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2D Ductwork Drafting

Thursday, October 26th, 2017

Tips and tricks for drafting 2D ductwork in Design Master HVAC.



Good afternoon everyone. This is David Robison with Design Master Software. We’re going to be doing training on our HVAC software for AutoCAD this afternoon. We’re going to be looking at some 2D duct work drafting techniques. The first thing I want to look at is drawing branches off of vertical ducts.

I’m going to zoom in on a little spot here were we can put some duct work in. And I’m going to go ahead and insert a duct here. I’m going to put in a vertical duct. We’ll go from 5 feet up to 15 feet. So we have a vertical duct. And a lot of times you’ll have a vertical duct and then you need to have something coming off of it, some sort of branch.

And it can be a little tricky to set that whole thing up, or it used to be. But we actually threw some coding in there to make it pretty simple to do. So if you have the vertical duct, all you need to do is draw a horizontal duct off of it and it will prompt you to insert the break. You can snap to it either with an end point, a center point since it’s a circle, we’ll also snap to the duct so you want to connect to that centerline.

And if we draw a horizontal duct off of that vertical duct, it will see that you are inserting a duct connected to a vertical duct and it will prompt you for the elevation of the horizontal duct we just put in. We’re going to pull all the other settings from that duct that we’re connecting to, but we need to know where to make the connection. So you can connect it at the top if you just want an elbow, but if you did want a tee, you could just type in a different value here.

I could type in 10 feet, and then we will get a duct at 10 feet elevation. So if we query this duct, you’ll see we have a duct there at 10 feet. And when we query this vertical duct, we actually have two ducts there now, one going from 5 feet up to 10, and then one going from 10 up to 15.

So it broke the duct for us automatically so that we had a place to make the connection to get the tee in there so that when we do our sizing and everything else you can actually have multiple sizes above and below the tee. And the fitting works out nicely both in 2D and in 3D. So that’s if you have a vertical duct and you need to draw something off of it, that’s how you can do that.

And if you need to do it, you can put another branch on there. And again, it will ask you for the elevation. So we can put something else, and it will do the break again. And just for completeness, you can draft all that in 2D so that we see what it looks like.

So when you do those branches, it does it’s best to put some sort of fitting on there to make the vertical duct look nice. In this class we’re going to just jump between a couple of different topics. So leaving vertical ducts now we’re going to take a look at eccentric transitions. So when you put in our ductwork by default, everything is based on the centerline.

So everything’s centered and on that centerline there. So if I query this duct, and change it’s width and draw this double line, we’ve got a symmetrical transition. If you’re hugging a wall or something like that, you often want to have the transition flat on one side or the other to put an eccentric transition in there.

The way you do that with our software is you modify the ductwork and you change the horizontal alignment setting. The default is centered for a centerline. You can also do flat on right or flat on left. And basically it will turn that centerline into the left edge or the right edge of the ductwork.

So if we change it to flat on left and click okay, it will redraw the ductwork using that as the left edge and then varying the width to the right. And that is how you get the eccentric transition. So if you need to have an eccentric transition, you change the alignment of your ductwork.

And then, at some point, you probably want to transition back to a centerline. If you can, you want to just keep the whole section flat on left or right. And then when you turn a corner, something like that, that’s a natural spot to change it back to a centered alignment. And it will put in the fitting nicely based upon that.

So it will go from the flat on left to the centered and it will get the fitting in the right spot. There are times where you want to continue along the same straight run, but you want to change here to a centered duct. And obviously, if we come in here and change this to centered, things are not going to work out very well.

So when we draw that in 2D, we go from it being a side of the duct to being the center of the duct. So the way that you handle this, is you actually need to put in a transparent duct there and move this centerline. So you do need to line this centerline up nicely. We can use grips and snap points to do that.

And then we want to put in another duct connecting these two. And if we query that duct, we have an option called transparent. If you change your duct graphics to transparent, we won’t actually draw anything for that duct, it’s just going to mostly keep the airflow connection going so that your CFMs are calculated correctly.

And then when we draw that in 2D, it will draw this piece here with flat on left, it will draw this piece centered, and this piece is being ignored. We do end up with this extra end cap, or just break in the duct work. You can remove that with our various fitting commands.

One is no fitting. You run that and select the end of this duct, it will take the fitting off and so then it kind of looks like one seamless duct. And at that point you can go on with it being a centered duct. So if you want to, for example put a break in there and change this if it drops down to 14 inches there, now we’ve got these centered transition.

