AHU with Face and by pass
Chris Schneider
Jason Koh
I'm trying to work out how to implement a Face and Bypass Zone in this system, Do I use the HVAC_Zone, or is this meant to the area supplied? It's one of a few things missing in the system but I think a critical one, we have hunderds of these types of units.
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Chris Schneider
Gabriel Fierro
Hi Chris:
Thanks for your question!
I want to make sure I’m understanding you correctly – I’ve heard face section and bypass section, but not face zone and bypass zone. Am I correct to interpret “face zone” as what’s labeled ‘face’ in this diagram?
The “Zone” concept in Brick is not about regions of equipment (like AHUs) but about logical groups of spaces, i.e. all rooms supplied by the same terminal unit. Brick could create “face zone/section” as an equipment so it could be “isPartOf” the AHU, but that doesn’t feel clean to me either. To rephrase Jason’s question: can you let us know how you want to use this information? Is the goal to identify which AHUs have face/bypass regions, or is it to localize a sensor as being in that region?
Brick isn’t quite OO, but you can easily compose information to create what you need. Say I created a “brick:Face_Section” equipment as I suggested above. Then I could model an AHU with a Face_Section as:
:ahu a brick:AHU ;
brick:hasPart :face_sec, :zone_sec, :heat_coil, :cool_coil .
:face_sec a brick:Face_Section .
# etc…
ASHRAE 223P (https://open223.info) has the kind of detail where you can define the face and bypass regions as “connections” between the different coils or input/output points of the AHU itself. I can put together a quick example of this if you’d like, but it’s probably more detail than you need.
Best,
Gabe
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Chris Schneider
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Gabriel Fierro
Hi Chris:
I think it’s an awkward thing to model with Brick because we don’t have a concept to represent a “region” of space (like the region of space between 2 dampers) or even the ducts/pipes between entities in the model.
How would you like to think about the face/bypass “thing”? Is it an “Equipment”? Or perhaps a “Collection” of equipment? (I think I like “collection” better). I could create an “EquipmentGroup” subclass of “Collection” which you could then subclass into a “FaceBypassDamperGroup” which is a NodeShape which says it must contain 1 Face Damper and 1 Bypass Damper. Then your AHU can “hasPart” your FaceBypassDamperGroup. I’ll try to put together an example this evening to do
Your use of Brick sounds really cool, and I would love to learn more about what you’re doing so I can make sure we are supporting you. I really appreciate you taking the time to write this up! Sorry my responses have been slow --- I was out sick past couple of days.
Best,
Gabe
From:
Chris Schneider <cschn...@bar-tech.com.au>
Date: Thursday, June 12, 2025 at 5:13 PM
To: Gabriel Fierro <ga...@brickschema.org>
Cc: Jason Koh <bk7...@gmail.com>, Brick User Forum (Unified Building Metadata Schema) <brick...@googlegroups.com>
Subject: Re: [Brick] AHU with Face and by pass
We have been creating our own brick elements but I don't even know what to inherit from in this instance.
A face and bypass zones is part of an Ahu with a damper/opposing dampers which allow air to pass through a coil or bypass it. It's more like a vav hot deck cold deck. We program them independent of the unit and pass back control similar to a vav. We are actually a little bit further advanced with brick than a lot of companies and are looking to use it to define systems for automatic programming but we need this relationship and would prefer it to suit a logical update in later stages of brick. We also do have standard zone units so I think f/b would inherit from them.
Even if you just give us an object to inherit from we can build it in our system and show you what the end results look like.
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Chris Schneider
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Chris Schneider
@prefix brick: <https://brickschema.org/schema/Brick#> .
@prefix bmcs: <https://openbmcs.com/schema/brick-extensions#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix skos: <http://www.w3.org/2008/05/skos#> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
# ============================================
# Multizone AHU Classes for OpenBMCS Extension
# ============================================
# Base multizone AHU class
bmcs:Multizone_Air_Handling_Unit a owl:Class ;
rdfs:subClassOf brick:Air_Handling_Unit ;
skos:definition "Air handling unit with multiple integrated zone control modules that can serve different zones with individual temperature and/or flow control" ;
rdfs:comment "A multizone AHU contains integrated terminal units rather than serving remote VAV/CAV boxes" .
