Ceilings falling

Sounds like the condensate isn't draining (gravity drainage) or the condensate pump (if fitted) is broken/badly fitted/inadequately sized.

Get A/C guy back to sort it...

Del I have check the sump under the evaporator found not problems there. Drain is gravity and is clear. Even got condensate on the drain line due to the cold air being force through it.

Ah..I think I get it..

The A/c unit is probably just working on the air below the false ceiling...so the Air above is still humid and therefore condenses on any cold surface...

Maybe you need to circulate air though the space above the cieling too...maybe a dehumidifer rather than just A/C? Running out of ideas now..

Just a guess...but it's possible

yeah - I'd try using a fan to circulate the cool air below through the area above the ceiling. And maybe supplement the AC with a dehumidifier if it's not sufficient by itself.

This is a common problem for the first year of a concrete structure's life. There is a lot of trapped moisture in the still -curing concrete. Ventilation of the space will rectify the problem.(circulation of the conditioned air from the living space below or ventilation to the outside enviroment

i suppose to control Humidity AC is provided Then it may not work ,you need to achive low air temperatures with out moisture for whatever process you are working Find out what is the humidity specification for your process,then depending upon your process requirements you have to achive the same .the soluation for your problem would be you need to check if the AC unit installed is for comfort cooling or process cooling.If its for comfort coling and out let air temperature of air is set low to dehumidyfie the air ,then you will have the problem for life.you may need to take deeper look at your problem.

crm

Insulate all cold surfaces in the attic including your ductwork.

I have a similar problem. in a very large space (9000sf or so). However, the space above the ceiling is used for return air. In theory there should be no condensation. There is a metal roof deck above. I am getting all sorts of condensation and it is difficult to find where it is coming from. I may find a VAV box with a little and a duct piece here and there with some. I found the roof drain gutter ( which was built so it was not visible) was leaking. I am checking the joints between roof and walls to be sure they are sealed properly and checking the operation of the outside air damper and the amount of ventilation air into the system. I have had my head above the ceiling in heavy rain to see if the roof leaked any where. I wonder if the roof (metal standing seam type) is insulated properly and the vapor barrier is in tact. I found some pipe with bad insulation and a few other things but nothing that would account for the extensive problem. I put temperature and humidity recorders above the ceiling to track temp and humidity and found the humidity to be very high. To make matters more interesting I have another building next door constructed the same way at the same time and there is no problem.

ozzub,

It is possible that the AC unit may have been improperly sized for the space. An oversized unit will cool the air down to the target temperature too rapidly for the air to be adequately dehumidified via condensation forming on the chiller coils.

However, the other issue is likely not only inadequate insulation on the air supply ductwork, but an improper vapor barrier either on top of, or integral to the duct's insulation.

Just throwing some fiberglass batting or pressed fiberglass boards on the ductwork won't do. Fiberglass (without a built-in vapor barrier that has all seams properly taped/sealed) doesn't keep out moisture, it acts more like a sponge in fact.

You might want to look into installing closed cell neoprene type insulation (e.g., armaflex)

You have to figure out where the moisture is coming from. Is it from outside make-up air or the process? I would think that moisture from the new construction would not be very significant -- but should be considered.

Usually humidity problems arise from ventilation air. For your area, on a humid day, ventilation air could carry more than 80 grains of excess moisture per pound of dry air. Assuming 6 outdoor air changes an hour, in 24 hours, for a space 30' x 50' x 10', this would amount to 225 gallons of water that has to be condensed and removed from the ventilation air daily -- this is about 9 tons of cooling load to condition the outside air.

If the moisture is coming from ventilation air, then you have to dry that source of air better. The common solution to humidity problems is to mechanically cool ventilation air to below 55 F. Reheat the ventilation air with the condenser hot gas, if necessary, to avoid overcooling the space. Then mix the ventilation air with return air with further cooling if necessary to meet space temperature requirements.

If it is the process that is adding most of the humidity to the air then some other means of dehumidifying the recirculated air stream is needed. The simpliest would be an air handler with a cooling coil that is kept as cold as possible and space temperature is maintained with a face and bypass damper around the coil. For a clean room a desiccant system may be the solution. They give very good humidity control and are often used for systems that need clean sterile air and very good humidity control.

If you have a drop ceiling, the moisture content of the air above the ceiling will tend to be the same as in the conditioned space, when measured in grains of moisture per pound of dry air. Unless there is an impermeable membrane in the ceiling, vapor pressures will tend to be equal between the ceiling space and the conditioned space. The celing space may also be a plenum -- the path for the return air. If the supply air to the space is colder than the air temperature that can support that level of moisture, the ducts will sweat, unless they are properly insulated.

There is another option though it may prove a little more costly than insulating all cold surface's which can be a slow process of elimination for the problem. Consider converting the system to an updraft system. Installation of a false floor with porous characteristic's may prove the best. The false deck can be as little as 1" in added hight , can usually be installed with little or no production interruptions. Just wait to redirect your existing ducting till once the new floor is installed. Depending on your layout you may even be able to eliminate most of your existing ducting for that room and reduce overall unit efficiency and load on the AC unit.

Howetwo is right on! All of the duct insulsation and other fixes will just be luck if the source of the moisture is not identified and controlled. You mention that you need to control the moisture for your process and a big hole in the wall and a lot of traffic in and out. These are moisture sources and need to be addressed. Air curtain fans, strip curtains or air lock entries may be needed to control the entry of new moisture, then duct insulation has a chance to do it's job. -- JHF

You said "a clean room". Yet from all indications, i.e., a lot of traffic in and out, a large hole cut in the wall, condensation and falling ceiling tiles, I'm curious as to what specifications your clean room is required to meet.

According to Federal Standard 209D cleanrooms are contamination free environments for manufacturing and assembly. They range in size from small chambers to large scale rooms.

There are a number of points to consider while determining which cleanroom type fits the application. These include the cleanliness class, filtration, laminar air flow, construction, temperature and humidity control (essential for ESD control), and special features such as positive air pressure, pass throughs, personnel entry/exit air locks, and gowning areas.

Federal Standard 209 D defines the classes of cleanrooms and provides a qualified, standardized method for measuring the airborne particulates in a cleanroom.

The six classes of clean rooms established in Federal Standard 209D are; Class 1 (ISO 3), Class 10 (ISO 4), Class 100 (ISO 5), Class 1,000 (ISO 6), Class 10,000 (ISO 7), and Class 100,000 (ISO 8).

The class number refers to the maximum number of particles larger than one-half of a micron that would be allowed in one cubic foot of cleanroom air. A Class 100 cleanroom for example, would not contain more than 100 particles larger than half a micron in a cubic foot of air.

Perhaps this information will give you some useful rational when approaching management with costly repairs to the clean room and it's air conditioning system.

If you have condensation on surfaces within the room then the air at thhat point is at the dew point. Use a wet and dry bulb "sling" type hygrometer and establish the wet and dry bulb temperatures inside and outside the room. Look up a pyschromatric chart (your AC guy will have one) and compare the DEW point inside and outside the room. Unless there is a significant difference 8-10 degees C your Airconditioning is being swamped by the ingress of outside water vapour.

A de-humidifyer is a better proposition.

The temperature of the room does not matter - only the dew point.

Secondly - take a sample of the dessicant just before you seal it in the glass envelope. Seal it carefully and ask your supplier to test it for water content and comment. If the "dryness" has been used up you may have to re-dry your dessicant (in a proper ventilated dryer) immediately prior to use