Domestic Water Heater class

[jahrling]

I'm looking on where to place Domestic_Water_Heater, and it looks like it should be a subclassof Water_Heater. This is related to #215

Also think it needs some subclasses:

brick:Domestic_Water_Heater
├── brick:Storage_Water_Heater
│ ├── brick:Gas_Storage_Water_Heater
│ │ ├── brick:Atmospheric_Gas_Water_Heater
│ │ └── brick:Power_Vent_Gas_Water_Heater
│ ├── brick:Electric_Storage_Water_Heater
│ ├── brick:Heat_Pump_Water_Heater
│ └── brick:Solar_Water_Heater
│
├── brick:Tankless_Water_Heater (also: instantaneous / on-demand)
│ ├── brick:Gas_Tankless_Water_Heater
│ └── brick:Electric_Tankless_Water_Heater
│
├── brick:Indirect_Water_Heater (uses a hydronic boiler as heat source)
│
└── brick:Semi_Instantaneous_Water_Heater (small buffer storage + instantaneous coil)

Couple Q's:
Q1. brick:Boiler overlap: Should brick:Indirect_Water_Heater have a brick:isHeatedBy relationship pointing to a brick:Boiler? Or is that a relationship to be defined, not a subclass distinction?

Q2. Condensing vs. non-condensing: For gas heaters, thermal efficiency (condensing ≥ 90% AFUE) matters for controls modeling and energy simulation. Should this be a subclass or a property?

Q3. Commercial vs. residential: ASPE distinguishes "commercial water heaters" (>75,000 BTU/hr input) from residential, and DOE recognizes 200,000 BTU/hr as the threshold. Is this a subclass distinction, a capacity property, or out of scope for Brick? I'm thinking that it should be left out for now.

Q4. brick:Storage_Tank relationship: There is already a brick:Storage_Tank class. Should brick:Storage_Water_Heater be defined as a brick:Water_Heater that brick:hasPart a brick:Storage_Tank? Or is the combined appliance a distinct class? Also, sometimes these tanks (especially in heat pump applications) can have a small heater inside to overcome the minor loads in a building.

[jahrling]

Also, need to take into account a few relationships:

• brick:Hot_Water_System — system-level, references heater equipment
• brick:Domestic_Hot_Water_Temperature_Setpoint — already exists as a Point, implies an equipment hierarchy above it
• brick:Boiler subtree — should be clearly distinguished from DHW heaters in documentation

Another issue: there is a Plant concept of multiple water heaters and multiple boilers together that achieve a higher BTU output. I feel like that is more Equipment (subclass of brick:WaterDistribution?) than Location (subclass of rec:UtilitiesRoom). The corollary is: https://project-haystack.org/doc/lib-phIoT/plant

[jahrling]

Thanks, @gtfierro !
A few additions on top of your hierarchy that I'm reviewing using the book ASPE Domestic Water Heating Design Manual , which are meant to fit your appropriate parent-child pattern:

Domestic_Water_Heater
├── Storage_Water_Heater
│ ├── Gas_Storage_Water_Heater
│ │ ├── Atmospheric_Gas_Water_Heater
│ │ ├── Power_Vent_Gas_Water_Heater
│ │ └── + Condensing_Gas_Storage_Water_Heater (left out due to Q2 above but this is one place it could work)
│ ├── Electric_Storage_Water_Heater
│ ├── + Oil_Storage_Water_Heater (oil-fired)
│ ├── Heat_Pump_Water_Heater
│ │ ├── + Integral_Heat_Pump_Water_Heater (packaged tank+HP)
│ │ └── + Split_Heat_Pump_Water_Heater (remote compressor)
│ ├── Solar_Water_Heater
│ └── + Heat_Reclaim_Water_Heater (refrigeration/HVAC waste-heat reclaim)
├── Tankless_Water_Heater
│ ├── Gas_Tankless_Water_Heater
│ └── Electric_Tankless_Water_Heater
├── Indirect_Water_Heater
│ ├── + Storage_Indirect_Water_Heater (boiler-fed coil in storage tank)
│ ├── + Tank_In_Tank_Indirect_Water_Heater (double-tank)
│ ├── + Instantaneous_Indirect_Water_Heater (see hybrid note below)
│ └── + Steam_Water_Heater (steam-to-water via HX)
└── Semi_Instantaneous_Water_Heater (see hybrid note below)

New top-level/source types:

• Oil_Storage_Water_Heater — fuel-oil-fired; common in oil-heat regions and a DOE-recognized category.
• Heat_Reclaim_Water_Heater — recovers waste heat from refrigeration condensers / HVAC (hot-gas reclaim). Distinct heat source; high efficiency when loads match.
• Steam_Water_Heater — steam-to-water (instantaneous or storage feedback / feed-forward), very common in large institutional plants and district heating.

Sub-types under existing #780 leaves:

• Heat_Pump_Water_Heater → Integral_ vs. Split_ (packaged vs. remote compressor) — meaningful for controls and where specific components are placed.
• Indirect_Water_Heater → Storage_, Tank_In_Tank_, Instantaneous_ indirect variants.

Another topic (new issue?):
Instantaneous_Indirect_Water_Heater, Semi_Instantaneous_Water_Heater, and steam feed-forward heaters are hybrids. Meaning, they are tankless-like and indirect/buffered and are therefore not Storage XOR Tankless. Rather than this stiff hierarchy, this is probably best as a cross-reference.