Electricians often treat rotary isolators and main switches as interchangeable - but they serve two different purposes. One is for safe isolation under load, the other is for switching the entire installation. Pick the wrong one and you risk nuisance trips, non-compliance, or an isolator that can’t legally be used as the site’s main point of isolation.
Quick Answer: A main switch isolates the entire consumer unit and is designed for no-load switching only. A rotary isolator is a heavy-duty device designed for on-load isolation, machinery shutdown, and outdoor/industrial environments. Use a main switch inside a board; use a rotary isolator when you need local, load-breaking isolation.
Browse the full range here: Rotary Isolator Switches.
This guide breaks down the real-world differences, compliance rules, and when each device should be installed.
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What Each Device Actually Does
Before choosing between them, you need to know the job each one is designed for. Here’s the functional difference in plain terms.
Main Switch
A main switch is the primary isolation device for a consumer unit. It disconnects the whole board but is only designed for off-load switching. You should not use it to break load on live machinery or outdoor equipment.
- Purpose: Board-level isolation
- Location: Inside consumer units
- Switching type: Off-load
- Common rating: 100A DP/4P
Rotary Isolator
A rotary isolator is built for load-breaking isolation, machinery shutdown, and safe working on equipment. They’re usually IP65-rated and suitable for harsh, outdoor, or industrial environments.
- Purpose: Local isolation under load
- Location: Near equipment (motors, compressors, EV chargers, HVAC, PV isolators)
- Switching type: On-load
- Common rating: 20A–125A, 4-pole
Where You Should Use Each One
Once you know what each one does, the next question is where they actually belong on an install.
Use a Main Switch When:
- You’re isolating an entire consumer unit
- The installation is domestic or light commercial
- You don’t need load-breaking capability
- You’re working inside an enclosure, not outdoors
Most household boards, garage units, and heat pump/EV-ready consumer units use standard main switches. See all options here: Main Switches.
Use a Rotary Isolator When:
- You need local on-load isolation for equipment
- You’re installing outdoors or in dusty/wet environments
- You’re isolating motors, plant equipment, or PV/EV/HVAC supplies
- You need 4-pole switching (AC or DC)
They’re standard on commercial and industrial installs where under-load disconnection is required.
Regulation Differences Installers Need to Know
Regulation Reminder: BS EN 60947-3 defines the switching duty for isolators. Only rotary isolators rated for AC-23A or AC-21A loads are suitable for on-load isolation. A standard main switch is not rated for this duty.
- Main switches → meet isolation requirements for consumer units (BS EN 61439)
- Rotary isolators → meet load-breaking duties for machinery and equipment (BS EN 60947-3)
Installer-Favourite Rotary Isolators
Here are reliable AC and DC rotary isolators widely used for plant, PV, EV and general isolation:
- 80A 4 Pole AC Rotary Isolator (IP65)
- 63A 4 Pole AC Rotary Isolator (IP65)
- 40A 4 Pole AC Rotary Isolator (IP65)
- 32A 4 Pole AC Rotary Isolator (IP65)
- 20A 4 Pole AC Rotary Isolator (IP65)
- 125A 4 Pole AC Rotary Isolator (IP65)
- 100A 4 Pole AC Rotary Isolator (IP65)
For DC isolation (solar, battery, PV arrays):
Browse all isolators here: Rotary Isolator Switches.
FAQs
Installers ask these questions all the time when mixing main switches and isolators on site.
Can a rotary isolator replace a main switch?
No. A rotary isolator is for equipment-level isolation. A main switch isolates an entire board and fulfils the consumer unit’s mandatory isolation requirement.
Can a main switch disconnect under load?
Not safely. Main switches aren’t designed for load breaking. Use a rotary isolator if load-break capability is required.
Do EV chargers require a rotary isolator?
Many do for local isolation, especially in commercial settings. Check the charger manufacturer’s installation guidance.
Are outdoor main switches allowed?
Not typically - they’re not IP-rated for harsh environments. Use an IP65 rotary isolator instead.
👉 Need reliable on-load isolation? Browse all Rotary Isolators