TK 56430-18-IP-EN
35
Understand Compressor Speeds
Proper compressor speed is critical to preventing premature compressor failure. Select a compressor that meets the
requirements for the specific application. There are three speeds to consider:
Table 2.
Minimum Compressor Speed
Value
750 RPM for all Compressors
Importance
This is the compressor RPM during engine idle. Lubrication of the compressor has been verified operating at this speed
and above, but may not be sufficient and cause accelerated wear at lower speeds.
Table 3.
Compressor Peak Efficiency Speed
Value
2400 RPM for all Compressors
Importance
This is the compressor speed at which Thermo King rates unit capacity because it provides the highest performance
versus reliability. This speed provides the capacity quoted in the current selection guide. Going faster than 2400 RPM
gains minimal capacity.
Table 4.
Compressor RPM at Highway Speed
Value
3000 RPM for all Compressors
Importance
This is the maximum speed the compressor should run continuously in order to maximize reliability.
Important:
The compressor must never exceed this speed for more than two seconds at a time.
How to Calculate
This is the compressor RPM at highway speed (about 70 MPH) when vehicle is in its highest gear. Refer to (
).
Note:
Vehicles with manual transmissions must be handled differently as the shift points and times at higher RPMs are
varied by the driver.
Table 5.
Compressor RPM During Shifting
Value
Maximum 6000 RPM for all Compressors
Importance
This is the speed the compressor endures for brief periods during acceleration, up shifting or down shifting.
Important:
The compressor speed should never exceed 6000 RPM at any time, including shifting.
How to Calculate
This is the compressor RPM when the engine is up shifting or down shifting – at its peak engine shift point. Refer to
(
“Calculate the Compressor Speeds,” p. 36
Choose the Best Compressor Pulley
To achieve the optimal compressor speeds, the correct compressor pulley must be selected from the table below.
Changing the pulley size will change compressor speed.
N
No
otte
e:: The 4.69 in. (119 mm) diameter pulley is standard on a Thermo King swash plate compressors.
Compressor Pulley
Diameters Available
4.69 in. (119 mm) diameter
5.43 in. (137 mm) diameter
6.14 in. (156 mm) diameter
