When there is gas in the system overflowing, the gas will climb up the pipeline and finally gather at the highest point of the system. However, the automatic exhaust valve is generally installed at the highest point of the system. When the gas enters the valve cavity of the exhaust valve and collects in the exhaust valve Of the upper part of the valve, with the gas valve increases, the pressure rise, when the gas pressure is greater than the system pressure, the gas will make the cavity surface water down, the float drops with the water level, open the exhaust port; gas exhausted, the water level rise, Also will rise, close the exhaust port. By the same token, when negative pressure is generated in the system, the water level in the valve chamber drops and the exhaust port opens. Since the ambient atmospheric pressure is larger than the system pressure at this time, the atmosphere will enter the system through the exhaust port to prevent negative pressure. If you tighten the valve cap on the exhaust valve body, automatic exhaust valve to stop the exhaust, under normal circumstances, the bonnet should be turned on. Exhaust valve must be installed vertically, must ensure that the valve body float in the vertical state, can not be horizontal or inverted installation; due to gas density than water, will climb along the pipeline to the highest point of the system and gathered here, in order to improve exhaust efficiency , Exhaust valves are generally installed in the highest point of the system; in order to facilitate maintenance, the exhaust valve is generally used together with the cut-off valve, so remove the exhaust valve is not required to shut down the system; exhaust valve must be installed after the black loosen Dust cap can exhaust, but can not be completely removed, in case of exhaust valve leakage, tighten the dust cap. Hazard of gas in circulating pipe of HVAC system. The main hazards are as follows: 1. Exacerbated the pipeline corrosion, because the gas in oxygen, more prone to physical or chemical reactions; 2. the formation of gas blocking, reducing air conditioning cooling or heating effect, wasting a lot of energy, and Now the concept of low-carbon environment incompatible; 3. Affect the water cycle, resulting in circulating pump vortex, circulating pump idling burn! Therefore, the HVAC system will install automatic exhaust valve.