Ammonia compressor low-side compound gauges are usually calibrated to read from:

The calibration range for ammonia compressor low-side compound gauges is typically designed to accommodate the expected operating conditions of ammonia systems. These gauges need to accurately measure both the vacuum created in the compressor's low side and the pressure that occurs during operation.

Choosing a range that goes from 30" of vacuum to 300 psig allows for a comprehensive measurement capability. The vacuum end of this range ensures that the gauge can effectively record low-pressure situations, which are common in refrigeration and ammonia systems. The upper limit of 300 psig covers typical high-pressure scenarios encountered in these systems.

This calibration ensures that the gauge can deal with the fluctuations in pressure and vacuum that occur, providing technicians with critical information for diagnosing and maintaining ammonia compressor systems. Effectively, this range allows for the recording of both high pressures, which could indicate issues if they exceed normal operational parameters, and low pressures, helping to assess the performance of the system.