[Research Request] Calling Global Electrical Users: Your Voice is Needed to Enhance Revit Electrical Load Analysis Workflow!

[starry.cui]

Hi global electrical users,

Your feedback has been invaluable to us, and we’re thrilled to let you know that we’re now considering enhancing global Revit electrical load analysis workflow. We would be delighted if you are interested and have around 45 min time for a remote interview. Please fill out this survey (taking around 2 min) to let us better know you before the research session. We would talk about your local distribution systems and load calculation practices.

This will give us a chance to gain even more information about your challenges and expectations, so we can continue to make strides toward improving the Revit electrical workflow experience. Plus, as a thank you for your time and contributions, there’s even the possibility of receiving some incentives after research projects!

Looking forward to hearing from you,

Starry

[starry.cui]

Hi global electrical users,

Your feedback has been invaluable to us, and we’re thrilled to let you know that we’re now considering enhancing global Revit electrical load analysis workflow. We would be delighted if you are interested and have around 45 min time for a remote interview. Please fill out this survey (taking around 2 min) to let us better know you before the research session. We would talk about your local distribution systems and load calculation practices.

This will give us a chance to gain even more information about your challenges and expectations, so we can continue to make strides toward improving the Revit electrical workflow experience. Plus, as a thank you for your time and contributions, there’s even the possibility of receiving some incentives after research projects!

Looking forward to hearing from you,

Starry

[MichaelWarwick7522]

Hi, apparently 10+ years is not enough experience! It might be that I don't size electrical equipment, I do get involved in sizing electrical distribution boards and cables though, perhaps the first step would be to establish the nomenclature used globally.

[MichaelWarwick7522]

Hi, apparently 10+ years is not enough experience! It might be that I don't size electrical equipment, I do get involved in sizing electrical distribution boards and cables though, perhaps the first step would be to establish the nomenclature used globally.

[starry.cui]

Hi vedipoc426,
So glad to hear that you are interested in our research. Sorry that I am not sure which survey answer is yours. Could you please contact me through email (starry.cui@autodesk.com), so that I know your email and can talk about more research details then.

Many thanks 🙂
Starry

[starry.cui]

Hi vedipoc426,
So glad to hear that you are interested in our research. Sorry that I am not sure which survey answer is yours. Could you please contact me through email (starry.cui@autodesk.com), so that I know your email and can talk about more research details then.

Many thanks 🙂
Starry

[starry.cui]

Hi Michael,
Your experience also sounds very valuable for us. Currently our team would like to better understand the behavior of automatic transfer switch. If you have time or interest on this topic, would you mind to have a 45min remote interview with us? 😄 You can reach me through email (starry.cui@autodesk.com).

Best,
Starry

[starry.cui]

Hi Michael,
Your experience also sounds very valuable for us. Currently our team would like to better understand the behavior of automatic transfer switch. If you have time or interest on this topic, would you mind to have a 45min remote interview with us? 😄 You can reach me through email (starry.cui@autodesk.com).

Best,
Starry

[MuirEng]

Hello Starry,.

I have a great deal of experience with Revit in the electrical domain and I could provide feedback, but I must tell you that up to a point around 5 years ago I spent a great deal of time and energy attempting to influence and improve Revit’s electrical capabilities including a failed attempt to establish an expert user group and a dedicated subforum within the official Revit MEP forum. I've had conversations with the MEP product manager. I’ve posted many ideas for improvements on the ideas forum and exactly zero have been implemented to date. For a short time a quarterly online workshop was set up by one of your colleagues and I twice presented seminars demonstrating our workflows, hoping that by doing so this would lead to a community of knowledgeable users that Autodesk might listen to.

I’ve since given up this quest as futile and to be frank I simply do not believe that AutoDesk has a genuine interest in understanding of the needs of electrical designers and then addressing the limitations of the product which in turn lead to all kinds of kludges and workarounds.

If not for a very good add in by a third party that converts Revit MEP electrical from critically flawed to more or less functional we would likely have abandoned Revit and returned to AutoCAD years ago.

I do not know what you mean exactly by “electrical load analysis workflow”. When everything is connected properly in the model then loads flow up in a reasonably accurate fashion to the main supply switchboard. The categories for which loads can be assigned is a bit of a mess but I believe it can be made to work. We don't normally switch on the load categories on our panel and switchboard schedules. For us this is not a high prority and I'd prefer to see development resources allocated elsewhere. 

