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Apparently there are some very sensitive readers on this site. With respect, tombmech, I did acknowledge your website suggestion when I was writing my original response, but deleted it in my rewrite and neglected to put it back in. I had in fact already visited this website before your...

Thanks. I've been to the website and it has a lot of good information. I'm also going to attend Fred Bauman's daylong course at the ASHRAE show in January and hopefully learn a bit more. I'm a little surprised that the air flow is that much less than a conventional system. I realize that the...

I've heard this response before. I'm wondering if the air flows calculated for S/A at 55F will be the same for 65F for underfloor. This may be so, as cooling loads in the occupied zone will be less, i.e. some of the lighting and wall loads don't reach the occupied zone and will only serve to...

Has anyone found a software program (or other method) that will calculate cooling loads in the occupied zone using an underfloor air distribution system?

Does anyone have information on the efficiency of glycol run-around coils for heat recovery on air systems? I've heard around 50%.

Quark, Let me know what your email address is and I can send you a copy of the the ASHRAE article that discusses this issue. Chims

Amen to what Lilliput1 said. When you're in the oil and gas business, you're dealing with millions of lost dollars per day if the system doesn't work. O&G companies are willing to put the money into the design up front rather than field fixes. In the HVAC business, we're quite often dealing...

Correct. That's where the challenge lies and maybe where this whole thing falls apart. That's why I was wondering if anyone has ever done it before.

Mint, I don't disagree with your analysis, but I am still supposing that the pressure in the system is constant to guarantee the delivery of 10,000 cfm. This could be by dampers or VAV boxes or whatever it takes. Yes, the pressures upstream of the fan have changed, but I can make changes...

Mint, I don't think I've explained the conditions clearly enough. Given a hypothetical fan delivering 10,000 cfm at a specific pressure. No return fan and the O/A duct is sealed tight. Therefore 10,000 cfm in the return duct at a specific pressure. I need 1000 cfm of O/A and 9000 cfm of R/A...

Thanks for the input, Mint Julep. Airflow varies with the square root of the pressure. If we know three of the variables we can calculate the fourth. By knowing the air flow and static pressure at a particular point in the system(i.e. the return airflow and static pressure) I can now...

Has anyone ever used static pressure as a method of determining airflow? Example: Seal the outside air damper up tight, so the return will equal the supply airflow. Measure the static pressure in the return air duct at the inlet of the AHU. Then use the fan laws Q1/Q2=square root of (P1/P2)...