System Introduction - NuAire 7 Series Maintenance Manual

The relative humidity control system is programmed with a Humidity Control alarm system. The HC alarm
system is designed to prevent the uncontrolled injection of humidity into the Incubator chamber.
Uncontrolled injection has two primary causes. The easiest one to detect is a bad or disconnected RH sensor.
If the measured output voltage of the humidity sensor falls outside of the normal range, an HC alarm is
declared without delay by the control board. This portion of the HC alarm system is not selectable, and is
active any time the RH control system is enabled.
A second option menu selectable part of the humidity control alarm system was designed to detect an RH
sensor that is out of calibration or not responsive. During an RH recovery, if the inject solenoid is engaged for
too long, or if it cycles on and off too many times without reaching setpoint, an HC alarm is declared. The
length of time or the number of cycles that a solenoid turns on before an alarm declaration is user adjustable
(see Section 8.8.4 for the user selectable portions of the system). This portion of the humidity control alarm
system is also inhibited by a cold evaporator box signal sent via a snap disc thermostat mounted on the
evaporator box. It is also inhibited by a low reservoir water level signal sent via a float switch in the reservoir.
Both conditions will light the yellow LED labeled RH reservoir.
No matter what event triggers an HC alarm, the alarm sequence is always the same. First an alarm is sounded
(with audible and visual clues) and the RH evaporator box heat is turned off. After 2-1/2 hours, the air-inject
solenoid opens and will run for a period of one half hour. At this time (three hours from alarm declaration),
the air solenoid turns off, and the RH inject solenoid turns on and stays on until the alarm is cleared. This
gives the user some humidity in the Incubator, but prevents the continuous, uncontrolled injection of hot
water vapor. Temperature and gas control are unaffected by humidity control alarms (see Section 11 Error
Indicators & Troubleshooting for identifying and responding to the humidity control alarm indicators. Read
section 9.4 before determining the RH set-point and/or calibrating the system.

8.3 System Introduction

The NuAire Incubator Control Electronics (NICE) system is designed to service the control requirements of the
US Autoflow Incubator chamber. Temperature and CO
optimum conditions for culture growth within a chamber. Operator input is coordinated through the control
panel keypad and status displays. Below figure shows the various inputs and outputs of the system.
OM0123
Rev 15
level are controlled by preset values to provide
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