THERMO 2000 ComboMax Ultra 50 Electric Boiler with Integrated Hot Water | 18 kW - 240V
18 kW of hot-water heating and instantaneous domestic hot water, in 60 in of height: Thermo 2000’s ComboMax Ultra 50.
Model numberCOMBOU50-18
514 316-2973 · sales@airgreen.ca
Quick facts
18 kW of heating in the format of a water heater, plus the home’s hot water
Plenty of heat, little space
A large bungalow with a finished basement needs solid heating output, but its mechanical room is often small. Thermo 2000’s 18 kW ComboMax Ultra 50 resolves that contradiction: 61,416 BTU/h at 240 V in a unit 60 in high and 22 in in diameter, weighing 325 lb empty. It is the same format as the smallest ComboMax Ultra 50 units and, according to the manufacturer, that of a conventional water heater.
Output is split between four identical 4.5 kW elements, on four stages. The boiler adds them according to demand, to feed a radiant floor, radiators or hot-water baseboards. This size is aimed at homes in Laval, on the South Shore or the North Shore whose heating load justifies 18 kW, which we confirm with a calculation before recommending it.
An electrical load to plan for
With 18 kW, electricity is the starting point. Thermo 2000 publishes a current of 75 A at 240 V, a 100 A breaker and Cu 4 or Al 2 wire. The home’s electrical service must have that capacity available, on top of the range, the dryer and the other appliances. If the building is supplied at 208 V, the manufacturer states that output is multiplied by 0.75 and current by 0.867.
Hot water, without a hot water reserve
The 48 US gal tank holds the heating water. Drinking water flows through parallel copper coils immersed in that water and heats up on the way; no hot water is stored, which reduces the risk of Legionella according to Thermo 2000. The manufacturer publishes 64 US gal in 10 minutes and 152 US gal in one hour, for water delivered at 110 °F, cold water at 40 °F and boiler water at 180 °F. The T2 UltraSmart controller gives priority to domestic hot water, and the pre-mounted thermostatic mixing valve tempers the water at the taps.
What AirGreen’s installation covers
We start with a free estimate at your home, in Montreal, Longueuil or elsewhere in Greater Montreal: heating load calculation, electrical load calculation, hot water needs and location. The written quote specifies the unit, the 100 A circuit, the loop components and the work.
On installation, the unit is set in place and connected, by qualified personnel, to the heating loop (1 in male NPT) and to domestic water (3/4 in female NPT). We make the electrical connection, fill and purge the loop, set the controller, then check all four stages and the hot water temperature.
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.
Have your home and panel assessed for free: written quote and financing available for the 18 kW ComboMax Ultra 50.
A lot of heating output in a small footprint
The COMBOU50-18 spreads 18 kW over four identical 4.5 kW elements and four stages. Its 48 US gal tank also heats drinking water, which flows through copper coils without being stored.
- Large bungalows with a finished basement heated by radiant floors or radiators
- Homes whose mechanical room cannot take a taller unit
- Replacing a high-output electric boiler and a water heater
- Projects where the electrical service has capacity for another 75 A
Specifications
From the manufacturer’s documentation. A value the manufacturer does not publish is not listed.
What to know before installing
- The unit draws 75 A at 240 V; Thermo 2000 specifies a 100 A breaker and Cu 4 / Al 2 wire. The electrical service must have that capacity available.
- At 208 V, output is multiplied by 0.75 and current by 0.867, according to the manufacturer.
- 1 in male NPT heating connections and 3/4 in female NPT domestic water connections.
- Maximum working pressure of 30 psi (207 kPa) on the heating side and 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
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Frequently asked questions
Is my electrical service big enough?
The unit draws 75 A at 240 V and Thermo 2000 specifies a 100 A breaker with Cu 4 or Al 2 wire. It depends on what your service already feeds; we do the load calculation during the free estimate, before anything is ordered.
What happens on a 208 V supply?
According to the manufacturer, output is multiplied by 0.75 and current by 0.867. The boiler works, but with less heat available; we check that it is enough for your home.
Why the 50 rather than the 70 at 18 kW?
Heating and electrical load are the same as the COMBOU70-18. The COMBOU50-18 is shorter, narrower and lighter: it fits when space is tight and the 50 model’s hot water output covers your needs.
Does heating come after hot water?
Yes. The T2 UltraSmart controller gives priority to domestic hot water, then runs the heating pump when the thermostat calls.
What maintenance does it need?
Thermo 2000 announces minimal maintenance and an expected service life of more than 30 years. We show you the basic checks at start-up.
An 18 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.