What does PY stand for in fire protection drawings? The icons of spray pump, hydrant pump, wet test alarm valve, pressure gauge and gate valve in fire CAD drawings are …

Py is smoke exhaust in ventilation or alarm diagram, that is to say, it is spray pressure switch in water diagram; X hydrant button pump start and feedback line, H fire telephone, D24V power line, S alarm bus.

In this system, all circuits are basically weak current lines, so it is generally called "weak current for fire fighting". For weak current, it can generally be understood as low voltage, that is, alternating current is below 50 Hz and 220 volts, and it can also be understood as direct current is below 24 volts, which is selected according to the occasion; Or as a small current.

compose

Weak current system will be composed of different systems on different occasions. For example, the weak current system in the hotel consists of an automatic fire rescue system, a monitoring video system and a central air conditioning system. The wireless city weak current system consists of management garage, access control system and the above management system. Therefore, the weak current system will be different for different occasions. The article refers to the weak current system in public places, and its composition can be divided according to functions, including safety prevention system and automatic control system.