Getting in the Flow with Revit HVAC

Been spending some time trying to get more into the sizing part of duct for Revit… we’ve been working on a project for a client that required well formed systems.  When I turned the duct systems checking tools on, I kept getting some really nasty little errors that I couldn’t figure out…and a couple of items that should work, that didn’t…at least from my understanding of how duct systems should be defined. So here’s the notes from what I learned.

         Regardless of whether the program can define a system when adding  a duct or not, I found that systems normally aren’t “well connected” when you follow this method. I’ve gotten repeated errors, that I believe came down to how I was adding the duct.  The safest method for defining a system and getting the duct sizing results needed, is to create the system first by selecting the targets, such as air terminals. Selecting the source equipment (such as a VAV) once you’ve defined the duct system usually creates the most stable system, and results in the fewest errors with the data tables.

         This includes upstream systems, such as the primary air supply to the VAV boxes. One big issue we’re having with vendor provided air handling units is the lack of good, clearly named connections. No matter who the vendor is, open the family up and put in a connection name, such as primary supply or return air intake. This way, when you are defining the upstream systems, you can select the correct connection even if there are multiple connections.

         The biggest problem I ran into happened in regards to the flow direction settings at the connectors. In order for a system to be sized correctly, the source (such as the VAV box) should have the flow direction set to OUT, and the Flow Configuration set to Calculated:

  

         A loss method should also be specified – so if you set this to specific loss, make sure you put a value in here – leave it at 0 and you’ll get an error.

         The reciprocal is on the target, or air terminal. Check the flow connection, and make sure it’s set to In for supply air, and leave the flow configuration set to either preset or system. The default air terminals are set to Preset, but you can change this. If it’s set to Preset, flow factor is disabled, and you can set the loss method to coefficient or specific loss. As with the VAV, if no value is set for specific loss for pressure drop, you’ll get an error.

          
When using the Calculated/Preset combination, the airflow for the equipment is set to match the total airflow assigned to all components downstream. If you have 10 diffusers at 50 CFM, that means you’ll have 500CFM assigned to the VAV box as the calculated value in this configuration.

System flow configuration is a little different – instead of using an aggregate airflow total from all diffusers, the system will calculate the equipment airflow based on a percentage allocated to each air terminal.  If you set the flow configuration to System, and have the loss method set to specific loss, you can specify a flow factor (using a factor between 0 and 1 – with the total of all air terminals equal to 1):

If the loss method for a system flow configuration is set to Coefficient, then you can also set the loss coefficient value for the connector itself(and pressure drop will be disabled):

As with the specific loss method, if you leave these values set to 0, you’ll get an error.

Be aware that Revit already has a loss coefficient tables defined for fittings, based on ASHRAE  Duct Fitting Database, which assigns a loss to specific fittings and accessories. By assigning a coefficient directly to the air terminal, the Equal Friction/Static Regain methods for duct sizing will return better results.

If you are using specific loss, I’d recommend using a shared parameter for that value, so it can be changed without having to directly edit the connector in the family. Use the Associate Parameter tool to add the parameter. By using a shared parameter, you can also include this as part of a schedule or tag.

Here's the help file's description of what each of these settings is for:

This should help you a few of those nagging duct sizing issues - have a great day!

David B.

Wrapping up on 2012, and getting ready for 2013

Man, what a year...we're seeing more and more projects based in BIM, and our staff continues to improve on their skill sets. Overall, despite the lingering tough economic conditions, we keep pushing forward and working to improve on the gains we've already made. Looking forward, next year should be an improvement, now that the election is past. But that doesn't mean we can go back to our older methods of producing projects.

We had a great conversation with one of water guys about BIM, and we talked about the issues we expose are not necessarily tool-based, but more design workflow based. CAD gave us a great ability to "hide" flaws in the design process, but BIM kicks the rock over and exposes all of the weakness you may have in a design. It's up to the project engineers and designers to get back to making sure their designs work first, and a 3D model really demonstrates this well. So next year will include more training for that level of employee, that will hopefully help alleviate fears about change, and keep them moving forward.

So here's my look back and look forward:

Autodesk University 2012 - this year, the crowd was really energized and wanting more. One of the general feelings I get now is that we can't rest on laurels from previous classes. Yikes - the students are on to us, and we (the instructors) really need to raise our game for next year. For the first time, it felt like the crowd had a better understanding of the basics of BIM, and fewer of the fears. The AU crowd's adoption of technology was very obvious. When I stepped out from behind a screen as Dr. Shots, about 50 iPads, tablets and cell phones popped up and started recording...I got a little "discombobulated" and almost cracked up...and yes, I promise to go slower in that class and cover a few less items (thanks for the feedback!). Nobody seemed to mind that they weren't any handouts - which is a great step for creating a more sustainable environment, as we used to kill quite a few trees every year...

