ECN Forum Forums Code Related Discussion NEC & other Code issues A Common HVAC Quirk

Pictured is a four-square box with every knock-out removed. I often find this when the box mounts a control transformer for HVAC work. Within the box is a 120-volt line supplying power to the transformer; outside the box thermostat wires are connected to the transformer output.

I see this so often it can’t be a fluke. Just what are the installers trying to accomplish?

Previously owned (used) boxes??
Ventilation?
HVAC guys not knowing what they are doing?

My guess ventilation.

Yeah, let that fire in the box breathe

Yeah, these boxes have always puzzled me.
First, I see them so often that I don’t think it’s random chance. Surely the HVAC trade isn’t THAT boring. Maybe it’s just a way they have of disposing the “oops” boxes, where they removed the wrong KO.
My first thoughts went to “ventilation,” but there’s nothing inside to ventilate! The one thing that might get warm — a box-mounted control transformer — hangs outside the box.

HVAC folks are a strange breed. It may be the most sequestered trade. When my wife was banging out houses as fast as they could be built, stacking trades was common but nobody wanted to be there when the HVAC guys had the house.

Reno:

I think that removing 12 KOs is a really bad 'ooops'

No one can be that bad.

Somebody is bored?