lessons learned: service clearances

Lesson learned: Just because an AHU fits inside the mechanical room does not mean it truly fits.

Early in my BIM/VDC career, I learned a valuable lesson about service clearances.

I could probably write a book on the topic of service clearances now, but this one specific project really changed the way I view them during constructability.

I was working on a project where two air handling units physically fit within their designated mechanical rooms. On plan, everything looked fine.

Then we reviewed the approved equipment submittals.

One unit required 66 inches of cooling coil pull clearance. The other required 87 inches.

Neither room had enough space to remove the coils from inside the room.

At that point, we discussed whether the mechanical rooms could be enlarged, but the walls were already established and revising the room layouts was no longer a realistic option.

When the walls cannot move and the equipment is not changing, you have to think outside the box.

Or, in this case, outside the room.

The solution was to provide access through the adjacent walls.

For the unit requiring 87 inches of clearance, an access door was added so the coil could be pulled through the wall and into the adjacent corridor during future service or replacement.

The other unit was more complicated. There was a ramp on the opposite side of the wall, so a permanent access door was not practical. Instead, the team incorporated a removable wall panel. Under normal conditions, the wall maintains its finished appearance. When major service is required, the panel can be removed to create the necessary coil pull path.

Was it the ideal condition? No.

But it gave the owner a realistic maintenance solution without enlarging the mechanical rooms or significantly relocating the equipment.

This project also reinforced why approved equipment submittals are so important during BIM coordination.

The design drawings may show a general equipment footprint, but the submittal tells us what is actually being installed

A generic model can look perfectly coordinated while hiding a major long-term access problem.

Even though we found a workable solution, it still felt like a failure. The issue had been solved, but it should have been identified earlier, before options became limited.

But that experience completely changed how I approach mechanical rooms during constructability reviews.

Since then, I have looked at mechanical spaces with the assumption that the actual equipment (or the required service clearance) may be larger than what appears on the design drawings.

I would rather be conservative and raise the question early than discover after the room is built that a coil cannot be removed.

Best-case scenario, the approved equipment fits exactly as planned.

But when it does not, the GC and trade partners should already have a workable solution, not a surprise waiting for the owner years later.

#BIM #VDC #MEPCoordination #HVAC #Constructability #Submittals #MechanicalCoordination #TradeCoordination #FacilityMaintenance #LessonsLearned