Calculator
Formula used
This calculator converts your device list into a gang requirement using modular “units”. A unit can be one normal switch, a keypad segment, or any module width you define.
ModulesWithSpare = TotalModules × (1 + SparePercent / 100)
RequiredGangs = ceil(ModulesWithSpare / ModulesPerGang)
The suggested box plan divides the required gangs into groups that do not exceed your “Max gangs per box” setting, using a simple practical approach.
How to use
- Set Modules per gang to match your plate style.
- Enter each device used for garden loads and zones.
- Add Spare capacity for future greenhouse expansion.
- Choose Max gangs per box for a realistic layout.
- Press Calculate and review required gangs and plan.
- Use Download CSV or Download PDF to share.
Example data table
| Scenario | Devices | Modules / gang | Spare (%) | Required gangs | Typical use |
|---|---|---|---|---|---|
| Small greenhouse | 4 | 1 | 15 | 5 | Lights, fan, pump, and a spare position. |
| Zone-heavy irrigation | 10 | 1 | 20 | 12 | Many valves plus headroom for new beds. |
| Modular plate system | 8 | 2 | 10 | 5 | Two modules per gang style plates. |
Why gang sizing matters in garden control
Smart switching brings lights, pumps, fans, heaters, and mist zones onto one wall location. Correct gang sizing avoids crowded boxes, reduces rewiring, and keeps controls intuitive during seasonal changes. Planning gangs early also helps you group circuits by task, such as propagation, irrigation, and ventilation, improving safety and daily workflow.
Convert devices into modular width units
Each smart device occupies space on the plate. A standard paddle usually counts as one unit, while scene keypads, dimmers, or modular frames may use two or more. List every controlled load, enter quantities, and assign a unit width per device. The calculator totals line modules so mixed hardware styles can be compared consistently. When you standardize units, you can evaluate whether to separate high-current relays from low-voltage keypads, keeping wiring neat and reducing interference. This approach supports future upgrades like energy monitoring or automated shade control during peak season.
Build in realistic spare capacity
Gardens evolve: you add a new bed, expand drip zones, or split a grow light circuit for better photoperiod control. Spare capacity adds planned room for these upgrades without replacing the entire plate. Many installers target 10 to 25 percent spare modules for hobby greenhouses, and higher for commercial spaces with frequent layout changes.
Translate modules into required gangs and boxes
After adding spare capacity, total modules are divided by modules per gang and rounded up. Rounding up matters because partial gangs still require a physical opening. The box plan then breaks the total into practical multi-gang groupings that do not exceed your maximum per box setting, simplifying rough-in and trim-out discussions.
Use results to document and coordinate installation
Exported CSV supports takeoffs and quoting, while a PDF snapshot is useful on-site. Share the device list, assumed unit widths, spare percentage, and suggested box plan with your electrician. Confirm compatibility for neutral wiring, depth, and heat limits, then label each gang to match your irrigation map and lighting schedule for faster troubleshooting.
FAQs
Q: What does “modules per gang” mean?
A: It represents how many module units fit into one physical gang opening. Use 1 for standard wall devices. Use 2 or more for modular frames where multiple narrow modules share one gang width.
Q: How should I set modules per device?
A: Assign the module width that matches your hardware. Most paddles, relays, and dimmers are 1. Multi-button keypads or combo units may be 2. If unsure, check the manufacturer’s wall-plate diagram.
Q: Why add spare capacity?
A: Spare capacity reserves space for future irrigation zones, extra lighting circuits, or a replacement device. It reduces the chance you must cut drywall later. Typical planning ranges are 10–25%, depending on how often your system expands.
Q: Does the calculator handle multiple boxes?
A: Yes. After computing required gangs, it suggests a practical plan by splitting gangs into groups up to your chosen maximum per box. It is a layout aid, not a code-compliance design.
Q: Can I use this for low-voltage controls?
A: Yes. Treat each control station module as a device and set an appropriate unit width. Still confirm separation rules, transformer location, and enclosure requirements for mixed-voltage systems with your installer.
Q: What should I verify before installation?
A: Confirm box depth, wiring volume, neutral availability, device heat limits, and whether relays are needed for pumps or solenoids. Label gangs to match your garden zones, and keep a printed PDF in the electrical panel area.