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Disconnect switches: what they do
What a disconnect switch is, how it differs from a breaker, the appliances Québec’s Code requires one for, and when to replace it.
In short
This guide explains the disconnect switch: the box that cuts power to a single appliance, close to that appliance.
- A disconnect switch is a safety switch: it cuts power to an appliance, a heat pump or a hot tub for example, so it can be worked on with the power off.
- A breaker, on the other hand, cuts the power by itself when it detects an overload or a fault.
- In the 2018 edition of the Code, an air conditioning or refrigeration unit has its disconnect within sight, less than 3 m from the unit.
- It gets replaced when the box is rusted or cracked, when the handle sticks, or when the appliance it feeds changes.
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What it does
The disconnect switch cuts the power to an appliance so it can be worked on with no current.
It sits close to the appliance it controls: near the outdoor unit of a heat pump, for example.
A lockable model keeps anyone from switching it back on during maintenance.
A circuit’s protection and control devices cut all of its ungrounded conductors at the same time, according to the Régie du bâtiment du Québec’s guide (2018 edition of the Code).
Disconnect or breaker
| Disconnect switch | Breaker | |
|---|---|---|
| What it does | Cuts power to an appliance so it can be worked on with the power off | Cuts the power by itself when it detects an overload or a fault |
| Where it is | Near the appliance | In the electrical panel |
| Who operates it | Whoever services the appliance | It trips by itself; you reset it at the panel |
The appliance has its circuit from the panel and, depending on the case, its disconnect next to it.
A breaker that keeps tripping is diagnosed on its own: see Breaker keeps tripping.
Where the Code requires one
These rules come from the Régie du bâtiment du Québec’s quality control guide, which cites the 2018 edition of the Code.
- Motors: a separate disconnecting means for each motor branch circuit. A motor’s disconnect is within sight and less than 9 m away, or lockable in some cases.
- Air conditioning and refrigeration: a disconnect in a suitable location, within sight and less than 3 m from the unit.
- Oil or gas heating (117 kW or less): a dedicated branch circuit with a disconnecting means, which isn’t mounted on the appliance and is marked to show which appliance it controls.
Another case, outside that RBQ guide: a hot tub is fed by a circuit of its own, protected against ground faults and fitted with a disconnect switch. See Hot tub and pool wiring.
For a heat pump, the details are in Heat pump electrical requirements.
When to replace it
A disconnect switch gets replaced when:
- its box is rusted or cracked;
- its handle sticks;
- the appliance it feeds changes.
Replacing 100 A disconnect switches and the water heater disconnect is among the general electrical jobs we do most often.
Replacing a disconnect switch is electrical work: in Québec, that work is reserved for electrical contractors, even for an outlet.
A disconnect switch to replace?
The price depends on the job and the access; the exact price is written in the quote, before the work.
Send my quote requestWhat we do
We replace 100 A disconnect switches, the water heater disconnect and those of outdoor appliances.
For a new appliance, we install the disconnect with the circuit, and we check that the panel can take the load. See Is 100 amp service enough?.
The quote is written and free. If we find something when we open up, we call you before going further.
Frequently asked questions
What is an electrical disconnect switch?
It is a safety switch that cuts power to an appliance, a heat pump or a hot tub for example, so it can be worked on with the power off.
What is the difference between a disconnect switch and a breaker?
The breaker cuts the power by itself when it detects an overload or a fault; it is in the panel. The disconnect switch is operated to cut an appliance during maintenance; it is near the appliance.
When is a disconnect switch required?
In the 2018 edition of the Code: for each motor branch circuit, for an air conditioning or refrigeration unit (within sight, less than 3 m away) and for a fuel-burning heating appliance of 117 kW or less. Outside these rules, a hot tub also has its own disconnect switch.
When should it be replaced?
When the box is rusted or cracked, when the handle sticks, or when the appliance it feeds changes.
Can I replace it myself?
No. In Québec, electrical work is reserved for electrical contractors, even for an outlet.
A rusted disconnect or an appliance to connect?
We replace disconnect switches and install them for new appliances; the exact price is in the quote.
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Sources
Consulted on October 30, 2026.