Marvair Scholar 2.0 I&S Manual 04/2022 Rev.2
40
(set by the Defrost Timer), the system will examine the Defrost Control thermostat
Input (
DFC
). If this input is on (the thermostat is closed), indicated by Output being
on, the system will go into Defrost mode based on the defrost time default = 30min
(30, 60 & 90min) At this point the Outdoor Fan Motor relay (
OFM
) is de-energized
and the reversing valve is energized. In this mode heat is being applied to the
outdoor coil to remove any possible buildup of ice on the coil. The Defrost Control
Switch (
DFC
) comes on at roughly 28°F and goes off at approximately 56°F. During
the Defrost Cycle, the unit will continuously examine the DFC input and when it
switches off OR the system has been in defrost for 10 minutes, the system will revert
back to normal heating mode. By having a maximum time for the Defrost Cycle to
operate, the system will not go into Defrost and remain in Defrost mode if a Defrost
Switch malfunctions. If the Electric Heat During Defrost (
EHDD
) function has been
selected, the Heat Contactor (
HTR
) will come on to supply supplemental heat during
the Defrost Cycle.
Note:
the defrost time is accumulated, Ex; if the 30min defrost time is selected, that
is the time it will take to go into defrost mode. While in defrost if the defrost function
is interrupted by a power outage or a sequence , the timer will stop and resume
where it left off, so if you had 10 minutes left to go into defrost and there is a power
surge, instead of starting over from 30 minutes, the defrost function will now start
at the 20 minute mark and the unit will only have 10 minutes left before it goes into
defrost.
User can also test the defrost function by going to the “Preset Timer” screen and
select “Test On”, this will bypass the defrost preset time and go straight into defrost.
Which the unit will run in defrost for 10 minutes before it is reset and end the defrost
test or user can just turn the test to off. (Keep in mind that in order to test the defrost
the unit should be in mechanical heating mode).
M. Anti-Short-Cycle Timer
The Anti short cycle protects the system compressor from short cycling due to
excessive on and off, this can happen when there is a fault or someone turning the
system off and on for troubleshooting purpose etc. This timer starts timing when
the compressor turns off and prohibits it from running again until the time period as
elapsed.
ASCT Settable from PLC screen;
• Minimum = 3 seconds
• Maximum = 10 minutes
• Default = 3 minutes
Содержание Marbair VAA2030-2048-2060
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