Duct Sizing by Equal Friction Method using Varitrane Software 1

[solidspaces]

The ducting from our Air Handling units goes all the way to the VAVs and from there to the diffusers. Each VAV serves about 4 diffusers in the rooms.
We are using Trane Company’s VARITRANE equal friction duct sizing software for the design. There are a couple of difficulties being encountered.
According to one option in the software, we can input the data of all the duct sections till the VAV. The software assumes this to be the end point of the ducting and it does not generate duct sizes downstream of the VAVs.
The other software option is to input all the duct sections right up to the diffusers, but in this case there is no option to input the VAV data or its insertion loss.
Please advise how to circumvent this problem.
Another problem is that the program generates the duct sizes of the critical path and asks if the noncritical path should be resized. We would like it to resize the noncritical path branches to benefit from the smaller duct sizes that will result, but we would like to provide volume control dampers in the beginning of each noncritical branch to have some means of adjusting the air flow.
Any feeback will be appreciated.

 

[cry22]

I'd stay away from such software, it is hardly reliable.
Take Trace 700 for example: It is what it is today because users like us keep sending questions regarding all sorts of bugs and ask for some wish lists to improve the software. Trace is at 30 years old and it is still full of bugs and keep being updated every year to fix reported bugs by users.

Varitrane is hardly used by engineers, this means that the software is weak, does not have input and feedback from users to improve. It is therefore unreliable.

 

[willard3]

Learn to do your own duct calculations.

I've been doing this for a very long time, and the largest and most common mistakes I have seen concern air systems.

 

[solidspaces]

Thanks for the replies.
Sizing manually using the ductulator is a breeze, but there are 145 AHUs whose ducting has to be sized. It is simply not feasible to play with the ductulator as it would take ages to do hand calculations.
It comes as a surprise that the software of a reputed manufacturer like Trane has not been debugged before release.
The Contact Us page of Trane however needs to be debugged, because the comments box on their web form does not come on. Even thought it is visible but is switched off.
WEll I will try to find Trace 700
Thanks

 

[Drazen]

You can differ ducts downstream of VAV's from those upstream by applying diversity factor upstream (upstream should be 1.0). If, however, you have lot of VAV's and need to check minimum entry pressure for all, than solution is to make separate ducting systems for upstream and downstream ducts.

As downstream piping is small, it is possibly simpler to calculate that part manually. I don't do that, as putting all ducting in software gives me accurate bill of materials and other statistical stuff, all in one project file (that's the main reason to use software at all).

Putting your dampers is as simple as putting constant pressure drops on duct sections where dampers are to be installed - every software should have such an option, and pressure drops have to be obtain from damper data sheet. Software should also give you some balancing report, which assists in dampers sizing.

 

[Drazen]

ah, sorry DOWNSTREAM should be 1.0

 

[tcihvacff1]

Try McQuay Ductsizer