Packaged Heat Pump System Tosot Rooftop R32 3 Ton | Montreal, Laval, Longueuil, South Shore and North Shore
Replacing a gas or propane rooftop unit with a 100% electric heat pump
On many commercial roofs in Montreal, Laval and Longueuil, the heating still comes from a natural gas or propane rooftop unit. When that unit reaches the end of its life, the question comes up: replace it with the same type of equipment, or switch to electricity. The TOSOT TK-H03TC/NhA-D(U) model answers the second option. TOSOT, a brand of the Gree group, describes it as a "DC Inverter Rooftop Ultra Heat Fully Electric Heat Pump": an all-electric packaged heat pump, which needs no gas, and which delivers heating as well as air conditioning from a single outdoor cabinet.
Like the old rooftop unit, this cabinet brings together the compressor, the coils and the fan, then connects to the building's duct system. The difference lies in the heat source: instead of a burner, an R-32 refrigeration cycle draws heat from the outdoor air to move it inside in winter, and reverses the process in summer. This 3 ton Rooftop R32 posts a rated capacity of 36,000 BTU/h.
What the conversion changes for your building
- No more gas supply or propane tank for this unit: the heat pump runs on electricity alone.
- No combustion in the cabinet, so no combustion products to vent on the roof.
- A 208-230 V single-phase supply (1 phase, 60 Hz), which suits buildings with no three-phase service, with an MCA of 35.0 A and an MOCP of 40.0 A according to the spec sheet.
- Air conditioning in the same unit, from -5 °C to 52 °C outdoors, with a SEER2 of 18.0 and an EER2 of 11.2.
The old gas or propane connection stops being used. Taking it out of service is planned with the qualified trades before the heat pump goes in, and we factor that into the project schedule.
36,000 BTU/h nominal: reading "3 ton" correctly
The name "3 ton" refers to the rated capacity of 36,000 BTU/h. The certified values, the ones that appear on AHRI certificate 218471411 and ENERGY STAR certificate 4624791, are 34,000 BTU/h in cooling at 35 °C and 34,000 BTU/h in heating at 8.3 °C. We base our calculations on the certified values; the rated value mainly serves to name the size.
Because the compressor uses DC Inverter technology, capacity varies with demand. The TOSOT sheet publishes a range of 8,600 to 36,100 BTU/h in cooling and 9,000 to 39,600 BTU/h in heating at 8.3 °C. On the mild days of spring and fall, the unit can therefore run at the bottom of its range instead of starting and stopping endlessly.
One point deserves particular attention during a conversion: the capacity of the old burner must not be copied over as is. A gas rooftop unit was often chosen on other criteria, sometimes with a generous margin. We calculate the real heat losses of the space instead, then we check that the 3 ton, with or without backup heat, covers those needs.
Heating without gas through the Quebec winter
The main worry for owners leaving gas behind is the deep cold. This model is ENERGY STAR Cold Climate certified and runs in heating mode at outdoor temperatures from -30 °C to 24 °C. The certified data gives two reference points:
- 21,800 BTU/h at -8.3 °C (17 °F), the certified rated capacity at that temperature;
- 29,000 BTU/h at -15 °C (5 °F), measured at maximum compressor speed, with a COP of 1.90.
The second figure is higher than the first because it does not measure the same thing: one is a rated value, the other corresponds to the compressor pushed to its maximum speed, as the ENERGY STAR Cold Climate criterion requires. The COP of 1.90 indicates that at -15 °C the unit delivers 1.90 units of heat for every unit of electricity it draws. The Inverter rotary compressor with vapour injection (EVI) is part of the equipment TOSOT describes for this "Ultra Heat" model, which delivers heating down to -30 °C.
The optional 5 or 10 kW electric backup heat
A gas rooftop unit gave the impression of a reserve of heat always on hand. To get that margin back, TOSOT offers optional electric backup heat kits of 5 kW or 10 kW on the 3 ton. These kits are electric heat strips: they turn electricity into heat without the effect of the heat pump, and therefore serve as a supplement during deep cold rather than as the main source.
The choice between 5 and 10 kW depends on the heat loss calculation and on the capacity available at the electrical panel, since the kit adds its own load to the circuit. The 15 and 20 kW kits are offered only on the 4 and 5 ton models; if your space needs one, it is often a sign that the capacity of the unit itself has to be reviewed.
Reusing the location and the ducts of the old unit
In most conversions, the goal is to keep what already works: the opening in the roof, the duct system and, if possible, the control. Here are the points we check before confirming that the TK-H03TC can take the place of your rooftop unit.
Roof curb and vertical or horizontal connection
The cabinet measures 44 × 35-7/16 × 49-1/4 in. (1,120 × 900 × 1,250 mm), in width, depth and height. TOSOT publishes the dimensions of the roof curb: we compare them with the existing curb to find out whether it can be kept or whether an adaptation is needed. The ducts connect vertically, through the bottom, or horizontally, through the side, which makes it possible to follow the old unit's configuration in many cases. The installation clearances published in the spec sheet are respected around the cabinet.
Weight and roof structure
The heat pump weighs 523 lb net and 545 lb gross, and holds 150 oz of R-32 refrigerant. We compare that weight with the one of the unit being removed and we check the condition of the structure and of the curb before setting it in place. Getting it up to the roof is part of the planning we prepare with you.
Airflow and static pressure on existing ducts
A duct system designed for a gas rooftop unit was not always sized for a heat pump. The centrifugal indoor blower on the 3 ton moves 1,120, 800 or 700 CFM depending on the speed (high, medium, low), with an external static pressure of 0.5 in. as standard and up to 0.7 in. at maximum. We measure the existing system to confirm that these values suit it, and we flag the sections to correct where needed. The air passes through an aluminum air filter, and the published sound pressure is 63 dB(A).
Keeping your 24 V thermostat or moving to the TOSOT thermostat
If your old rooftop unit was controlled by a 24 V thermostat, it is possible to keep that principle: the heat pump accepts a standard 24 V thermostat from another manufacturer, provided the one chosen handles heat pump operation. The other option is the TOSOT RS485 thermostat. The standard controller listed on the sheet is the XE7C-23/H. We help you choose based on how the space is used and on your occupants' habits.
The steps of a conversion with AirGreen
- A visit to the old unit, the roof curb, the ducts and the electrical panel.
- A calculation of the heat losses and the cooling needs of the space.
- The choice of backup heat: none, 5 kW or 10 kW, based on the calculation and the panel.
- Planning the decommissioning of the gas or propane supply with the qualified trades.
- Removal of the old rooftop unit, installation of the heat pump, connection to the ducts and commissioning.
- A walkthrough of the thermostat and the settings with your team.
To compare several capacities or several brands of the Gree group before deciding, see our selection of packaged heat pumps, which presents the Rooftop R32 models we install, from 2 to 5 ton.
Planning the conversion of your rooftop unit
We convert gas and propane rooftop units into electric packaged heat pumps in Montreal, Laval, Longueuil, on the North Shore and on the South Shore, for businesses, offices and multiplexes connected to ducts. 100% free on-site estimate anywhere in Montreal, Laval, Longueuil, the North Shore and the South Shore: call AirGreen at 514 316-2973 to have your current unit, your ducts and your panel assessed. AirGreen inc., RBQ licence 5645-9605-01.