cooling control (CTRL). This is an adjustable item through the COOL MOD setting in the Control Adjust menu
of the control. In order to prevent short cycling of the mechanical cooling unit, the 369 ensures the

Cooling relay

is operated for a minimum amount of time. The minimum run time (MIN RUN) and minimum off time (MIN OFF)
are adjustable settings in the Control Adjust menu of the control.

COOLING GROUP (CG)

A cooling group is a group of heating zones that are a part of a cooling zone. This function allows zones which
are assigned to the cooling group to be doing cooling, while zones which are not assigned to the cooling group
are heating. A heating zone can be assigned to the cooling group by selecting CG through the ZN COOL
adjustment in the Zone Adjust menu of the control. Zone 6 (

tN1 6 or Indr 6) is always a member of the cooling

group; therefore, there is no option for removing this zone from the cooling group.

COOLING INTERLOCK (INTRLOCK)

In order to prevent simultaneous heating and cooling, the 369 provides a cooling interlock. Once all the heating zones assigned to the
cooling group have been satisfied for a period of time, the control will allow cooling operation to occur. This time is adjustable through
the INTRLOCK setting in the Control Adjust menu of the control. Once any zone assigned to the cooling group requires heat, cooling
operation is terminated.

- 01/09