Luminaires Mounted in Ducts

[cdcengineer]

Here's a new one for me...

Strange new electrical installations are springing up here in Colorado. The legalization of medical marijuana facilities has ignited a market for electrical installations in these establishments. Most, if not all AHJ's/building dept's. are requiring electrical engineer's to stamp the designs.

I was approached about a project where the owner wants to install a direct-ducted luminaire which is made by a specialty cultivation company. The luminaire is listed. And it appears the manufacturer intends for it to be installed with 8" duct connected to either end. However, I have never been asked if it was acceptable to install a light connected to a duct. In review of NEC articles 110, 300 & 410, I see only one real obstacle to their request - NEC 300.22(B).

According to the owner and mechanical engineer, this is a common installation practice. I have concerns about the possibility of the luminaire somehow energizing a semi-rigid duct, as there is no way to fasten an equipment ground between the luminaire and duct w/o opening up (and possibly losing the listing) and modifying the internals of the factory wiring.

Moral, political or personal opinions regarding this new industry aside, does anyone know if the IBC or mechanical codes might dis-allow such an installation. Or perhaps an NEC requirement which might either prove or dis-prove this type of installation method?

Thanks,

DC

 

[LEO2854]

Here's a new one for me...

Strange new electrical installations are springing up here in Colorado. The legalization of medical marijuana facilities has ignited a market for electrical installations in these establishments. Most, if not all AHJ's/building dept's. are requiring electrical engineer's to stamp the designs.

I was approached about a project where the owner wants to install a direct-ducted luminaire which is made by a specialty cultivation company. The luminaire is listed. And it appears the manufacturer intends for it to be installed with 8" duct connected to either end. However, I have never been asked if it was acceptable to install a light connected to a duct. In review of NEC articles 110, 300 & 410, I see only one real obstacle to their request - NEC 300.22(B).

According to the owner and mechanical engineer, this is a common installation practice. I have concerns about the possibility of the luminaire somehow energizing a semi-rigid duct, as there is no way to fasten an equipment ground between the luminaire and duct w/o opening up (and possibly losing the listing) and modifying the internals of the factory wiring.

Moral, political or personal opinions regarding this new industry aside, does anyone know if the IBC or mechanical codes might dis-allow such an installation. Or perhaps an NEC requirement which might either prove or dis-prove this type of installation method?

Thanks,

DC

Is the duct directly conected to the fan coil unit?

If so would that not make the duct work grouned?

 

[cdcengineer]

Interesting thought... I'll have to ask the Mech engineer how that side of the system is terminated.

 

[USMC1302]

Is the fixture mounted inside the ductwork? I believe they make UV lighting systems that mount in ductwork for air sanitizing. What is the application for?

 

[cdcengineer]

It's actually not mounted in the duct, but is intended to have a 8" duct connected to either end. The application was stated in my first post.

 

[USMC1302]

Just curious as to what purpose the duct on both ends of a light fixture serves?

 

[cdcengineer]

They tell me it's to exhaust the heat. Fan on one end, intake louver on the other.

 

[USMC1302]

Thanks, understood.

 

[steve66]

IMO, the duct can and should be grounded. But not necessarily through the light. The duct could be grounded by contact with the building steel, or with a wire ran to building steel, or one of many other ways.

Light fixtures with supply or return diffusers that connect to HVAC ducts are very common. Its a very common option for most commercial 2x4 or 2x4 light fixtures. Here is a Lithonia example:

http://www.acuitybrandslighting.com/library/LL/documents/SpecSheets/2SP-AIR-2X2-CF-SC.pdf

However, in the end, its up to you to decide if the fixture is acceptable or not. You might base your decision on any listings the fixture has (UL or ETL, etc), or on the lack of any such listing.

 

[cdcengineer]

Thanks Steve. I have seen those AIR fixtures by Lithonia and other mfg's. however, I was unaware that they connected to ducts. I thought they were for intake or diffusing through the use of the plenum above?

 

[steve66]

Thanks Steve. I have seen those AIR fixtures by Lithonia and other mfg's. however, I was unaware that they connected to ducts. I thought they were for intake or diffusing through the use of the plenum above?

They can be either. If you look on page 87 of the lithonia catalog, it shows both ducted supply and return, and also just transfering to the plenum.

The first link on this webpage is probably the fastest way to see it:

http://www.lithonia.com/PSG/

Then just type in 87 in for the page at the top.