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MR850 Technical Manual * Revision J * Issued November 2005 * Ref. 185041340 (185041713 internal)
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then the chamber set point will automatically be increased in 0.5 °C steps (1 °C steps for non-
invasive mode) until the minimum power is achieved. The maximum amount of compensation
applied is either 3 or 5 °C depending on the mode and software version (section 6.4 Diagnostic
Menu details how compensation is applied for each software version).
If conditions improve and too much power is being applied, then the MR850 will automatically
reduce the chamber set temperature.
NOTE: Excessive condensate may form in the breathing circuit if the auto HC function is used
with turbine driven ventilators (i.e. ventilators that use room air). It is recommended to switch off
the auto HC function in these situations if the condensate becomes excessive.
NOTE: Auto HC function is factory set to enabled on all MR850 models.
Manual Humidity Compensation
For manual HC the level of compensation should be increased until beading condensate is
observed on the inner walls of the humidification chamber. It should be noted that if
environmental conditions change then it might be necessary to re-adjust this setting. For
example, a fall in room temperature could produce a build up of unwanted condensate in the
delivery circuit. A reduction in this setting may stop further build up.
NOTE: The previous manual HC setting is restored when power is applied to the humidifier
Refer to section 6.4 Diagnostic Menu for further information regarding this feature.
Activating/Deactivating Humidity Compensation
Refer also to the diagnostic menu in section 6.4
1. Access the diagnostic menu by pressing the mute and mode buttons together for 1
second, the diagnostic menu is entered, indicated by the display of two rows of dashes
‘= = =’. Releasing both buttons will allow the diagnostic menu to cycle automatically
through the menu.
2. The first item is “HC” this is the humidity compensation item, press and hold mute to
access this function.
3. The setting may show either ‘0’ or ‘-A-‘ to change the setting press both mute and mode
buttons simultaneously for 1 second, the humidifier will beep twice and the setting will
increase. Release both buttons.
4. To increase again repeat step 3. To decrease the setting press the mute and power
buttons for 1 second.
5. To exit the menu, release all buttons, the menu will continue to cycle until ‘end’ is
displayed, the menu will automatically exit.
Temperature Display
To alert users during normal operation that either manual or automatic HC mode has been
enabled, the decimal point on the temperature display will flash. Each of the two modes can be
further identified by the flash rate, where auto HC mode has a slower flash rate than manual HC
mode.
Note: The displayed temperature may also be higher than normal indicating (up to 39°C) the
amount of compensation present.
4.1.6 Breathing Circuit Recognition (Software version 7.00 onward)
Fisher & Paykel Healthcare has developed a range of breathing circuits that offer optimum
performance for the type of treatment selected while working within recommended operating
conditions. Some of these breathing circuits require a slightly modified controller to optimize
performance. To do this the MR850 must first recognize what type of delivery circuit has been