Viconics H270 User Manual
Page 5
5
CONTROL SCHEMATIC:
Fig. 7 Control schematic
FIGURE 8: HUMIDITY SETPOINT RESET BY OUTSIDE TEMPERATURE
The H270 humidistat has an optional outdoor
temperature sensor. This sensor is 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 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 LT (-20
°F).
The setpoint decrease from original setpoint down
to the lowest setpoint determined by the parameter
rE. In the example, Figure 8, rE was set to 20%,
therefore the humidity setpoint dropped from 45%
to 20%.
If you don’t use the outdoor reset feature, put a
jumper between terminals 6 and 9 (supplied with
the humidistat.)
pb = proportionnal band
d2 = differential between output #1 and #2
db = dead band between humidification
and dehumidification
SET POINT
50%
db
OUTPUT #1
d2
HUMIDIFICATION
35%
30%
45%
40%
pb
0%
HUMIDIFICATION
100%
OUTPUT #2
100%
0%
d2
OUTPUT #1
DEHUMIDIFICATION
65%
55%
60%
0%
70%
DEHUMIDIFICATION
100%
0%
100%
OUTPUT #2
LT = -20°F
O
U
TSID
E AIR
TEM
PER
ATU
R
E
-20°F
Note: rE, HT, LT parameters can be changed with C263 programming tool
20%
25%
-40°F
rE = 20%
USER
SETPOINT
35%
%RH
30%
40%
45%
HUMIDITY SETPOINT RESET BY OUTSIDE TEMPERATURE
HT = 32°F
32°F
-4°F
14°F