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MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)
14
Stand-by (Software versions: 5.45 & 5.70)
• Heater wire power is set at 30 %.
• Control of chamber temperature is attempted, within the following limits:
• Heater plate temperature is limited to 60 °C.
• Heater plate power is limited to 20 %.
Stand-by (Software version: 6.00 onward)
• Heater wire power is set at 15 %.
• Control of chamber temperature is attempted, within the following limits:
• Heater plate temperature is limited to 50 °C.
• Heater plate power is limited to 20 %.
NOTE: The temperature alarm algorithm continues to function in stand-by.
4.1.4 Power Up Sequence
The purpose of the power up sequence is to perform internal checks on various parts of the
humidifier and provide the user with a visual and audible check.
Internal self test sequence:
1. Test presence of heater wire.
2. Test correct operation of heater wire triac.
3. Test correct operation of protection relays.
4. Test integrity of temperature/flow probe.
Visual/Audio test sequence:
1. The temperature display and indicator LEDs turn on.
2. The temperature display is blanked and indicators set to their default.
3. Display shows humidifier model number i.e. 850.
4. Display is blanked.
5. Display shows software version number.
6. Display is blanked and an audio tone of 2100 Hz sounds.
7. Normal display.
4.1.5 Humidity Compensation (HC) mode (Software version 6.00 onward, except 7.23)
Normal ambient environments between 18 °C and 26 °C do not affect humidity output of
temperature controlled heated humidifiers. However once the ambient temperature increases
above 26 °C, and/or the temperature of the incoming gas becomes greater than 32 °C, e.g. due
to ventilator heating, then the humidity output maybe reduced.
This can be identified by the lack of beading condensate on the inner walls of the humidification
chamber and rectified by modifying the breathing circuit or humidifier settings. Increasing the
length of breathing circuit between the ventilator and the humidification chamber will assist in
cooling the gas before it enters the chamber and improve humidity output.
If beading condensate does not form, humidity output can be further improved by increasing the
humidifier’s chamber set point. This can be achieved by accessing the HC mode (or Tc) in the
Diagnostic Menu (see section 6.4) and either manually selecting a level of chamber temperature
compensation or letting the automatic mode do it for you.
Automatic Humidity Compensation
When automatic HC mode is selected the humidifier calculates the power required to
adequately humidify the gas flow through the chamber. If the minimum power level is not met