LED downlighters in plastic trunking?

[Sam Gangee]

A qualified electrician friend is proposing to fit LED downlighters in 3" plastic trunking, which is screwed to the reinforced concrete kitchen ceiling. He thought it would "look neat".

I told him that I feel this is a bad idea because the LED driver heatsinks will be unable to get rid of the heat, so the air inside the trunking will become increasingly hot until something gives!

He's now considering alternatives but asked me to ask you experts for suggestions, please. One possibility is a suspended false ceiling, giving about 8" gap. I'm still concerned that there would be a heat build up but maybe the concrete ceiling would "sink" it away.

(I'm not an electrician but I'm an Electronics Engineer with a B.Eng.)

 

[RF Lighting]

Can't see any issue with it personally.

 

[Sam Gangee]

OK, maybe I should explain my thoughts further. (Part of my degree course was Thermodynamics.)

Suppose you take a plastic drainpipe, held horizontally and sealed at both ends. Inside the pipe is a fire bar connected to a variac. You wind up the voltage gradually. There comes a point where the heat energy radiated by the fire bar exceeds the heat energy passing through the plastic pipe and being dissipated into the air outside the pipe. When this equilibrium state is exceeded, the air inside the pipe becomes steadily hotter until something catastrophic occurs. In this example, the pipe would probably melt.

In the case of the LED lamp drivers, which are dissipating a few Watts each, it's possible that the heat can pass through the plastic trunking quickly enough so that the equilibrium stage is never exceeded. However, plastic is a good heat insulator, which is why I have my doubts.

 

[RF Lighting]

Loft insulation is a great insulator and doesn't bother them.

Use direct to mains lamps if you're really bothered.

Not sure just how much heat you think they'll generate, but it's less than that.

 

[OwainDIYer]

A qualified electrician friend is proposing to fit LED downlighters in 3" plastic trunking, which is screwed to the reinforced concrete kitchen ceiling. He thought it would "look neat".

If you like the lighting style of a London Underground platform ...

What's wrong with LED track lighting? Will give you a better spread of light than downlights in trunking.

https://www.tlc-direct.co.uk/Products/GLTH300W.html