If you are interested in a conversation please let me know,

Thank you.

[MuirEng]

Hello Starry,.

I have a great deal of experience with Revit in the electrical domain and I could provide feedback, but I must tell you that up to a point around 5 years ago I spent a great deal of time and energy attempting to influence and improve Revit’s electrical capabilities including a failed attempt to establish an expert user group and a dedicated subforum within the official Revit MEP forum. I've had conversations with the MEP product manager. I’ve posted many ideas for improvements on the ideas forum and exactly zero have been implemented to date. For a short time a quarterly online workshop was set up by one of your colleagues and I twice presented seminars demonstrating our workflows, hoping that by doing so this would lead to a community of knowledgeable users that Autodesk might listen to.

I’ve since given up this quest as futile and to be frank I simply do not believe that AutoDesk has a genuine interest in understanding of the needs of electrical designers and then addressing the limitations of the product which in turn lead to all kinds of kludges and workarounds.

If not for a very good add in by a third party that converts Revit MEP electrical from critically flawed to more or less functional we would likely have abandoned Revit and returned to AutoCAD years ago.

I do not know what you mean exactly by “electrical load analysis workflow”. When everything is connected properly in the model then loads flow up in a reasonably accurate fashion to the main supply switchboard. The categories for which loads can be assigned is a bit of a mess but I believe it can be made to work. We don't normally switch on the load categories on our panel and switchboard schedules. For us this is not a high prority and I'd prefer to see development resources allocated elsewhere. 

If you are interested in a conversation please let me know,

Thank you.

[starry.cui]

Hi Brian,

I understand your frustration and disappointment with the past experiences you've had while trying to influence and improve Revit's electrical capabilities. It's evident that you've invested a significant amount of time and effort in attempting to address the limitations and push for enhancements. At Autodesk, we value the feedback and suggestions from our users, and we are constantly working to improve our products based on customer needs and demands. Looking at the your previous requests, some of your requests are actually implemented like "Most recently used" and search, frame as parameter to Spares, tag the elevation for electrical fixtures and edit any Panel and Circuit property from the Panel Schedule view. And some of other requests are on our radar. Please stay tuned.

However, it's essential to recognize that software development often involves various priorities and considerations. While we would love to address every user request immediately, we have to carefully balance resources and focus on areas that have a broader impact or align with our strategic goals. But please know that your feedback is still valuable to us! We will continue to listen to our users' needs and try to incorporate meaningful changes whenever possible. Regarding the "electrical load analysis", the new function allows electrical designers and engineers to capture electrical design requirements directly within the software, reducing the burden of disconnected workflows. The new functionality includes creating an electrical analysis model for preliminary design, enabling efficient load analysis and planning before placing physical electrical families in the Revit model. - here are the two links for more information (link 1; link 2). We are about to have a usability test this Oct, if you are interested, we are more than delighted to know your feedback.

Thank you for your understanding, and it would be great if you list your biggest challenges in Revit (please rank them), once we have developed something, we will contact you for internal research or usability test. We are here to support you in any way we can.

Starry

[starry.cui]

Hi Brian,

I understand your frustration and disappointment with the past experiences you've had while trying to influence and improve Revit's electrical capabilities. It's evident that you've invested a significant amount of time and effort in attempting to address the limitations and push for enhancements. At Autodesk, we value the feedback and suggestions from our users, and we are constantly working to improve our products based on customer needs and demands. Looking at the your previous requests, some of your requests are actually implemented like "Most recently used" and search, frame as parameter to Spares, tag the elevation for electrical fixtures and edit any Panel and Circuit property from the Panel Schedule view. And some of other requests are on our radar. Please stay tuned.

However, it's essential to recognize that software development often involves various priorities and considerations. While we would love to address every user request immediately, we have to carefully balance resources and focus on areas that have a broader impact or align with our strategic goals. But please know that your feedback is still valuable to us! We will continue to listen to our users' needs and try to incorporate meaningful changes whenever possible. Regarding the "electrical load analysis", the new function allows electrical designers and engineers to capture electrical design requirements directly within the software, reducing the burden of disconnected workflows. The new functionality includes creating an electrical analysis model for preliminary design, enabling efficient load analysis and planning before placing physical electrical families in the Revit model. - here are the two links for more information (link 1; link 2). We are about to have a usability test this Oct, if you are interested, we are more than delighted to know your feedback.

