THERMO 2000 AltSource 70 Thermal Mass Electric Boiler | 18 kW - 240V
The 18 kW AltSource 70 pairs 71 US gal of water with four 4.5 kW elements: a high-capacity electric backup for a hot-water loop supplied by a renewable source.
Model numberALTSOURCE70-18
514 316-2973 · sales@airgreen.ca
Quick facts
A hot-water loop, a renewable source and 18 kW of backup with 71 US gal of thermal mass
A plex, a loop, a renewable source
In some plexes in Montreal and Longueuil, a single hot-water loop supplies the radiators of several dwellings. When the owner hands most of the heating to an air-to-water heat pump or to geothermal, the loop needs a backup that matches it. Thermo 2000’s AltSource 70-18 plays that role: it is a thermal mass electric boiler designed as the backup source of a renewable-energy heating system, and the manufacturer presents it as the only high water volume electric boiler on the market.
The features that matter
- A 71 US gal water tank, the AltSource 70 volume.
- 18 kW at 240 V, or 61,416 BTU/h, split into four 4.5 kW elements over four stages.
- Water heated from 50 °F to 190 °F (10 °C to 88 °C), for cast-iron radiators as well as a radiant floor.
- The T2 UltraSmart controller and its outdoor sensor, which modulate output and water temperature to the weather and shut heating off in mild weather.
- Two modes: standalone electric by default, or automatic transfer on an external contact.
Thermo 2000 also offers an optional 26.2 sq ft parallel copper coil heat exchanger to heat or preheat domestic water.
Preparing the job
On the electrical side, Thermo 2000 lists 75 A at 240 V, a 100 A breaker and Cu 4 / Al 2 wire gauge; at 208 V, output becomes 13.5 kW at 65.2 A. We review the building’s electrical service before confirming the quote.
On the hydronic side, the unit connects in 1 1/4 in male NPT and operates at a maximum pressure of 30 psi. With cast-iron radiators, the manufacturer recommends a #90 expansion tank; with baseboards or a radiant floor, a #60. Finally, the AltSource 70-18 weighs 380 lb before filling and measures 24 in in diameter and 28 in deep with the door: in a plex basement, access is checked before installation day.
What we do
After the free on-site estimate, you receive a written quote that specifies the boiler, circulator, expansion tank, the domestic water option if you choose it, and the electrical work. Our technicians then install the unit, connect it to the loop and the circuit, mount the supplied outdoor sensor, relief valve and air vent, then fill, purge and set up the system. Thermo 2000 covers the tank and coils 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.
Let’s talk about your building
We serve Montreal, Laval, Longueuil, the North Shore and the South Shore. Ask for your free estimate and receive a written quote; financing is available.
A backup for extensive hot-water loops
The AltSource 70-18 suits buildings where one loop serves several rooms or several dwellings, and where an air-to-water heat pump, geothermal or solar does most of the heating. It keeps 71 US gal of water in reserve and adds up to 18 kW in four stages.
- Plex whose dwellings are heated by a shared radiator loop
- Large house with a radiant floor, baseboards and radiators on the same loop
- Backup for a high-demand geothermal system
- Project that includes domestic water preheating with the optional heat exchanger
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. At 208 V, output drops to 13.5 kW (65.2 A).
- With cast-iron radiators, the recommended expansion tank is a #90 (#60 for baseboards or a radiant floor); neither the tank nor the circulator is among the supplied parts.
- The unit weighs 380 lb before filling and measures 24 in in diameter and 28 in deep with the door: basement access is checked at the estimate.
- Maximum working pressure of 30 psi (207 kPa): the existing loop must respect it.
- 30 psi (207 kPa) relief valve
- Drain valve
- Temperature and pressure gauge
- Automatic air vent
- Heating elements
- UltraSmart controller
- Outdoor sensor
Manufacturer documents
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Frequently asked questions
Can the AltSource 70-18 serve a plex?
It can serve as the backup for a shared hot-water loop, with 61,416 BTU/h at 240 V according to Thermo 2000. The right size depends on the building’s heat needs and the main source: we assess them during the free estimate.
Which expansion tank is needed with cast-iron radiators?
Thermo 2000 recommends a #90 tank with cast-iron radiators, and a #60 with baseboards or a radiant floor.
What electrical load does it represent?
75 A at 240 V, on a 100 A breaker with Cu 4 or Al 2 wire gauge. We review the electrical service before confirming the quote.
How does the unit get to the basement?
It weighs 380 lb before filling and measures 24 in in diameter and 28 in deep with the door. We check the stairs, doors and floor during the visit.
Can domestic hot water be added?
Yes, with the 26.2 sq ft parallel copper coil heat exchanger Thermo 2000 offers as an option (12 gpm max., 125 psi max.).
An 18 kW AltSource 70, 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.