# Base class for zone terminals within multizone AHUs
bmcs:Multizone_Terminal_Unit a owl:Class ;
rdfs:subClassOf brick:Terminal_Unit ;
skos:definition "Terminal unit integrated within a multizone AHU that serves a specific zone" ;
rdfs:comment "Parent class for various types of zone control modules in multizone AHUs" .
# ============================================
# Specific Zone Terminal Types
# ============================================
# 1. Face/Bypass Terminal (constant volume, variable temperature)
bmcs:Face_Bypass_Terminal_Unit a owl:Class ;
rdfs:subClassOf bmcs:Multizone_Terminal_Unit ;
skos:definition "Constant volume terminal unit using face and bypass dampers to modulate discharge temperature while maintaining constant airflow" ;
rdfs:comment "Face damper controls flow through coil, bypass damper controls flow around coil" .
# 2. Simple Damper Terminal (variable volume, no temperature control)
bmcs:Damper_Only_Terminal_Unit a owl:Class ;
rdfs:subClassOf bmcs:Multizone_Terminal_Unit ;
skos:definition "Terminal unit with a single modulating damper for variable air volume control without local temperature control" ;
rdfs:comment "Relies on AHU supply air temperature for zone temperature control" .
# 3. Heating-Only Terminal (with modulating damper and heating)
bmcs:Heating_Terminal_Unit a owl:Class ;
rdfs:subClassOf bmcs:Multizone_Terminal_Unit ;
skos:definition "Terminal unit with modulating damper and heating capability (electric or hot water)" ;
rdfs:comment "Can modulate airflow and add heat but cannot cool below AHU supply temperature" .
# 4. Cooling-Only Terminal (with modulating damper and cooling)
bmcs:Cooling_Terminal_Unit a owl:Class ;
rdfs:subClassOf bmcs:Multizone_Terminal_Unit ;
skos:definition "Terminal unit with modulating damper and cooling capability (chilled water or DX)" ;
rdfs:comment "Can modulate airflow and add cooling but cannot heat above AHU supply temperature" .
# 5. Heating/Cooling Terminal (full temperature control)
bmcs:Heating_Cooling_Terminal_Unit a owl:Class ;
rdfs:subClassOf bmcs:Multizone_Terminal_Unit ;
skos:definition "Terminal unit with modulating damper plus both heating and cooling capabilities" ;
rdfs:comment "Provides full temperature and airflow control for the zone" .
# 6. Variable/Constant Switchable Terminal
bmcs:Dual_Mode_Terminal_Unit a owl:Class ;
rdfs:subClassOf bmcs:Multizone_Terminal_Unit ;
skos:definition "Terminal unit that can operate in either constant volume or variable air volume mode" ;
rdfs:comment "Typically used for zones that require constant volume during occupied hours and VAV during unoccupied" .
# ============================================
# Example Implementation
# ============================================
@prefix bldg: <urn:building#> .
@prefix unit: <http://qudt.org/vocab/unit/> .
# A multizone AHU with different zone types
bldg:AHU-West a bmcs:Multizone_Air_Handling_Unit ;
skos:definition "West wing multizone AHU serving 6 zones with mixed control strategies" ;
brick:hasPart
bldg:AHU-West_Supply_Fan,
bldg:AHU-West_Return_Fan,
bldg:AHU-West_Cooling_Coil,
bldg:AHU-West_Heating_Coil,
# Different types of zone terminals
bldg:AHU-West_Zone1_Terminal, # Face/bypass
bldg:AHU-West_Zone2_Terminal, # Simple damper
bldg:AHU-West_Zone3_Terminal, # Heating only
bldg:AHU-West_Zone4_Terminal, # Face/bypass
bldg:AHU-West_Zone5_Terminal, # Dual mode
bldg:AHU-West_Zone6_Terminal . # Heating/cooling
# Zone 1: Face/Bypass for conference room (constant volume)
bldg:AHU-West_Zone1_Terminal a bmcs:Face_Bypass_Terminal_Unit ;
brick:isPartOf bldg:AHU-West ;
skos:definition "Conference room zone - constant volume with temperature control" ;
brick:feeds bldg:Conference_Room_Zone ;
brick:hasPart
bldg:Zone1_Face_Damper,
bldg:Zone1_Bypass_Damper ;
brick:hasPoint
bldg:Zone1_Discharge_Temp,
bldg:Zone1_Zone_Temp_Setpoint,
bldg:Zone1_Airflow_Sensor .