Thank you for your understanding, and it would be great if you list your biggest challenges in Revit (please rank them), once we have developed something, we will contact you for internal research or usability test. We are here to support you in any way we can.

Starry

[MuirEng]

Hi Starry, thanks for your reply. I'll attempt to provide some feedback about what I see as the main issues with the product from our point of view as consultants using Revit to produce contract drawings for electrical work. 

[MuirEng]

Hi Starry, thanks for your reply. I'll attempt to provide some feedback about what I see as the main issues with the product from our point of view as consultants using Revit to produce contract drawings for electrical work. 

[Jboone4HV2J]

I would like access to see wire, conduit size and to control as I see fit.

Cable tray should also be capable of adding weight per foot.  Routing is not always so easy to master when the tees have to go down and into a gear or what ever.

[Jboone4HV2J]

I would like access to see wire, conduit size and to control as I see fit.

Cable tray should also be capable of adding weight per foot.  Routing is not always so easy to master when the tees have to go down and into a gear or what ever.

[Jboone4HV2J]

Also, engineers are not very good at looking at voltage drops along a length of run from panel to last receptacle.  They normally skip this part of design and go with a kill design.  The point is, that I can provide a #10 wire at the first 100' then drop off from that with #12 at some point, But Revit can not handle this part of design.  Knowing voltage drop laws will save a lot of money and materials (which should be of interest to all).  I have done this with some large school buildings.  I don't think Revit tells me what voltage drop is at any point in a run.

[Jboone4HV2J]

Also, engineers are not very good at looking at voltage drops along a length of run from panel to last receptacle.  They normally skip this part of design and go with a kill design.  The point is, that I can provide a #10 wire at the first 100' then drop off from that with #12 at some point, But Revit can not handle this part of design.  Knowing voltage drop laws will save a lot of money and materials (which should be of interest to all).  I have done this with some large school buildings.  I don't think Revit tells me what voltage drop is at any point in a run.

[dbutts7]

A keen point of interest to use to create the relationship between the analytical load components and the physical representation of the model. Every engineer/designer I know is looking for this as a end-goal, with data shared between the two. That was the intent when we helped Autodesk design the P&ID modeler tool - I think development in this direction is critical.

thanks - David B.

[dbutts7]

A keen point of interest to use to create the relationship between the analytical load components and the physical representation of the model. Every engineer/designer I know is looking for this as a end-goal, with data shared between the two. That was the intent when we helped Autodesk design the P&ID modeler tool - I think development in this direction is critical.

thanks - David B.

[Jboone4HV2J]

The flex conduit for mechanical is great.  Why doesn't electrical have anything like that?  It can simply be transferred to electoral by changing its family type.  We have nothing for flex to transformers or other equipment.

Open up conduit, bus duct and cable tray to have shared parameters for length of runs?  I was finally able to make some of these parameter's but it is not as simple as adding them like other groups.  The height above (and assigning a level) is especially difficult to get out of these families since we can not edit them so we can include parameters we need.  We are at the whims of Revit to adjust the top, center or bottom of these runs.  I want things to be more consistent with the height, top bottom or center across all heights, not to have one center and another at the bottom.  BE CONSISTANT.

I also want to include weight of cable tray at any points in a cable tray or run of conduit.  Some clients are very strict about weight and the amount of sway of these systems.  How can we possibly be scientific about hangers when it is so difficult to judge weight in a specific magnitude of earthquake?  I know this is a stretch, but a vital roll of what I think Revit should deliver at some point on every aspect of building.  If I tell Revit my weight of wire and conduit per foot, I would hope that you would help me determine what sort of hanger to use, or if I can look at structural steel column would support, or use my data to help determine weight limitations.

Cable tray and conduit connections need more work to help me get these systems connected, some seem buggy when trying to connect.  Going from front, back, top, and 3d is very difficult at times.  Maybe incorporate arrow keys to help in some of this.  Offsets in cable tray is very difficult too.

[Jboone4HV2J]

The flex conduit for mechanical is great.  Why doesn't electrical have anything like that?  It can simply be transferred to electoral by changing its family type.  We have nothing for flex to transformers or other equipment.

