I understand your post, I need to learn more about the design of residential hvac systems.
When designing a new system are you trying to reach a certain static pressure? Is it according to the units' design static pressure and will the information be found on the unit itself?
Are there quick equations to calculate the friction loss of ducting over 100 feet?
I really appreciate your time and sharing your expertise with me. Thank you very much.
The static pressure of a system of ductwork and diffusers is dependent on each individual system. You're not trying to reach a certain static pressure, you just want to make sure that the fan can provide more pressure than the system needs.
Example: Your longest ductwork run in your house has 200 linear feet of ductwork, and 10 elbows (you care about the worst case scenario, longest distance linearly, most elbows, etc). If you use your Trane Ductulator as mentioned in previous posts (I have one on my desk and use it just as often as Mr. lkapigian) and you size all of your ductwork to a friciton loss of 0.08 per 100ft, then you will have a total of .24" static pressure drop on your system due to ductwork. (200 linear feet = 0.16, typically we count 1 elbow as 10 equivalent ft, so another 100 ft worth, gets you to .24") You need to select your fan with .24" ESP at a minimum, but you also need to account for a filter at around .125-.2, etc.
Like was mentioned, typically residential is around 0.5" ESP, however I've only done a residential design once, and I went with 0.75" as I had a little bit longer runs, etc. (I also grew up in a house where the air never made it to the 2nd floor, and I was the only one up there, so I over shoot ESP slightly to make sure there's no little boy sweating his balls off in the summer time)
You always select your fan to "overcome" the static pressure of the given ductwork system.
Edit: Something else. Whoever you're buying your equipment from, they will have a cut-sheet of the fan coil you're using, and there will be a fan chart in there telling you how much cfm and at what static pressure you can get out of the fans. Usually, for a house, we select the equipment based on the cooling load (unless you're in Canada, then maybe you care more about heating load) and usually the fans will have enough ESP to handle it. I'd find it hard to believe you're system would require more than a half an inch, an would be willing to bet it doesn't.
Also, something else to note, your longest run, you will need to account for your diffuser/grille at the end, they tend to require around .1" of ESP. (I just opened my Titus catalog, your standard wall diffuser with a 22.5 degree deflection kept under NC20 requires 0.074" of ESP.
Having clicked on your previous heat pump sizing chart I was a little afraid to click this link, lol.
But really, that's a pretty good resource. It reminds me of SMACNA, which is also a great resource for helping to calculate equivalent lengths, etc.
Edit: Holy smokes, upon further inspection, this damn thing would have helped me 2 weeks ago when the SMACNA book didn't cut it. I was looking for a proper take-off for an extremely tight cell chase in the housing block of the jail I'm working on right now. This bad boy's getting saved for later use. Thanks for that!
I should take a photo of mine. I've had it for so long, that it is about completely worn out. It's never had the luxury of seeing a desk, only a service van.
Originally Posted by lkapigian
next to my calculator, my ductulator sits and gets used everyday...it is an important tool so few have.....it is not only for designers, but for an educated technician and installer
I couldn't help it. I just had to print out the Air Conditioner or Heat Pump Sizing Chart and cut out the holes. I think I need page two.
Either that or a bigger front yard to put the curb further away. I've currently got a three ton A/C, and my house wouldn't fit in the 4-5 ton cut-out. I probably need to upgrade to 7.5 or 10 tons to be properly sized.
I couldn't help it. I just had to print out the Air Conditioner or Heat Pump Sizing Chart and cut out the holes. I think I need the second page.
Either that or a bigger front yard to put the curb further away. I've currently got a three ton A/C, and my house wouldn't fit in the 4-5 ton cut-out. I probably need to upgrade to 7.5 or 10 tons to be properly sized.
Yup, you are undersized....make sure to print the page in full scale to avoid errors
Couldn't help but photo my Ductulator. Just try and tell me that baby hasn't been around the block a time or two.
Saw a brand new one on someones desk a year or so ago. It was so pretty. I had this urge to steal it. It was weird. Because I'm not a thief. And it cost less than a Jackson. And easily available. So to steal it just made no sense. But I still wanted it.
Anyway, mine still works; heh heh.
Might buy a new one just because they are so pretty . . .
Couldn't help but photo my Ductulator. Just try and tell me that baby hasn't been around the block a time or two.
Saw a brand new one on someones desk a year or so ago. It was so pretty. I had this urge to steal it. It was weird. Because I'm not a thief. And it cost less than a Jackson. And easily available. So to steal it just made no sense. But I still wanted it.
Anyway, mine still works; heh heh.
Might buy a new one just because they are so pretty . . .
awesome, can't see the picture on my phone will check it out tomorrow
BBeerme, just call your local Trane rep?? When I switched jobs 2 months ago, I left mine at my old firm because when you get laid off, you basically run out the door. I have a nice new shiny one on my desk here at the new office.
If you work on/with Trane consistently, they should send you 5 of em...
Hmmm, interesting thought. Maybe I'll try that. Hard to imagine our local branch would give one away, especially when they're on the shelves with the other parts to be sold. But I've got a 'relationship' with them now. At least relative to when I bought that one in the photo somewhere shy of thirty years go.
If I wear out a tool, my employer will replace it, so I'd love to go that route and just put it on one tag or other for some job. But it still works.
It's just not as pretty as those new ones.
Originally Posted by stevereigh
BBeerme, just call your local Trane rep?? When I switched jobs 2 months ago, I left mine at my old firm because when you get laid off, you basically run out the door. I have a nice new shiny one on my desk here at the new office.
If you work on/with Trane consistently, they should send you 5 of em...