One part that I left with mixed feelings about was the integration of shared data between BIM and other applications. There are a lot of new ventures out there, but it seems that we're only getting pieces, instead of the whole, big picture. At this stage in the development of BIM and other data-centric models, it seems that Autodesk would have a better idea of where they want this to go. We really need some focus to bring all the different pieces together, so that we're not all developing the same applications with different degrees of results. There are a lot of great new products, but some leadership from Autodesk on this other than talking about how we're all going to be in the cloud (without providing more specifics) would really be helpful at this point. Even in my own class, where the topic was about how we developed our own application to deal with linking data between applications, left me with more questions that answers. It will be interesting to see if they come up with a more uniform method for controlling the export and import of data - for example, the dbLink extension needs a lot of work (dynamic versus static, user control of what data is exported, etc.).

While there's lots of space at Mandalay, I'm personally glad we're going back to the Venetian - better quality of service, a more central location, which all lead to better attendance. Next year should really be a great event, and I can't wait. And yes - I'm already working on all NEW classes, with new material - keep doing the same thing and it gets stale quickly...

Changes in the Autodesk Sales Model - if you've ever been in a sales channel, you had to know this was coming. Web-based purchases, cloud-based software, annual versus perpetual licensing...all of these lead to the coming demise of the Autodesk reseller channel. Financially it doesn't make sense for Autodesk to keep supporting the channel, when in reality, we're no longer getting much out of them that bring additional value to the product sale. Support is direct with Autodesk through subscription, and most of the issues we have, the reseller can't fix since there either flaws in the program, or very simple " how do I..." questions. It's a bit sad, but savvy resellers should be looking to the add-in market, as well as the more refined services. Not every company can afford to have a BIM manager or developer on staff, so that market should be sustained...but it will have to be self-sustaining.

From the user perspective, the suites have been golden. They're still a bit pricey, but I'm using more of Inventor now than I ever have, and having a single version of Revit has been really nice. It makes the management of the tools much easier, but 50gb installations can be tough...hey, I'll wait. Next year, I'll be looking forward to upgrading to a more powerful system, so it will be interesting to see how the laptop versus tablet market is rolling along next fall.

Odds and ends:
-If you are in college, working on your engineering or architecture degree, take Revit classes - students with Revit experience or any 3D modeling experience are like gold to us.
- If you are a 30 CAD draftsperson, learn how to get up to speed in BIM AND Design - one without the other doesn't make for a very long term career outlook. Get at least a two year associates degree - that's better than nothing. If anything, really start looking at the post design market and tools. Applications like Navisworks still need solid users, and offering digital coordination/estimating/fabrication services is still not a bad idea.
- If you are a project manager or business owner, learn and understand BIM. Many people in the profession that haven't bought in to this are getting behind in the game. You've got to understand how this works and how it affects a project's bottom line. Stop hiding behind "how productive we are with plain AutoCAD"...with current trends showing BIM being more prevalent in the market that 2D now, all you're doing is kidding yourself.
- And if you are a facility owner, that hasn't starting requiring BIM as part of your deliverables, please step to the back of the bus...the rear door now opens automatically. Anyone had any validation or compliance issues lately, and had to deal with hundreds and thousands of paper documents, drawings, etc. with no real organization? Layer it - start with renovations, additions, and build your models over time, if you can't afford to get a good as-built modeled. It doesn't matter if it's AutoCAD Architecture/MEP, Revit, Bentley, ArchiCAD, or anything else. IFC is improving, and the next generation of users is going to wipe us all out if all we leave them is a stack of papers...go ahead...ask your kids...

For everyone, please enjoy the holidays. Spend some time with your family and friends - recent events have shown us that you can't take time for granted. Have a Merry Christmas and Happy New Year - we'll see you next year!

Take care - David B.

Revit 2013/AutoCAD MEP 2013 IFC Improvements

This post is part of an AU class this year, MP1465, Supercharge Your AutoCAD® MEP 2013. It came up as we started working with outside vendors that are solid AutoCAD MEP users, but not Revit users - and that's what we're using.

First up, know the rules:
- Architecture and Structure items convert pretty nicely, with ACAD Arch walls converting to Revit walls. You may need to swap some styles, check justifications, etc. but getting the overall model works pretty well.
- MEP objects come into Revit from ACAD MEP as in-place families, but if you setup your import options, and have your classification definitions assigned to MEP objects in ACAD MEP, then they come in as "pipes, pipe fittings, duct, etc.". Be aware - they don't have the same behavior as a duct, pipe, etc. that was created with native Revit tools. But you can add connectors as needed to make these types of connections.

Here's the excerpt from the class (or as I like to call it, the "tease")...

IFC stands for Industry Foundation Class, and it’s a file format that is universally shared between CAD platforms. The intent is that an object in a program like AutoCAD MEP can be converted into the same type of object in Revit, or other BIM applications.

