THERMO 2000 ComboMax Ultra 50 Electric Boiler with Integrated Hot Water | 15 kW - 240V
15 kW over four stages and instantaneous domestic hot water, in the compact 48 US gal tank: Thermo 2000’s ComboMax Ultra 50.
Model numberCOMBOU50-15
514 316-2973 · sales@airgreen.ca
Quick facts
15 kW spread over four stages, in the compact format of a water heater
Four stages to follow the home’s needs
Thermo 2000’s 15 kW ComboMax Ultra 50 heats in four steps. It combines two 3 kW elements and two 4.5 kW elements, which are added according to demand up to 51,180 BTU/h at 240 V. On a cool autumn day, a single step is often enough; in the depth of winter, all four work together. The output drawn thus follows the home’s needs through the season.
In the same 48 US gal tank, parallel copper coils make domestic hot water. Drinking water flows through them and comes out hot, without being stored. Thermo 2000 publishes 61 US gal in 10 minutes and 134 US gal in one hour, for water delivered at 110 °F, cold water at 40 °F and boiler water at 180 °F.
The homes that benefit
This size suits homes heated by radiant floors on two levels, older homes in Montreal with hot-water radiators and properties in Laval or on the North Shore where the owners want to combine heating and hot water in a single appliance. The T2 UltraSmart controller manages both functions: it gives priority to domestic hot water, sets its temperature and runs the heating pump when the thermostat calls.
Electrical and location
Thermo 2000 specifies a 240 V single-phase circuit with an 80 A breaker and Cu 6 or Al 4 wire. At 208 V, output is multiplied by 0.75 and current by 0.867, according to the manufacturer; we take that into account when choosing the size.
Despite its 15 kW, the unit keeps the footprint of the other 50 models: 60 in high, 22 in in diameter and 325 lb empty. Connections are 1 in male NPT for heating and 3/4 in female NPT for domestic water. Maximum working pressure is 30 psi (207 kPa) on the heating side and 125 psi on the domestic water side.
What AirGreen’s installation covers
It all starts with a free estimate at your home, in Longueuil, on the South Shore or elsewhere in Greater Montreal. We assess the heating load room by room, your hot water needs, the electrical panel and the location, then give you a written quote.
On installation, the unit is set in place and connected, by qualified personnel, to the heating loop and to domestic water; the 80 A circuit is connected. After filling and purging, we set the controller, check that all four stages switch on correctly and verify water temperature at the taps.
AirGreen is a family business established in Montreal for more than fifteen years, holding RBQ licence 5645-9605-01 (ventilation, refrigeration and electrical). Thermo 2000 covers the tank and coils for 15 years in residential use (10 years in commercial use) and electrical and mechanical components for 2 years.
Let’s talk about your home: free estimate, written quote and financing available for the 15 kW ComboMax Ultra 50.
Heat in steps and hot water for the whole house
The COMBOU50-15 spreads its 15 kW over four elements and four stages. The same 48 US gal tank feeds the heating loop and the copper coils that make domestic hot water on demand.
- Homes heated by radiant floors on two levels
- Older homes with hot-water radiators
- Mechanical rooms where only a water-heater-sized unit fits
- Owners who want to combine heating and hot water
Specifications
From the manufacturer’s documentation. A value the manufacturer does not publish is not listed.
What to know before installing
- 240 V single-phase circuit with an 80 A breaker and Cu 6 / Al 4 wire, according to Thermo 2000.
- At 208 V, the manufacturer states that output is multiplied by 0.75 and current by 0.867.
- 1 in male NPT heating connections and 3/4 in female NPT domestic water connections.
- Maximum working pressure: 30 psi (207 kPa) on the heating side, 125 psi on the domestic water side.
- 30 psi heating relief valve
- 125 psi domestic hot water relief valve
- Tank and heat exchanger drain valves
- Temperature and pressure gauge
- Automatic air vent
- 12 psi pressure regulator
- Check valve (ASSE 1012 / CSA B64-3)
- Thermostatic mixing valve
- Heating elements and T2 UltraSmart controller
Manufacturer documents
Explore the range
Electric boilersSee allSame brand
THERMO 2000See all
Frequently asked questions
Why four elements of different ratings?
The COMBOU50-15 combines two 3 kW and two 4.5 kW elements on four stages. Output is added in steps according to demand, instead of switching on all 15 kW at once.
Does a 15 kW model take more room?
No. It has the same format as the other ComboMax Ultra 50 models: 60 in high, 22 in in diameter and 325 lb empty, the space of a conventional water heater according to Thermo 2000.
What breaker should be planned?
Thermo 2000 specifies an 80 A breaker and Cu 6 or Al 4 wire on a 240 V single-phase circuit. We check your electrical service’s capacity during the free estimate.
Do I need to keep a separate water heater?
Generally not: the unit makes domestic hot water, 61 US gal in 10 minutes and 134 US gal in one hour according to the manufacturer (water at 110 °F, cold water at 40 °F, boiler water at 180 °F). We confirm that these values cover your needs.
Does the warranty change if the unit is used in a business?
Yes. Thermo 2000 covers the tank and coils for 15 years in residential use and 10 years in commercial use. Electrical and mechanical components are covered for 2 years.
The 15 kW ComboMax Ultra 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.