CNF4 Ventilation Unit

The optional CNF4 Heating and Ventilation Unit (LI-COR part number 7900-145) is used to prevent condensation or frost buildup on the CNR4 pyrgeometer windows and pyranometer domes. Condensation on the pyrgeometer windows will absorb far-infrared radiation and lead to measurement errors. These can be avoided by using the CNF4. See the manufacturer’s documentation for more information.

Note: Due to heat dissipation from the CNF4, measurements of sensor temperature may be less accurate. However, the improvements in accuracy that result from heating will be larger than errors that result from heating.

Components

The CNF4 Heater/Ventilation Unit includes the heater/ventilator, three pan-head machine screws with washers, four flat-head screws, the protective shroud, and the CNF4 power cable.

In addition, the CNF4 installation kit includes:

Component	Description	Part Number
2 Gray DIN Terminals	Positive power supply	331-12885
2 Blue DIN Terminals	Ground	331-12959
2 Shorting Blocks	For power supply terminals	331-13646
2 DIN Relays	Power supply control	290-14669
2 DIN End Brackets	To secure the DIN terminals	331-12922
DIN Terminal Cover	Separate DIN terminal blocks	331-12825
Wire Leads	5 11.5 cm 18 gauge red; 1 11.5 cm 18 gauge black; 2 30 cm 20 gauge blue

Installation

There are three general steps to installing the CNF4 in the Biomet Station:

• Assemble/Install the CNF4;
• Install the hardware in the Biomet System;
• Configure the heater and ventilator timers.

These are described in the following pages.

1. Assemble the CNF4.
2. After attaching the temperature and sensor cables to the radiometer, attach the heater/ventilator to the CNR4 body using the three machine screws.
3. 
4. • Route the cables around the fan in the ventilator.
   • Attach the protective shroud with the remaining four screws.
   • Attach the ventilator power cable.
2. Install the CNF4 Control Components.
3. Gather the CNF4 installation kit components and install them in the enclosure as shown.
4. 
5. These components can be installed on the DIN rail to the right or left of the AIO modules or a section of DIN rail in the upper left of the enclosure.
3. Install the Power Supply/Controller Wires.
4. The power supply and control wires are required to actuate the relays and provide the timer-controlled power supply to the CNF4 heater and ventilator.
5. 

6. Description	Wire Lead	Terminals Connected
   CNF4 Power (+)	11.5 cm Red	DIN Terminal 14 to Heater Power (+) Terminal
   CNF4 Power (-)	15 cm Black	DIN Terminal 18 to Heater Power (-) Terminal
   Ventilator Relay Control Signal	30 cm Blue	DIO1 Terminal 6 (I/O 4) to Left Relay 4/A2
   Ventilator Relay Power	11.5 cm Red	DIN Terminal to Left Relay +3/A1
   Ventilator Power	11.5 cm Red	DIN Terminal to Left Relay +1/L1
   Heater Relay Control Signal	30 cm Blue	DIO1 Terminal 8 (I/O 5) to Right Relay 4/A2
   Heater Relay Power	11.5 cm Red	DIN Terminal to Right Relay +3/A1
   Heater Power	11.5 cm Red	DIN Terminal to Right Relay +1/L1

4. Wire the CNF4 to the Controlled Power Supply.

5. Description	Color	Connection
   Ventilator (+)	Yellow	Left Relay 2/T1
   Ventilator (-)	Brown	Blue DIN Terminal
   Tachometer (+)	Green	not used
   Tachometer (-)	Gray	not used
   Heater (+)	Black	Right Relay 2/T1
   Heater (+)	White	Right Relay 2/T1
   Heater (-)	Red	Blue DIN Terminal
   Heater (-)	Blue	Blue DIN Terminal
   Shield (black)	Black	Blue DIN Terminal

6. 
5. Configure the Timer Controls.
6. The CNF4 Heater and Ventilation Unit is supported by programs Biomet_101 and Biomet_103. Follow the steps below to configure the CNF4:
   1. Select Graphical Setup and click Edit.
   2. 
   2. Scroll down to the NetRad configuration block. Click it and select Edit Properties.
   3. 
   4. All fields in the resulting dialog are configured automatically from the previous steps. To set the timer for the heater click the Heater... button.
   5. 
   3. Check the Enable Heater box. Then set the Time, Interval, and Duration.
   4. 
   5. • Time: The time that the heater will be enabled
      • Interval: Interval between activations
      • Duration: Duration of the activation
   6. For example, if Time is 19:30:00, the Interval is 24:00:00, and the Duration is 01:30:00, then every 24 hours—at 19:30 (7:30 pm)—the system will power the heater for 1 hour 30 minutes.
   4. The ventilator is configured similarly, except that it uses DIO Channel 4.

Note: The heater and ventilator are controlled by separate relays so they can be configured independently.

Typically the heater should be on 1 hour before sunset to 1 hour after sunrise. Read the manufacturer's recommendations for more information.