Revit MEP - Wire Size AWG vs MM

I wrote a post about this subject before. There is an app at the Autodesk Exchange Apps that offers trap door access to revise the bias toward AWG size versus.

It is called Convert Wire Size (AWG to MM) and it sells for $4.00 USD. I haven't used it myself but for those firms that need wire size reported in millimeters squared it may be the solution you need/want until Revit itself allows us to switch the criteria directly itself.

I'll be curious to hear how well it satisfies what engineers are asking for.

Revit MEP - Silly Revit - We Don't use those Pipe or Duct Sizes

If you don't take the time to fine tune your project templates then you'll find Revit will offer you all kinds of pipe and duct sizes. These are available in the drop down lists during placement and then later if you run Duct/Pipe Sizing.

If you don't take the time to fine tune your template you'll find Revit gives you a duct size of 11" after completing its Duct Sizing, regardless of the fact you only choose from even sizes. It's easy to blame silly Revit...but it's our fault. The Duct and Pipe Sizes are controlled via Mechanical Settings, the duct sizes for Rectangular are shown below.

We need to either delete sizes we never want or just un-check them in either column or both, Set it and forget it.

Oh, the same is true of conduit and cable tray.

Revit MEP System Browser - Systems and Families

When you examine the information in the System Browser there are separate items for Systems and the Families that are related to them.

We can delete a System if necessary via a Right-Click.

Be careful though, you can also delete a family the same way!

Who's Your Daddy? Logical Relationships in Revit MEP

This is an echo of a post from October 2011. I emphasize this concept in every session I do that is focused on Revit MEP and I think it's worth stating again.

Revit MEP elements, like electrical panels and receptacles or HVAC equipment and diffusers, have a Parent - Child relationship. Revit calls this a Logical Relationship. In contrast the physical relationship is described with duct/pipe but there is no equal for electrical systems. It could be with conduit or cable tray but no such relationship exists yet.

The other day we were chatting about this in class and I blurted out "You know, like who's your Daddy?" I was kidding but one of the guys said that it will actually help him remember to start with the "child" part of the relationship. For example, you start with a receptacle and create a power circuit (system), then choose the Daddy, the electrical panel it gets power from. This relationship continues up through the grandparents, great grandparents etc. When everything is assigned correctly you can see this family tree in the System Browser.

So if it helps, when you are creating relationships between elements with Revit MEP, just remember "Who's your Daddy"! START with the child and then assign the Daddy.

Revit 2016 - Loss Method and ASHRAE Tables

Fittings and loss errors have been annoying in Revit MEP for quite some time. If we were striving for a warning free model then we'd be confounded at every turn by fittings and their loss for loss. In Revit 2015 R2 and 2016 we've got the option to assign fitting's Loss Method parameter to Coefficient from ASHRAE Table.

The ASHRAE Table Settings dialog displays graphical information that is associated with duct fittings table. We can choose from among the fitting descriptions in the table or accept the default one that is already selected.

If you select a fitting randomly and check this out you may find the dialog set to None. It only starts to work when components are well connected. That means, if you see warnings associated with fittings, its likely those fittings are not part of a well connected network yet.

Revit MEP - Circuit Length Calculation

I received an email asking if I thought it would be possible to use a Line Based family to calculate wire length for circuiting purposes. It was prompted by reading an earlier post about using them for Egress Path calculation and documentation. I think it's a reasonable approach for Egress Paths because there is no such tool or concept already in Revit.

Electrical circuits on the other hand do calculate their length already, granted it does so simplistically. It combines the X/Y/Z distances of the devices from the panel (and each other) to arrive at a total circuit length.

A friend some years ago sent me a PDF that showed a bunch (a couple shown above) of different equipment and device layout schemes he did to better understand how Revit arrives at a value for Circuit Length. What it shows is that Revit does nothing to factor in obstacles which force the wiring to go up or down or around the things that are more than likely going to increase the total circuit length.

To be fair...how could it really? How detailed is the model? How long do we want the software to interrogate the model, the linked models to do a better job? It's a bit like requiring all conduit to be modelled, even 3/4" conduit feeding single gang boxes in a wall when there isn't a single stud in the model. Like with so many things in life, it's about context.

It's one thing to put a single gang box on a wall to indicate one is required here and another thing entirely to run conduit to all the way to it when you can't be sure it can really go there. Or like showing a pair of outlets back to back on a demising wall in a residential project where fire rating and sound attenuation would require them to be separated by a minimum distance.