Open up conduit, bus duct and cable tray to have shared parameters for length of runs?  I was finally able to make some of these parameter's but it is not as simple as adding them like other groups.  The height above (and assigning a level) is especially difficult to get out of these families since we can not edit them so we can include parameters we need.  We are at the whims of Revit to adjust the top, center or bottom of these runs.  I want things to be more consistent with the height, top bottom or center across all heights, not to have one center and another at the bottom.  BE CONSISTANT.

I also want to include weight of cable tray at any points in a cable tray or run of conduit.  Some clients are very strict about weight and the amount of sway of these systems.  How can we possibly be scientific about hangers when it is so difficult to judge weight in a specific magnitude of earthquake?  I know this is a stretch, but a vital roll of what I think Revit should deliver at some point on every aspect of building.  If I tell Revit my weight of wire and conduit per foot, I would hope that you would help me determine what sort of hanger to use, or if I can look at structural steel column would support, or use my data to help determine weight limitations.

Cable tray and conduit connections need more work to help me get these systems connected, some seem buggy when trying to connect.  Going from front, back, top, and 3d is very difficult at times.  Maybe incorporate arrow keys to help in some of this.  Offsets in cable tray is very difficult too.

[Jboone4HV2J]

There is more and more talk these days about getting nothing for so many years and paying such high rent for something we don't have any return for.

[Jboone4HV2J]

There is more and more talk these days about getting nothing for so many years and paying such high rent for something we don't have any return for.

[starry.cui]

Hi David,

It is great that you have contributed to the development of P&ID modeler. And I am so glad that you call out the value and importance of bridging analytical and physical data. It is on our radar! We absolutely understand its value and importance for the users. Therefore, we are actually planning some research to know better about relevant user scenarios and understand the details how to bring more values in user workflow. It would be more than delighted if you could participant in our future research and co-create something together (my contact: starry.cui@autodesk.com). 

Looking forward to your reply,

Starry

[starry.cui]

Hi David,

It is great that you have contributed to the development of P&ID modeler. And I am so glad that you call out the value and importance of bridging analytical and physical data. It is on our radar! We absolutely understand its value and importance for the users. Therefore, we are actually planning some research to know better about relevant user scenarios and understand the details how to bring more values in user workflow. It would be more than delighted if you could participant in our future research and co-create something together (my contact: starry.cui@autodesk.com). 

Looking forward to your reply,

Starry

[starry.cui]

Hi James,

Sorry to hear the frustration and disappointment and also appologies for the late responses. 

"....The point is, that I can provide a #10 wire at the first 100' then drop off from that with #12 at some point, But Revit can not handle this part of design..."

"Cable tray and conduit connections need more work to help me get these systems connected, some seem buggy when trying to connect. "

--- I sort of understand the issue, but in order to better understand it, could you please also write me a email (starry.cui@autodesk.com) with relevant data set for the buggy issues and related electrical code regarding the voltage drop laws, if it is possible? So, I can also loop other team members to have a look at it.

regarding the hangers issues, I left a message to my colleague who work on "mechanical supports". 

For other issues of parameters of conduits, cable trays and bus duct, please bear with me that I am not really a expert of all electrical physical features :D.But I will explore the relevant features in Revit and get back to you in the next few days.

Best,

Starry

[starry.cui]

Hi James,

Sorry to hear the frustration and disappointment and also appologies for the late responses. 

"....The point is, that I can provide a #10 wire at the first 100' then drop off from that with #12 at some point, But Revit can not handle this part of design..."

"Cable tray and conduit connections need more work to help me get these systems connected, some seem buggy when trying to connect. "

--- I sort of understand the issue, but in order to better understand it, could you please also write me a email (starry.cui@autodesk.com) with relevant data set for the buggy issues and related electrical code regarding the voltage drop laws, if it is possible? So, I can also loop other team members to have a look at it.

regarding the hangers issues, I left a message to my colleague who work on "mechanical supports". 

For other issues of parameters of conduits, cable trays and bus duct, please bear with me that I am not really a expert of all electrical physical features :D.But I will explore the relevant features in Revit and get back to you in the next few days.

Best,

Starry

[Jboone4HV2J]

Here is a good article on the tap rule from Mike Holt.  The main objective is to keep voltage drop off conductors as much as possible.  Other than that you have to do a foot by foot calculation of wire up to any point in a circuit.

https://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/FeederSecondaryTapRules~20020326.htm

https://www.ecmweb.com/national-electrical-code/code-basics/article/20900291/understanding-the-rules...

https://library.e.abb.com/public/9e7ae3c8094341488549ef5a3e791064/ABB-1742-WPO_NEC_Tap_Rules.pdf

https://up.codes/s/feeder-taps

https://quizlet.com/764902401/26401-load-calculations-feeders-and-services-flash-cards/

I used this technique for a very large school where corridors were long and electrical rooms was rare and far between.  Usually we can go about 75 feet with #10, or #8 for 200' where voltage drop start being affected,  and start dropping off #12 when circuit is ok.  #12 makes more sense when wiring receptacles on a 20A breaker of course.

