Pressure Relief Valve and Air flow rate conversion

I am considering this supplier for pressure relief valve http://www.air-diffusion.co.uk/PDF/3216 ... dt-web.pdf the D-PRF model. In order to get the right weghted option I am being asked what the air flow rate of the system is. well, of course it doesnt exist yet! I'm considering a Daikin system FBQ35 that has a published air flow of 9 (low) and 14.5 (high) m3 / min. I have a control room (size 9m2) and Live Room (12m2). Can anyone help me with the equation to convert from m3 / min to cfm ? Seems everyone here want to conver to Litres/sec first to confuse me even more. The supplier above seems to think that the air handler is too powerful to get to 100 cfm, so i'd also like to know for a given duct size of 200mm (8 ") would this work In addition, do i need to consider centrifugal fan for fresh air supply ? confused...i am! many thanks for your help John

I found a useful conversion ratio as shown in the image attached therefore unless i'm mistaken, 14 m3 / min would be about 511 CFM. What are the factors in the system design that need t be considered to get nearer t the goal of 100 CFM at the register ? Many Thanks

14m3 is actually 495ft3 (which is volume rate not velocity...) some options for reducing the velocity include: a variable or low speed AC unit which can be set to the desired speed, and/or using a size change in the duct to cause the speed to reduce because you are expanding the duct.

Hey thanks gullfo and sorry for not saying so sooner :oops: So i've actually now got a Mitubishi P Series Mr Slim spec'd at 780 / 600 m3 / hour Air Flow rate (see attached specs) What i'm planning to do is have this unit feed both my rooms - which are approx 9M^2 and 6M^2 (incorrectly stated above) The current plan, from all the research here, is to mount the air Handler via isolation hangers, provide a fresh air feed almost directly into the Air Inlet flange of the handler and about 3M back from that (still on the return side) have an exhaust. I'm struggling to find a local duct supplier who can provide a Barometric relief valve, and i think now that i may have to provide a butterfly damper which i will manually set. I'm not sure this is going to work acctually but its the only way i can think of to avoid building static pressure to the point of no fresh air intake, other than periodically opening the external door. So my question, is there a way that I can roughly work out the size and length of ducting required to keep volume high and velocity low as possible, given the physical contrints of my structure ? Many Thanks John

guys, any thoughts on this for me ? cheers John

last attempt bump :?:

doubling the AREA of the duct reduces the air velocity by a factor of 4. 8" round duct is about 50sq in. 12" duct is about 114sq in. so going 4" more in diameter (if using round duct) effectively doubles the duct size. convert m3 to ft3 multiple m3 by 35.31467 9cmm x 35.31467 = 317.83203 cfm this may help also: http://www.engineeringtoolbox.com/air-d ... d_669.html

Many thanks Glenn, i'll check out the site