CONFORTO AT AT1243 Electric Boiler | 12 kW - 240V
The Conforto AT1243 is a 12 kW, 240 V wall-mounted electric boiler whose output is spread over four 3,000 W elements, in four stages.
Model numberAT1243
514 316-2973 · sales@airgreen.ca
Quick facts
A 12 kW electric boiler that heats in small steps
The idea: four stages instead of two
In Quebec, heating demand changes a lot between a cool October evening and a January night. The Conforto AT1243 answers that gap with four 3,000 W elements, turned on one by one in four stages. In mild weather, a single element can be enough; as the cold sets in, the boiler adds a second, then a third, up to the full 12 kW at 240 V, or 41,000 BTU/h according to the manufacturer.
The controller also rotates the elements: it is not always the same one that starts first. An immersion sensor at the heat exchanger outlet controls the stages and prevents short cycling.
In the AT series, the AT1243 sits next to the AT1226, with the same output but fewer, larger elements. If your loop feeds a low-temperature radiant floor, or if you like heat that follows the weather closely, the AT1243 deserves your attention.
In a Quebec home
Take a new North Shore house heated by a radiant floor, or an older Laval house with radiators and an indirect water heater. In both cases, the AT1243 mounts on the wall, weighs about 70 lb (32 kg) as shipped and connects to the loop with 1 1/4 in NPT fittings. The loop must supply at least 4.1 gpm for a 20 °F ΔT.
Electrically, Conforto requires a dedicated 240 V single-phase circuit, with a minimum ampacity of 70.0 A and maximum protection of 70 A. The controller also provides inputs for a flow switch, a low-water device and a load-management signal from the electricity provider.
The indirect water heater, if it is part of the project, is sold separately. The controller gives it its own setpoint and priority, so domestic hot water comes before room heating.
Installation by AirGreen
We start with a free on-site estimate, then give you a written quote that details the boiler and the loop components. On the day, our technicians mount the unit, make the water and electrical connections, fill and purge the circuit.
Commissioning matters as much as mounting: we check that the four stages come on correctly, set the heating setpoint to your emitters and, where applicable, the domestic hot-water setpoint with priority. Finally, we explain the yearly maintenance Conforto requires for its limited lifetime warranty.
AirGreen is a family business established in Montreal for more than fifteen years, RBQ licence 5645-9605-01.
Your free estimate
Montreal, Laval, Longueuil, North Shore or South Shore: ask for your free estimate and your written quote. Financing is available.
A 12 kW boiler that steps up 3,000 W at a time
The AT1243 heats a hydronic loop by turning on its four elements one by one, as demand calls for them. It is the other 12 kW model of the AT series, next to the AT1226, which has fewer elements.
- Low-temperature radiant floor in a new or renovated house
- House heated by radiators, where demand varies a lot between fall and winter
- Replacing a four-element 12 kW electric boiler
- A loop that also feeds an indirect water heater
Specifications
From the manufacturer’s documentation. A value the manufacturer does not publish is not listed.
What to know before installing
- Dedicated 240 V single-phase circuit: minimum ampacity of 70.0 A and maximum protection of 70 A, per Conforto.
- The loop must deliver at least 4.1 gpm to the boiler (20 °F ΔT).
- The boiler works in stages, without modulation; the manufacturer’s documents do not mention an outdoor sensor.
- The controller has inputs for a flow switch and a low-water device; the quote lists the loop components to plan for.
- Conforto limited lifetime warranty: indoor residential use in Canada, yearly maintenance required; labour and shipping excluded.
Manufacturer documents
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Frequently asked questions
How is it different from the AT1226?
Same output (12 kW, 41,000 BTU/h at 240 V) and same power supply. The AT1243 spreads its 12 kW over four 3,000 W elements in four stages; the AT1226 uses fewer elements, each one larger. With the AT1243, each step is therefore smaller.
Can it heat a radiant floor?
Yes. Conforto designs the AT series for low-temperature radiant heating, as well as high-temperature baseboards and radiators. We set the heating setpoint to suit the floor.
What electrical circuit is needed?
A dedicated 240 V single-phase circuit. Conforto lists an element current of 50.0 A, a minimum circuit ampacity of 70.0 A and maximum protection of 70 A.
Can it make domestic hot water?
Yes, with an indirect water heater sold separately. The controller gives it a separate setpoint and priority over space heating.
What warranty does Conforto offer?
A limited lifetime warranty: 5 years on the heat exchanger and the components installed by the manufacturer (section A), then the heat exchanger at no charge up to 20 years and prorated after that. Indoor residential use in Canada; for commercial use, 2 years on parts and 10 years on the heat exchanger. Yearly maintenance required.
A 12 kW Conforto AT1243, installed and tuned by AirGreen
Tell us about your project: we check the sizing, confirm availability and send you a quote. Or let our technicians install it for you.
Specifications from the manufacturer’s documentation, checked on October 19, 2026.