Fan Static Pressure

[herschmidt]

Hi All:

Where I can find the static pressure of diferent kind of air handlers and roof top unit?
I tried Carrier, Trane sites but I didnt have luck.

Thanks for the inputs.

Hernan

 

[blutfort]

That information is typically in the RTU/AHU catalog. For example the York data is available at

http://www.yorkupg.com.

In the catalogs you will find fan curves for the different peices of equipment. Trane has that data available at

http://www.trane.com

in their catalogs also. I just verified the availability at both sites.
The data isn't always available as a plain old fan curve however. Often times it is just a table of BHP and RPM at different CFMs and Statics.
Some manufacturers conceal the data from the general public and you may have to request a copy of a catalog if you are looking for a specific line and manufacturer.
My guess is you are looking for something specific, but asked a general question. So I feel I haven't really helped you any.

 

[herschmidt]

Hi blutfort:

May be my question wasnt clear enough, what I'm trying to do is design a duct system, so the first thing that I need is the load calculation (I have that) and the CFM that I have to deliver to each room, what I need now is the static pressure of the air handler or unit at the design condition ( Im using a 7.5 ton unit rooftop), in order to make the duct design.

Thanks for your input and I will try those site again.

Thanks.

Hernan

 

[blutfort]

Hernan,
Here is a direct link to the catalog for the Trane 3-10 Ton Packaged RTU's.

http://www.trane.com/CPS/Uploads/UserFiles/DXUnitarySystems/Light Rooftops/RT-PRC025-EN_03012007.pdf

Fan performance tables start on page 46 of that specific catalog.
If you go with York you are going to want to select the Predator line I believe.

No what's confusing me is what you are claiming your next step is. If I had the cfm to each room and the "equivalent" length of the runs, I'd then get out my "duct-u-lator" and begin sizing duct to meet my spacial needs.

Most off the shelf RTUs are going to be hard pressed to support more than 2.0 "wc of external static pressure at nominal CFM. Depending on the size and the casing you might be not be able to get more than 1.5.

 

[marcoh]

I think you should be designing the duct, calculating the pressure required for your duct design and then select the fan to do the duty you require. For a typical installation, a typical unit should provide enough static pressure.

Suggest you contact your local sales rep and they will give you all the info you want.

 

[atlas06]

You sound like you know enough to be dangerous.

I think Mr or Mrs Schmidt is looking for a way to calculate duct losses thru duct system. Those manufcaturer sites will not size your static pressure for you.

Use 0.1"/100' of ductwork if that is waht you really need, look up some table for elbows (just add 50%), add your volume dampers, supply registers static pressure, outside louvers, filters, casing, system effect, return air ducowrk, RA volume dampers, registers, cooling coil, heating coil, etc.. and any other component you may have in your system such sound attenuators, and some safety factor for bad workmanship.

Mr Schmidt, as you can see, the losses are not just from your ductwork, you should not be trying to be a Mechanical Engineer. You are an electrical engineer, stay that way.

Just from your question, one can tell that this your first shot at HVAC design. You could use some serious guidance. I would not trust your calculations at all, let alone your system choice. I doubt that you have looked at ASHRAE 62, 90.1, IMC requirements for ventilation and so on.

As a mechanical engineer, I never tried to size a switch gear even if I feel that I could take a shot at it.

 

[herschmidt]

Mr atlas:

I tough that this is a forum where people can ask question and some people answer those question. I think it doesnt matter if you are an electrical or mechanical engineer, what it is important is try to resolve the problem.

Thanks for your imput and for your advice, but I think that asking and studing about this topic i can design the ductwork that I need.

I saw a lot of mechanical engineer sizing ductwork using the 0.1"/100' of ductwork when they dont know what is the static pressure of the fan, so if you dont know this value how you can use this friction rate, Am I rigth or wrong?

Thanks Hernan Schmidt

 

[willard3]

I'm with Atlas, get a Mechanical Engineer to do the job....you will muck it up because of what you don't know and have to hire an ME in the end to fix it or the bonding agent will......

Do you want an ME doing AIC on main breakers after an exchange on a web board?