[Jboone4HV2J]

Here is a good article on the tap rule from Mike Holt.  The main objective is to keep voltage drop off conductors as much as possible.  Other than that you have to do a foot by foot calculation of wire up to any point in a circuit.

https://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/FeederSecondaryTapRules~20020326.htm

https://www.ecmweb.com/national-electrical-code/code-basics/article/20900291/understanding-the-rules...

https://library.e.abb.com/public/9e7ae3c8094341488549ef5a3e791064/ABB-1742-WPO_NEC_Tap_Rules.pdf

https://up.codes/s/feeder-taps

https://quizlet.com/764902401/26401-load-calculations-feeders-and-services-flash-cards/

I used this technique for a very large school where corridors were long and electrical rooms was rare and far between.  Usually we can go about 75 feet with #10, or #8 for 200' where voltage drop start being affected,  and start dropping off #12 when circuit is ok.  #12 makes more sense when wiring receptacles on a 20A breaker of course.

[MichaelWarwick7522]

To calculate electrical loads, you need to know the length of the cable and what is around it. Cables bundled together have to be upsized compared with single cables, and cables that are in an insulated environment, e.g. run in insulated walls, need to be upsized compared with cables in open air. So, the first step to be able to usefully size cables in Revit is to be able to associate cables with cable containment. Current wire paths are really hard to work with and don't create an association so you can't see what other wire paths are in the same cable tray or conduit. 

[MichaelWarwick7522]

To calculate electrical loads, you need to know the length of the cable and what is around it. Cables bundled together have to be upsized compared with single cables, and cables that are in an insulated environment, e.g. run in insulated walls, need to be upsized compared with cables in open air. So, the first step to be able to usefully size cables in Revit is to be able to associate cables with cable containment. Current wire paths are really hard to work with and don't create an association so you can't see what other wire paths are in the same cable tray or conduit. 

[starry.cui]

@MichaelWarwick7522 

Hi Michael,

Sorry for the late reply. In order to size cable correctly, can I understand that the followings are missing?

1. the right length of cable, which means the wire pathes should align with cable containments e.g. cable tray, conduit...

2. Once the wire path could be connected with correspondent cable containments, the cable containments should carry the information like quantity, size of the wires that pass through the cable containment. And the wires should include the information like which cable containments which they pass through; whether they are bundled or not; whether they are in a insulated environment. So, you can upsize the wire correspondently.

And regarding "upsizing the cable", it is done by engineer experience or preferrence, or it is calculated accurately by certain rules?

@Jboone4HV2J 

Hi James,

Sorry for the late responses as well. Finally I was able to have more time to dig into the issues that you mentioned before.

When you posted "I would like access to see wire, conduit size and to control as I see fit." "Routing is not always so easy to master when the tees have to go down and into a gear or what ever." do you mean the same issues of getting right cable size?

Best,

Starry

[starry.cui]

@MichaelWarwick7522 

Hi Michael,

Sorry for the late reply. In order to size cable correctly, can I understand that the followings are missing?

1. the right length of cable, which means the wire pathes should align with cable containments e.g. cable tray, conduit...

2. Once the wire path could be connected with correspondent cable containments, the cable containments should carry the information like quantity, size of the wires that pass through the cable containment. And the wires should include the information like which cable containments which they pass through; whether they are bundled or not; whether they are in a insulated environment. So, you can upsize the wire correspondently.

And regarding "upsizing the cable", it is done by engineer experience or preferrence, or it is calculated accurately by certain rules?

@Jboone4HV2J 

Hi James,

Sorry for the late responses as well. Finally I was able to have more time to dig into the issues that you mentioned before.

When you posted "I would like access to see wire, conduit size and to control as I see fit." "Routing is not always so easy to master when the tees have to go down and into a gear or what ever." do you mean the same issues of getting right cable size?