# Zone 2: Simple damper for storage area (VAV, no reheat)
bldg:AHU-West_Zone2_Terminal a bmcs:Damper_Only_Terminal_Unit ;
brick:isPartOf bldg:AHU-West ;
skos:definition "Storage area - variable volume only" ;
brick:feeds bldg:Storage_Zone ;
brick:hasPart bldg:Zone2_Damper ;
brick:hasPoint
bldg:Zone2_Damper_Position,
bldg:Zone2_Airflow_Setpoint .
# Zone 3: VAV with heating for perimeter office
bldg:AHU-West_Zone3_Terminal a bmcs:Heating_Terminal_Unit ;
brick:isPartOf bldg:AHU-West ;
skos:definition "Perimeter office - VAV with hot water reheat" ;
brick:feeds bldg:North_Office_Zone ;
brick:hasPart
bldg:Zone3_Damper,
bldg:Zone3_Hot_Water_Coil ;
brick:hasPoint
bldg:Zone3_Discharge_Temp,
bldg:Zone3_Zone_Temp_Setpoint,
bldg:Zone3_Valve_Position .
# Zone 5: Dual mode for lab space
bldg:AHU-West_Zone5_Terminal a bmcs:Dual_Mode_Terminal_Unit ;
brick:isPartOf bldg:AHU-West ;
skos:definition "Laboratory - CAV during occupied, VAV during unoccupied" ;
brick:feeds bldg:Lab_Zone ;
brick:hasPart
bldg:Zone5_Damper,
bldg:Zone5_Electric_Heater ;
brick:hasPoint
bldg:Zone5_Mode_Command, # CAV/VAV mode
bldg:Zone5_Occupied_Flow_Setpoint,
bldg:Zone5_Unoccupied_Flow_Setpoint .
# Zone 6: Full heating/cooling for computer room
bldg:AHU-West_Zone6_Terminal a bmcs:Heating_Cooling_Terminal_Unit ;
brick:isPartOf bldg:AHU-West ;
skos:definition "Computer room - precise temperature control" ;
brick:feeds bldg:Computer_Room_Zone ;
brick:hasPart
bldg:Zone6_Damper,
bldg:Zone6_DX_Cooling_Coil,
bldg:Zone6_Electric_Heater ;
brick:hasPoint
bldg:Zone6_Discharge_Temp,
bldg:Zone6_Zone_Temp_Setpoint,
bldg:Zone6_Cooling_Enable,
bldg:Zone6_Heating_Enable .
# ============================================
# SHACL Shapes for Validation
# ============================================
@prefix sh: <http://www.w3.org/ns/shacl#> .
bmcs:FaceBypassTerminalShape a sh:NodeShape ;
sh:targetClass bmcs:Face_Bypass_Terminal_Unit ;
sh:property [
sh:path brick:hasPart ;
sh:qualifiedValueShape [ sh:class brick:Damper ] ;
sh:qualifiedMinCount 2 ;
sh:message "Face/Bypass terminal must have at least 2 dampers"
] .
bmcs:DamperOnlyTerminalShape a sh:NodeShape ;
sh:targetClass bmcs:Damper_Only_Terminal_Unit ;
sh:property [
sh:path brick:hasPart ;
sh:qualifiedValueShape [ sh:class brick:Damper ] ;
sh:qualifiedMinCount 1 ;
sh:qualifiedMaxCount 1 ;
sh:message "Damper-only terminal must have exactly 1 damper"
] .
Chris Schneider
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I also found out controller is deprecated... HUH? Why, this is quite important.
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