Performing Electrical and HVAC Model Clash Detection in Revit

Now that we've created a rich electrical model in Revit, we have a model that is full of electrical equipment. We have lighting fixtures, we have power equipment, switches and receptacles. We can take all of this information and compare it to a different model.

For example, electrical to HVAC. Let's dive in to see what that means visually. So let's go to our project browser.

We want to find under ceiling plans, our L2 lighting plan. Let's double click to open that up. Here is our lighting plan.

And if we zoom in towards the top, we'll go to classroom 5004. And what we have are our lighting fixtures that we modeled here in our electrical model. But we also have air terminals.

Now these are from the linked HVAC model. We have an air terminal, that's a return. And then we have two supply terminals right here.

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Now these look pretty good. They may not be overlapping, but let's go ahead and create a clash together. Let's take one of these light fixtures, just click on it and drag it until it's overlapping one of the air terminals, creating an obvious clash.

That air terminal is now occupying the same space as that light fixture. And that would be a clash or an interference, something we want to avoid before getting into construction and realizing that two things need to occupy the same space. So Revit has this built-in tool to find these interferences.

Hopefully it finds this obvious one that we just created together and it should find some others as well. Yours will look different than mine because we've modeled it all differently. And so that's okay if you have different interferences than I do.

To run this, we're gonna go up to the Collaborate tab. And from there, we want to find Interference Check. And we want to run an interference check.

Now I've found that less is more when it comes to interference checks. At the beginning, it's super tempting to check all of the boxes and compare them to all the boxes of another category. But that creates a very challenging report to sift through.

So what we want to do is start with categories from our current project. And here is where we can select Lighting Fixtures. And take care to select the Lighting Fixtures.

The lighting devices are the light switches. They're very tiny and they may not have any clashes at all. So select Lighting Fixtures.

And we're gonna compare that to a different model. We'll pull this down. And this time we'll select Background HVAC.

And here we can check our Error Terminals box. And then we can click OK. And that runs a clash detection or an interference report.

Now before we dive into this, we'll notice a couple things we can do here. One, there is a Show button. And I would say don't click it yet.

I've found it to be somewhat buggy in Revit. So sometimes it works. Sometimes it doesn't work and you have to rerun your interference check and then it will work.

So let's skip clicking that for now. The button next to that is Export. Let's go ahead and try that.

So Export. And we can export our interference check. You can save this anywhere you'd like on your computer.

I'm saving mine to a VDCI folder. But save it wherever it makes most sense for you. The trick here is to give it a name.

We want to call it BIM323 Interference Report. And then we need to put our name here as well. So I'm going to go ahead and add our name, which is first, last.

Kind of a long file name, right? BIM323 Interference Report. Your first name, your last name. And then put the word before.

This is before we do anything to it. Just the initial report. Go ahead and save that.

It creates an HTML file and that's the only option. If we go ahead and go to our file browser, wherever you save that file, you should be able to find it. So here's mine.

It's that BIM323 Interference Report. First name, last name, and then before. When we open up one of these, it's going to just be a real basic file.

So it looks something like this. And it says Interference Report at the top. And it has our lighting fixture and then it compares it to the HVAC model.

And that's all there is to it. Now it looks like a lot to take in. We will dig into this a little bit deeper in a moment, but here's our before.

We can see how many clashes we had and then we'll compare it to our after in a little bit. Let's move that off to the side. Now we'll stick on level two here for now.

And again, that show button can be buggy, but what we can do is simply click on one of the interferences and it can be a little hard to see at first, but what they do is they turn orange in our models. We can see that it's an orange color and that's one of our interferences. And so we can see what happened here.

It looks like the HVAC model was modeled a little bit lazily to the right and my lighting fixture was modeled a little bit lazily to the left. So this may not be a case where I need to bother the HVAC engineer. I can simply move one of these out of the way.

Now they will stay orange as long as it's selected, but I can still work in my model. I can click that lighting fixture and it's important to note, I don't wanna change the HVAC model. It's not owned by me.

If I make a change to it, it won't reflect in their model per se. So I want to only update my electrical model and I'm gonna move that lighting fixture out of the way until it's no longer clashing that terminal. Now they can share an edge, but they can't overlap.

So I might pull it further away and then move it right to the edge. And then let's see what happens. If I click this refresh, I have one less clash and it's no longer orange.

It's no longer a clash at all. I've solved it essentially. Now you may not like that solve.

You can see now my model is a little bit off. I'm okay with it. It's not something I need to raise a flag to the engineer, but it might be in your case.

Maybe yours is really nitpicky. You need to get everything perfect. And so you might raise a flag, reach out to the HVAC engineer and share your clash report.

But let's keep going. There might be some other more obvious ones. For right away, I clicked one that happened to be really obvious.

