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We will understand about HVAC Three way valve and their function, working mechanism and types Let's start video and get information about the HVAC 3-way valve This HVAC|MEP tutorial Channel by Tanweer Ahmed HVAC 3-way valves have two types One is called mixing valve and second is called diverting valve What is the difference between mixing and diverting valves? The mixing valve is called that which has two inlet ports or pipes and one outlet port or pipe Suppose that we have a wash sink where we normally hand wash there is one cold water pipeline and another is a hot water pipeline at that tap point, both hot & cold water mixed when manually we open the tap water there hot and cold water comes out and mixed which is discharge or outlet from a Tape water that comes out of it is mixture of both hot and cold So we call this mixture which is used in Wash Sink. Similarly, in HVAC the three-way valve is known as mixing valve, that why it is called mixing valve because water coming form two inlet with different temperature from one is coming hot water and the other is cold water and mixture of both a point of discharge at one outlet So the water that comes out through the mix is also called mixing three-way valve It has two inlet ports, where water is coming from two sides and one is discharge port, water being discharge from there So it is called three-way mixing valve.
Secondly three-way valve is diverting valve Mostly diverting valve is used in HVAC which you have seen in AHUs or FCUs So there always three-way valves are installed in discharge pipeline of coil for HVAC units. Water is flowing in a coil, it is called Inlet and the line is coming out of the coil is called discharge line or outlet line this discharge or outlet line has three-way valve, this is basically diverting valve, it is not mixing valve. Don't mix both valves with each other If you think that diverting and mixing valve are same and use these or if you misunderstand about function then vibration will transfer in equipment, Equipment may be damaged, loses in pipeline may observed, abnormal sound may be happen So these types problems will be in future and you will not get the right quantity of flow So Let's understand what is diverting valve? Water is coming form one side pipeline in diverting valve On one side will intake and discharge from two sides How is this? Suppose the water flowing in AHU that inlet one side of pipeline and also outlet from another side of pipeline We will install this in return pipeline of AHU or FCU and returning water pipeline will distribute in two pipeline How distribute two pipelines? one is going forward and one is being bypassed below side what happens is that whatever water requirement, it will flow according to the water requirement and rest will bypassed.
Understand it in such a way that most of time you have seen it, the motor is fixed with three-way valve or actuator is fitted with it, it also call motorized valve or three-way valve Those motorized valve basically attached with controller or temperature sensor When the temperature is sensed that set temperature of room is achieved then this motorized would close the three-way valve. This is not really closing the three way valve but this is diverting, the flow that returning, this won't return but it is diverted, or bypassed. Let's suppose that any flow needed to AHU coil then the same flow coil will enter into AHU coil and the remaining no needed, it will divert or bypassed One thing to keep in mind that the diverting valve does not 100% closed nor 100% not open Quantity of flow is regulate proportionally, it may high or low and not balance properly. But only the work diverting. Suppose, if the vehicles are going through road and the road is blocked then temporary way is made for movement of vehicles This three-way diverting valve is used in HVAC, this is not a permanent solution for flow requirement or balancing the water flow.
This will not proper flow nor balanced But some energy is saved that's why this diverting valve is used Simply say that 3-way used with AHU is diverting valve according to temperature requirement the amount of water need in coil will flow accordingly It is 100% normally open when the temperature is reached then this is diverting. It is come towards close. In this case, the 3-way valve has a second discharge line because it has two discharge pipelines One is going and another one is going and if you don't need flow according to temperature set then this flow will divert in the second pipeline and actually discharge means water flow is diverting the other side and change direction that's why it is called 3-way diverting valve This 3-way valves used in the case of where water's flow or chilled water or hot water So water flow should be constant like constant chilled water system is used What happens in it that pumps are constant flow, this means that whatever flow of system is designed This is fix design as much as the pumps will run speed then water will reach AHUs or FCUs through chiller but different AHUs are installed, there is more than one AHUs or FCUs In this case, pumps are running and water flow is circulating The water pipelines you have given to AHUs according to flow as per design If whichever unit shuts down then the pipeline pressure will be increased Due to high pressure then water is flowing more in other AHUs In this case, 3-way valve divert the flow of water due to AHUs off then water is not going in AHU but bypass from AHU pipeline and diverting or goes back circulating to the chiller pumps It means, water did not enter into the coil of AHU but bypass pipeline often seen in 3-way valve then the water is divert form here and circulation and flow of water's quantity will be same and water flow will remain constant So this is difference in 3-way valve which is used as mixing valve and also diverting valve Friends, another thing you should note that mixing valve this is good modulating valve however, diverting valve is not modulating valve.
So what is modulating valve? Modulating valve is that when the water is flow, so water is mixing and hot & cold water is coming, the amount of water is more or less according to the temperature so this will be modulate, its means that same flow of water is needed or it may needed a closer quantity or it should be similar, so it will be closer to what you need While, diverting valve is not modulating valve, it just making purpose of on or off and while mixing valve is doing modulating valve If we say it simply, what is purpose of 3-way valves? 3-way valve doing work of mixing, 3-way valve doing work of modulating, 3-way valve doing work of On/Off and 3-way valve doing work of diverting.
These four are working: mixing, diverting, modulating and On/Off 3-way valves are used for these four purposes and it has two basic types one is mixing valve and second is of diverting valve These 3-way valves mostly used for variation of temperature and variation of flow These are used in HVAC systems, Processing Systems and these 3-way valves used in constant flow system and these 3-way valves are not used in variable flow systems, while, 2-way valves used in variable flow systems What is 2-way valve? I will tell you in next video with this grant permission to Tanweer Ahmed till next video ALLAH HAFIZ.