exhaust fan not sucking the air from garbage room
exhaust fan not sucking the air from garbage room
(OP)
Hi guys,
I am facing a problem on garbage room, there is not proper air exhausted and smell is coming to outside. I checked the garbage extract fan, found it is working and air is also discharging. But in garbage room, air is not drawing through duct and air is return to garbage box. So the positive pressure in garbage room. So I have doubt on the capacity and static pressure. The details are below
Building =g+71 floor.
garbage room Area =1194.7 ft2
Height = 12 ft.
Volume = 14,336 ft3
Duct effective length(EL)=950 FT.
EXISTING UNIT DETAILS
Duct = 31 inch.
CFM =2884 CFM.
STATIC =1.7WC.
What will be the problem? Any answer would be appreciated.
thanks
moideen-dubai
I am facing a problem on garbage room, there is not proper air exhausted and smell is coming to outside. I checked the garbage extract fan, found it is working and air is also discharging. But in garbage room, air is not drawing through duct and air is return to garbage box. So the positive pressure in garbage room. So I have doubt on the capacity and static pressure. The details are below
Building =g+71 floor.
garbage room Area =1194.7 ft2
Height = 12 ft.
Volume = 14,336 ft3
Duct effective length(EL)=950 FT.
EXISTING UNIT DETAILS
Duct = 31 inch.
CFM =2884 CFM.
STATIC =1.7WC.
What will be the problem? Any answer would be appreciated.
thanks
moideen-dubai





RE: exhaust fan not sucking the air from garbage room
I am assuming you are supplying air, and exhausting air. No return in a garbage room; that would be silly.
Sounds like you have 12 ACH of exhaust which seems OK.
Have you confirmed you are supplying less than 2884 CFM into the room (confirming negative room pressure)?
Can you confirm rooms adjacent to the garbage room are positively pressurized in relation to the garbage room?
I am assuming the exhaust system duct work is entirely negatively pressurized (the fan is the last piece of the exhaust system)?
Could you clarify this statement?
Sounds like you need to get a Test and Balance contractor in the room to perform some measurements.
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
Is is windy at all? Even with 12 ACH ... gusts of air through garage doors is going to play a big role.
Might be reverse stack effect, especially if the tall building (71 stories) is in a hot climate. Air in the building will tend to fall down and pressurize the floors below it. Air tightness between 1st and second floors should be checked, especially in the garbage room.
Is this building in Dubai? Chapter 4 "Tall Buildings" in the 2015 ASHRAE Guideline - HVAC Applications book has a section specifically for Dubai and its stack effect challenges.
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
Could you sketch something or take some photos and upload them?
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
You say the garbage room is on ground floor adjacent to or in a parking garage? How is the garage being vented?
You mention a chute with doors going up through the building; do the chute doors open to an indoor space or are they exterior to the building envelope?
Is the garbage chute being ventilated?
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
Check the seal and closing mechanism on the chute doors. If the seals around the doors are bad (or do not exist), then I am not surprised you have problems. Also if the chute doors are getting stuck open, you are pulling garbage odors right past them. This would also explain why when the fan is running you are not getting air flow in the garbage room. At 71 floors, if a chute door near the top looses its seal of gets stuck open, the fan is going to pull air from the indoor corridor before it pulls from the garbage room.
I'd recommend adding a ground floor exhaust fan for the garbage room. Additional fan(s) to serve the middle and lower portions of the garbage chute. Add or increase the amount of outside air in the corridors.
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
Tiny leak at each floor's garbage door = all your air.
If all of those leaks are cool, conditioned (dense) air then the leaky air will fall to the garbage room and out the open door, thus "air is return to garbage box".
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
is this an existing building or newly constructed and occupied building.?
RE: exhaust fan not sucking the air from garbage room
A large number of the Garbage chutes installed in high rise buildings are built of short sections of tapered metal tube slip jointed together. There are no fasteners inside the chute and the sections are merely held in place from the outside by the support brackets at the time of installation.
I have worked on these chutes where the sections have slipped allowing air to leak into the duct from the joints. The cure has been to get into the duct on a bosuns chair. secure brackets to the duct, pull it back to its correct position then use truss head pull fasteners from inside the duct to secure it. Not an easy task .
B.E.
You are judged not by what you know, but by what you can do.
RE: exhaust fan not sucking the air from garbage room
There is no any compactor inside the chute, but has a cleaning system which do not make any blockage. There is no any fan control as per the door openings.
If we consider the total effective length accounting door opening effect, maximum required static is .5”wc. As per catalog available 1.7’WC.
RE: exhaust fan not sucking the air from garbage room
How was this flex duct connected ? was it through the garbage door , or was it tapped into the chute through a branch of some sort.
Does your trash chute look like this?
You are judged not by what you know, but by what you can do.
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
I am sorry I do not see any notation or instance of that flex duct I only see the sweeper. Was it supposed to be there?
Now that you have the fan working you can do a better check for leaks.
I am presuming that you have checked all of the access doors .
If the access doors are good the only other source for leaks is the chute itself.
You have seen my prior remarks on that. If you do have to work on the chute, put safety nets in, on the floor above the worker.
It is amazing how some people in high rise buildings can get around lock outs and placards to drop their trash down the chute.
Is there any way you can get into the chase to inspect the exterior of the chute ?
B.E.
You are judged not by what you know, but by what you can do.
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
Good luck , the repair when you find the leak is the hardest part.
B.E.
You are judged not by what you know, but by what you can do.
RE: exhaust fan not sucking the air from garbage room
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: exhaust fan not sucking the air from garbage room
RE: exhaust fan not sucking the air from garbage room
I have had personal experience in High rise buildings, of builders who are doing remodeling, throwing things they are, not, supposed to, down those chutes, including bricks and stones from demolished walls. In one building I had to repair they punched a 9" dia hole through an elbow near the trash compactor.
B.E.
You are judged not by what you know, but by what you can do.