A screw compressor can work in a hot workshop on three conditions: duct its heat outside, draw in the coolest air available, and fit a larger dryer than for a temperate room. Our configurator raises the dryer capacity by 20 % when the room goes above 25 °C in summer, and by 40 % above 35 °C. Without these precautions, the machine ends up tripping on summer afternoons.
This situation is common near the furnaces of a foundry or forge, described on our page on compressors for foundries and forges, but also under a metal roof in high summer.
Why heat is a problem
A compressor turns a large share of the electricity it uses into heat. It cools itself with the room air: the hotter that air, the less it cools. Three effects add up:
- the screw element and the oil run hotter, and the controller stops the machine if the temperature exceeds its limit;
- the compressed air leaves hotter. On our screw compressors, it leaves at no more than 15 °C above ambient temperature. In a 35 °C room, it can therefore enter the dryer at 50 °C;
- hot air holds more water. The dryer has to remove more, and the drains work harder.
The maximum operating ambient temperature is in your compressor's manual. Compare it with the actual room temperature on a summer afternoon, not in the morning.
Step 1, duct the hot air out
This is the most effective measure. The compressor fan blows hot air out through a grille: connect a duct to that outlet and run it outside. The compressor no longer draws in its own heat.
- Keep the duct short, with few bends. A duct that is too long holds back the fan. If it has to be long, ask our technicians whether an extra fan is needed.
- Provide a fresh air inlet low down in the room, with enough cross-section, on the shady side if possible.
- In winter, a damper can send that warm air back into the workshop.
Our article on the compressor room gives the general ventilation rules.
Step 2, size the dryer for summer
The refrigerated dryer is sized on the compressor's flow, then increased according to the room temperature. Our configurator applies these factors:
| Room temperature in summer | Factor on dryer capacity |
|---|---|
| up to 25 °C | × 1.0 |
| 25 to 35 °C | × 1.2 |
| above 35 °C | × 1.4 |
Example with an S 150, which delivers 2,200 l/min at 8 bar:
- room at 30 °C: 2,200 × 1.2 = 2,640 l/min, rounded up to 2,650 l/min of dryer capacity;
- room at 38 °C: 2,200 × 1.4 = 3,080 l/min, rounded up to 3,100 l/min.
With an S 220 PM set to 10 bar, which delivers 3,200 l/min: 3,200 × 1.4 = 4,480 l/min, rounded up to 4,500 l/min in a room above 35 °C.
A dryer that is too small lets water through in summer, just when the air holds the most. Our article on which air dryer to choose explains the technologies.
Step 3, 4-in-1 or standalone compressor
The K 150 combines compressor, 340 L receiver, refrigerated dryer and filtration. It is convenient, but the whole unit sees the same heat, dryer included. It suits you if you can install it in a ventilated room with ducting.
In a room that stays above 35 °C, a standalone compressor from the S series gives more freedom: you choose an oversized dryer and can place it in the coolest area, with a prefilter upstream.
Step 4, handle water and servicing
- Condensate. Hot, humid air produces a lot of water in the receiver and the dryer. An automatic condensate drain at each low point avoids forgetting. Condensate contains oil: collect it and have it treated.
- The cooler. A hot workshop is often a dusty one too. A layer of dust on the fins is enough to push the temperature up: clean it at every check.
- The intake filter. Check it more often than in a clean workshop.
- Service intervals. First service at 500 hours, then every 1,500 hours, with a reminder on the controller. Worn oil protects less well at high temperature: do not put off the oil change until after the summer.
If the machine still trips, our article on compressor overheating lists the checks to make before calling after-sales service.
The right reflex
Measure the room temperature at the end of the day during a hot week, enter it in the configurator, then send us a quote request with a rough plan of the room: we size the compressor, dryer and ventilation together.
For your trade: Compressor for foundries and forges.