Revit MEP: Rules, Links, FAQ and Resources

[mjdanowski]

Welcome to the AUGI Revit MEP forums!

Within these forums you will find a vibrant, community of Revit MEP users who will be more than willing to help you with your hair-pulling, absolutely aggravating Revit problem! Feel free to post whatever questions you may be having, regardless of how simple it may be, however please post in accordance with the following guidelines:

1. Like all AUGI forums, please post in accordance with the AUGI Forum Rules & Guidelines

2. Play Nice! We all know that Reviting can put you in a bad mood from time to time (to say the least), but remember that everyone on the forums are here to help! Be considerate in your posts and everyone will be more likely to help you with your problem.

3. Use the Appropriate Forum - Please use the appropriate forum under the "Revit MEP Support" category.

4. Don't post or ask about confidential information, specifically information held under an NDA (non-disclosure agreement)! As a general rule of thumb, if you cannot find information on a new Autodesk product through a simple Google search, you probably aren't supposed to know it yet.

5. Read the FAQ - Please read the FAQ under this post and check if your question has already been answered. I will try to keep it as updated as possible as I see more common questions.

If you have any additional questions or concerns, please feel free to PM me!

Informative Links:
Inside the System - The blog of Kyle Berhardt, Revit MEP Project Manager. Contains many informative videos and articles on different functions of Revit MEP.

Revit MEP Resource Center - Autodesk's official resource center with tutorials and guides.

Revit MEP Download Page - Where you can find content extensions, web updates and product downloads.

Key Terms and Acronyms:

BIM: Building Information Modeling (Link)
Element: An element is a single piece of the Revit Model, such as a single light fixture, receptacle, duct fitting, or pipe. Sometimes referred to as an instance.
Family: A family is a mid-level organizational element which is the closest relative to a block in AutocCAD. Usually a family is a separate file from your project, and usually represents different types of geometry. Families are usually made up of many different types.
Model: In Revit, the model is that which you are actually building. It represents both the 3D geometry, and the parameterized of information behind it.
Parameter: A parameter is the basic building block of all things Revit. In parameters you keep dimensions, loads, calculations and designations for all of your model. Parameters come in 4 different varieties; System, Project, Shared and Family.
System: A system in Revit is that which represents a logical link between different elements. Systems include electrical circuits, an HVAC supply line or a chilled water supply for an air handling unit.
Type: A type in Revit represents a different set of parameters under a family. Different types are generally used when you have a large number of elements with similar properties which you want to define within its own group. A good example of this are lighting fixtures, information for a type "A" lighting fixture will always be the same for all of its type.
View: A view is that which pulls information from a model to create perspectives, analysis and presentation of a model. Views include floor plans, ceiling plans, elevations, part plans and even schedules.



Common Errors:

Line Too Short: This error occurs when you essentially try to squish something into nothingness. For a good example on why you get this error, go into Revit and make an "H" with three detail lines, drawing the center "connecting line" last. Revit will automatically constrain that center line to the outer two, so if you move one of the outer vertical lines, the center line will extend or shorten itself accordingly. Now take the right vertical line and drag it right on top of the left vertical line. When you do this you will get the "line too short" error because that center line has nowhere to go and you are essentially making it disappear, hence the delete option. You will generally hit this error a lot when dealing with constraints. If you get it after changing the dimension parameters of a family in a project, check to make sure you didn't accidentally constrain something which would cause this problem.

Flow Direction Mismatch: Oh boy, my favorite error! You get this when dealing with either piping and/or HVAC duct systems and are trying to correctly connect two mechanical or plumbing elements. The cause of this error is because a connector on one side of the system does not coordinate with a connector on the other end. Within your HVAC or plumbing connector, there is a nice little parameter called "Flow Direction" which can be set to either "out" or "in." This parameter must be coordinated with all the connectors in the system or you will get this error. Flow usually goes from out -> in in general scope of a system. If you have two pieces of equipment with "out" and no equipment with "in," it will error. Though it seems easy, it is pretty easy to get confused with this. The one thing to remember is that the flow direction is in relation to the connector from the system. A perfect example of where this can be confusing is with an exhaust air terminal. An exhaust terminal will exhaust air out of the family making you think that it should be set to "out," however the connector is receiving air from the system and therefore should be set to "in." It takes a while for this to become second nature, but even then on complex systems it can get a little frustrating. The best way to avoid it is to make simple sample systems when you first create your families to make sure everything is set correctly. It is a lot easier to do it then way then when you have 30 things connected to it.

Duplicate Mark Values: Every time you place an element into the model, that element is assigned an incremental "mark" value under a parameter of the same name. When you have a worksharing enabled model with two or more people working in it, elements are placed by each user with similar mark values because each user is unaware of the other users actions. There is really no way to avoid this, and the only way to make the error go away is to manually rename every element, which is unrealistic.