So that’s how you do the eccentric transition, and that’s how you can transition, change your duct work back to being centered again. Next, we’re going to take a look at the options we have for our fitting settings. So when you put in your duct work, by default it comes in with some fittings.

And we’ve got defaults in there. You can change them in options if you ever want to change what your default fittings are, under options you’ve got various fitting settings here. So it chooses what your default fittings are. You can always override that however. If for whatever reason, that default isn’t right for that situation, you can make changes.

So if we put in some elbows there, and draw that, the elbows by default they’ve got a 1.5 radius. If you need a different radius on your elbows, you can run the Radius Elbow Command and select an elbow. And when you do that, it will prompt you for the radius of the elbow of the fitting.

So we can do two, and we can get a bigger radius. We can come over here, and do one. So that’s how you can adjust the radius of those elbows. If you have square duct work, we can also toggle turning vanes on and off. If you do your square elbow, first of all, we don’t do turning vanes on round duct work.

So if you say yes turning vanes, it will ignore you and leave them off because you can’t actually get the turning vanes in there. So if we change the duct work to rectangular, now since we asked for turning vanes it will put those turning vanes in there.

So you have the option, by default, turning vanes probably come on. If you want to turn the turning vanes off, really, you can run the fitting and when it prompts you can say “no” and then you’ll get a square elbow without turning vanes. Changing the radius and adding or removing turning vanes, both changes the graphics and also impacts the pressure drop calculations.

So if you are doing any of our pressure drop calculations, they will change based upon the fittings that are being chosen. So it’s not purely graphical. It actually does have an impact on the rest of the model in the calculation mostly at the pressure drop stage. If you make a bunch of changes, and then you realize, you know what, I just want Design Master to choose my fitting here again, I don’t actually want to over ride it, we have the Reset to Automatic Fitting Command.

If you run that, and you select one of your fittings here, it will put it back to what the default is. So that’s how you get it back to just having Design Master choose the fitting, so that if you want to have it just be chosen automatically and not be setting that anymore. We’re going to make a tee here now.

One here, and I’m going to change this size. So when we do a tee, again, Design Master puts in your fitting for you automatically.

And we’ve had a number of different options for tees that you can choose from. And so under the fittings, those are all down here. So by default we’re putting a boot tee in. You can put in a conical tee. And you select a fitting, give it just one duct there. There we go. So we can get a conical tee happening.

We have the straight tee, and that’s where it will draw it basically just coming straight off the duct without any sort of connection happening. We have what we call the transition tee, and that’s where the branch is coming off of the transition itself. Those last three all have to be ducts at 90 degrees.

This one actually works nicely even if you are at some other angle. So if you are looking at something like that, I did not mean to erase that one. I’m going to erase this duct so it’s out of the way. So if you do this at a different angle, we will redraw the fitting nicely based upon that angle of that piece of duct work.

But we also have the variable angle branch, which is basically a straight tee that’s going at a different angel. So it will look something like that. And those are all of the tees that we have.

So those are the options you have for changing your tee fittings. The transitions all default to a 15 degree angle. Again, that’s set in options, so you can change what that’s set to. You can adjust that using our Adjust Transition Length command.

When you run this it will prompt you to select the duct at the end of the transition. Basically, it starts at the break point here. So this transition starts right here. And it’s ending here by default. If we want to stretch it out, we can select a point here, and it will stretch out that transition for you. So if you need a longer transition for any purpose or a shorter, you can adjust it that way.

And it will stay that way until you redo it. If you change it back to an automatic fitting, it will reset that setting as well and go back to the 15 degree angle. There are two fittings that require a little bit different arrangement of your ducts.

Everything else here, you’ve got your ducts just kind of in your standard branching configuration. The Offset Fitting and the Split Fitting are a little bit different in how they require you to draw the duct work. So the Offset Fitting is when you’ve got some duct work and rather than putting elbows here, you just want to have a little piece of duct just kind of going from this piece here to this one here.

It ends up looking like this, if I can actually get it on that pull down. My screen is not big enough. I’ll go to this pull down here, fittings, and then…oh it was just in a different spot. So there’s my offset duct. If I select this duct here, basically I’m saying the entire length of that duct is the fitting, and the duct work is going to be drawn…the fitting is basically going to go between this duct here and this duct here, and we’ll just draw a fitting in between there.

