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Rev 2.0
63-7048 1998 Honeywell Inc.
Page 18 of 22
dewpoint increases slightly in response to the humidifier cycles. During this
period the relative humidity sensed in the duct is as low as 13 %. Because the
H1008 controls based on dewpoint, it is able to cycle intermittently during the
temperature recovery period when the relative humidity is artificially low. This
ensures that the dewpoint is maintained dewpoint below the window
temperature.
Figure 13 shows additional field test data taken the following night at the same
site. In this case the humidifier was wired to operate each fan and heat cycle,
simulating a humidifier operating when the sensed relative humidity is below
the humidity setpoint. In many cases this will occur each time the furnace is
running. The effect of the heating of a standard humidistat, like AutoTrac
,
is
to lower the sensed relative humidity, essentially creating a humidifier lock-on
condition.
-20
-10
0
10
20
30
40
50
60
70
80
90
100
03:00:00
03:30:00.0
04:00:00
04:30:00
05:00:00
05:30:00
06:00:00
06:30:00
07:00:00.0
07:30:00
08:00:00
0
5
10
15
20
25
30
35
40
Outdoor Temp.
Window Temp.
Dewpoint
Furnace Cycles (W)
Humidifier Cycles Fan Cycles (G)
Duct RH
Room Temp.
Duct Temp.
Time
Temperature (
o
F) / Relative Humidity (%)
Digitial Output
Figure 13 – Variation in Duct Temperature and Relative Humidity
Simulated AutoTrac
Performance (Setting ~ 4)
March 12, 1998 – Minneapolis, Minnesota