Nautel XR12, Руководство по предварительной установке, Страница: 29 / 76

XR12 Transmitter Pre-installation Manual Cooling requirements
Issue 0.17 2005-08-31 Page 4-3
Cooling
Do not allow the transmitter room ambient air temperature to exceed 50°C at sea level (de-rate 3ºC
per 500 m or 2ºC per 1,000 feet above sea level). Cooler temperatures are recommended in order to
improve the reliability of the transmitter.
Ensure that hot air from the transmitter is not drawn back into the transmitter’s cool air intake.
Cooling plant requirements
Calculating BTU cooling requirements
To determine the number of British thermal units (Btu) being generated per hour as waste heat,
multiply the average RF output power (in watts) by 0.19 (the heat factor at rated power) and then
multiply the product by 3.413.
Closed loop or forced air cooling systems
Closed loop or forced air cooling systems can be used, so long as the air is well filtered to prevent
dust and insects from entering the transmitter, and so long as a minimum of 1,400 cubic feet per
minute (CFM) at 0.5 pounds per square inch (PSI) is supplied to the intake duct.
Table 4.1: Cooling plant requirements for the XR12
Transmitter
output (watts)
Waste heat
(watts)
BTU/hour
(x1000 Btu)
Modulation
Air conditioning
required in a closed
system (tonnes)
12,000 3,400 11.7 100% 0.97
12,000 3,000 10.6 85% 0.88
12,000 2,300 7.9 0% 0.65
Note: Program content is typically equivalent to 85% tone modulation. The air conditioning
requirements identified above address only the thermal output of the XR12 transmitter itself.
Remember to add air conditioning capacity to support other equipment and sources of heat.