> For the complete documentation index, see [llms.txt](https://docs.strata.hendersonengineers.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.strata.hendersonengineers.com/workflows/mechanical-planning/sources-and-equipment.md).

# Sources and equipment

Create mechanical sources, configure equipment, and place equipment.

A source represents the primary air-handling equipment (RTU, AHU, DOAS, etc.) serving one or more zones. Source configuration determines what appears in the mechanical equipment schedule.

***

## Creating a source

**In Data view:** Press `Y` to add a new source row.

**From the left sidebar:** Select zones → use the **Group Into Source** action.

**From canvas selection:** Select zones on the canvas → use **Group Into Source** in the right panel.

***

## Equipment configuration

When a source is selected, the right panel displays the equipment configuration fields.

> 📸 **Screenshot — Source equipment configuration** A selected source with the right panel showing Source Equipment Type, Supply Fan, Cooling Source, Heating Source, and the Unit Features toggles, plus the building summary tonnage above.

### Diversity Factor

Engineer-adjustable slider, **0.5–1.0** (step 0.05, default **1.00**). Reflects the estimated proportion of connected zone airflow in use simultaneously — lower values reduce the source's Airflow (and the tonnage that follows from it), since not all zones peak at once.

### Equipment (Source Equipment Type)

Select the equipment type from the available catalog. This determines the equipment designation in the schedule and drives relevant calculations.

### Supply Fan

| Option              | Description            |
| ------------------- | ---------------------- |
| Constant Volume     | CAV (fixed airflow)    |
| Variable Air Volume | VAV (variable airflow) |

### Cooling Source

| Option | Description              |
| ------ | ------------------------ |
| DX     | Direct expansion cooling |

### Heating Source

| Option       | Description                 |
| ------------ | --------------------------- |
| Electric     | Electric resistance heating |
| Heat Pump    | Reverse-cycle heating       |
| Gas          | Gas-fired heating           |
| Not Required | No heating coil             |

### Unit Features

Multi-select. Specifies optional coils and features included in the unit. Selected features appear abbreviated in the equipment schedule.

| Code | Feature                   |
| ---- | ------------------------- |
| PH   | Preheat Coil              |
| CC   | Cooling Coil              |
| RH   | Reheat Coil               |
| HR   | Exhaust Air Heat Recovery |
| HGR  | Hot Gas Reheat            |
| HP   | Heat Pump                 |
| HRHP | Heat Recovery Heat Pump   |

***

## Nominal Size

**Nominal Size** (Tons) is the equipment size you select for the source. It's a field you set, not a calculated value.

Open the **Nominal Size** field at the bottom of Equipment Details in the right panel, or edit the cell directly on the source row in [Data view](/workflows/mechanical-planning/data-view.md). You can:

* Pick a size from the list of common tonnages, or
* Type your own value when the project calls for something off-list

Strata marks its recommended size in the list with a star. The recommendation comes from the source's Cooling Load — the cooling load densities of the spaces beneath it applied to their areas, adjusted by the source's **Diversity Factor**. See [Loads and Densities](/workflows/mechanical-planning/loads-and-densities.md).

Leave Nominal Size blank and Strata falls back to the recommended size everywhere the value is used — the equipment schedule, the Excel export, the topology view, and the source map. Once you enter a value, that value is used instead.

The building summary in the right panel shows total tonnage across all sources.

***

## Placing equipment on the floor plan

Once a source is fully configured (equipment type set, zones assigned), it can be placed on the canvas.

1. Select the source.
2. In the right panel, select **Place Equipment**.

> The **Place Equipment** button is disabled if the source is missing required configuration or has no assigned zones.

Equipment placement is visible on the canvas as a symbol. It can be repositioned by dragging.

***

## Removing zones from a source

Select the source in the left sidebar tree → use the **Ungroup** action for the zone. The zone returns to the unassigned state.

***

## Deleting a source

Select the source → press `Delete` or use the delete action. Zones previously assigned to the source return to unassigned.

***

## Multi-source editing

Select multiple sources (Ctrl + Click) to edit shared fields simultaneously. Fields with differing values across the selection show "(Mixed)" as a placeholder. Setting a value applies it to all selected sources.

***

## Related

* [Zones](/workflows/mechanical-planning/zones.md)
* [Loads and Densities](/workflows/mechanical-planning/loads-and-densities.md)
* [Mechanical Equipment Schedule](/reference/exports/mechanical-equipment-schedule.md)
* [System Hierarchy](/reference/reference/system-hierarchy.md)