Hooking up a heat pump: what the electrician checks first, and why

The nameplate decides the circuit

On the outdoor unit, a label gives two key values: the minimum circuit current and the maximum protection. It’s with these numbers, not out of habit, that the electrician chooses the wire and breaker size. The heat pump gets its own dedicated circuit. A central unit needs more than a wall-mounted one.

Wall-mounted, central, backup heat

• Wall-mounted: one or more indoor heads, one outdoor unit, a modest circuit.
• Central: connected to the furnace ducts, more powerful.
• Electric backup heat: a coil that takes over in extreme cold. That’s what sends the load soaring: one more large circuit, sometimes the move to 200 A.

Why backup heat? According to Hydro-Québec, most air-source heat pumps have a minimum operating temperature, between −15 °C and −25 °C, below which their heating capacity is reduced. It therefore recommends planning a backup source, for example the existing electric baseboards.

The outdoor disconnect

A switch that cuts power to the outdoor unit, for safe servicing. The RBQ’s quality control guide requires, for any air-conditioning or refrigeration equipment, a disconnecting means in a suitable location, within sight and within 3 m of the unit.

We also place it so it’s accessible, even in winter.

The load calculation

Heat pump, backup heat, water heater, range, EV charger: it all adds up. The calculation tells you whether your service is enough.

Why add them up? In winter, air-source heat pumps go into defrost mode, and some systems then run the backup heat at the same time. This is the method of Ontario ESA’s Bulletin 8-3-15, based on the Canadian Electrical Code, and it’s the one our load calculation uses.

On a 100 A service with electric heating, a central unit with backup heat rarely fits without an upgrade. We tell you before you buy. See Load calculation: is 100 A enough? and Upgrading from 100 A to 200 A.

Who does what

The heat pump installer mounts the unit and does the refrigeration. The electrician does the circuit, the disconnect and the hookup, and makes sure the panel can keep up. The two coordinate so the unit starts on the planned day.

For a heat pump or a wall-mounted air conditioner, the RBQ states that the installation requires a contractor licensed in the right subclass:

• refrigeration (15.10), or small refrigeration systems (15.9) if the cooling capacity doesn’t exceed 20 kW;
• electrical (16), if the installation requires electrical work.

Before hiring someone, check their licence in the RBQ’s licence holder register.

What to send us before you buy

• The model you chose, or its spec sheet: it shows the nameplate values.
• A photo of the panel and, if possible, of the meter.
• Your current heating: baseboards, electric furnace, oil.
• The planned location of the outdoor unit.

With that, we tell you whether the panel can keep up, before the unit is ordered.

In winter: let the heat pump do the work

Hydro-Québec’s tips:

• Heating mode, not Auto mode: the air conditioning could start on a mild, sunny winter day.
• The heat pump at a comfortable temperature (for example 20 °C) and the baseboards 2 to 3 °C lower (for example 18 °C): they then only run when needed, especially in extreme cold.
• The outdoor unit kept clear of snow and vegetation.
• Indoor and outdoor filters cleaned at the start of each season, following the manufacturer’s recommendations.

The LogisVert rebate

Hydro-Québec’s program offers assistance for some eligible heat pumps (the guide consulted states $50 or $120 per 1,000 BTU/h depending on the model). Conditions and eligible models are in the official guide: check them before buying. It’s all explained in Heat pump rebate: LogisVert.

With LTE Électrique

We do the electrical hookup of wall-mounted and central heat pumps and air conditioners, in Sherbrooke and the Eastern Townships: load calculation, dedicated circuit according to the nameplate, outdoor disconnect, coordination with your installer. If the panel can’t keep up, we tell you before, not after. The price is announced in advance, fixed or hourly depending on the project, and labour is guaranteed for 2 years. Send us the model and a photo of the panel: the estimate is free, within 24 hours.