In order for an object to be exported to IFC, it has to have an object classification assigned. To look at the default styles go to ProgramData\Autodesk\MEP 2013\enu\Styles directory and open the IfcShareBldgElements (MEP).dwg file.

 

In the style manager, look at the classification definitions under Multi-purpose objects. IFC properties can be assigned to these objects:

 



Once the items are selected, the classifications tab lists the information associated with an MEP object that will be exported:

 

To use these in a file, and assign them to MEP objects, you have to copy them into your current drawing. Use copy and paste in the style manager to add both classification definitions to the current drawing.

Select OK to exit the style manager. Now that they’re in the drawing, you can edit the properties of objects to assign the classification. I’ll grab the ductwork, and then go to the properties palette:

For most other parts, IFC Type Classifications are mapped to MvPart Objects (such as equipment, panels, and devices) automatically. This classification is added in the Autodesk Catalog Editor by default. You can modify this classification or add more classifications to the content library in the Autodesk Catalog Editor.

Once you’ve added the correct classifications to MEP objects, review the IFC export settings. From the application menu, select the Export tool, and then select IFC. The options are located on the export dialog, and the object tab lists all objects that loaded into a drawing – you can choose to add or remove objects as needed.

After you review the options, you can run the export. The IFC file is created in the project folder. To test this, I’m going to open the file in Revit. Before doing this, open the IFC Import options on the Application menu, under Open:

Before importing an IFC file, you need to go through and map IFC class names to Categories and sub-categories. This tells the MEP object what is used to control its display in Revit.

Once the IFC file is imported, it will appear something like this:

The imported objects take on most of the characteristics of the equivalent objects in Revit. You may need to check IFC mappings in both the AutoCAD MEP file and the Revit file during this process, but this represents a major leap in compatibility between the applications.

Be aware that imported objects may not completely take on the behavior of a normal duct. For example, the duct is treat like a duct with properties assigned, but it does not include the connection, system or sizing behavior. You have to add a connector to attach duct to it.

I don’t care what anybody says…this is really cool…

Happy BIM'ing - see you in Vegas!

zzzz....uh...huh? AU is in a week? Geez, I overslept..

Wow, where does the time go? Autodesk University (#au2012) starts classes one week from today...and the last couple of months have been crazy, getting all of the handouts, datasets, powerpoints, props, home movies, etc. finished. But I'm about there...

And when you finally get a moment to reflect, you hope you've put something together that really hits home with users. This year's approach was a little different - I wanted to find what the really obscure little things were that come up as support issues, and get them addressed. But I also needed to hit on the bigger picture, and make sure that the day to day items - using systems, making families quickly from scratch, or from manufacturer's content, etc.

And then I an email from an engineer I know, saying that he doesn't think MEP BIM is ready for primetime yet. And I couldn't disagree more, but if you don't train your staff for a few years, then, yeah - you're likely to have the same attitude. So here's what I think - Revit MEP 2013 and AutoCAD MEP 2013 represent the best two MEP design applications on the market, hands down. Both have their strengths, but both require you to make some changes to your design process.

Here's an example. In one of my classes, we talk about adding an instrument connection to a duct or pipe. The instinct says, add a tap. Instead, if we're making this connection at a fitting, such as a duct tee or flowmeter, why not add the physical connection to that component? It will stay connected to the part, if the part moves or changes size, the connection is still there. It can be fabricated into the part prior to being added in the field, so that may save a little "field fit and finish" time.

That's one of the challenges that comes with BIM. If you're still in the drafting mentality, then all you're thinking about is a line or circle - but in BIM, you HAVE to think more from a DESIGN standpoint. It's all about making a more easily constructable building, that's more sustainable while allowing for creativity in the design.

The beauty of AU is that it's a gathering of like minds, that are looking for that tip, or method, that helps you stay current with technology, or gain that competitive advantage. We're driven to find better ways to leverage our tools, and make life easier for ourselves (as though it isn't already). And we really want to find ways to interconnect all of this information, and come up with the big picture, that satisfies the client's and end users needs (think airport electrical outlets).

So take a little time this week - network with your peers, get to know some of the industry leaders, and take advantage of some of the best and most passionate instructors in the world. We'll all be hanging out in the same place - so come by, say hello, and let's talk about the future. And if you can't make it, check our AU Virtual - last year, tens of thousands did - so the learning doesn't stop on November 30th. I'm ready - are you?

See you in Vegas!

'Peat and Repeat....Additional Revit Labs coming soon for AU 2012

Looks like my two Revit MEP labs will be repeated, due to demand. If you tried to get into either one of these sessions, but couldn't, check back this week. I've approved them being added, and are just working on the details for the time and location with the AU event staff...so stay tuned!

