THERMO 2000 AltSource 50 Thermal Mass Electric Boiler | 18 kW - 240V
The 18 kW AltSource 50 brings together four 4.5 kW elements and a 48 US gal tank: a 61,416 BTU/h electric backup for large homes heated by a renewable source.
Model numberALTSOURCE50-18
514 316-2973 · sales@airgreen.ca
Quick facts
18 kW in four stages and 48 US gal of water: the electric backup for large homes that rely on renewables
What the AltSource 50-18 is
Thermo 2000’s AltSource is a thermal mass electric boiler designed as the backup source of a renewable-energy heating system: geothermal, air-to-water heat pump or solar. The manufacturer presents it as the only high water volume electric boiler on the market. In its 50-18 version, it pairs a 48 US gal tank with four 4.5 kW elements, for 18 kW at 240 V, or 61,416 BTU/h.
The four elements come on in four stages. The T2 UltraSmart controller, supplied with its outdoor sensor, modulates output and water temperature to the weather, shuts heating off in warm weather and offers a Boost mode. It runs in standalone electric mode by default or in automatic transfer on an external contact.
Electricity first
At 18 kW, the electrical question comes first. Thermo 2000 lists a current of 75 A at 240 V, a 100 A breaker and Cu 4 / Al 2 wire gauge. That is a significant load for a residential electrical service, which must also serve every other appliance in the house. In a building with a 208 V supply, output becomes 13.5 kW at 65.2 A.
During the estimate, we therefore review the loads on your panel. If the service needs to be changed, the written quote says so clearly, so you have the full picture before deciding.
In a large home in Laval or Montreal
This size is meant for large homes in Laval or Montreal heated by geothermal or an air-to-water heat pump, with a radiant floor, hot-water baseboards or radiators. The AltSource 50-18 keeps the compactness of the AltSource 50: 22 in in diameter, 25 1/2 in deep with the door, 56 7/16 in high and 280 lb before filling. It connects in 1 in male NPT and operates at a maximum pressure of 30 psi.
Installation and commissioning
Our written quote covers:
- the AltSource 50-18 boiler and its supplied accessories (relief valve, drain valve, temperature and pressure gauge, air vent, outdoor sensor);
- the circulator and expansion tank, which Thermo 2000 recommends as a #30 for baseboards or a radiant floor and a #60 for cast-iron radiators;
- the electrical connection and, if needed, work at the panel;
- filling, purging, controller setup and a final check with you.
Thermo 2000 covers the tank for 15 years in residential use and the electrical and mechanical components for 2 years. AirGreen is a family business established in Montreal for more than fifteen years, holding RBQ licence 5645-9605-01 in ventilation, refrigeration and electrical work.
Ask for your estimate
We serve Montreal, Laval, Longueuil, the North Shore and the South Shore. The estimate is free, the quote is in writing, and financing is available.
The backup for large homes
The AltSource 50-18 is meant for homes with a high heating demand that rely on geothermal, an air-to-water heat pump or solar for most of the work. Its four 4.5 kW elements come on in stages according to the cold.
- Large house heated by geothermal and a radiant floor
- Backup for an air-to-water heat pump in a home with a high heating demand
- Multi-storey house with hot-water baseboards and radiators
- Mechanical room where high output must fit in little space
Specifications
From the manufacturer’s documentation. A value the manufacturer does not publish is not listed.
What to know before installing
- Thermo 2000 lists 75 A at 240 V, a 100 A breaker and Cu 4 / Al 2 wire gauge: the electrical service must be able to carry this load.
- At 208 V, output drops to 13.5 kW (65.2 A).
- The circulator and expansion tank are not on the list of supplied parts; recommended tank #30 for baseboards or a radiant floor, #60 for cast-iron radiators.
- Height of 56 7/16 in; weight of 280 lb, plus the water in the tank once filled.
- 1 in male NPT fittings; maximum working pressure of 30 psi (207 kPa).
- 30 psi (207 kPa) relief valve
- Drain valve
- Temperature and pressure gauge
- Automatic air vent
- Heating elements
- UltraSmart controller
- Outdoor sensor
Manufacturer documents
Explore the range
Electric boilersSee allSame brand
THERMO 2000See all
Frequently asked questions
Is my electrical service enough for 18 kW?
Thermo 2000 lists 75 A at 240 V and a 100 A breaker. We review the loads on your panel during the free estimate; if the service needs to be changed, the quote says so.
What output at 208 V?
13.5 kW at 65.2 A, according to the manufacturer. We take this into account before recommending this size.
How do the four elements work?
The 18 kW is split into four 4.5 kW elements, over four stages. The T2 UltraSmart controller modulates output and water temperature on the outdoor temperature read by the supplied sensor.
Which expansion tank is needed?
Thermo 2000 recommends a #30 tank with baseboards or a radiant floor, and a #60 with cast-iron radiators. It is added to the quote, along with the circulator.
Which standards does the unit meet?
Thermo 2000’s specification sheet lists CSA C22.2 No. 165-92 in Canada and UL 834 in the United States.
An 18 kW AltSource 50, installed 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.