The setting of fire damper in HVAC system

The setting of fire damper in HVAC system

In the HVAC design, there are many types of valves for fire prevention and smoke exhaust, and the valve settings are different for different applications.

Starting from the specification, GB15930-2007 "Fire Valves for Building Ventilation and Smoke Exhaust Systems" only specifies three kinds of valves: fire damper (FHF), smoke exhaust fire damper (PFHF), smoke exhaust damper (PYF), of course this standard The definition and symbol classification mark are non-mandatory provisions, which means that other valve types other than the above three types of valves can appear.

　　 It can be seen from the definition that the fire damper (FHF) is always open at 70°C, the smoke exhaust fire damper is always open at 280°C, and the smoke exhaust valve (here equivalent to the exhaust port) is always closed.

　　 Question 1: Is there a 70℃ normally closed fire damper?

There should be DFHF (B70℃), that is, 70℃ normally closed electronically controlled fire damper, normally closed, it can be opened by electric control, manual and electric reset, fuse closed at 70℃, it is used in gas fire-fighting rooms that usually do not need exhaust ( Such as an air-conditioning archive).

　　 Question 2: Is there a 280℃ normally closed smoke exhaust fire damper?

　　I personally think that there is no 280℃ normally closed smoke exhaust fire damper. It can be seen from the definition that the smoke exhaust fire damper is mainly used for exhausting smoke, and 280℃ fuse is closed for fire prevention. Since it needs to be used when exhausting smoke, it is more reliable to make the normally open valve, which can prevent the normally closed valve from failing to open in the event of a fire.

　　 If it is an exhaust and smoke exhaust system that does not usually exhaust air, but only needs to exhaust smoke during a fire, use a normally closed smoke exhaust valve/exhaust outlet + normally open 280℃ smoke exhaust fire damper. (If the smoke exhaust port comes with a 280°C fuse, can you not use the normally open 280°C PFHF?)

There is a kind of "automatic smoke exhaust fire damper", which is usually closed and opened when a fire occurs. This is similar to the action of a smoke exhaust valve, but generally does not have the fire prevention function of 208 degrees Celsius fusing, while the automatic smoke exhaust fire damper can The fuse is closed at 280°C. The valve should be installed on the pipe of the exhaust system or at the suction port of the exhaust fan. I personally think that the "automatic smoke exhaust fire damper" here can be replaced with a normally closed smoke exhaust valve/exhaust outlet + a normally open 280°C smoke exhaust fire damper. At this time, the smoke exhaust outlet is opened and the interlocking fan starts. If it is installed at the end of the fan suction port and the exhaust pipe, when a fire occurs, all the "automatic smoke exhaust fire dampers" need to be activated in a chain, and the fan needs to be started in a chain. The control is more complicated. If one of them fails to open, the system cannot operate normally. The reliability is not as good as the normally closed smoke exhaust valve/exhaust outlet + normally open 280℃ smoke exhaust fire damper.

　　 Question 3: Is there a normally open smoke exhaust valve?

　　The exhaust valve here is equivalent to the exhaust vent. For the common plate exhaust vents and multi-leaf exhaust vents, the common ones on the market are normally closed, and generally do not need a normally open exhaust vent. For the exhaust vents of the exhaust air and smoke exhaust system, "single-layer shutters + 280℃ electronically controlled smoke exhaust fire damper" can be used for control.

　　 Question 4: What are the applications of 70℃ fire damper?

There are many applications for fire dampers, such as the air-conditioning return duct, the inlet and outlet of the ventilation fan, the inlet of the air shaft, the pipe crossing the partition wall or floor of the fire zone/deformation joint/important room/machine room/room with high fire risk, vertical duct Connect with each level of horizontal duct. Fire damper is required in many occasions.

　　 Question 5: For air conditioners that do not have an air conditioner room, such as fresh air ventilators, ceiling-mounted air conditioners, etc., how to set the fire damper?