Best,

Starry

[Jboone4HV2J]

Does Revit expect to know what I want in conduit or cable tray or are we going to AI (no where close right now) everything without giving users a choice of what to use?  There is no way in the world Autodesk could predict what I want in conduit, and I don't guess they would care what the weight of conduit and which wires to use, how many wires, with varying sizes I might add.  The tees would be something for cable tray, with the same characteristics of conduit but all those things are just as important, especially wire and number of them.  Hangers play a very important roll here too as I am designing now.  Unistrut and its calculations of weight are very important for clients who have very strict rules for securing and lateral bracing.  Does any of this matter?  Very much so on the very back end of contractors.

I can send you some pdf's with some vey interesting bills of materials that as far as I know, have never been seen before with these very important items I listed above.

Cable tray is very difficult to route too yes.  They lose characteristics very easily when we have to move the tray, which happens frequently because of collisions.

[Jboone4HV2J]

Does Revit expect to know what I want in conduit or cable tray or are we going to AI (no where close right now) everything without giving users a choice of what to use?  There is no way in the world Autodesk could predict what I want in conduit, and I don't guess they would care what the weight of conduit and which wires to use, how many wires, with varying sizes I might add.  The tees would be something for cable tray, with the same characteristics of conduit but all those things are just as important, especially wire and number of them.  Hangers play a very important roll here too as I am designing now.  Unistrut and its calculations of weight are very important for clients who have very strict rules for securing and lateral bracing.  Does any of this matter?  Very much so on the very back end of contractors.

I can send you some pdf's with some vey interesting bills of materials that as far as I know, have never been seen before with these very important items I listed above.

Cable tray is very difficult to route too yes.  They lose characteristics very easily when we have to move the tray, which happens frequently because of collisions.

[starry.cui]

@Jboone4HV2J 

Hi James, I totally understand the needs of "weight per foot" parameter.It makes sense.

But could you please help understand better your request about "height" parameters and the "parameter consistancy"?:

1. which Revit version do you use for now? Here is a screenshot of R24 (see the first attachment). It shows height/ elevation related parameters. In R23, we have done some improvements about elevation parameters. I dont know whether it helps.

2. If it doesn't help, please see the second attachment. I listed all possible elevation points, could you please let me know which are the parameters that you need the most?

Regarding the tap rules, I am still reading the materials that you provided. But I will definitely get back to you in this regard.

Best,

Starry

[starry.cui]

@Jboone4HV2J 

Hi James, I totally understand the needs of "weight per foot" parameter.It makes sense.

But could you please help understand better your request about "height" parameters and the "parameter consistancy"?:

1. which Revit version do you use for now? Here is a screenshot of R24 (see the first attachment). It shows height/ elevation related parameters. In R23, we have done some improvements about elevation parameters. I dont know whether it helps.

2. If it doesn't help, please see the second attachment. I listed all possible elevation points, could you please let me know which are the parameters that you need the most?

Regarding the tap rules, I am still reading the materials that you provided. But I will definitely get back to you in this regard.

Best,

Starry

[Jboone4HV2J]

I am using 2023 on my current project.

I prefer a bottom parameter for cable tray, because that is where my rack would be placed with a level parameter.  but not all cabletray connector have a consistent height adjustment.  In other words, tray may be able to be adjusted with bottom parameter, but connectors use something differently.  Why would this eve happen?

When having to change height of cable tray after the fact,,,  of course the tees didn't ant to cooperate, and it was a real mess having to back thought the four miles of tray to adjust all tray and fittings to make it work.  Now things are disconnected and hard to control the branch.

Changing any one elevation when there 4 miles of tray is not going to help much there are are so many attachments involved, but I prefer the bottom on ALL connections.  Of course there are 90's and other verticals runs too.

[Jboone4HV2J]

I am using 2023 on my current project.

I prefer a bottom parameter for cable tray, because that is where my rack would be placed with a level parameter.  but not all cabletray connector have a consistent height adjustment.  In other words, tray may be able to be adjusted with bottom parameter, but connectors use something differently.  Why would this eve happen?

When having to change height of cable tray after the fact,,,  of course the tees didn't ant to cooperate, and it was a real mess having to back thought the four miles of tray to adjust all tray and fittings to make it work.  Now things are disconnected and hard to control the branch.

Changing any one elevation when there 4 miles of tray is not going to help much there are are so many attachments involved, but I prefer the bottom on ALL connections.  Of course there are 90's and other verticals runs too.