We really need to standardize all the possible tags for AHUs and VAVs. Mainly the 2 of them together. Here is an example:
Typically you might have 10-50 VAVs that are connected to 1 AHU, but other times you might have those same VAVs connected to multiple AHUs. The AHUs could rotate or you might have 2 or 3 AHUs that serve a bunch of VAVs. What we need to do is be able to have a dynamic TAG for this. Meaning we actually have a history that stores what AHUs are serving which VAVs. Maybe from 8pm to 4am you only have AHU-1 serving the VAVs, but from 4am-10am you have AHU1 and AHU2. All we need to be able to do is have a TAG that binds to a history that shows which AHU is serving the VAV. Does this make sense at all?
This is important as we do AHU/VAV optimization we need to be able to calculate things easily. We need to be able to handle these use cases.
Brian FrankTue 26 Apr 2011
Typically you might have 10-50 VAVs that are connected to 1 AHU, but other times you might have those same VAVs connected to multiple AHUs.
What is the physical mechanism that controls this? Do all the AHUs just dump into a common duct?
How do you determine when an AHU is feeding a VAV? Is it the fact that the AHU is on (fan is active). Or is there some damper in place which would determine it?
As an overall strategy, I think the best way to model this from an analytics perspective is to create a group of AHUs, then have the VAV reference the group instead of an individual AHU. Something like:
dis: AHU-Group
ahuGroup
dis: AHU-1
ahu
ahuGroupRef: AHU-Group
dis: AHU-2
ahu
ahuGroupRef: AHU-Group
dis: VAV-A
vav
ahuGroupRef: AHU-Group
That way the ahuGroup can be used to perform joins between the various indirect references.
Grouping AHUs is also useful in its own rights for analytics. For example if AHUs were linked in this way, you would probably want to make sure they were all cooling or heating at the same time and not fighting one another.
Winston HetheringtonTue 17 May 2011
In reference to the earlier comment from Jason Briggs, I would suggest the his scenario is possible,but it is seldom used. To execute the connection too other sources of supply would involve many dampers and complex control sequences. The comment about simultaneous heating and cooling would not be a much of an issue as might be perceived since AHU's supplying VAV devices seldom provide heating from the main system, more often as an component of the VAV device itself.
Jason Briggs Tue 26 Apr 2011
We really need to standardize all the possible tags for AHUs and VAVs. Mainly the 2 of them together. Here is an example:
Typically you might have 10-50 VAVs that are connected to 1 AHU, but other times you might have those same VAVs connected to multiple AHUs. The AHUs could rotate or you might have 2 or 3 AHUs that serve a bunch of VAVs. What we need to do is be able to have a dynamic TAG for this. Meaning we actually have a history that stores what AHUs are serving which VAVs. Maybe from 8pm to 4am you only have AHU-1 serving the VAVs, but from 4am-10am you have AHU1 and AHU2. All we need to be able to do is have a TAG that binds to a history that shows which AHU is serving the VAV. Does this make sense at all?
This is important as we do AHU/VAV optimization we need to be able to calculate things easily. We need to be able to handle these use cases.
Brian Frank Tue 26 Apr 2011
What is the physical mechanism that controls this? Do all the AHUs just dump into a common duct?
How do you determine when an AHU is feeding a VAV? Is it the fact that the AHU is on (fan is active). Or is there some damper in place which would determine it?
As an overall strategy, I think the best way to model this from an analytics perspective is to create a group of AHUs, then have the VAV reference the group instead of an individual AHU. Something like:
That way the ahuGroup can be used to perform joins between the various indirect references.
Grouping AHUs is also useful in its own rights for analytics. For example if AHUs were linked in this way, you would probably want to make sure they were all cooling or heating at the same time and not fighting one another.
Winston Hetherington Tue 17 May 2011
In reference to the earlier comment from Jason Briggs, I would suggest the his scenario is possible,but it is seldom used. To execute the connection too other sources of supply would involve many dampers and complex control sequences. The comment about simultaneous heating and cooling would not be a much of an issue as might be perceived since AHU's supplying VAV devices seldom provide heating from the main system, more often as an component of the VAV device itself.
Winston