Field Controls HHSC+, User Manual, Page: 12 / 20

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Circulate % may be set equal to or greater than the Ventilate %, to cause the HVAC fan to run longer per
cycle, for extra circulation, filtration, and UVC treatment if desired, or if the HHSC is used for circulation
only. For instance, if Ventilate % is set to 33% and Circulate % is set to 50%, with the cycle period set to 30
minutes, every thirty minutes the HHSC+ will activate the HVAC fan, open the FAD damper for 10 minutes,
and continue to run the fan for another 5 minutes (.33 x 30 = 10, .50 x 30 = 15) if the thermostat does not
cause the fan to run during the period.
Circulate % may not be set less than Ventilate %, because the HVAC fan must operate when the FAD
damper is commanded to be open by the HHSC+. The Circulate % setting will automatically “follow” the
Ventilate % setting if it is adjusted higher, but will not “follow” it lower.
DAMPER MONITOR
The HHSC+ can continuously monitor the FAD fresh air damper for proper operation, if the feature is
enabled and the yellow wire from the damper pigtail (included) is connected to terminal VS-IN on the
HHSC+ (see Figures 1,2, 3). If enabled and the HHSC+ repeatedly detects a malfunction of the damper,
the status LED will turn to red, and the display will indicate that a damper malfunction has been detected.
NOTE: this feature is optional and may be disabled if desired. If the yellow pigtail wire is not connected to
the HHSC+, the HHSC+ will automatically disable the feature.
If this feature is to be enabled, ensure that the FAD damper pigtail’s yellow wire is connected to terminal VS-
IN, and select “Automatic” in the Damper Monitor menu item window. The HHSC+ will then automatically
test the damper and its connection. If the damper responds properly, the display will indicate that the
damper is detected and the Damper Monitor feature will be enabled. If the damper does not respond
properly or the yellow wire is not connected, the HHSC+ will automatically disable the feature.
This feature may also be disabled manually at any time by selecting the Damper Monitor menu item
window and selecting “Disabled”, even if the yellow pigtail wire is connected. If an outdoor thermostat or
other device is used to prohibit fresh air ventilation when extreme outdoor conditions exist (wired in series
between the FAD blue wire and terminal VO, see (Figure 6), the feature must be disabled to prohibit false
malfunction detection.
Daylight Savings Time mode: If this feature is enabled, the HHSC+ will automatically adjust its clock time
by changing the time by one hour on the specified dates for transitioning to or from Daylight Savings time
to Standard time, regardless of the time zone. This feature is important for keeping the Inhibit Mode time
schedule correct (see Inhibit Mode feature section), without any changes needed by the user. This feature
may be disabled for those areas that do not observe Daylight Savings Time changes.