CAD-Mech

The Life and Times of an Associate Principal Designing Building Mechanical Systems On-Screen with AutoCAD & Revit MEP.

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Location: Colorado, United States

Sunday, February 17, 2008

Revitization & Condenser Farming

No resolution with the Aggravation #1. Agg#2 was resolved by the CAD Manager getting the last vestiges of Font#2 from our setup routines. Apparently the font had been rejected but not before some scripting allowed it to leak into some drawingss

Agg#3 was essentially resolved by the ScaleListEdit routine I created. Unfortunately, the unwanted scale types only disappear in the active drawing temporarily because of the scale types in the Xref files. Save the active drawing, close and reopen it, and the unwanted scale types are back in action. Only way to clean it completely is to flush all the Xref files. That is difficult to keep current when we have 30-40 unit plans in a floor plan for a condo project that updates every two weeks over four months design cycle.

Thursday brought a presentation on Autodesk Revit MEP Suite for about two hours. Yep, we're looking at starting that road down the 3D path. I started looking into it July 2007 prior to our upgrade of computers. I ended up with seven pages of information for which three pages were related to design with 3D CAD.

It will be an interesting shift. I've been fortunate that since getting into this engineering business to have an inherent understanding of depth when dealing with the layout of mechanical equipment, piping and ductwork. Still have occasional problems with that when one or more trades installs something in conflict with ductwork or a change in the walls and ceilings alters the available space for mechanical elements.

We're seeing a motherboard problem on the some of the Dell Quad-Core workstations. Three out of twenty have required replacement. The indicator of a problem is the sudden failure of the keyboard. Only way to keep using the machine is to switch to a PS2 keyboard. I can't recall seeing the PS2 connector on the back of the computer but perhaps there is one.

Project-wise, I was pulled from the 13-story apartment building for the 3rd incarnation of the DD set. No problems on my part, I had to move onto a restaurant design and high-end condo project. Neither one could wait for design work. Air conditioning on the apartment building will now be provided by split-sytem DX with the condensing units located on the roof. Seriously long runs of DX piping with small tonnage equipment is not something I've done in the past as it goes against conventional thinking. It's been done locally in the marketplace on a few projects by a particular mechanical contractor.

The architect needed to see a layout concept for placement of the condensing units at the roof which amounts to the 14th floor. Last Thursday and Friday I spent time laying out the condensing units on the roof of the apartment building. Turned out there are 156 condensing units on the roof. Freaking amazing thing to see that much equipment on a roof; it's all wrong. At least I got the plan out to the architect for a first-pass review on an 11x17 PDF plot.

The restaurant design is a fast design effort. It's been around for about four months but no one has able to give us air flow rates for the exhaust hoods. We got the information on Thursday with a revision on Friday. Saturday I was able to layout exhaust ductwork routed to the scrubber (gotta keep the air clean as it is discharges out the sidewall of the high-rise building.) Got the makeup air unit and a good chunk of the supply air ductwork laid out. Did HVAC load calcs as well. No info on kitchen equipment yet despite having asked the kitchen consultant three times over the four-month time period so I'm having to estimate heat gain from the cooking equipment. More work in the coming week.

The high-end condo is not moving all that fast. The most critical issue has been the air flow size of the range hoods in the kitchens. The smallest range hood is a nominal 900 cfm and the larger hood is a nominal 1200 cfm. Local code here requires makeup air in a residence when the range hood exceeds 450 cfm. There is a field alernate option that allows up to 850 cfm of exhaust on a range hood when the kitchen is substantially open to the rest of the living area. So if two or three walls are not present and the kitchen is open to the living room and dining area, the inspector can allow the ommission of makeup air. If the kitchen is substantially isolated from adjacent living areas, makeup air must be provided. The cost of providing makeup air is about $3000 for the electric heating coil, supply fan, filter rack and ductwork for each condo. With 20+ residences on the project, the construction cost is not to be trifled with.

The coming week will be very exciting based on some of the emails I've seen today at my office account.

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