[mjdanowski]

General Revit Questions:

Q. Help, I can't find my element! (and I dont mean my Honda)
A.One of the biggest things to learn in Revit is how to manipulate your current view. Many times you will place something in the model only to not see anything but a friendly warning message that you just lost your run of pipe. There are many ways to go about finding lost elements, here are a few big ones:
a) View Depth: Right click and go to View Properties->View Depth. This will open up your view depth dialogue which essentially shows where you are making your cut into the model, how deep you are viewing and how high you are viewing. If you set a receptacle and your bottom range is set to 45" then there is a good possibility you will not see anything mounted at 18"
b) Check your insertion Elevation!: Did you just make a duct run at 30,000ft? Does your light fixture accidentally have a default mounting height of 0"? If you insert something on the 5th floor, more then likely it will not show up on 2nd floor views. This may sound kind of stupid, but checking mounting height is and extremely good habit to get into, because I assure you this will happen.
c) Did you turn it off?: This is the number one frustrater of lost elements! Many times you will turn certain categories off for whatever reason in your graphical overrides menu (View Properties -> Visibility/Graphics Overrides) and forget about it. Then when you try to place something of that category it does not show up, much to your frustration.
These are just some of the possible offenders with lost elements, but are also the major ones.
d) Is it phased correctly?: It is possible your view is set up to only show certain phases on a multi-phase project. Check what phase your element is inserted under and then check the phase visibility of your view.

These are just some of the possible offenders with lost elements, but are also the major ones.

Q. How to I put the architects model into my model?
A.This is done through what is called a "linked model." Much like XREFs in AutoCAD, linked models provide us with much of the functionality of a XREF, but in 3D and with a few more added features. To link a Revit model into your model go to File -> Import/Link -> Revit. This will then bring you to a dialogue where you can choose which model you wish to link. You will also notice that when you go to the "Import/Link" menu, you have the option to bring in many other formats, including .dwg should you wish to use a 2D plan view and/or details.

Q. What is the difference between annotation and model? Can I have one without the other?
A. This is a question that is usually asked by those who are just starting out in Revit and are trying to get a library/work flow going. The difference between an annotation and a model element is that a model is the "physical" representation of what you are building, while the annotation is the "plan" representation of the model. For example, with a wall mounted receptacle, you could have a physical model of a receptacle that protrudes 1/4" from the wall. Unfortunately on plan, this is kind of hard to show since it is so small. In the MEP industry we use symbols to represent a receptacle because of this, and Revit can do the same thing if you so desire. Annotations can be stand alone symbols, representing no models, or they can be nested with a model to represent it in a variety of ways. Model elements can also be stand alone, with the only plan representation being their physical outline, or symbolic line work. Through the use of parameters you have an extremely large amount of options with regards to presentation of your different elements, keeping a good balance between actual BIM representation and clean, coordinated drawings.

Q. How do I get architectural Room names in space tags?
A. When you place a space where a room is bounded, the space will retain certain information from that room. Specifically, the room name and number will show up as instance parameters for that space. Default space tags only link to the parameters for the space name and number. To fix this, go into your space tag family and change the linked parameter from "Space Name" and "Space Number" to "Room Name" and "Room Number". To do this you will need to select the parameters listed under "room" in the drop down menu.

Q. I hear manufacturers are starting to make Revit families of their products, is there a place I can find them?
A. Yes, you can either find them from the Autodesk Seek feature within Revit, or you can check out a list compiled by forum regulars over Here. The Seek database will also have all the "generic" Revit content for just about everything else as well. If you need a family, go there.

Q. How to I make a standalone leader?
A. The easiest way to go about doing this is to create a new annotation symbol family. Go to R -> New -> Family and then select the template for the generic annotation family. From here, there will be two reference planes defining an origin. The good news is, the family is already done. Save it to whatever your heart desires and then load it into a project. When you try to place it, the annotation symbol will be blank. This is ok since we only want the leader. While selecting the black annotation, go to your ribbon and click "Add Leader". This will add a leader off of the non-existent symbol and you have your standalone leader line.

[mjdanowski]

Electrical:

Q. How do you make a one-line/riser diagram for your model?
A. Unfortunately at this time, there is no feature to do this automatically. However, that does not mean you can't do it in Revit! Any sort of drafting is quite easy to accomplish using drafting views and annotation symbols. Revit bases its symbology annotation in paper space, so once you have a good symbol library going, it is quite easy to deal with drafting as a whole. Using drafting views for such thing also lets you utilize the great project management tools within Revit.

Q. Whats the deal with panel schedules?
A. As of the 2011 release of Revit MEP, panel schedules are (almost) fully customizable and ready for use through a very usefull template system.

