Drying systems are essentially the same as a wet system, the main difference being that the pipe branches in the building are filled with air instead of water. The water reaches the shut-off valve, and is only released into the pipe network when the air pressure disappears when one or more sprinkler heads release. To ensure that the pipes are dry at all times, without condensation, all pipes must lie with a slope towards the low point. At the low points, they must be draining points, which can be checked regularly. Such drainage points are made with a small container of antifreeze, so that condensate that collects does not freeze and damage the pipe.

Water supply

In principle, the water supply for dry plants is similar to that for wet plants, but a 25% higher capacity is required in relation to the hazard class. In practice, this means that 1000 liters per minute must be calculated for a church building.

Sprinkler Central

The sprinkler valve for drying systems distinguishes between the water pressure on the main line and the air pressure in the sprinkler system. To maintain a constant air pressure on the pipe network, a compressor must be installed. This compressor must have a pressure tank of at least 50 liters. It is connected via a reduction valve which ensures constant air pressure on the system regardless of the pressure on the pressure tank. If the compressor should fail, or there is an air leak on the system that is larger than the compressor can refill, the system will trip. To protect against a faulty tripping, a low-pressure alarm is fitted. This alarm is normally sent to mobile for operational monitoring, or f. Ex caretaker or church servant. With the help of this alarm it will be possible to avert an error trigger.

Advantage

• Same benefits as for a sprinkler wet system
• Drying systems can be used in unheated buildings

Disadvantage

• The facility that has to lie with a slope is more difficult to adapt to the building construction.
• The plant requires somewhat more frequent and more extensive inspection and maintenance than a wet pipe system.