So right here, that's a clash I can't really resolve on my own. I'm almost halfway into that air terminal. Nothing I can do about it.

I really need the HVAC engineer to update their terminals. So I will leave this one in the report. There's nothing for me to fix.

I want to send this as a reported clash. I might be a little more careful in my model. Like maybe I'll move it over to where it really belongs.

So this fixture right here, it looks like I really could move it over a little bit. One thing to note is I've turned on thin lines. If I don't have that turned on, it's up at the top, you can see it can be really tough to tell the clash detection sometimes.

So one thing to try in your model as you're going through this is to turn on that thin lines here. You see the toggle makes a big difference. Sometimes the thick lines hides the entire clash.

So let's turn back on thin lines and keep working that way. So there's one I'm going to leave. Let's click on the next one and see if we find it.

Okay, there it is. Okay, this one again, it's just a little bit of sloppy modeling. They're just barely overlapping.

I'm going to move this over just a tiny bit. There we go and hit refresh. And now there's one less clash.

So I've solved another clash. Let's go ahead and zoom out and find a couple others. And again, yours will be different than mine probably because we modeled this in separately.

So feel free to make the changes that you need to. Maybe you're a super careful modeler. You already modeled these not clashing and you may not have a ton and that's okay too.

Let's go ahead and find another one here. That's down here. This one to me is a little bit bigger of a clash.

That HVAC terminal is pretty far off from where it needs to be. I'll leave that in my report. And I've got one last one here.

All right, up there. So I can click this and I can move it and resolve that clash. Okay, so let's refresh it one more time.

And now I just have two in my report. And you might ask yourself, it didn't find the really obvious one. So that shows it, it's not perfect.

Unfortunately, this one wasn't found. It was a super obvious clash. So sometimes we have to know that take this report with a little bit of grain of salt.

It doesn't always find every single clash. This one I have to resolve manually. We'll put that back into place.

And there we go. Let's go ahead and refresh our report. No change.

We are good to go. Now that might be a little disconcerting that didn't find a super obvious one. There could be something else going on.

Like maybe they just aren't in alignment with each other. So let's dig into this just for a quick moment here. And let's go ahead and go to view.

And we'll do a section right through here and see if in another dimension, maybe there's no way that they would conflict. So let's double click here. And let's go up to that second level.

All right, so we can see what is going on. This light fixture is modeled below the ceiling. And so even if it's overlapping completely that air terminal, there's not a clash because clashes or these interferences, they're allowed to share one edge with each other.

So even though I moved it, it didn't overlap completely. So what I'd have to do with this one is remodel it and make sure it's actually modeled in the ceiling that it's a surface mounted fixture. So that is the limitation to know when it comes to clash detection that maybe in the floor plan, there is no conflict even though really maybe there should be.

All right, so enough taking a look at the details. I'm gonna delete that section there. I've got my report.

And now I can export it. I've made my list smaller. If you weren't able to get yours tremendously smaller, that's okay.

We're really just trying to learn how this works. So let's go ahead and click export. Again, it's an HTML file.

We're gonna have the same name essentially wherever you save it as BIM 323 Interference Report first and last name, which is your first and last name. And this time we'll call it after. Save it to a directory on your computer.

It's going to be an HTML. Go ahead and save it. And then we'll pull up that directory in our file explorer and find that after file.

And when we open up that after file, you can see, for example, I've got now just two. So here's my before with several and here's my after with just a couple. You might ask yourself, how is this report possibly helpful? It just says, you know, lighting fixtures, plain surface light versus air terminals.

Like what, where, why, how? There's so many questions. Well, what this report gives us are a couple of little codes. And these codes actually are helpful.

If you send this report to an HVAC engineer and you say, hey, there's clashes with these Revit IDs. So it says ID and there's a numeric code. And all they have to do is copy that code and find it in their model.

Let's go back to Revit and we can close our report for now. And if we go up to the manage tab, manage, one of our options here is to select by ID and it's in the inquiry tab. So inquiry, select by ID and using copy paste.

We copy that ID from a report and then we'll paste control C to copy, control V to paste, click okay. And it will find it. It should highlight it.

There it is. I can also run that same deal. I go back to my manage tab, select by ID and I'm gonna zoom somewhere else first.

Let me zoom just off to the side here and select by ID. I will paste in the ID and click the show button. And the show button is not perfect, but it does work pretty well when it's selected by ID and it zooms right to that light fixture.

In the HVAC engineers case, they will zoom right to their air terminal by ID. It's a pretty quick way to find things in a really complex model. It works pretty well.

So there it is. And that's that report I can generate to make sure I get all of my clashes resolved. All right, that is it.

You've done a great job checking this model, looking for interferences. And next up, we can go ahead and finalize our drawing set.