Oil-Fired Air Heaters

An oil heater with flue (indirect, e.g. the Master BV series) has a heat exchanger and a chimney — the exhaust goes outside and only clean, dry, odour-free air enters the room, at an efficiency of about 80–85%. An oil heater without flue (direct, e.g. the Master B series) sends the exhaust into the room together with the heat, reaching almost 100% efficiency but requiring constant ventilation. The indirect type is chosen for garages and workshops with people present, the direct type for well-ventilated halls and yards; both cover outputs up to about 110 kW.

The primary fuel is diesel, and some models also allow kerosene and light fuel oil. Petrol and waste oil must never be used — they risk damaging the burner and starting a fire. In winter use winter-grade diesel, because below about -10°C ordinary diesel thickens and clogs the fuel filter. The tank of portable units typically holds from around a dozen to several dozen litres, which at 20–30 kW is enough for several hours of operation without refuelling.

Diesel consumption is roughly 0.1 litre per hour for every 1 kW of output, so a 20 kW unit burns about 2 l/h and a 50 kW unit about 4–5 l/h. At a diesel price of around PLN 6.5/l this works out to roughly PLN 10–14/h for a 20 kW model and PLN 26–33/h for a 50 kW one. With a thermostat the burner switches off once the room is warm, so the average daily cost is often 30–50% lower than these peak figures.

For a room about 3 m high with average insulation, plan on roughly 1 kW per 3–5 m², and for a poorly insulated or tall hall about 1 kW per 2–3 m². A garage up to 30 m² is heated by an 8–12 kW unit, a 60–100 m² workshop needs 20–30 kW, and a 250–400 m² hall calls for 60 up to 110 kW. In frost and with thin walls, pick the output from the upper end of the range.

Safe heating of an enclosed garage or workshop with people present is provided by an oil heater with flue (indirect) — the exhaust, including carbon monoxide, is led outside through a chimney. A direct model is suitable there only with constant, intensive ventilation. Keep at least 2 m clearance from flammable materials and fit a carbon monoxide detector. Master models have an overheat sensor and flame control that cut off the fuel in the event of a fault — a standard feature in units rated above 100 kW.

An oil heater most often cuts out and smokes because of a clogged fuel filter or burner nozzle, poor-quality or waxed diesel, and incorrect pump pressure. Black smoke usually means too much fuel or too little air (a dirty intake or fan wheel), while shutting down shortly after starting points to a dirty flame-sensing photocell. First replace the filter, check the fuel, and clean the nozzle and photocell; the fuel filter is worth changing about every 150–200 operating hours. If the symptoms return, adjust the pump pressure — a correction of 0.1–0.2 bar can clear the smoking — or send the unit for service.

The Master B series consists of portable direct heaters (without flue) that return almost 100% of the heat to the room — for well-ventilated halls and yards. The Master BV series are indirect units with a heat exchanger and chimney: the exhaust goes outside and the air stays clean, at the cost of about 80–85% efficiency. The Master F series are stationary designs, permanently mounted as part of a hall's or workshop's fixed heating installation.

Most Master oil heaters have a built-in thermostat or a socket for a room thermostat that maintains a set temperature (typically in the range of about 5–35°C) and switches off the burner once it is reached, cutting fuel use by as much as 30–50%. Even so, a liquid-fuel appliance should not be left completely unattended for many hours, especially a direct model in an enclosed room. For night-time operation choose an indirect model with safety features together with a carbon monoxide detector.

Buying pays off for users who heat regularly throughout the season — the cost of the unit is spread over many months of work, and the equipment is always on hand and covered by warranty. A 20–30 kW Master heater for a garage or workshop usually pays for itself within 1–2 heating seasons compared with repeated rental. Renting can make sense for a one-off drying job lasting a few days. NORWIT.PL sells the units together with service and parts, which for regular use is more cost-effective than hiring one repeatedly.

Heating a hall of 100 m² and about 3 m high with average insulation calls for an oil heater of roughly 20–30 kW. If the hall is poorly insulated, has a high ceiling or large doors, the requirement rises to about 30–45 kW. A 30 kW model then burns roughly 2.4–3.2 litres of diesel per hour, and less with a thermostat, because the burner runs in cycles.