Veris Industries VH7200 SERIES Install - Manual (Page 12)

12
Humidity setpoint reset by outside air temperature
If an outdoor air sensor is connected at the thermostat
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.
20%
25%
30%
35%
40%
-40°F -20°F 0°F 20°F 40°F
45%
%
RH S
e
tp
oi
nt
Outside Air Temp.
RH HT = 32°F
RH LT = -20°F
RH Set = 45%
RE Sp = 20%
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 (VH7270 Models Only)
The VH7270 models include 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
humidistat.
Note: this high limit function is not a safety device. For
critical situations, provide installation with normal protections
required to ensure a safe operation.
Troubleshooting guide
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 %
Symptom Possible Cause Corrective Action
Digital display
shows missing
digits or erratic
segments Defective display Replace humidistat
RH sensor is out of range Verify the remote RH sensor or the internal RH sensor
System Mode in
Dehumidification or Off Change the system mode parameter to Humidification
System Mode in Auto but there
is a Dehumidification demand
at the humidistat Wait: when a Humidification demand will occur at the
humidistat, humidification will resume
Humidistat does
not call for
humidification.
(Hum LED is OFF)
High limit sensor is controlling
the humidifier output by forcing
it to 0% Wait: when the supply humidity will drop below the high
limit setpoint, humidification will resume.