Bird Technologies 8630B Series - Manual (Page 22)

Bird 8630B Series Moduload RF Load Resistor
6
The proper operation of this equipment depends on these conditions
being maintained.
The time delay relay keeps the interlock switch open for a
predetermined interval (set at about 2 seconds, nominal), to allow the
minimum flow of 2.5 gallons per minute to be established. This
safeguard feature ensures proper operation of the cooling system
before RF power is applied to the load, preventing resistor damage or
burnout. As an additional safeguard, an over temperature
thermoswitch, normally closed at or below +85°C (+185°F) for the
8630 series and at or below +79°C (+174°F) for the 8630B series, is
wired in series with the flow switch for protection from overheating
due to overloading of the load.