Steve, Give me a call later this afternoon. Fred Golisano [log in to unmask] (408) 557-7039 ______________________________ Reply Separator _________________________________ Subject: [TN] ASSY: Exhaust Fans, Ducting, and suck power... Author: "TechNet E-Mail Forum." <[log in to unmask]>, at corp Date: 5/6/98 6:05 AM Hello Technetters! I've got a problem that hopefully somebody can teach me a little=0As= omething about. It has to do with exhaust requirements and our Trek Trito= n IV=0Athat we'll be getting in a week or so=85(at least I got that make-= up DI water=0Aissue taken care of...thanks to all of you! The next problem is; I just got the quote for the exhaust duct-work = that=0AI need to get done, I gave it to my boss, who then promptly had a = cow. What the moo'ing was all about is that the quote is around 11K. Both= he=0Aand I are having a hard time understanding why the company is quoti= ng us a new=0Aexhaust fan to replace the one we already have up on the ro= of...and yes, it's=0Astill there after the day before yesterday (we're in= Sunnyvale, California=0Aabout a mile or two from where the tornado was).= I should probably describe what I currently have, what equipment I'm= =0Agoing to be exhausting, and what the quote is actually for. I wanted to exhaust 4 machines from one exhaust fan up on the roof. = There=0Awill be a Heller 1700 convection oven which the specs say I need = 500 cfm, a=0ASoltec Prisma wave solder (I can't remember what kinda' suck= it needs, the=0Aspec is on my desk at work), a waste water evaporator co= ming off a ultrasonic=0Astencil cleaner (which has it's own exhaust blowe= r rated at 1600 cfm so it=0Areally won't add a whole lotta load), and las= t but not least our Trek=0ATriton...and that seems to be the culprit behi= nd the big buck expenses. Trek spec's say that it needs a -1.5 in. hg. negative pressure in th= e=0Aduct, the HVAC company that quoted us says the fan we currently have = doesn't=0Asuck enough, but I think it sucks pretty good. They want to com= pletely replace=0Athe fan we have which means a crane rental, and cutting= a different hole in=0Athe roof with all the associated work that goes al= ong with that. Before we had the company quote our duct work, me and our facilities= guy=0Achecked to see how much the fan we have sucks. We went up on the r= oof and=0Achecked to see what kind of unit we had. It's a Dayton unit, so= we checked=0Awith Grangers (they sell Dayton), and based on a 2-hp, 1725= -rpm motor with a=0A3.5" dia. pulley, and a 24.5" centrifugal ventilator = type fan with a 9"=0Apulley, they said we would get around 5700 cfm which= we thought was plenty,=0Abut they never mentioned anything about negativ= e pressure...we didn't ask=0Athough', I was mainly concerned about cfm un= til I was told that the fan needed=0Ato be replaced. This is the first time I've been aware of a negative pressure requir= ement=0Ainside the exhaust duct of any equipment that I've worked with...= but I only=0Aknow enough about ducts and exhaust fans to be dangerous. I = know that if the=0Aexhaust system isn't set up correctly, you can have al= l kinds of process=0Aproblems, that's about it. The company that was in this building before us, left the exhaust fa= n and=0Aa good portion of the duct work up, and they were exhausting 4 re= flow ovens, 2=0Awave solders, and a ultrasonic stencil cleaner evaporator= . I know that because=0Awe found a layout drawing of the production floor= they had, plus I also knew=0Asome of the people who worked for the compa= ny that was here. So that's adding=0Ato my confusion of why we need a dif= ferent type of exhaust fan. The only horizontal duct runs from the main manifold will be to the = wave=0Aand the reflow, the moisture laden exhaust from the cleaner and ev= aporator=0Awill be making more or less a straight shot up through the roo= f as they will=0Abe located beneath the exhaust fan...that much I know ab= out, you don't want=0Aany chance for the moisture to re-condense inside t= he duct and start=0Acollecting there, or to start to run back inside the = machines. So what am I missing? I've kinda' heard that this could be the case = of a=0Aunion shop just charging us way too much, but like I said, I'm not= a guru on=0Athis stuff. Can anybody enlighten me? Thanks again!!! -Steve Gregory- ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################