Making HVAC Drawings
(Alternative titles: How to make a HVAC drawing// How to make a mechanical drawing// How Consulting Engineers make their drawings)
I want to write down the process of developing HVAC drawings. HVAC drawings (as well as Electrical, Plumbing, Fire Sprinkler, and Life Safety system drawings) are made according to the constraints defined by architectural drawings. In essence you need architectural drawings to see the layout of the building and the clearances you have to work within. The architectural floor plan becomes the background drawing for HVAC (and other fields). The first thing you need to do is to prepare the architectural plan to be used as your background drawing. To do this you need to clean up the drawing (by turning off layers that have things of mainly architectural interest) and then ‘dimming out’ the drawing. You want to dim out walls, doors, etc in the architectural floor plan so that when you put your mechanical (HVAC) stuff on top of it, your stuff would stand out. As a general rule, entities belonging to a particular field must stand out in comparison to others, in the drawings of that field. [So, in Plumbing drawings, plumbing items must stand out in comparison with elements of architectural, mechanical, and other systems.]

This is how I dim out an architectural drawing to give me a workable background for the HVAC drawings.

Save the Architectural floor plan drawing under a different name. In AutoCADD environment go to Layers using the Layer tool (alternatively, go to the ‘Format’ drop down menu, then click on ‘layer.’) When you see all the layers, highlight one layer; hold the CTRL key, and scroll down to highlight all other layers. Then click on one layer; and change the color to Color 9. This will change the color of all layers.

I believe it is possible to change all the layers of a drawing to any color by using LISP. This feature should come really handy if you have a number of architectural drawings to dim out. If you know how to do it using LISP, please let all of us know. We shall be thankful.