BTU VENTILATION CORPORATION ● OFFICE 888-884-8070 ● FAX 218-346-7485 ●
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XT-70 Control Panel 66
OPEN FRESH AIR DOOR TO 100% Once the outside temperature and humidity have been confirmed to be
warm and dry enough the system will go into the Cure mode and the fresh air doors will open to 100%.
BURNER SW AUTO If the outside temp is to cold or moist the system will check the burner switch. If it is
not in auto then the system will reticulate the air with the fresh air door closed. With the burner switch in auto
the burner will fire off and control temperature to the Setpoint.
CPH < HMAX This checks the outside humidity to determine if the outside air is dry enough to bring in during
the burner operation. The fresh air doors will be modulated to control the humidity to the Humid Setpoint. If the
CPH is not less than HMAX then the fresh air doors will remain closed.
MOD DOORS WITH HUMIDITY PID When in the burner mode and the outside air is dry enough the system
will modulate the fresh air doors to control the humidity to the Humid Setpoint.
If the Cure switch is off then the system will switch to the COOLING MODE part of the
flow chart.
REF ONLY TIME CLOCK If the time clock is set to REF Only then the system will switch to Refrigeration
and not run in Cooling. The time clock should be set to Cooling or Run for normal operation.
OSA < START TEMP This decision will take the system to either Refrigeration or Cooling. If the outside tem-
perature is not less than the start temperature, then the system will try and run in refrigeration. Cooling air will
be available if the outside air is less than the start temperature.
REFRIGERATION BRANCH
RUN ONLY TIME CLOCK For the refrigeration to run the time clock must be in the Run mode. If not the
system will go into STANDBY.
REFRIG SW AUTO If the refrigeration switch is in auto then the system will run in refrigeration, if not then it
will go to the timed mode and reticulate the air.
COOLING BRANCH
STANDBY TIME CLOCK If the time clock is set to standby the system will stop and go to standby.
CPH < HMAX The system will now check the outside humidity to see if it is dry enough. The CPH is the cal-
culated plenum humidity. When the outside humidity is warmed up to the plenum temperature it will be dryer.
The HMAX is the desired highest plenum humidity. If the CPH is less than the HMAX then the cooling branch
will be followed. If not then the system will go to Refrigeration.
BURNER SW AUTO If the burner switch is in auto then the system will consider if it needs to dehumidify.
With the switch off the system will go straight to Cooling.
DEHUMID MODE This branch looks to see if the system is already in a dehumid mode, if so it will look to
see if it can terminate the dehumidification.
9.2
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