THERMO 2000 AltSource 70 Thermal Mass Electric Boiler | 4.5 kW - 240V
The 4.5 kW AltSource 70 combines a 71 US gal tank with a single electric element: a low current draw backup for a renewable heat source.
Model numberALTSOURCE70-4,5
514 316-2973 · sales@airgreen.ca
Quick facts
71 US gal of thermal mass and 4.5 kW of backup for homes that rely on renewable energy
A large water reserve, a single element
Thermo 2000’s AltSource 70-4.5 is a thermal mass electric boiler: its tank holds 71 US gal of water. The manufacturer presents it as the only high water volume electric boiler on the market and designs it for a specific role, as the backup source of a renewable-energy heating system. Geothermal, an air-to-water heat pump or solar collectors handle most of the heating; the AltSource tops it up.
In this size, the electric side is deliberately small. A single 4.5 kW element, in a single stage, delivers 15,354 BTU/h at 240 V. It is the leanest combination of the AltSource 70: this model’s full water reserve for the lowest current draw.
The homes where this size makes sense
This size suits owners who have invested in a well-sized renewable source and want a discreet electric backup. A well-insulated house in Longueuil with a radiant floor tied to geothermal, a South Shore property with solar thermal collectors, a new house with an air-to-water heat pump: in each case, the main source does most of the work and the AltSource keeps the home comfortable when it falls short.
On the electrical side, Thermo 2000 lists a 30 A breaker and Cu 10 / Al 10 wire gauge at 240 V. At 208 V, output drops to 3.4 kW (16.3 A). 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.
Preparing the location
A 71 US gal reserve takes up space and weight. The unit measures 24 in in diameter and 28 in deep with the door, and weighs 380 lb before the water is added. We check the access path to the mechanical room and the strength of the floor. The loop connects through 1 1/4 in male NPT fittings and operates at a maximum pressure of 30 psi. For the expansion tank, Thermo 2000 recommends a #60 with baseboards or a radiant floor, and a #90 with cast-iron radiators.
If you also want to preheat domestic water, Thermo 2000 offers an optional 26.2 sq ft parallel copper coil heat exchanger. We discuss it from the first visit.
Installation by AirGreen
The on-site estimate is free and the written quote details the unit, the circulator, the expansion tank and the electrical work. Our technicians then install the boiler, connect it to the loop, mount the outdoor sensor, make the electrical connection, fill and purge the system, then set the controller. 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.
Ask for your estimate
We serve Montreal, Laval, Longueuil, the North Shore and the South Shore. Tell us about your renewable source: we send you a written quote for the AltSource 70, and financing is available.
Plenty of water, little electrical output
The AltSource 70-4.5 is meant for systems where the renewable source does almost all the work. Its 71 US gal tank forms a large thermal mass, and its single 4.5 kW element takes over as needed.
- Geothermal system feeding a radiant floor
- Solar thermal collectors that need an electric backup
- Air-to-water heat pump in a well-insulated house
- Preheating domestic water with the optional coil heat exchanger
Specifications
From the manufacturer’s documentation. A value the manufacturer does not publish is not listed.
What to know before installing
- The unit weighs 380 lb, plus the water in the tank once filled, and measures 24 in in diameter and 28 in deep with the door: we check the access path and the floor before installation.
- Dedicated 240 V single-phase circuit with a 30 A breaker. At 208 V, output drops to 3.4 kW (16.3 A), according to Thermo 2000.
- Thermo 2000 recommends a #60 expansion tank for baseboards or a radiant floor, and a #90 for cast-iron radiators.
- The circulator and expansion tank are not on the list of supplied parts: the quote specifies them.
- 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
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Frequently asked questions
Why choose 71 US gal rather than 48 US gal?
A larger volume of water stores more heat. The choice between the AltSource 70 and the AltSource 50 of the same output depends on your system and the space available: we advise you during the free estimate.
What heat emitters can it supply?
Thermo 2000 gives recommendations for baseboards, a radiant floor and cast-iron radiators; the expansion tank varies with each case (#60 or #90). Water can reach 88 °C (190 °F).
Can it preheat domestic water?
Yes, with Thermo 2000’s option: a 26.2 sq ft parallel copper coil heat exchanger rated for 125 psi maximum, with 3/4 in domestic water connections (NSF 61).
Is the controller included?
Yes. The T2 UltraSmart controller and the outdoor sensor are among the supplied parts, along with the relief valve, drain valve, temperature and pressure gauge and automatic air vent.
What warranty does Thermo 2000 offer?
15 years on the tank and coils in residential use, 10 years in commercial use, and 2 years on electrical and mechanical components and accessories.
A 4.5 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.