For a plaster spraying machine with no built-in compressor, you generally need a compressor giving around 1,000 L/min per spray gun, margin included. A 7.5 kW mobile screw compressor such as the M 75 is enough for one gun and a blow gun. For two machines on the same site, move up to the M 220.
Does the machine already have a compressor?
That is the first question. Many spraying machines, mixer pumps or mortar pumps, have a small built-in compressor. Others only have an air inlet and need an external compressor. Check the rating plate and the manual. If the built-in compressor has failed or is too small for the gun you want to use, an external one takes over.
Our page on the compressor for construction and precast concrete covers all the air needs of a site with mains power. Here we focus on spraying.
How much air does a spray gun use?
Air does not push the mortar through the hose: the pump does that. Air atomises the mortar as it leaves the gun. Its use depends on the air nozzle and the material. As a guide, a render spray gun often uses between 300 and 600 L/min, and a hopper gun for small jobs between 250 and 400 L/min. Air pressure is set on the machine following the manual, and is generally well below the compressor's pressure.
The calculation, step by step
Take a facade job with one spraying machine and its gun.
- Spray gun: 500 L/min, figure taken from the manual.
- Blow gun to clean tools and surfaces: ≈ 150 L/min.
- Total: 650 L/min.
- 25% margin: 650 × 1.25 ≈ 810 L/min.
The M 75 delivers 1.0 m³/min at 10 bar, or 1,000 L/min. It covers this demand with room to spare, on a 180 L receiver.
With two crews and two machines: 2 × 500 + 150 = 1,150 L/min, then about 1,440 L/min with the margin. One M 75 is no longer enough. The M 220 delivers 2.0 m³/min at 12.5 bar on twin receivers of 180 L in total.
M 75 or M 220?
| Case | Demand with margin | Model |
|---|---|---|
| One spray gun and a blow gun | ≈ 810 L/min | M 75, 1.0 m³/min, 240 kg |
| Two spray guns on site | ≈ 1,440 L/min | M 220, 2.0 m³/min, 680 kg |
| Spraying plus a breaker | Depends on the breaker | M 220, to check case by case |
Both machines in the M series are electric screw compressors on a receiver and wheels. They plug into the site distribution board on 380 V three-phase. Check its capacity before you arrive: our article on the three-phase screw compressor covers the connection.
For a job lasting a few months, we also rent screw compressors from 5.5 to 132 kW, M series included, with servicing included and no long-term commitment.
Traps specific to spraying
Water in the air. Damp air spits droplets at the gun, marks the fresh surface and makes the spray uneven. On the M series, drain the receiver every day and fit a filter at the outlet. Our article on water in compressed air explains draining.
Oil. Our compressors are oil-lubricated. For a finishing plaster or a light-coloured facade, fine filters hold back oil aerosols before the machine.
Frost. In winter, water freezes in hoses and couplings. Store the compressor under cover at night and drain the hoses.
Distance. Set the compressor close to the machine, not at the foot of the farthest scaffold. An overly long hose drops the pressure at the gun.
Noise. On an urban or occupied site, the M series' sound level of 68 to 72 ± 2 dB(A) is a real advantage.
To check your demand, use the configurator or send your machine's manual with a quote request to buy or rent.
For your trade: Compressor for construction and precast concrete.