Control Cab Cooling

djw2k3 · Nov 16, 2003

Hi all,

We have just installed a stainless steel electrical control cabinet, about 2000mm high, 1500mm wide and 500mm deep, with large double doors on the front.

We have found that the heat build up in this due to ambient outside temparture and sunlight to be much more an issue than thought. Afetr experiencing a very warm day we got temperatures inside the cab of 50-60 deg c! Needless to say the the PC and PLC inside it were not very happy.

This cabinet when closed is sealed enougfh to allow positive pressure inside, it is positioned on a shipping berth hence the need for some pretty good protection.

We are now looking at options of cooling, a air-con unit is an option but pricy and I am a little skepyical about a heat echanger being in this environment for longevity.

Discussing it in the office one of our engineers recalls using a system that relies on compressed air which is expanded through an orifice providing cooling. Is anyone out there familiar with such a system.

Thanks

Dave

busbar · Nov 16, 2003

See:

http://www.itwvortec.com/vortex_coolers.php

Their energy efficiency may be limited.

buzzp · Nov 17, 2003

Another cooler is exair,

http://www.exair.com/misc/product_applications.htm

. There little unit runs on compressed air for heating and for cooling. Never tried it but seems like it would work great.

djw2k3 · Nov 17, 2003

You gotta love these forums, thanks busbar and buzzp exactly what I was after

busbar · Nov 18, 2003

Square-D used to sell one of these brands, too. {Couldn’t find them on their website.}

Caveats: 1.) They may need to be served with dry/oilless "instrument air" to limit freezing/fouling.

2.) In terms of energy used for equivalent cooling capacity the air-powered products are rather inefficient compared to conventional mechanical refrigeration, but if you have plenty of air close by, they are a quick-and-dirty fix.

3.) It’s been a while, but I believe the non-cabinet ends of the devices run very hot.

nbucska · Nov 18, 2003

It may be a cheapoer option to move it to a shaded / conditioned place with extended/remote controls.

<nbucska@pcperipherals.com>

60hzhmmm · Nov 19, 2003

djw2k3: The vortec coolers busbar linked are very effective. And very reliable. HOWEVER, they require constant uninterrupted plant air. If the plant air stops often a totally unrelated "thing" controlled by a different gang,(the ones with pipe wrenches), you get puzzling electrical equipment failure, this is often a problem.
After many years of putting electrical equipment into enclosures in oil fields it became very clear to me that shade was the superior solution. It's quiet, zero energy, reliable, cheap, and effective. Remember every square meter of sunlight represents about 1kW of energy being dumped into one two or three faces of your enclosure. People cook food that way....

BrianG · Nov 26, 2003

I agree with 60hzhmmm: from experience of installing telemetry cabinets in the middle east, shading is essential. If you erect a suitable shade and it's still too warm inside, one other option you can consider is one or more "heat pipes" . If you have not come across these they come in various sizes and are essentially a special sealed tube with a refrigerant liquid inside. A heat exchanger picks up heat from the sensitive areas inside and dumps it to a heat exchanger in the shaded area outside. Heat is transmitted from one end to the other by a convection/condensing process and no other power is required. The only problem is that you would have to cut suitable holes in the cabinet to pass the tubes through to the outside.

jraef · Dec 2, 2003

The problem with any heat exchanger is that it MUST have at least a 10 degree (F) temperature delta to begin being effective, so if you need to keep your cabinet at 40 C, the outside air must be no more than about 35 C. Then you must calculate heat load inside and solar gain from exposed surfaces.

I know it is expensive, but consider an AC. If the compressor issue bothers you, do a search for solid state Thermo-Electric coolers (TEC), aka peltier effect cooling. They are available in NEMA 4 and corrosion resistant versions now.

Quando Omni Flunkus Moritati

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