Q. My face based light fixture will not host on the ceiling/floor!
A. Right next to your type selection drop down menu you will see three little buttons with the mouseover of "Place of Vertical Face," "Place on Face" and "Place of Work Plane." By default, Revit will try to place faced based families on a vertical face, to get it on a floor or ceiling you need to click the middle "Place on Face" button. This will fix the problem most of the time, but there are instances where face based fixtures and ceilings don't get along. The best way that I have found to get around that is to place the fixture in a 3D view, and then copy/move then around as needed in plan view. The 3D view is always good for getting the right elevations.

Q. My electrical parameter values are not showing up in my load calculations/panel schedules.
This can be due to a lot of reasons, here are the most common:
1. You did not link the family/shared/system parameter to the connector. Unless you link your parameter in the type settings dialogue to the parameters on the connector, you will not see a correlation to the two. You can link the parameter by clicking the little box next to the name in the connector.
2. You must set Voltage and Number of Poles parameters as a type parameter to have them stick to what they are set up the the properties dialogue. If you do not do this, you will be prompted in the project for this information, bypassing whatever you originally set.
3. Your element is not truly within the space which you want it to be. Check space boundaries and make sure your fixture is within it for it to show up in the power density and summation calculations. Generally speaking, the origin of the family is the point which needs to be inside.

Q. How do I get multiple circuits on one junction box or device?
There are multiple ways to do this. The big problem is that multiple circuit devices have two things which must be accomplished; logical (electrical) connection and annotative connection.

-The first, and most obvious way to do it is to physically place two connectors on the junction box family. When you create a circuit with the family you will be given the option of which connector to use. The problem with this is that you cannot have a two arrow home run, though you could potentially fudge it by overlapping the two single arrow ones.

- The next option is creating "dummy fixtures" which do not show up on plan, but are electrically connected to a fixture that is. To achieve two home-run arrows, you must have two fixtures connected by wire elements which are on separate circuits. With a circuit containing only one element, this cannot be done with the visible fixtures. To get around this, you can create a dummy fixture which is not visible in plan, connect it with a hidden or invisible wire, and then put that on another circuit. This will create the two circuits for your one visible fixture.

Q. My electrical device is hosting to a ceiling, but the symbol isn't showing up! What gives?
A. Many family categories within Revit do not have a category option to "maintain annotation orientation", such as lighting fixtures and electrical equipment. This check box, which is located in the family categories box of a family allows for any annotation symbols to show up should the family be placed on a non-parallel plane. Without this option, anytime you host a family of such a category on a sloped ceiling, the symbol will not show up. Annotation, in its native form will only show up on views parallel to its orientation. When it is hosted on a sloped surface, it disappears on plan. To get around this you can either change the category of the family to something which does have this option (electrical fixtures, lighting devices), or use a detail component.

[mjdanowski]

Mechanical:

Q. My duct fitting family has been possessed by the devil!
A. Ducts and/or pipes going bonkers when trying to use a certain fitting can be a common problem with a few different causes/solutions. The biggest one of course is an elevation difference, have you made sure that the two connecting ducts are at the same elevation? If not, Revit is going to try to route and place fittings as needed to get to point A to point B, sometimes with rather unsavory results. Another possibility, is that your fitting family is in itself corrupt. To remedy this you need to reload from the latest Revit MEP catalog. In a project however, to reload the definition correctly, the new family from the catalog needs to be "newer" then the old one in the project. To do this, open up the new family to be loaded, change a parameter to something random and back and then save. This will make the family file "updated" as of when you changed the parameter.(Thanks Kyle.B)

Q. I am told my duct system is not "well connected," what does this mean?
A well connected duct system will not have any open ends, loose connectors or what you could consider "leaks". This means if you just terminate a duct at a wall without an endcap or diffuser attached it to, it will not register in system calculation because Revit gets confused. To fix this instance of the error, make sure you put endcaps when a duct terminates, this fix will help you the majority of the time.
A "well connected" error will also originate when you do some crazy connector to a fitting or device that doesn't sit well, isn't orthogonal or misses the connector. Many times you will think you have connected two duct elements, but in reality they are just sitting right next to each other with no logical connection. Finding where in a duct system this disconnection is occurring can be a bit of a hassle, but there are a few tricks to help you square everything up.
First, all ducts connected to a certain system type connector will inherit that system type, such as supply etc. The place where the ducts stop inheriting this property in your system is where the fault has occurred. To make things right, just stretch the problem duct back, and then pull it up again connecting it with the round connector symbol. This strategy will also work for finding faulty connections as well. Duct elements which don't move when an adjacent duct is moved are not connected to it, and therefore a faulty connection.