I am working in a recreation center and there is a bed humidity problem in the combination shower/locker room area. There is a rooftop ventilation fan pulling out air and there is a small 8x12 supply air vent in the area also. Question is does this area also need a makeup air unit or is it standard practice to use only the exhaust fan... Granted the return air grilles are filthy and they need to be cleaned but I was just wondering what else do I need to be looking for as a cure to the humidity problem... For return air from the room there is a grille also on the door that leads to the restroom and then it is further transferred to the AHU by means of another door leading to a hallway. Any help would be appreciated
The grille in the door is a transfer grille not a return grille.
The exhaust rate from the locker room should be greater than the '8x12' supply air. The locker room should be 'negative' compared to what is on the other side of the door with the tranfer grille so air should pass through that door grille into the locker room. There should be no returns from the locker room, just supply and exhaust.
You should check what the required exhaust rates are in your area, it could be so much air per toilet/urinal/shower or perhaps 2 CFM exhaust per square foot of the locker room. The minimum amount of exhaust depends on your local codes.
The HVAC system should be bringing in fresh air to replace the amount that is being exhausted.
The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.
Sounds like you need to scrap that system and put in what is mostly used in the industry for that application which would be an outside air heat recovery unit with a desacant wheel.
Here are some pics of theory...lots of companys make them now. You can add a desicant wheel that turns real slow that dehumidifies the air. As the wheel turns, the desicant is rejuvinated by passing warm air over it on the opposite side....lots to explain but I am in the middle of watching the colts and steelers in the playoff game......
I have a much cheaper solution, and will save you money also.
Turn down hot water temp to about 80 deg!
I'd see if I could find the blueprints for this locker room.If there are no specs. on the M drawings take a look at the E pages for the fan schedule.Find out the cfm capacity of the exhaust fan, and make sure there is a provision for make up air. There is probably at least a grille intended to supply air to the exhaust fan. Your local bldg dept has standards for this application,it may be the standard mech code or they may strengthen the code.Measure the cubic feet of the entire area exhausted -Length x width x height.Then find out how many air changes are required for a locker room in your locale. Remember, the fan capacity is expressed in CFM - cubic ft per minute-
Do the math and see if the fan is doing the job.
Let's say the room is 12'000 CUBIC ft. and the fan is rated at 2,000 cfm, well you're gonna get a complete air change every six minutes, or, 10 air changes per hour.
See if the make up grille is the correct size. Say, 40 SQ inches per 100 cfm,just shooting from the hip.Make sure nobody put window screen over it to keep out the heffalumps when they go to gallopin' as we see them do down Texas way during the dog days.Take off the window screen and put up some half inch hdwe. cloth.
Go up on the roof and check the drive sheaves and belt.The drive sheave is probably worn from a vee to a U and they don't make U belts anymore, so change it. It's probably a VP so make sure the drive and driven sheave ratio will make the fan move the required amount of air.
A make up air fan is better as MA grilles get clogged and kicked in,causing the exhaust fans to take air from elsewhere..like your nice conditioned office space air.Put an Ma fan in and keep it away from the flippin plumbing vents. Set the exhaust to pull a bit more air than the MA fan is pushing so your room runs at a slight negative like the previous post said.It keeps the odors moving from a less desirable to a more desirable place.
And thats just a bit of what he "V" in HVACR is there for.
Leave the Wheels to Ezekiel for now. I hear Texas is already dry as cracker juice.
"Iron sharpeneth iron..."
now that's funny and so true
If it ain't broke don't fix it!