NEMA 4 Enclosure With Louvers??

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NEMA 4 doesn't exactly allow for louvers . . .

Here's NEMA's information on enclosure ratings:

NEMA Enclosure Types

The purpose of this document is to provide general information on the definitions of NEMA Enclosure Types to architects, engineers, installers, inspectors and other interested parties. [For more detailed and complete information, NEMA Standards Publication 250-2003, "Enclosures for Electrical Equipment (1000 Volts Maximum)" should be consulted. This Standards Publication as well as all other NEMA publications are available from IHS @ 800 854-7179 or http://www.global.ihs.com]

Definitions

[from NEMA 250-2003]

In Non-Hazardous Locations, the specific enclosure Types, their applications, and the environmental conditions they are designed to protect against, when completely and properly installed, are as follows:

Type 1

Enclosures constructed for indoor use to provide a degree of protection to personnel against access to hazardous parts and to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt).

Type 2

Enclosures constructed for indoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt); and to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (dripping and light splashing).

Type 3

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow); and that will be undamaged by the external formation of ice on the enclosure.

Type 3R

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow); and that will be undamaged by the external formation of ice on the enclosure.

National Electrical Manufacturers Association Approved by NEMA Enclosures Section 1300 N. 17th Street, Suite 1752 Nov 2005 Rosslyn, VA 22209 Page 1 of 2 NEMA Enclosure Types

Type 3S

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow); and for which the external mechanism(s) remain operable when ice laden.

Type 3X

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow); that provides an additional level of protection against corrosion and that will be undamaged by the external formation of ice on the enclosure.

Type 3RX

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow); that will be undamaged by the external formation of ice on the enclosure that provides an additional level of protection against corrosion; and that will be undamaged by the external formation of ice on the enclosure.

Type 3SX

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow); that provides an additional level of protection against corrosion; and for which the external mechanism(s) remain operable when ice laden.

Type 4

Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); and that will be undamaged by the external formation of ice on the enclosure.

National Electrical Manufacturers Association Approved by NEMA Enclosures Section 1300 N. 17th Street, Suite 1752 November 2005

Rosslyn, VA 22209

Quite simply, NO, you cannot have ANY kind of opening for ventilation in a NEMA 4 enclosure. Period. If your equipment needs cooling and it needs to be in a NEMA 4 enclosure, then you have two viable choices: A NEMA 4 rated closed loop air conditioner or a NEMA 4 rated closed loop heat exchanger. The difference is, the heat exchanger needs a minimum of a 10 degree (F) temperature delta, the AC does not.

There are also what are called "Vortex Coolers" which use compressed air, but they are wildly expensive to operate and I am not sure if they violate NEMA 4 requirements or not, because they need to have a "breather" to vent the air. There are also a few TEC units (Thermo Electric Cooling, a.k.a. Peltier effect cooling) available now, but I have not yet seen one UL rated for type 4.

Not true about the vortex coolers, JRaef, they are completely separate and the box remains sealed--They are completely inefficient, true, but in a nasty environment, they are paralleled to to nothing. The heat coming out of the exchanger is enough to scald flesh off the bone and the cooled enclosure remains sealed. I have used a few where the cooling fans of VFDs were continually compromised from dust and debris.

The vortex coolers put out a relatively large volume of very cold air. So in practice, even though they are very inefficient, their duty cycle tends to be quite low. The ones I have installed tended to give a 1-2 second burst every 5 min or so. The use of plant air was not excessive and the installation cost wasn't very high. With no moving parts, maintenance was minimal.

The ones we had run off of a thermostat.

http://www.iscsales.com/products/vortec/vortexcoolers.html

Kilgore,

Same with mine - we used and old honeywell room thermostat to operate a 24V air solenoid.

LG_DAVE

www.legrand.co.uk they have both composite and SS boxes

Try www.hoffmanonline.com maker of electrical enclosures including NEMA 4. Call there Customer Service I have found them to be very knowledgeable.

A walk in the park! Under cat4 enclosure definitions, you may pre empt louvers within a secondary shield ahead of the input fan louvers. Repeat the same for the output fan louvers: Open louvers are protected. Installing guards will further protect from foreign objects. In case of a internal explosion, debri is kept within the Cabinet. Additionally, if you complement with internal ducts ahead /after louvers, gas/fluid flow will not suffer.

Read the part about hose directed water. The NEMA test is 100CFM from a 1 in nozzle, aimed from ANY direction. No amount of baffles, shields etc. is going to stop that!

I con cure, only a closed secondary cooling loop can do that. Also make allowances for condensation.

Brad