Some things are still conceptual (schematic) in nature even in fairly detailed models. If we start modeling every stud then perhaps it becomes more reasonable to expect more system detail too. Then again if I have to create a run of (15) 3/4" conduits across a wall or ceiling I probably ought to model that situation because it's going to take up a lot of space and everyone else ought to be aware of it.

It's also been my observation that no matter how good software gets at a task there are always outliers that dismiss its results as still wrong. That written, it does matter and Revit should improve how it does calculations and how much say we have in the outcome because the length it calculates is also used internally to contribute to other calculations like wire sizing and voltage drop.

Setting aside how circuit length should be calculated (it might surprise you to know that engineers don't always agree on this), I'd consider this approach if my task was to determine how much wire was needed, a little closer to actual requirements than might show up in the circuit properties. I'd create a schedule focused on Electrical Circuits.

What you see above: I created a couple panels and added a bunch of duplex outlets. I assigned them to circuits. The schedule's second column is Revit's calculated length, no more effort on my part than placing devices, creating circuits and choosing a panel.

I sorted the schedule by Panel and then Circuit, provided a header for Panel and footer for totals. I added a parameter for Length Factor (a number) and then a Calculated Parameter for Total Estimate (a length) which uses a formula of Length Factor * Calculated (column 2).

Then I consider each circuit's circumstance and enter in a factor that increases or decreases Revit's own calculation according to how easy or hard the actual wire run or routing will be...or at least what I think it will be. A factor of 2 doubles the length etc. This calculation doesn't factor into load calculations like for Voltage Drop...but then neither would using a line based family.

This doesn't account for situations that might share a neutral (or ground) or runs that are comprised of individual conductors in conduit (like THHN or THWN) or a wiring combined into a common jacket like Cerro's NMB (a typical household wiring product).

That's the risk/difficulty of automatic calculations, the closer you examine situations the more outliers there are. It can be a bit like arguing about something being 99.6 percent correct. If it costs another $1000 to get to 99.9 or 100%...is that difference worth it?

Linked File Revit MEP has Colors

Revit MEP can assign system colors to their pipe and duct systems. It is easier for them than using a lot of Filters like was required in the past. If you are one of the other trades (architect for example) and link an MEP model and you see color it's probably because they are using this feature. This is what it looks like in the MEP model. I focused on the Domestic Cold Water as an example.

Now the file has been linked to an architectural model. The colors assigned to the pipe system are still applied to the elements. You might be tempted to try to alter the settings of pipe and duct systems in the Project Browser, IF you've noticed that your architectural template has them. I'll save you the trouble, it won't do anything to them.

If you don't want to see those colors you CAN override them with Filters.

I've opened Visibility/Graphics and then created a Filter. In the Filters dialog, if you select only the Duct categories, Flex Ducts, Flex Pipes, Mechanical Equipment and all the Pipe categories, then the "Filter by:" will allow you to choose "System Classification", set it to "is greater than" and "" (empty field).

This should catch all the mechanical elements in linked file and look like this afterward.

Remember to take advantage of a View Template to control this more easily and consistently.

Revit mEp - Design Master

I've been hearing good things about this add-on for Revit from Design Master.

If you're doing electrical work then you ought to have a closer look at it.

It has a tab for HVAC but it appears to only support AutoCAD for that, for now?

Synchronization and Disconnected Systems

This is a bit idiosyncratic but if it helps sort out an issue then its worthwhile to echo it (based on a discussion at the Autodesks NG).

Imagine this scenario:

• An Air Terminal has an 8' elevation. A Duct rises from the Air Terminal to a elevation of 10'-0" and connects to a horizontal run (also at 10'-0" elevation), running parallel to the ceiling.
• User 1 raises the Air Terminal to an 9'-0" elevation. The vertical piece of duct connected to it changes in length, but no user is recognized as Edited by (owning/borrowing) for that element.
• User 2 decides to lower the horizontal duct (at 10'-0") to 9'-0". It is necessary for Revit to change the connected vertical Duct between the Air Terminal and the Duct to do so.

There are no warnings or alerts as these users do this. If a user decides to modify the series of elements, then a warning appears. A warning appears during Synchronize with Central only if this additional attempt to modify the element is made.

At the beginning I wrote idiosyncratic because it is easy to avoid if we agree not to work on each others elements. I would not ordinarily expect another user to decide to lower a duct that is connected to elements that I'm already working on. If we don't discuss what areas in the model we are focused on then it can easily happen. It is important to be aware of what others are working on. The Worksharing Display features can help us see what others are currently working on, if you don't really want to talk to your co-workers...but it's still a good idea.

