Enclosures

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This maybe a stupid question, but are all Nema 3R Enclosures, insulated enclosures.

I am specifying an enclosure for a VFD that is being relocated from an indoor to an outdoor location. I am putting an electric heater into the enclosure to ensure no condensation on the equipment. Hoffman offers a heater and a guide to selecting a heater. But one big selection criteria is if the enclosure is insulated or not.

I am specifying this: http://www.hoffmanonline.com/produc...42327&searchfor=A60H3616SSLP3PT&view=overview

Is this an insulated enclosure?
 

cadpoint

Senior Member
Location
Durham, NC
UL

UL

I looked at the literature, I can only recommend a phone call in the morning to Hoffman. I jumped over to the UL listing it's quite long and heavily cross-listed to other UL listing.

The two pages to see UL508A is Here

And the UL database is Here

Y
ou can just insert the file number in the database that is listed at the bottom of the link "File No. E61997"
and give you more information.

I couldn't direct link my researching due to UL site and their software.

Enjoy
 

jim dungar

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Location
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PE (Retired) - Power Systems
Standard 3R (outdoor) enclosures are not insulated.
Insulation is a relatively expensive adder.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Standard 3R (outdoor) enclosures are not insulated.
Insulation is a relatively expensive adder.

We insulate cabinets now and then by gluing foam board on the inside of it. The glue and foam board is not real expensive. Usually the labor costs more.

My guess is that it will be more cost effective to get it pre-insulated rather than doing it yourself if you can get it that way.

I have never seen any standard NEMA3R cabinet that came insulated.

BTW, the insulation eats up space in the enclosure that you need to account for.
 

Jraef

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Nobody that I know of sells enclosures that are pre-insulated, it poses too many problems with regard to component location and mounting. It's usually something that is done as a final step in assembly.

The reason Hoffman wants to know in the heater selection is because of heat losses through the box walls when you are trying to keep it warm inside. Think about it for a minute, if it's cold outside, do you want to heat an insulated house or an uninsulated house? Same thing. So if you tell the Hoffman software that you want to maintain 40F inside of a steel box when it's -10F outside, you will need a much bigger heater to keep up with the exposed steel surface area sucking heat out of that box. But if it was insulated, you need a smaller heater.

Also keep in mind that this works exactly the other way around in fall and spring when it's 70F outside and the VFD is running. You could be radiating the VFD created heat through the steel sides, but if it's insulated, you will have to run an air conditioner.
 

jim dungar

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We insulate cabinets now and then by gluing foam board on the inside of it. The glue and foam board is not real expensive. Usually the labor costs more.
UL requires the insultation to be 'mechanically fastened in the enclosure. I know Hoffmann welds all sorts of 'studs' onto the side walls and then uses clips to hold the inplace.

I, also, have field insulated non-UL listed enclosures using adhesives and high density foam with 'aluminum' coating.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
UL requires the insultation to be 'mechanically fastened in the enclosure. I know Hoffmann welds all sorts of 'studs' onto the side walls and then uses clips to hold the inplace.

I, also, have field insulated non-UL listed enclosures using adhesives and high density foam with 'aluminum' coating.

It never occurred to me that UL might require some kind of mechancial fastener for insulation. But I checked UL508a and it is there. it also says the adhesive has to be evaluated for that purpose. I usually just buy construction adhesive in the caulk tubes.

I also use the foam with the aluminum foil coating as it seems to hold up better. I have the shop tape the seams with aluminum foil tape and tape around cutouts as well.
 

Jraef

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I have also seen some sort of paint that was sold as insulating, it had some sort of ceramic or something suspended in it. A friend used it on a shipping container that he was using as a control house that was going to be full of MCCs and VFDs. Before the equipment was loaded inside, I went in on a sunny day and was amazed at how effective that paint seemed to be. 100F outside, 75F inside, in the direct sun, no AC. I'll try to get the name of it and post it.
 
Thanks for the replies. We are exhausting the enclosure, so I am not worrying about it getting too hot. But I guess there is nothing you can specify that is pre-insulated. Interesting.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I have also seen some sort of paint that was sold as insulating, it had some sort of ceramic or something suspended in it. A friend used it on a shipping container that he was using as a control house that was going to be full of MCCs and VFDs. Before the equipment was loaded inside, I went in on a sunny day and was amazed at how effective that paint seemed to be. 100F outside, 75F inside, in the direct sun, no AC. I'll try to get the name of it and post it.

I had something going out in the desert sun one time that the customer refused to have any kind of mechanical ventilation on. I used a large NEMA3R enclosure and had the door removed and insulated all around on the inside and then installed the smaller enclosure inside it. It was basically a quick sun shield. I wonder how well it worked.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I have also seen some sort of paint that was sold as insulating, it had some sort of ceramic or something suspended in it. A friend used it on a shipping container that he was using as a control house that was going to be full of MCCs and VFDs. Before the equipment was loaded inside, I went in on a sunny day and was amazed at how effective that paint seemed to be. 100F outside, 75F inside, in the direct sun, no AC. I'll try to get the name of it and post it.

I don't see how it could stay 75F inside a cabinet for long with 100F outside though. it would eventually equal out.

White shiny paint is pretty effective at preventing heat absorbtion from direct sun. but can't do all that much for conduction.
 

Jraef

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Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
I don't see how it could stay 75F inside a cabinet for long with 100F outside though. it would eventually equal out.

White shiny paint is pretty effective at preventing heat absorbtion from direct sun. but can't do all that much for conduction.
Oh undoubtedly it would have eventually heated up, I didn't mean to imply it defied the laws of thermodynamics. But unprotected, that box would become unbearably hot in 10 minutes normally. It had been in the direct sun for probably over an hour at that point, so the paint was definitely insulating, and a lot more than I would have thought possible.

Found a reference, I guess it was an additive, not the paint itself.
http://www.hytechsales.com/insulating_paint_additives.html
 

templdl

Senior Member
Location
Wisconsin
I used to think the hears warmed the enclosure and I always wondered why these little tiny space heaters were used in such large switchgear enclosures.
Guys, it's not the warm but it's the heater circulating the air because of the warm air convection. With the air circulating and the dew point raised slightly moisture isn't given the opportunity to condense on the metal and electrical parts.
Aften times heaters are switch off when the equipment is energized and operating because it generated its own heat. Most gear that is energized all the time often times does not require a space heater.
 
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