　　 At this time, it is not necessary to install a fire damper, install a fire damper on the return air pipe, and set a fire damper for the return air. I personally think that if there is a fire, the air conditioner can be shut down directly by the fire control room, and no fire damper is required. If there is no control center, you can install a fire damper on the return air duct and interlock the air-conditioning host. When the return air temperature is 70°C, the air-conditioning host will fuse and shut down. Setting a fire damper on the air supply duct does not work because the wind enters the air conditioner through the return duct first, and setting a fire damper on the return duct can meet the requirements.

　　Question 6: Should the fire damper of the main pipe of the return air be interlocked with the air-conditioning host?

　　 I personally think that a chain air-conditioning host is needed (if possible).

　　 Question 7: Does the air-conditioning fresh air intake pipe need to install a fire damper?

　　 Personally think it is not necessary. Especially if fire dampers are installed for both return and supply air, there is no need to install fire dampers at the fresh air intake. And generally the air intake is located outdoors, and according to the requirements of the specification, keep a horizontal distance of more than 10m or a vertical distance of more than 3m from the exhaust port (the exhaust port is on the top). Generally, the flue gas will not enter the air conditioner from the fresh air port, so it is generally not necessary to install Fire damper.

　　 Question 8: When the air-conditioning duct is connected to the air shaft, if it does not pass through the fire compartment and the air shaft only has this air pipe, it is not necessary to install a fire damper?

When the air-conditioning duct is connected to the air shaft, if it does not pass through the fire compartment, and the air shaft has two or more air pipes (that is, the common air shaft for multiple systems), it is necessary to install 70°C at the place where the air pipe is connected to the air shaft The fire damper is normally open, and a check valve must be installed after the fire damper. If the duct passes through the fire compartment, a fire damper must be added.

　　 Question 9: On which side is the fire damper installed?

　　I personally think that the fire damper should be installed on the same side as the air flow direction, that is, if it is an air supply pipe, the fire damper should be installed on the side that has not penetrated the wall. Fire dampers should be installed on both sides of the deformation joint. If there is no space on the side where the fire damper needs to be installed or it is not convenient to install, it can be changed to the other side according to the construction requirements?

　　 Question 10: If the fan outlet is directly opened with louvers to the outdoors, do you need to install a fire damper on the fan outlet side?

　　 For the fan in the fan room, the outlet is directly opened with louvers to the outdoors, where the fan outlet does not need to be equipped with a fire damper. If a 70℃ normally open fire damper is installed and the fan is interlocked, of course, this valve will only work if the fan room catches fire and the duct is burned through, and the fan outlet is directly connected to the outdoors through the louver. This valve has little effect. If the outlet duct of the fan needs to pass through important rooms/fire-prone rooms/fire compartments and other locations before it can lead to the outdoors, a 70°C fire damper should also be installed on the outlet side of the exhaust fan in the fan room.

　　 Question 11: Does the outlet side valve need to be interlocked with the fan?

　　 I personally think that the valve and fan chain are more secure, that is, when a fire occurs in the fan room, the smoke can be placed in other areas and the fan can be shut down in a chain. For the air supply fan in the fan room: set a 70℃ normally open fire damper on the side of the fan outlet against the wall (within 200mm), and interlock the fan to shut down. If the fan inlet directly leads to the outdoor shutters, no fire damper is required at the fan inlet. If the duct at the fan entrance needs to pass through important rooms/fire-prone rooms/fire compartments and other locations before it can lead to the outdoors, a 70℃ fire damper must also be installed on the inlet side of the air supply fan in the fan room. This valve is a good energy chain fan Close (see question 10).

　　 Question 12: When the fan is not in the fan room, how to set the fire damper at the inlet and outlet of the fan?

　　Similar to question 5, it is considered that it is necessary to install a 70°C normally open fire damper at the inlet of the exhaust fan/outlet of the blower and the interlocking fan should be closed. It is not necessary to have both ends.