Duct Connectors

[1N.]

I saw Kyle's movies on his blog and it makes more sense now, but do you have any other
tips on tricks how to figure connectors for each type of equipment. Need to have final answers on a burning VAV connectors question.
VAV example: I am saying that inlet connector should be Preset/IN/Specific loss...and Discharge connector needs to be Calculated/Out/Not defined-for single duct VAV....expert in the office says it can be reverse too(except flow direction still the same) and I tested and it works too if I have the AHU connector to Calculated. So I guess is still propagating the data in the right direction(opposite of the airflow)....and I have not the right argument to say he is wrong or we are both right in this case. F1....I think tutorials kind of suck explaining duct connectors.

[JoelLondenberg]

VAV example: I am saying that inlet connector should be Preset/IN/Specific loss...and Discharge connector needs to be Calculated/Out/Not defined-for single duct VAV.... AHU connector to Calculated

I agree with you, with one addition - the flow for both the inlet and outlet connectors on the VAV are mapped to the same flow parameter. This allows the flow set at the air terminals to define the flow of the VAV box, and continue upstream to define the flow at the AHU.

Data should propagate from the point of use, upstream to the suppling equipment. Air terminals drive VAV's which drive air handlers. The need determines the equipment.

[1N.]

Thanks for the reply I was almost sure but I still wanted somebody to agree with me...:)
Not understanding completly linking of connectors. In the same VAV case again do I have to link them? It doesn't seems like is effecting anything.
My next question is what you do when you add Hot water coil to this VAV? Do you have it as part of the VAV family or you prefer to have it as separate family and how do you set up the connectors of that? Calculated on the discharge and Preset on the inlet again so it pushes the data again to the VAV and further in the system to the AHU?

[JoelLondenberg]

To link the connector to a parameter, go to the properties of the the connector and pick the tiny button on the right hand side of row (see the picture). Then select the flow parameter you are using. Do this for both the inlet and outlet connector, this will let the outlet connector (calculated remember) to collect flow data from the air terminals and write that data in to the parameter. The inlet connector (preset) now has it's flow set by that parameter.

As for hw coil, for all equipment that functions as a package, I build as a package. Make the size of the box flexible so you can make it larger for different coil arrangements or smaller when there is no coil.

[1N.]

I know how to link connector to parameter. My question was about linking the two connectors and what that does. I don't see the diffrence between linked and not linked connectors. When is that important?

[1N.]

Joel, thanks for all your responses. I was reading one of the AU papers and there I received answer on my question about linking 2 connectors.
" Linked connectors only have effect when the System Type is set to Global, which is common for fittings and in-line components such as dampers, valves and pumps."
My next question is on connectors again.
This seems to be great issue some times in our office. Do we blindly trust all
the connectors that come with Revit MEP content? I think I understand them, but sometimes the generic Revit family says totally different thing that what I am thinking, so now I am really not sure if I am right or the Autodesk approved content is right. I did notice few discrepancy here and there, but let me just give you example. Trying to create Fan Power Box-Series family.


This is what Revit standard block is having on the 3 connectors.( I tested it in a system and the data is not propagating at all)

1. SUPPLY/ CALCULATED/ IN / SPECIFIC LOSS – PRESSURE MAPPED TO NONE, AIRFLOW MAPPED TO PRIMARY AIRFLOW

2. RETURN/ CALCULATED / IN / SPECIFIC LOSS – PRESSURE MAPPED TO PLENUM AIR PRESSURE, AIRFLOW MAPPED TO PLENUM AIRFLOW

3. SUPPLY/ CALCULATED / OUT / SPECIFIC LOSS – PRESSURE MAPPED TO PRIMARY PRESSURE, AIRFLOW MAPPED TO OUTLET AIRFLOW

This is my version and I think is working. Did few tests. Created system and data is propagating to the unit, still not sure if I am doing something wrong.


1. SUPPLY/ PRESET/ IN / SPECIFIC LOSS – PRESSURE MAPPED TO PRIMARY, AIRFLOW MAPPED TO PRIMARY AIRFLOW

2. RETURN/ PRESET / IN / SPECIFIC LOSS – PRESSURE MAPPED TO PLENUM AIR PRESSURE, AIRFLOW MAPPED TO PLENUM AIRFLOW

3. SUPPLY/ CALCULATED / OUT / NOT DEFINED – PRESSURE MAPPED TO NONE, AIRFLOW MAPPED TO OUTLET AIRFLOW

info on how series box work:

You might think that setting up one of these boxes would be very similar to the parallel box, but in fact they are very different. The biggest difference is the fan inside will always run. When the space is calling for full cooling the primary damper opens to its design flow and the fan gets all of its airflow from the main air handler. The design cfm of both the fan and the primary air must be the same. Too much primary air will dump out the back of the box. When there is not enough primary airflow the fan will draw in return air mixing it with primary air and cause the discharge temperature to by high. When the space temperature is satisfied the primary air damper goes to its minimum design and the fan then draws in return air from the back of the box to allow for a constant flow into the space. Here are the steps in setting up the balance of this box:

[sec-k]

Regarding your question of whether or not to blindly trust the connectors in the out of the box content, I'd say no. I've come across connectors that weren't set correctly. Attached is a diagram I made up showing various connector scenarios that I'd like for you all to look at and discuss. I think I have a pretty good handle on connectors, except for the loss method part. Let me know if you think there is anything on the diagram that needs to be corrected.

Regarding series fan powered VAVs, I understand how they operate, but have never designed a system using those types of units. When you schedule these boxes, do you typically include plenum airflow or just primary airflow. When you size your upstream duct size, you only take into account the primary airflow, correct? Therefore, is it necessary to provide a plenum (fan) air connector?

[sec-k]

I think I already see an error. The rooftop unit return air connector should be set to calculated instead of preset. However, if I had a plenum return instead of a ducted return, would the return air connection be set to preset and mapped to the CFM parameter?

[1N.]

I think I already see an error. The rooftop unit return air connector should be set to calculated instead of preset. However, if I had a plenum return instead of a ducted return, would the return air connection be set to preset and mapped to the CFM parameter?


I always wondered what approach you take when you have plenum.
Marked up your sketch and I agree for ducted return you have it as calculated not defined.
Put few tip on good handouts and blogs to watch on connectors.
Kyle's movies are just great:
http://inside-the-system.typepad.com/my_weblog/2007/11/go-with-the-flo.html
and the ME204-3 paper from Autodesk University 20008 is my #1 reading and justify
my trip to Vegas this year.
For Fan Power Boxes I do use Primary and Plenum airflow, but I don't have project on that to test it. We usually do VAV single duct so it is pretty simple.

[sec-k]

I have watched Kyle's videos many times and have downloaded them all for future reference. Is the ME-204-3 white paper available online or was it just for AU attendees?

Regarding the plenum (fan) connector.... Since that connector is not ducted or "connected" to anything, will that result in an unassigned system?