Warming Unit Power-On-Reset; Temperature Modes; Airflow Modes; Standby Mode - 3M Bair Hugger 775 Service Manual

Warming Unit Power‑On‑Reset
The warming unit automatically performs the following power-on-reset
sequence after you connect the warming unit to a properly grounded power
source (See Figure 1):
• Performs all self-test functions.
• Illuminates indicator lights and all pixels in the alphanumeric
display momentarily.
• Displays the text "MD 700's" and the software revision level in the
alphanumeric display.
• Sounds the alarm (three low-level clicks).
• Enters the Standby mode with the high fan setting selected by default.
NOTE: The low fan setting indicator light will not illuminate during
power up.
If the warming unit loses power for less than 1 second, the warming unit
software will return the warming unit to the operating mode you selected
prior to the power loss. However, if the warming unit loses power for longer
than 1 second, the warming unit software will reset when you restore power.
The warming unit will then enter the Standby mode with the high fan setting
selected by default.

Temperature Modes

The warming unit has 4 operating modes: Ambient, 32°C, 38°C, 43°C.
To select the 32°C, 38°C, 43°C, or Ambient mode, press the corresponding
button. The warming unit will operate within the specified temperature
range, shown in the table below.
TEMPERATURE MODE TEMPERATURE OF DELIVERED AIR
32°C 32°C ± 1.5°C
38°C
38°C ± 1.5°C
43°C 43°C ± 1.5°C
Warming unit will supply air at
Ambient
room temperature
After you select a temperature mode, the following events occur:
• Corresponding temperature indicator light illuminates.
• Blower operates at selected fan speed.
• Heater activates except in Ambient mode.
• Temperature mode timer and hour meter activate.
• Temperature at the blanket-end of the hose appears in the
alphanumeric display.
• Temp in Range indicator light illuminates when the temperature at the
blanket end of the hose is within ±1.5°C of the selected setting; this
indicator light does not illuminate in the Ambient mode.
Airflow Modes
The warming unit has two preset fan speed settings: a default or high fan
setting ( ) and a reduced or low fan setting ( ). The warming unit will
reset/default to the high fan setting each time the warming unit is powered
up or Standby is selected. The low fan setting ( ) may be preselected while
in Standby prior to selecting the desired temperature.
Standby Mode
To place the warming unit in Standby mode, press the Standby button.
When in Standby mode, the following events occur:
• Standby indicator light illuminates.
• Blower and heater are turned OFF.
• Alphanumeric display deactivates.
• Alarm and fault detection functions remain active.
• Operating timer pauses.
• Airflow mode resets/defaults to the high fan setting.
6
Fault Conditions
The warming unit software recognizes several nonhazardous fault
conditions including:
• Sensor failures
• Heater failures
• Computer failure
• Software failure
• Keypad failure
• Power supply failure
• Blower motor failure
• Forced over-temperature test failure
When a fault condition exists, the following events occur:
• Fault indicator light flashes.
• Audible alarm sounds.
• Blower and heater turn off.
• Fault code appears in the alphanumeric display.
• Up to 5 fault codes are stored in memory.
When the audible alarm sounds, press any button on the keypad to silence
it. The warming unit must be unplugged before it can be restarted. See
"Viewing the Fault Code Log" on page 8 and the "Fault Code Table" on
page 9 for more information about specific fault codes.
Over‑Temperature Condition
When an over temperature condition exists, the following events occur:
• Over‑temp indicator light flashes.
• Audible alarm sounds.
• Blower, heater, and operating mode indicator lights automatically
turn off.
• Fault code appears in the alphanumeric display (see page 9).
When the audible alarm sounds, press any button on the keypad to silence
it. The warming unit must be unplugged before it can be restarted.
Alternative Modes
The warming unit has 5 alternative modes that allow access to the service
and calibration utilities of the warming unit (see Figure 2 on page 7).

ALTERNATIVE MODES

DESCRIPTION
AltMode0 Hour Meter
AltMode1 Calibration
AltMode2 Fault Code Log
AltMode3 System Information
AltMode4 Over-temperature Detection Test
The Hour Meter mode displays the cumulative amount of operating time (in
Ambient, 32°C, 38°C, and 43°C modes) the warming unit has been in use.
The time is displayed in whole hours only.
The Calibration mode allows a technician to check and adjust the hose
end sensor calibration offset value. This should be done as part of routine
maintenance and after servicing the warming unit or replacing the hose.
The hose end sensor temperature can be altered a maximum of ±3.0°C by
adjusting the calibration offset value. In the Calibration mode, the warming
unit operates in the Ambient temperature mode, and the alphanumeric
display shows the current hose end sensor temperature and calibration
offset with 0.1°C precision.
The Fault Code Log mode sequentially displays the last 5 fault codes stored
in system memory. Please refer to the "Fault Code Table" on page 8 for
more information about a particular fault code.
3M™ Bair Hugger™ Warming Unit Model 775 – Service Manual