Instruction manual

Appendix D. CNF4 Heater/Ventilator
D.5 CNF4 Heater/Ventilator Maintenance
D.5.1 Testing the Heater
The optional CNF4 consists of a heater and a ventilator. To check the heater
unit, measure the resistance between the two heater wires (green and yellow).
The resistance value of the heating resistor inside should be around 15 Ω (cable
resistance should add about 0.026 Ω per each foot of cable). An infinite
resistance reading indicates the likelihood of a broken wire, or cable.
D.5.2 Testing the Ventilator
To check the ventilator, first measure the impedance of the ventilator motor.
The value should be around 30 Ω (cable resistance should add about 0.026 Ω
per each foot of cable). If the correct resistance value is measured, but the
ventilator still mal-functions, it is possible that the ventilator is stalled by an
object blocking the fan. Remove the black cover at the bottom side of the
ventilator unit, by prying it open with a small flat-head screw driver or by
pulling it straight out. Inspect the fan inside for any object that might impede
the fan’s rotation. Upon completing the inspection, put the filter and the cover
back in place.
D.5.3 Replacing the Filter for the Ventilator
The filter needs to be checked for every 6 to 12 months. Remove the black
cover at the bottom side of the ventilator by prying it open with a small flat-
head screw driver or by pulling it straight out. Inspect the filter for dust and
particles that might impede the air flow into the ventilator. The filter can be
cleaned with warm clean water, or can be replaced with the new one. You can
purchase the replacement filters, pn 26010, from Campbell Scientific.
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