Regarding the workflow above and not getting an error message, an Autodesk support person replied that they find an error message appears earlier to warn of the inconsistency when trying to reproduce the situation in the latest development build that will become Revit 2016. That means it is pretty likely Revit 2016 will prevent a duct element from being altered by two separate users when they interact with different elements that are both connected to it.

Revit MEP - Electrical Wire Size

Revit mEp is very American because it is hard-wired to do its calculations based on the AWG based wire sizes that are defined in the templates Autodesk provides to us. When you need to reference metric sizes/standards instead there is no place to change this bias and if you attempt to change wire sizes to metric equivalent (CSA or Sq. mm) values you'll find calculations, like Voltage Drop, either cease to work or you get strange results.

Working through this issue with a client recently they decided (or at least hoped) it would be acceptable to provide a chart that allowed the reader to cross reference the AWG size against the locally relevant size. This firm is based here in the USA but working on a project outside the USA. Perhaps in that context this could be forgiven by the client. I don't know how well that approach will work for firms that are working at home, outside the USA.

Fwiw, Autodesk IS aware of this bias. Providing more flexibility is among the many things they have to find time to include in future releases.

Revit 2015 MEP - Calculations and Performance

When Revit 2015 Update Release 3 became available a new MEP setting became available for Pipe and Duct Systems called Performance Mode. If you examine the Type Properties of a Piping system (or Duct) you'll find this additional setting.

The help documentation (link below) offers up this table to break down which system classification calculations are made available to us and which are able to take advantage of this new Performance choice.

This is intended to improve performance when working/editing large MEP system networks. For each system type we choose to assign this Performance setting to, Revit's system propagation is disabled on every system assigned to that system type. The Calculations parameter can be included in schedules, which can make it easier to toggle on and off. Keep in mind, if the file is opened in a previous build (not Update Release 3 or newer) then the parameter may/will not display correctly.

At first glance it doesn't seem much different from choosing None because to restore system propagation we have to change the setting back to use a calculation method, other than Performance or None. My initial expectation was that None would shut down calculations entirely and Performance would permit some calculations but do so in a way that would improve my experience or perception of performance, Revit's responsiveness as I work.

As I've learned from the developers, despite carrying a name that suggests to me otherwise, under the hood, using None does NOT tell Revit to completely ignore everything related to the connected network. This new Performance setting DOES allow Revit to completely ignore any system (as far as calculation propagation is concerned) that is assigned to the Performance setting.

As I understand them, the two choices are a trade off between accepting slower performance for each and every model (our) interaction (by choosing None) or having a quicker response (from Revit) for each model interaction, choosing instead to endure a longer wait after turning back on calculations (using Performance). Perhaps in a future release we'll just see None eliminated or replaced by Performance? At the very least I think the naming is a bit misleading.

A side effect of using this setting is that duct/pipe sizing and the System Inspector will not work on systems that are assigned to it either.

You can READ the Help Documentation HERE.

Revit MEP Pipe Appearance in Sections

I met Freddie at the BIM Workshop in Anaheim recently. We chatted for awhile about Revit (shock I know) and then a little about music. It was great to meet someone who wasn't necessarily required to know Revit but decided he wanted to learn Revit and has become quite good at it. The company he works for (TJP Engineering) specializes in water treatment systems for aquatic attractions.

He passed along a graphic that Chris Aquino (Autodesk support specialist) marked up for him when he was trying to sort out piping graphics in section views. Sometimes writing this blog only requires sharing what other people tell me, thanks Freddie!

Here's the image which has markups that explain the various conditions they discussed.

Quick Summary of Issues:

• No rise/drop symbol? Most likely the pipe is sloping "through" the section.
• If you see a "crosshair" or "target" it is probably the pipe beyond the fitting but within the Far Clip Plane of the view.

Btw, my Uncle Ben called me Freddie when I was a kid. I. Don't. Know. Why... :)

Revit 2015 R2 - MEP Move To for Circuits

Here's a subtle one for Revit mEp users, a new button shows up in Panel Schedules when you select a circuit.

Move To begins by selecting a circuit. You can choose another eligible slot in the schedule. You'll see the "No You Can't" icon at your cursor when you hover over ineligible locations in the schedule.

Revit will highlight eligible slots in the schedule by turning the cells green. If your schedule has a fixed number of slots and they are all filled up you'll have to reconsider the panel loads. You also need to move circuits up or down to create an open location. The Move To feature doesn't shift existing circuits around, it just moves a circuit a bit easier than using up or down when a slot exists for it to move to.

