FCU hookup, otherwise known as fan coil unit hookup, is an essential aspect of HVAC systems in commercial and residential buildings.
It involves connecting a fan coil unit to the building’s water supply, allowing hot or cold water to circulate and maintain a comfortable ambient temperature. Valves play a crucial role in the FCU hookup process, controlling the flow and temperature of the water as it circulates through the unit.
These valves come in various types and sizes and are selected based on the specific requirements of the building and its HVAC system.
Our blog post will delve into the different types of valves used in FCU hookup and how they affect the overall performance of the HVAC system.
Firstly, let us know what the FCU is.
FCU is a component of the chilled water system that is installed to provide cooling/heating for a specific space in the building.
It can be installed exposed or above the false, as approved by the architect.
Usually, we have three pipes that will be connected to FCU if it includes only a water cooling coil; in this case, the first pipe is the chilled water supply line, which will be a steel pipe; the second pipe is the chilled water return line which will also be a steel pipe, and the third pipe will be the condensate drain line, and usually, it’s a plastic pipe.
But when the FCU includes two water coils, one for heating and one for cooling, in this case, we will have five pipes, two of them will be steel pipes to be connected to the cooling coil as supply & return, then we have other two steel pipes will be connected to the heating coil, and the last fifth pipe will be a plastic pipe to work as a condensate drain which will be in between the drain pane in the FCU and the drainage line.
Also, FCU includes a fan that sucks the air, either complete fresh air or return air from space; then it sends this air to a copper cooling or heating coil, in which the chilled/hot water flows through it, then the temperature of the water inside the FCU’s coil is responsible for changing the supply air temperature which will be forced to the space.
FCU Hookup and its connections:
Now, we will provide a summary of the different valves and items that shall be available to ensure proper function and maintenance of the FCU.
1- Gate Valve or Isolation Valve:
From its name, we can expect its function; we use it to isolate the different items connected with FCU for maintenance purposes or testing & commissioning FCU.
2- Flexible connection:
We use it to absorb vibration from the FCU’s motor and prevent it from being transferred to the fixed item, such as the pipe, and we install it directly after the FCU’s coil.
3- Bypass Valve:
We use it to create a bypass connection between the supply and return water pipes. This connection is very important for flushing to prevent dirt and debris from the pipes from being transferred to the inner side of the coil, which can damage it.
4- Strainer:
We will install it on the supply water line to the FCU to ensure no dirt enters the inner side of the coil. We have an end plug at the strainer’s end, which we can remove for cleaning.
5- Control Valve complete with its actuator:
This valve will be installed on the return line of the cooling/heating coil when it’s a 2-way type, or we can use a 3-way valve on the bypass.
The purpose of this valve is to open or close and control water flow inside the coil to change the temperature in response to the space temperature signal until it reaches the set point.
Control of this valve will be via an attached actuator.
The actuator receives its signal from a BMS or the thermostat, then takes action to open or close the valve.
6- Balancing valve:
Also, it’s called a double-regulating valve, or DRV. It will be installed on the return water line and will adjust the flow rate in the FCU coil, ensuring no overflow is directed to the FCU.
The water balancing process occurs once during the project cycle, before the system’s operation.
By the way, we can replace the balancing+control valve with only one valve, which is PICV, which will be explained in another blog post.
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