Scholar V VAIVA Maintenance & Service Manual 10/2017 Rev.2
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Low Pressure Lockout
The Low Pressure (air conditioner) or Loss of Charge (heat pump) is designed to
guard against the operation of the system in the event of a loss of refrigerant. If the
Low Pressure Switch stays open for more than 60 seconds, the system will turn off
and a Low Pressure Lockout fault will be displayed on the HMI. The loss of charge
and low pressure switch open at 40 psig and close at 60 psig.
In cold weather the pressure in the refrigerant system is low prior to operation. When
the Scholar V unit starts in the heat pump mode during cold weather, low pressure
could cause the system to lock out. To prevent nuisance lockouts, the Scholar V unit
will not shut off if the Loss of Charge Switch (LPS) opens during the first 60 seconds
of operation and the switch has not cycled more than three times in an hour. In other
words, the compressor will start and operate for 60 seconds even with the LPS switch
open three times before causing a lockout on low pressure. This interval is adjustable
(requires user login).
High Pressure Switch
The system has a High Pressure Switch (HPS) that indicates a high system pressure.
When this occurs, the system will immediately set a High Pressure Lockout. This
lockout condition shuts the system off and displays a fault message on the HMI. The
high pressure switch opens at 650 psig and resets at 420 psig.
Ventilation Blower Fan Speed Control
See section 2.1 for Ventilation Settings.
VENTILATION FAN
SPEED CONTROL
Standard Ventilation Control
The
motorized fresh air damper with PowerVent and GreenWheel
®
ERV
ventilation options are equipped with a
fresh air fan speed control
. The fresh air fan
speed control operates both the ventilation intake and exhaust blowers together.
The
motorized fresh air damper with PowerVent and GreenWheel
®
ERV
ventilation options can be equipped with an exhaust fan air speed control, which
controls the ventilation exhaust blower independently of the fresh air intake blower.