So the size of that duct, of that fitting is controlled by where this duct ends up. So if we pull this duct over here, and redraw that double line, you get a slightly different looking fitting. So that’s how that fitting is being controlled. I’m going to take a drink of water for a moment. The other fitting, that is a little bit weird, is what we call the Split Fitting. That is where you have a tee, again like this, and I’ll just show you what the fitting looks like and then I’ll explain what you need to do to make it all work.

We actually have to have these additional breaks. And then we put the Split Fitting in. And it’s a fitting that ends up looking like this. So you just take the duct, and it’s being split into two pieces. And we’ll do transitions if the sizes don’t work out.

If all the sizes are the same, then those transitions will kind of disappear. But you have to have the extra pieces in there because these center lines don’t end up matching. Basically this center line here for the piece going straight actually is offset. So you would want to stretch this one and you want to use a little bit of care.

I’m just going to eye ball it. But you want to pull it over something like that. And then if we draw our double line, now you’ve got that center line offset from the center line here. So if you do have a fitting, we call it the Split Fitting. I’m not sure if there’s an official name for it in the industry, but that’s what our software calls it. And it ends up looking like that.

So if we want to adjust it we can pull this down here, and that’s going to control what this branch portion looks like. So you end up with these two pieces here. I’m going to go ahead and change their color so it’s clear which ones I’m talking about. And for those two yellow ducts, they’re not really used for positioning the duct work, they’re just keeping the connections to the other pieces.

And then the fitting is based upon those pieces beyond those yellow ones. So you have to have those yellow ones in there, but how those are laid out isn’t really used for the drawing of the fittings. The fitting is based upon the three blue ducts that we’ve got. I’m going to take a look at transparent ducts which we’ve already looked at here.

We’ve got a transparent duct there. Another common use for a transparent…there’s two other places you’d use a transparent duct. One is if you have a fitting that’s a weird fitting that our software can’t draw, you can just draft it in manually.

Draw up to the beginning, do a transparent duct through it, and then draw your duct outward. You can do the same thing with a VAV box. So if you have VAV boxes our software doesn’t really have any concept of equipment in it. So you insert your VAV box using standard AutoCAD, and then you draw a transparent duct through it. We’ve got some examples here.

I’ll go ahead and redraft this just to walk you through this technique. So if you have a VAV box like this, you draw a duct up to it. And that’s going to be a standard duct. You’ll just give it your standard settings.

You will go through it with another duct, and then you’ll go out of it with the last duct. And if you draw that in 2D you’ll see that we have duct work going through the VAV box, which isn’t really what we want to have happen. We want to have the airflow transfer, but we don’t want this duct to be shown. So if we query that center duct, you can change the graphics to transparent. And when we do that, it will know to not draft that duct for us.

So the air is going to continue to flow through that section, but it’s not going to draft anything in 2D for us. You’ll notice we’ve got this white line, so there’s still a fitting being inserted here. If that ends up causing problems for how everything looks when it’s printed, you can run the No Fitting Command again, and that’ll pull that fitting off.

And then you’ve got just a nice connection happening without any extra line work. If you have…if you want to have the pressure drop through that VAV box accounted for as well, you can set the pressure drop here when you query the duct.

So in addition to setting it to be a transparent duct, if you set the pressure drop or you set the static pressure at the end of the duct, that’s how you can model a VAV box with our system. Going back to our offset duct work, if you want to draw a vertical duct off of this, it’s not going to end up looking very pretty.

So if we…again, everything is based on the center line so if we do a vertical duct, go up to 20 feet, if you do something like that, you draw that in 2D. And it’s very confused at this point. If we switch it, I think to the other side, it kind of can work out if the whole thing is centered, but if the size changes it ends up looking a little weird.

So if we query this, let’s say that’s a 14 inch. And if I do flat on right, I think it’ll, it flips it to the other side but it’s still hugging the side there. And if you want to have it come out to center, it’s a little tricky to get that drafting done. So we have a specific command for that purpose. It is called the Offset Vertical Duct. So this is a command for inserting a vertical duct in a piece of duct work that’s either flat on right or flat on left.

The way this works, is you run this command, you select the duct that you’re going to connect to. So I’m going to put it in this 24 inch section here. Then you select the location for the center point of the vertical duct, eye ball it and put it approximately in the middle, and then it will ask for the NE

[SP] elevation. We’ll again go up to 20 feet. And it will put in this duct here. Excuse me, I’m going to take another drink of water. So on that duct, it’s actually going to be drawn as a vertical duct even though it has a bit of a horizontal distance happening there.

