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Humidity control, Humidity reset, High limit humidity sensor – Viconics VT7607 Installation Manual User Manual

Page 34: Maximum supply humidity, Control output level

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34 | PIR Ready VT76x7 Series-Installation Guide

H

UMIDITY

C

ONTROL


Humidity reset

Humidity setpoint reset by outside air temperature

If an outdoor air sensor is
connected

at

the

Terminal

Equipment Controller or a value
is received from the network, it
can be used to reset the
humidity setpoint during the cold
season

to

minimize

condensation on windows and
building structures.

When the outdoor temperature
falls below the selected high
temperature, parameter RH HT
(32

F in the example Figure 8),

the humidity setpoint will start to
decrease. The lowest humidity
setpoint will be reached at
selected

low

temperature,

parameter RH LT (-20

F).

The setpoint decrease from original setpoint to the lowest setpoint determined by the
parameter RE Sp. In the example, Figure 8, RE Sp was set to 20%, therefore the
humidity setpoint dropped from 45% to 20%.

If you don’t want to use this feature, set the RE Sp parameter to 90% RH.

High limit humidity sensor

The

VT76x7

series

includes

a

high

limit

sequence. This allows the
use of a remote 0 to 10
VDC humidity sensor to
limit the humidity in the
supply air. If no sensor is
detected

at

the

HL

connector, this sequence
is

disabled

at

the

Terminal

Equipment

Controller.

Note:

this

high

limit

function is not a safety
device.

For

critical

situations,

provide

installation with normal
protections required to
ensure a safe operation.

20%

25%

30%

35%

40%

-40°F -20°F 0°F 20°F 40°F

45%

%

R

H

S

et

p

oi

nt

Outside Air Temp.

RH HT = 32°F

RH LT = -20°F

RH Set = 45%

RE Sp = 20%

Fig.11

– Humidity setpoint reset by outside air

temperature

Fig.12

– High humidity limit vs. Control output level curve

Maximum Supply Humidity

100 %

0 %

50 %

Control

Output

Level

85 %

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