Revit MEP - Copy to Clipboard and Paste Aligned

Face-Based families don't seem to like when we use Copy to Clipboard and Paste Aligned. Specifically they may go where we want but they don't report the correct elevation value. For example these two Air Terminals are reporting 18'-0" after I used Copy to Clipboard and then Paste Aligned to Selected Levels, choosing Level 2.

They ought to report 8'-0" since that's their actual elevation above the floor, their host ceiling's elevation. You can see they are reporting an elevation that is equal to the offset from Level 1, the host level of their original ceiling. Using the Edit Work Plane tool is little help unfortunately. I tried it but Revit doesn't change their elevation value, I assume because they are already hosted by the ceiling I picked. That made me think of trying to host them to something else temporarily. Then I used Edit Work Plane again to host them on the original ceiling, no joy.

I resorted to using the Pin Trick. I pinned them and then used the Pick New tool. When I picked the ceiling as the new host the terminals stay put, because they are pinned, and Revit now reports the correct elevation again.

Quirky is alive in Revit!

Revit MEP - Choosing a Panel

This is a quick tip I picked up eavesdropping on a conversation with Martin Schmid (Autodesk). When you create a circuit and use Select Panel the list of panels in the drop-down on the Options Bar sorts the panels based on their proximity to your circuit's elements. That's pretty subtle and I never paid close enough attention to notice. I love subtle stuff!

Starting my Project after Receiving a Model

From a Revit MEP or Structure perspective getting a project started, without delving into subtlety, should look something like this.

• Link the architecture model - Auto - Origin to Origin
• Examine an elevation - Make sure your levels match theirs (it's also helpful to get a better sense of the scope vertically)
• Use Copy/Monitor to create (levels you don't have) and watch the levels for coordination (optional but a good idea)
• Room Bounding (MEP) - The arch link has a Type Parameter called Room Bounding, this should be checked if/when you are using Spaces
• Create views for each level after you've made sure yours match theirs
• Repeat this for each discipline, HVAC, Plumbing etc...
• Phases between files should be mapped (same place as Room Bounding, and to truly work they need the same names too)
  
• If you need your own grids to adjust how your documents look - use Copy/Monitor to get a watched set of your own grids

As I alluded to in the beginning, there are other subtle things like worksets that can factor in as well, but assuming the above is all done, you're ready to start adding your own work.

Space Naming still a Utility

Yes, sadly the Space Naming Utility for Revit MEP 2015 is STILL a utility, as in a separate download AND installation from the Subscription site.

It's just wrong, wrong, wrong...

2014 Revit OpEd

Revit MEP - Wish for a Secondary Option

When we select an electrical panel (Electrical Equipment category) Revit will display the Distribution System parameter on the Options Bar to make it easy to assign one.

I think the Options Bar is suffering from an ongoing case of nobody loves me anymore or at least an identity crisis of sorts. The persistence of the Properties Palette means that there is some redundancy between it and the Options Bar. We can change parameters in either place, Revit doesn't care. It's just a little confusing at first glance, at least for new users...but I digress.

Transformers have a parameter called Secondary Distribution System. I think it is fair to say that this parameter is overlooked easily and often. That's because it is hiding in the Properties Palette in the Electrical - Loads group, along with a bunch of read-only parameters.

Later when we attempt to use Select Panel it pokes us in the eye when we can't choose the transformer. I'd like the Options Bar to respond like this when we select a Transformer. Subtle change but adding it here would make this less subtle.

2014 Revit OpEd

Pick New - Changing a Host

Shawn at RFO shared a cool tip to help deal with orphaned MEP families when their host goes missing in the linked file they were depending on. When a ceiling is deleted and new ceiling is placed in the same location instead of switching ceiling types MEP families will end up as orphaned elements.

If these orphans really need to stay in the same location but be associated with a new ceiling (or other host surface) the Pick New tool is biased toward moving them to another host. When you attempt to click on the same host they often end up changing their position.

Shawn offered a simple fix. Just use the Pin tool to put a stake in them first. Then when you use Pick New they won't move and you can select their new host. Nice!

Revit MEP Family Wisdom - Family Origin

Another tip snipped from the Revit Family Editor Tutorial for Revit 2008 as mentioned in the previous post. You can download the PDF copy HERE.

Fittings (duct, pipe, conduit and cable tray fittings) expect the instance origin of the family to be the (projected) intersection of the connectors. In most cases for fittings, there is a point on the fitting where all of the connectors (if extended into the fitting) will collide. Fittings expect this collision to be placed at the original intersection of the Center (Front / Back), Center (Left / Right), and Reference Level work planes. For this reason, it is good practice to pin these reference planes before beginning to build the family.