Location, Location, Location
The location, as well as the installation, of pump gauges has been a problem in the HVAC industry for years. There is a lack of information on proper installation and the understanding of why the location of the pump gauges is extremely important for evaluation of the performance of the pump.
When evaluating the performance of a pump, one of the first tests a TAB firm will perform is a block-off / shut-off test, to determine the impeller size. However, with a gauge that is not installed in the proper location, this test may not allow proper pump curve determination and may indicate the wrong impeller size.
The following diagram indicates an installation that is wrong, which could affect the pump curves evaluation as much as 30% to 40%.
Most pump manufacturers provide threaded locations for proper installation of a gauge to evaluate pump curves. One must understand that the pump curve is based on pressure drop directly across the impeller.
The following diagrams indicate the manufacturer’s preferred installation.
The use of one gauge tapped into the provided ports allows a TAB firm to obtain a good measurement, which in turn can be related to the pump curve.
In discussions with many of the pump manufacturers, there is very little information published by them to educate the Mechanical Contractor on the proper installation of gauges and in many cases, the mechanical engineering details are incorrect. Not only is the gauge location important for TAB firms to evaluate pump performance, but for the facilities personnel who can use the gauges to ensure long term performance.