Just finished installing our system on my second clean room. Both systems were Trane and running 2 inch static pressure. We had merv 13 filtration for a pre filter our UV/PCO system in the middle and HEPAs next. We treated both the occupied space and the fresh air at the mixing box. One is where they make stints in Juarez Mexico and the other is a pharmacy in U of LH in KY. Just another HVAC system with more air changes higher filtration and higher static pressure. Nothing to loose sleep over
Just like what was previously said, "Cleanroom" is a very broad term. A true clean room has a room cleanliness classification associated w/ it. The old Federal Standard 209E & ISO Standard defines the number of acceptable airborne particles per cubic foot. The largest particles are the diameter of a human hair (3 micro inches)!
Clean rooms range from 12-600 air changes / hr. Also room pressure differentials need to be considered to keep out particulate from adjacent spaces. Most cleanroom applications involve semiconductor, electronics, and pharmaceuticals manufacturing and have tight temperature and relative humidity tolerances (+/- 1 to 2 deg F) .
Oh & by the way, the owner mostlikley will be monitoring particulate counts, temp & RH. These parameters are probably critical to the quality of product he manufactures. So if you inadvertently f-up and he has to throw out product because of your negligence...guess who he's coming after? Check your insurance policy, betcha it doesn't cover design related claims.
I am not trying to underestimate your design skills, but the point is unless you know what your doing, I would not attempt to design the system. There are clean room companies that do it for a living...stick to your skill sets, whatever they may be.
Thanks for the responses.
The thing is, it's a good customer, I'll find out the deal is and decide if I want to get involved or not.
If he has some fancy schmancy parameters then I will most likely pass.
I got enough problems with my skill sets as it is.
Had a meeting today with a aerospace company that makes components for airplane cabins, they have been having a real problem cooling the room. 2100 square feet, 75 ceiling mounted fan powered HEPA filters, 6 tons of cooling and they can't keep it much below 75 deg. on cool days, AC system runs non-stop. The set up is the return and supply both go into the ceiling space above the fan powered HEPA filters. the Hepa filters pull that down into the room and recirculate it through side wall vents that let the Hepa filters pull the air back up to the space between the ceiling and roof of the clean room.The problem they are having is to much presserization in the room the number of fan powered HEPA filters are pulling to much make up air into the room and continually flush the cooled air out of the room. They had a crew from Clean Rooms Int. spec. the room out and erect it. The AC system was put in and sized by a local contractor and there lies the problem . No spec was given to the size of cooling unit needed the amount of make up air that would be introduced or any exact values of the contruction of the clean room for sizing purposes. If you were given exact spec's on what to put in and how to install it I wouldn't be hesitant in doing the job , if they want you to size it I would decline unless an engineer from the clean room mfg. would sign off on it. JMO
Good to hear from you agian on this forum! You are one of the founders. I have enjoyed the past HVAC Newsletter's you have authored.
I have winged a setup inside certian type of clean room that used formaldehyde and had great success! but, only after the design engineer could not get it working properly.
The lab hired a outside engineer and another installing contractor. After over two years of constant technician over expose to formaldehyde, as the people in the lab wore badges that changed color due to warning of over exposure.
We changed out the system completely with a 100% outside air with a equal exhaust system. Dehumidification with electric reheat and hot gas bypass. This was in Florida, so very high heat load and humidity during 8 months of the year. We maintained inside 72 F at 45% to 50% humidity at all times.
A 30 ton Carrier condenser with unloaders and hot gas bypass on a 5 ton air handler with several stages of reheat. Used Johnson Control temperature and humidity controls, that we custom configured.
This setup has ran over 10 years with no problems, other than the solid state compressor protector every now and then after electrical ( lighting) storms during summer, would cause a major malfunction. We keep a replacement solid state on hand after two such events.
I would suggest telling the good customer to utilize a engineer of their choice to design the system, but allow or recommend you to install as per the design engineer recommendations. After that is over you can either work with the engineer to work out the problems or you can save the day by figuring out what additional need's to be done!
>set up is the return and supply both go into the ceiling space above the fan powered HEPA filters. the Hepa filters pull that down into the room and recirculate it through side wall vents that let the Hepa filters pull the air back up to the space between the ceiling and roof of the clean room.
That’s what I have typically seen in clean rooms. FFUs just re-circ the air that the AHU pushes in the ceiling space.
>The problem they are having is to much presserization in the room the number of fan powered HEPA filters are pulling to much make up air into the room and continually flush the cooled air out of the room.
Shouldn’t have anything to do with the FFUs, they just move air to the room from the ceiling and back. The AHU should be the only way any makeup air can be introduced. Simple test. Shut off the AHU and check a door. If the rooms go neutral you know it’s the AHU. The clean rooms I worked on try to hold 0.01” – 0.02”wc in the rooms, nothing to crazy. These where pharma sites, aka FDA approved meth labs.
Get a TAB contractor qualified for clean room work out there. Assuming the AC is the right size, a good balance should fix it.
generally most clean rooms that i have installed & worked on were sized at 200-250 cfms per ton & 1 cfm per sq foot, with head pressure controls, unloaders, & a hot gas bypass.
this would calculate in a cooling load of approximately 8.4 to 10 tons. other incidentals would be occupancy & equipment load. this is just a ballpark figure. i'd have to input it into a computer program at work to verify it. sounds like mech cooling way too short.
Who designed that or did ya just wing it?
Are you bringing in 15% fresh air?
Design is driven by the process used within the room. Get specs from someone who's got the clean room credentials the customer trusts.
We did a couple for Rx and they were a bit sophisticated, validation, etc.
Wing it should not be in your vocabulary on clean rooms.