As we know, the most popular HVAC equipment on the market today are 2-pipe systems and 4-pipe systems.
There may be many friends who don’t know what a 2-pipe system is and what a 4-pipe system is. Today I will introduce you to the difference between the two systems:
What is 2 pipe air conditioning?
The two-pipe air conditioner only composed of one coil and two pipes, cold water in summer and hot water in winter. Such a system as a whole can only provide cooling or heating at the same time.
The cost of the two-pipe system equipment is low, and the floor space is small, which can meet the HVAC requirements of multi-story or high-rise buildings.
What is 4-pipe HVAC ?
The four-pipe air conditioner consists of two sets of pipes. Each set of coils has one loop and there are four in total, so it is called four pipes.
Two sets of water pipes are respectively connected with cold water and hot water. It is possible to switch between cooling and heating at any time of the year. Therefore, while heating in some rooms, cooling in other rooms.
The four-tube manufacturing cost is relatively high and occupies a large space. It is suitable for buildings with large internal area or frequent switching of cooling and heating.
So, how does the thermostat control these two systems?
Please check the wiring diagram:
In the 2-pipe system, there is only one electric valve to control the water flow in the pipe. The valve switch signal sent by the thermostat can change the valve switch state and control the switching of cooling and heating.
In the four-pipe system, there are two valves, a hot water valve and a cold water valve, which control the circulation of the cold water pipe and the hot water pipe respectively. According to the signal sent by the thermostat, the corresponding electric valve is opened or closed to complete the change of cooling or heating.