Air Space considerations inside an enclosure

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controlsdude

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Hello all,

I'm designing an industrial enclosure, housing a PLC and other 24VDC components, using wire duct for routing wires. The PLC manufacturer requires 2 inches of air space surrounding the PLC. Is wire duct considered free air space? In other words, to make everything fit, I need 1.5 inches on one of the sides of the PLC, with wire duct.

Thanks in advance :)
 
Good question, IMO if the manufacturer requires 2" of air space then nothing can be within that 2" zone around the PLC. I would guess that they are the only ones who can answer the question since they came up with the 2" requirement in the first place.
 
I'm sure they want only free air space. However I have had less than 1" with the CLICK plc's and they work fine for many years. I'm sure that space might be more important if you have other stuff in that enclosure that generates a lot of heat.
 
If you can't rearrange it to get more space around the PLC maybe you can just move the PLC towards the door so that it is above the level of the duct. Or you could use the duct that you can mount a din rail on and mount the PLC on top of the duct. There are lots of options.
 
I have seen control cabinets located in high heat areas that used an air line with a venturi to cool the interior of the cabinet. Open the door and it felt well air conditioned. It also helped keep the interior clean from light pressurization.
I am not associated with this company, it shows a good example of how it works.

Vortex air cold and hot air Article

Vortex tubes utilize compressed air to create hot and cold air with no moving parts. They are small and ideal to be used for spot cooling.
www.nexflow.com www.nexflow.com
 
Bluegrass Boy said:
I have seen control cabinets located in high heat areas that used an air line with a venturi to cool the interior of the cabinet. Open the door and it felt well air conditioned. It also helped keep the interior clean from light pressurization.
I am not associated with this company, it shows a good example of how it works.

Vortex air cold and hot air Article

Vortex tubes utilize compressed air to create hot and cold air with no moving parts. They are small and ideal to be used for spot cooling.
www.nexflow.com www.nexflow.com
Click to expand...
Vortex tubes are fantastic devices, so long as you have a source of oil free dry compressed air readily available and that you don't look at the amount of energy it takes to supply that air. I once did an evaluation of a small one for some PLCs that were on cranes above an aluminum pot line (where the ore is melted to extract the aluminum). For a 20 x 20 x 8 box, the Vortex cooler required an air volume and pressure that would take 7-1/2HP of compressor power to attain. That would be a much much smaller Freon based air conditioner. In my case they had the air and didn't want to have to service an A/C unit so we used the Vortex cooler, just with everyone's full knowledge of the cost.
 
Jraef said:
Vortex tubes are fantastic devices, so long as you have a source of oil free dry compressed air readily available and that you don't look at the amount of energy it takes to supply that air. I once did an evaluation of a small one for some PLCs that were on cranes above an aluminum pot line (where the ore is melted to extract the aluminum). For a 20 x 20 x 8 box, the Vortex cooler required an air volume and pressure that would take 7-1/2HP of compressor power to attain. That would be a much much smaller Freon based air conditioner. In my case they had the air and didn't want to have to service an A/C unit so we used the Vortex cooler, just with everyone's full knowledge of the cost.
Click to expand...

I used to work for a compressor manufacturer. We loved for people to use vortex tubes!
 
Vortex tubes are cheap and simple and last forever. They make a lot of sense for some cases, for example, where cooling is only needed sporadically.

You need clean oil free air though or the inside of the cooled enclosure will be full of slime.

One of the things that is often overlooked is how expensive compressed air is as a utility. So always put a thermostat on a vortex cooler to minimize compressed air usage.

OTOH, often cooling needs are grossly overstated by looking at the worst case situation, but it is rare for a VFD to run full bore during the hottest part of the year. VFDs produce worst case heat only at maximum current and that is pretty rare in most cases. Even running at 10% less than max, the amount of heat generated by a VFD is dramatically reduced. The problem is that you can't really calculate this kind of thing very well.
 
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