Following the lead taken by ASHRAE Standard 51-75 and AMCA Standard 210-74, plus a very definite need for the determination of test accuracy on performance tests of field installations, an attempt was made to establish a range of errors likely to be encountered in the field testing of fans.

The preceding sections of this guide have described in detail the problems encountered in field testing. A number of examples of typical field installations have been presented. ·Innumerable other fan system installations are possible. Each installation has its own unique problems with regard to field testing.

Varying degrees of difficulty exist with regard to satisfactory measurement planes, methods of measurement, system instability, etc. Based upon field experience, minimum and maximum percentage errors were assigned to each measured quantity. Measured quantities include barometric pressure, temperatures, speed, power input, flow measurement area, fan pressures, etc. These individual minimum and maximum percentage errors are then combined statistically in order to arrive at a probable range of overall percentage error for the fan flow rate, pressure and power input. It is unlikely that any given field installation would lead to all minimum or all maximum errors. Agreement of the parties as to acceptable measurement tolerances should be established prior to testing.

For the purpose of a field test the error in results will be expressed in terms of fan flow rate, pressure and power input.