How to draw a 1 ton furnace with outside air system?

[SAndolsun]

Dear Autodesk Revit MEP users,

I am trying to draw a house in compliance with IECC (International Energy Conservation Code) 2012 which requires an outside air system used together with a furnace (DX cooling, gas heating). Among the components of Autodesk Revit MEP, I only could find a 3 ton furnace and an outside air mixer. The house I am drawing is pretty small and it only needs a 1 ton furnace. I need to connect the outdoor air system with the rest of the system but I have no idea how to do it in Autodesk Revit MEP. Should I be looking for the actual sizes of the furnaces to resize the 3 ton furnace manually or is there any smaller furnace component availabe in Autodesk Revit MEP than 3 ton that I can use? Is it even possible to use an outside air system with a furnace in Autodesk Revit MEP?

I look forward to hearing from you,

Thanks in advance for your help

Best Regards,

Simge Andolsun

[asommer]

What I do is look up what you want on the Internet, download a spec sheet with dimensions, and build it as a family from scratch.  You might get lucky if the manufacturer has revit files.

[SAndolsun]

Thanks but how about connecting and outdoor air inlet to the system? Also, I am not sure how I can connect a evaporator coil to a furnace to represent a typical residential system in Autodesk Revit MEP.  For the ones who are familiar with ASHRAE Handbook, I am actually trying to draw the system described in Fig.1 of Chapter 1 in ASHRAE Handbook HVAC Applications. Here is a quote from the book"

"Figure 1 shows a gas furnace, a split system air conditioner, a humidifier and an air filter. Air from the space enters the equipment through a return air duct. It passes initially through the air filter. The circulating blower is an integral part of the furnace, which supplies heat during winter. An optional humidifer adds moisture to the heated air, which is distributed throughout the home via the supply duct. When cooling is required, the circulating air passes across the evaporator coil, which removes heat and moisture from the air. Refrigerant lines connect the evaporator coil to a remote condensing unit located outdoors. Condensate from the evaporator is removed through a drainline with a trap."

In the above mentioned Figure 1, evaporator coil is located above the furnace. The evaporator coil comes after the fan when the direction of the air flow is considered.

Any advice on drawing this system in Autodesk Revit MEP is greatly appreciated.

Best Regards,

[asommer]

I would model all items as one piece of equipment, unless you want to schedule these separately.  You can add duct and pipe connections to the family in their proper locations to represent the actual unit, and you can use flow parameters and formulas to do some simple flow calcs in the unit.  Just add a duct connector on the unit for outside air.  You can do this outside of the unit, you will need a separate mixing box, and will probably have to be a custom deal.

You probably won't find anything OOTB that fits or works exactly the way you want, that's why I would build it from scratch.

Are you trying to perform load calcs with this project?

[SAndolsun]

Hi!

Thanks for your response. I actually do not need to make calcuations on Autodesk Revit MEP.  I am using a very detailed energy modeling program to model the air side. All I need is the physical apperance of the system that will allow me to obtain the duct lengths so that I can enter them into the energy modeling program  I am using. Would you please describe each component I should use in detail? Which of them can I find among the components of Autodesk Revit MEP and exactly which of them should I build from scratch?

I look forward to hearing from you,

Thanks for your help,

Best Regards,

[asommer]

The furnace unit will probably have to be built from scratch.  This is where you might pick a unit from the manufacturer, download the dimensional specs, and this will have duct and pipe connection locations.  Create a new family, and build it.  The separate humidifier, coils, and mixing box might be available OOTB, most have adjustable sizes.

I'm not sure how the OOTB mixing box works, the outside air should come in on the Return side of the Unit.  The Outside air will probably take on the "Return Air" System type, changing the "UP" or "Down" symbol.  If you are just getting duct lengths, this won't be an issue.

We usually deal with large commercial Rooftop units, where all this is in one "Cabinet" or box, I just draw the Outside Dimensions of the unit and place duct/piping connectors where the cut-sheet shows.