I’m going to query that duct and we’ll change it to 18 inches so that it drafts nicely. And we draw the double line. So it’s going to draw it as a vertical duct centered on the endpoint of that duct, but it’s keeping the connection back here. So it’s basically putting a vertical duct and then if you did a transparent duct back you could do this with standard duct work.

It’s kind of combining that together in a single duct, in a single command to simplify life for you. So if you do need to do an offset duct, you can do it that way. And then from here, you know like normal, you can draw your duct work off of that piece. And then everything will be nicely connected.

Something looking like that. We also, there’s a couple of commands for helping you clean up your drafting. Typically, you’ve got your snaps on, or ortho, and everything lays out nicely at 90 degrees.

If you ever have a case where you have ducts that are kind of offset from each other, or not quite in line, we have the command called Straighten Next and Straighten Previous. And this will take ducts that are not quite in line, and it will line everything up nicely. So if I turn ortho off, and I draw in some duct work here.

You know, nothing there is quite at 90 degrees, and it’s going to look a little messy if you try and draft it in 2D. I’ll go ahead and do that. So you know, nothing’s really matching up. It’s a little confused as to what do fitting here wise. We can run the straighten command. If we run Straighten Next, and select this duct, it will say, “Okay, this duct is on the right angle, and will match everything to it.Either 90 degrees or in line with it.”

So if I select this duct, it arranges everything to match nicely. Now these two ducts are still not in line, so you can kind of go along and select this next one, and it will take that final duct and put it in line. So that’s how you can get something laid out nicely if you’re at a slightly odd angle.

We have a corresponding command, that’s the Straighten Next, we also have a Straighten Previous. And with this command, you select a duct and it will look behind it. So if I select this duct, it’s going to straighten this one back here and will leave this one alone. Not that one. I can select this one right here. So it’s worth noting that our software does have the concept of next and previous with the duct work.

So if you’re looking…I’ll change the duct to yellow. So if you’re looking at that yellow duct there, the green duct is the next duct because it’s the one that the yellow duct points to. It’s the one that’s toward the diffusers. It’s usually going to be the smaller duct. It’s not necessarily in the air flow.

If this was a return duct, the air would be flowing opposite of the arrow heads. Because we kind of draw out toward the diffusers always. But the next is always toward the diffusers. And then previous ducts are back here. I’ll put those in pink. So if you’re looking at the yellow duct, the previous ducts are the pink ones.

So that’s what we’re looking at when we’re looking at previous. So if you ever come upon that terminology in our software, that’s what we’re trying to indicate there. We also have the Reverse One Duct and Reverse Duct Branch commands. This is where you have a duct drawn in, and again since we have directionality, if you drew the directions wrong you can flip it.

The Reverse One Duct will take a single duct and flip it. So you can take something like that and flip this one duct, which then kind of confuses everything because we have two ducts coming into each other. But you can do it. Flip that one back. You can also run the Reverse Duct Branch, and this will go along and reverse everything in a line.

So if I reverse this green, it reverses the yellow and this first pink and leaves these other two pinks alone, because they’re going to flow out nicely. So if you need to, you know, reverse a whole line of duct work, you can use that Reverse Duct Line command and it will flip everything for you. I’m going to take another drink of water.

The final command I’d like to show you is the Move Duct Run Command. This is where you have a line of duct work and you want to shift the whole thing together.

So we’ve got these three ducts here and we need to offset it because, you know, you’re adjusting your design. But it can be a little tedious, particularly if they’re offset like this, to get all of those pieces of duct work and to get them all to move at the same time and the same distance. That’s what the Move Duct Run is for. We can take that duct and say, “Okay. We’re going to move it from here over to here.”

And it’s going to offset everything that distance in that line. And it will pull these other pieces along, but not otherwise move them. So yeah, if you have a run of duct work with multiple branches coming off of it, that’s how you can move the whole thing at once rather than trying to get a nice selection box here and stretch it, whatever. You can just use that command to simplify that process.

I am going to take a pause for a moment here and give you a chance to type in any questions that you have either based upon what I have gone over or any other questions on HVAC. So we have the chat box in the interface, so if you have any questions, go ahead and type them down there and I can answer them.

Well, thank you all for coming. I’m not seeing any questions, so I think we are going to be done for the day. And we will talk in November about building load calculations, so come with your questions for that. And thanks for using the software, and we’ll talk to you next month.

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