Need ability to represent VRF systems

[connorjcantrell]

Opening a new issue to bring attention to a previously discussed topic: https://github.com/BrickSchema/Brick/pull/344

Fan Coil Unit/ Indoor Unit

The term "Indoor Unit" is equivalent to Brick's existing "Fan Coil Unit". We can also improve our ability to represent the various types of Indoor Units/ Fan Coil Units by defining the following:

• Wall [Mounted] Fan Coil Unit
• Ceiling [Mounted] Fan Coil Unit
• Concealed/ Duct Fan Coil Unit
• Floor [Mounted] Fan Coil Unit

Condensing Unit/ Outdoor Unit

The term "Outdoor Unit" is also referred to as a "Condensing Unit", which needs to be added to Brick. Condensing Unit is not to be confused with Condenser, which is a core component of a Condensing Unit along with a compressor and, in some cases, a reversing valve.

We can categorize Condensing Units as follows:

• Heat Pump Condensing Unit
• Cooling Only Condensing Unit

Branch Selector

It is worth mentioning that up to this point, all concepts can be used interchangeably with conventional cooling and heating systems and VRF systems. The distinction often lies in the presence of a "Branch Selector" between the FCUs and Condensing Units. Therefore, Brick will also need to introduce a Branch Selector Box class.

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If "Outdoor Unit" and "Indoor Unit" must be represented, we should make these an alias to "Condensing Unit" and "FCU" respectively. In summary, I propose introducing:

• Condensing Unit
• Branch Selector
• Wall Fan Coil Unit
• Ceiling Fan Coil Unit
• Floor Fan Coil Unit
• Duct Fan Coil Unit

[connorjcantrell]

I have intentionally left out the "Heat Recovery Condensing Unit" from the proposal. My rationale is that heat recovery in VRF systems is accomplished through the distribution of heat via Branch Selectors, which negates the need to define a separate condensing unit for heat recovery. I'm open to suggestions on how we should specifically represent Heat Recovery VRF systems. One possibility is to infer the presence of a heat recovery system based on the existence of Branch Selectors. Let me know your thoughts on this approach.

[connorjcantrell]

Additionally, when it comes to distinguishing between air-sourced and water-sourced condensing units, we can usually infer this based on its connection to a condenser water system. However, it might be worthwhile to have a discussion on whether we should explicitly define air-sourced and water-sourced condensing units, or if inferring their type based on their relationships within the system is sufficient.

[rmartinez-avila]

Wall mounted doesn't look like that. Looks like:

[rmartinez-avila]

Ceiling Unit is typically called "Cassette".

[rmartinez-avila]

The outdoor units should be categorized as Heat Recovery, Heat Pump, and Cooling only. Heat Recovery entails more than just the branch selectors diverting refrigerant. The outdoor unit is a special unit that is capable of mixed mode operation sending hot gas to the indoor and outdoor coils simultaneously.

Here is a good video explanation:

https://youtube.com/watch?v=r-NQEoPidX8

[rmartinez-avila]

Water-source units are connected to the condenser water system not chilled water.

[connorjcantrell]

@rmartinez-avila Thanks for the feedback and yes CW, not CHW. Cassette sounds good. Here's the updated proposal:

.
├── Branch_Selector
├── Condensing_Unit
│   ├── Cooling_Condensing_Unit
│   ├── Heat_Pump_Condensing_Unit
│   └── Heat_Recovery_Condensing_Unit
└── Fan_Coil_Unit
    ├── Cassette_Fan_Coil_Unit
    ├── Duct_Fan_Coil_Unit
    ├── Floor_Fan_Coil_Unit
    └── Wall_Fan_Coil_Unit

I realize it is common to use Indoor and Outdoor Unit to describe VRF equipment, do you have any opposition to using Condensing Unit and Fan Coil Unit? I understand the argument against calling it a "condensing unit" as a heat pump or heat recovery system does more than condense the refrigerant. However, I'm trying to avoid the scenario of introducing interchangeable terminology to the ontology.

[rmartinez-avila]

"Ceiling Mounted Cassette" would be complete.

[rmartinez-avila]

I think Condensing Unit and Fan Coil Unit are fine. Those terms are used for VRV/VRF all over the place and I've even seen them in some of their manuals.

[connorjcantrell]

To briefly summarize our discussion:

• We have identified a potential source of confusion in our current naming convention, specifically regarding the term "Condenser" and its definition. To clarify, we propose renaming the Condenser to "Condensing Unit" and updating its definition to accurately represent the entire unit, as opposed to just the Condenser Heat Exchanger.
  • Upon reflection, I would prefer to rename it to Condenser_Unit instead. This would allow us to preserve the established terminology of "Condenser"
• Introduce Reversing_Valve class, as it is a core component to Heat Pumps.
• Introduce a VRF_System class, which will give us interoperability with Project Haystack's existing VRF concepts.

[david-waterworth]

PS Your original picture (labelled "wall mounted") is what's often called a bulkhead system. And in my experience no-one can agree what an FCU is :)

[connorjcantrell]

@david-waterworth,

I appreciate your input regarding the bulkhead system. I must admit that my choice of illustration may not have been ideal, as my intention was primarily to demonstrate the operational concept of a wall-mounted FCU. I acknowledge that the illustration may not accurately represent a wall-mounted FCU, and I believe that rmartinez's image clarifies a wall mounted FCU most accurately.

I am open to receiving concrete feedback and possible concerns regarding the definition of an FCU.

[MatthewSteen]

The AHRI Performance Rating of Variable Refrigerant Flow (VRF) Multi-split Air-conditioning and Heat Pump Equipment has definitions that might be helpful here. For example...

3.2.21 Indoor Unit. A separate assembly of a Split System, excluding a service coil, that includes all of the following features:

• An arrangement of refrigerant-to-air heat transfer coil(s) for transfer of heat between the refrigerant and the indoor air
• A condensate drain pan
• An air temperature sensing device
• An integrated indoor blower such as a device to move air including the device’s associated motor

3.2.29 Outdoor Unit. A separate assembly of a Split System that transfers heat between the refrigerant and the outdoor air or refrigerant and water, and consists of an outdoor heat exchanger, compressor(s), an air moving device, and in addition for Heat Pumps, can include a heating mode expansion device, reversing valve, or defrost controls, or any combination thereof. VRF Water-source Heat Pumps do not have an air movement device.