So far we have a couple of tags related to modeling a pressure sensor:

• dischargePressure
• returnPressure

We also have filterDiffPressure and a proposed fanDiffPressure (which my understanding is often just a boolean point).

I want to use this topic to discuss the more advanced side of pressure measurement:

• static vs velocity vs total pressure
• use of fooPressure tags for other mediums (steam, chilled water, etc)

So far our convention has been to use a primary tag of the format "<where><what>". For example dischargeTemp is the temperature sensor of the air/liquid/gas being discharged from the unit (AHU, VAV, chiller, boiler, etc).

My understanding is that for air pressure we sometimes measure and wish to make the distinction between static and velocity pressure and the sum total of those two. We could potentially model those as different primary tags (dischargeStaticPressure, dischargeVelocityPressure, etc). But I believe it might be a better strategy to use an alternate tag and allow multiple versions of a dischargePressure point:

dis:"ahu-1 static discharge pressure"
equipRef:<ahu-1>
dischargePressure
staticPressure

dis:"ahu-1 velocity discharge pressure"
equipRef:<ahu-1>
dischargePressure
velocityPressure

dis:"ahu-1 total discharge pressure"
equipRef:<ahu-1>
dischargePressure
totalPressure

Some questions to at least consider:

1. does this seem like a better convention for long term strategy of modeling
2. is static/velocity sensors used for things other than discharge air?
3. is static/velocity distinction ever made for water/steam sensors?
4. how might this relate to various differential sensors used in air distribution systems?
5. what kind of analytics and optimizations would care about various distinctions between static and velocity pressures?

Brian, with respect to pressure sensor tags;

In response to your questions to consider

1. I am not sure what information is being measured for displaying. Most building operators would find the above example without significance. If however the measurements are used to calculate flow then the significance would be very relative. System discharge static pressure is also of significance as the value is the means by which system limits are measured and set including high pressure alarms.
2. Yes to display and set alarm values for supply or return fan static conditions.
3. Yes PSIG values are used extensively for steam, water and many other fluids associated with various pieces of equipment.
4. The static pressure and total pressure are used to calculate flow values, however they are not always displayed individually. Often flow only is displayed.
5. Static and total pressure values come into play extensively when considering air balancing while systems are operating and in retro-commissioning. This is especially so for VAV systems where decoupling of supply and return fans are often required as in multistage systems. Being able to choose various combinations of supply and or return fans for special purposes such as smoke control in larger buildings. These are just a few.

Winston