Class ID: MP1477-L  - REPEAT is MP6895-L!
Class Title: FASTER Families for Revit MEP!
Class Type: Hands-on Lab - Wednesday 1:00p

Class ID: MP1478-L - REPEAT is MP6889-L
Class Title: Perfecting the System for the Revit MEP Project
Class Type: Hands-on Lab - Tuesday 10:30am

Anybody got a throat lozenge I can borrow....?

thanks - David B.

Revit MEP Circuiting tips...poles or phase?

Ran into this one recently...we have a project with a new user that is adding devices to circuits. In the project she's working on, we have number of poles and voltage assigned as a parameter, but somewhere along the line added a phase parameter that was also equal to the number of poles...which, if you're the electrical designer, you know is wrong.

So here's my simple explanation, with a little help and clarification from my buddy Dan Stine...the Number of Poles in a circuit relate to the physical slot locations on a panel. The Phase refers to the A/B/C branches of a panel. Phase is a product of typical AC (or alternating current). Without going into great detail, know that Revit support single phase (panels with A/B branches, just like your house) or 3 phase (A/B/C - most commercial applications).

With electrical connections, you'll have these types of connections:

120/240 - these are single phase panels, with two poles - most commonly found in residential
120/208 - a three phase panel, more common in commercial applications. This type of panel also requires 4 wires to use all three slot sizes, from 1-3. In some cases, a 120/208 single phase connection can also be used - for example, in a apartment building.

120V is common in the US, but not common in other areas, such as Europe.

120V - A single phase, single pole Circuit - unless it's a GFI circuit, which could be single pole but 2 phase
208V/240V -  typically a 2 pole, 1 phase circuit, but also could be three phase (for example, in the event of a 208V GFI Circuit). 208 volt or 240 volt systems can both be either single phase 2 pole, or 3 phase 3 pole circuits.

Higher voltage panels for commercial and industrial applications are typically 277/480, indicating a one to three pole circuits. 277 volt circuits are almost always single phase, single pole, while most 460-480 volt circuits are 3 phase circuits. Depending on the power requirements, you can have 480 volt, single phase, 2 pole circuits - so make sure you check for this when specifyign your equipment.


In my simple little, non-electrical mind, it's a bit confusing, but from Revit, it's pretty straight forward.

If something is 120v, set the number of poles to 1. This will take up one slot in the panel, or one "circuit"

If something is 277v, set the number of poles to 1. The phase will also be set to one. For 208v/240v circuits, these can be single phase 2 pole, or three phase, 3 pole.

For 480V, in most cases, the number of poles will be 3. a 3 pole circuit takes up three slots, and can only be used in a panel that is defined as a 3 or 4 wire, 3 phase panel. You can have some systems, such as electric heat, use a 480v single phase, 1 pole circuit - again, check with your vendor before defining the circuit.

These are all set under electrical settings, for the distribution systems:

Revit requires that the proper combination of poles and voltage in order to add something to a circuit. There are two configurations for any type of a three phase panel - Delta, which doesn't include a neutral branch, and Wye, which does include a neutral.

Revit only recognizes single or three phase systems when you define your distribution system. For example, you might have a device or circuit, that requires 208v service but is single phase - you still have to assign the number of poles to 2. Otherwise, it can't be connected to a panel.

For more information, talk to a more reliable source than me - your local electrical engineer.

Hope this helps - if anyone wants to add to the conversation, knock yourself out!

thanks - David B.

A few shameless plugs...for AU 2012!

I gotta love our marketing people...they've really been grabbing on to social media and getting ourselves known for being thought leaders in the BIM arena.

So they put together a little highlight reel for the classes I'm teaching at AU this year, showing a few of the projects we've worked on in Revit, along with a few pics from previous classes...check it out!

http://www.youtube.com/watch?v=ZNBJzEG0ThM

Here's the list of classes I'm doing this year - in case you missed it:

 

Class ID: MP1414
Class Title: Revit MEP 2013 - On Steroids!
Wednesday - 10:00am

Class ID: MP1461
Class Title: You did WHAT? Revit MEP and AutoCAD P&ID? Amazing!
Thursday 1:00pm

PS - for the class above, I'm really excited about this one - we're doing stuff that everybody says we shouldn't be doing - but it's not just about the programming. It's about how we went through the decision and planning process, to come up with a solution that was cost effective for the company while giving us a competitive advantage in our market.

 

Class ID: MP1465-L
Class Title: Fast Content for AutoCAD MEP 2013
Tuesday - 5:30pm 

Class ID: MP1470
Class Title: Supercharge your AutoCAD MEP 2013!
Thursday - 10:00am

Class ID: MP1477-L
Class Title: FASTER Families for Revit MEP!
Thursday - 5:00pm 

Class ID: MP1478-L
Class Title: Perfecting the System for the Revit MEP Project
Wednesday - 8:00am


And you thought I was a geek...see you in Vegas!

later - David B.