Will my VFD overheat in a closed box?

[milemaker13]

I am installing a 5 hp fan using a VFD. The book says it will operate up to 131*F. Our plant is warm, around 80*. I want to mount this VFD inside a closed box to avoid dust, damage, ect. The VFD has cooling fins and a small fan.

Do you think this could raise the temp inside the box enough to be an issue? Would I need to ventilate the box? Or better to just mount the VFD to the wall, instead of inside a box?

 

[kwired]

I am installing a 5 hp fan using a VFD. The book says it will operate up to 131*F. Our plant is warm, around 80*. I want to mount this VFD inside a closed box to avoid dust, damage, ect. The VFD has cooling fins and a small fan.

Do you think this could raise the temp inside the box enough to be an issue? Would I need to ventilate the box? Or better to just mount the VFD to the wall, instead of inside a box?

Size does matter If you mount it on the wall it is in a much larger box called the plant.

It is going to dissipate heat. How much depends on loading characteristics. How much heat will the box contain depends on the design of the box and other factors. Out in the sun .. is going to be warmer before you even gain any heat from the VFD. You can install enclosure coolers if necessary, there is a variety of types out there.

 

[ptonsparky]

Don't be stingy with the size. We have been okay indoors with small lightly loaded drives. Your install manual should have some minimum sizing suggestions.

 

[Besoeker]

I am installing a 5 hp fan using a VFD. The book says it will operate up to 131*F. Our plant is warm, around 80*. I want to mount this VFD inside a closed box to avoid dust, damage, ect. /QUOTE]
Bad idea.

 

[mike7330]

You will overheat the VFD. You could use one of these products. You will need to size for your VFD load.
Just an idea?



http://www.exair.com/en-US/Primary ...binet Coolers/Pages/Cabinet Coolers Home.aspx
http://www.thermoelectric.com/2010/pr/ac/tm/indoors.htm

 

[templdl]

Have you ever thought to ask the VFD manufacturer what the minimum enclosure size that they recommend? That’s the first call that I would make. To do otherwise would be just and educated guess.
The other option would be to obtain the heating watts of the VFD and then ask an engineer calculate what the minimum physical size enclosure would be in order to dissipate the heat which would be based upon the surface area of the enclosure. This type of calculation is done all the time when a customer wants to place a dry type transformer into a TENV enclosure which is a very common practice.

 

[Joethemechanic]

http://www.exair.com/en-US/Primary ...binet Coolers/Pages/Cabinet Coolers Home.aspx

I like this idea.

 

[Cow]

Have you ever thought to ask the VFD manufacturer what the minimum enclosure size that they recommend? That?s the first call that I would make. To do otherwise would be just and educated guess.

This is really the best way. We've put VFD's in sealed boxes boxes before, AB's, and I think the rule of thumb for the box was something like 7 times the volume of the VFD for it to dissipate enough heat. Don't quote me though...

 

[Jraef]

This is really the best way. We've put VFD's in sealed boxes boxes before, AB's, and I think the rule of thumb for the box was something like 7 times the volume of the VFD for it to dissipate enough heat. Don't quote me though...

4 times the volume. Minimum, more is better. But that assumes 25C ambient (77F) so you (milemaker13) are a little warmer than that, I would err on the side of caution. 7 sounds pretty good to me.

So that means if your drive is 4W x 5H x 4D, that is 80 cubic inches, so you use a minimum enclosure of 320 cubic inches and work the dimensions backward within the limits you have from the VFD manual and your location. For example if you can't live with more than an 8" deep box, 320/8 = 40 sq. inches, so that would be the smallest footprint. But you will also likely see in the manual that you must have 2" clear on each side of the VFD, and it is 4"W already, so no less than 8" wide. So 40 sq.in. / 8" wide = 5" high. But the VFD is already 5" high, plus you likely need 4" of clear air top and bottom, so 13" minimum. Boxes come in standard sizes, so 16H x 8W x 8D would be what you end up with. That is 1024 cubic inches, which is 12.8X the initial volume, should work out just fine.

I SERIOUSLY doubt that this VFD says it can operate in 55C without derating though. Typically VFDs are rated for 40C ambient (104F) and will say the MAXIMUM is 50 or 55C with derating. I strongly suggest reading the fine print before you do this.

And by the way, unless your drive specifically SAYS it is in a NEMA type 1 enclosure, you cannot just hang it on the wall. The wiring would be exposed.

I have a big problem with those vortex air coolers by the way. One thing most people miss is the volume of air, CLEAN INSTRUMENT GRADE air, that they require. The smallest one on that web page from Exair for example costs almost $400 and it needs around 8SCFM of air at 100PSI, cleaned and dehumidified. That's roughly 3HP worth of air compressor to run it! These companies do NOT make that anywhere near clear in their data sheets, they make you find out the hard way AFTER you buy it and install it (been there, done that).

 

[bob]

Go ahead an make your box. On the front and back cut out the middle section leaving something like a picture frame.
Install 2 large A/C filters inside the box. That will allow air to flow and keep out the dust. Would that do what you want?

 

[milemaker13]

You are correct about the 55* max, derated above 40*.

The unit I am installing is Lenze AC Tech #ESV552N04TXB.

The 'B' at the end denotes a NEMA 1 enclosure.

A nema 1 screw cover box 16"x12"x8" will fit the drive with proper clearance.

So, it seems like it is up to us (and our plant conditions) if we hang it on the wall or put it in a box. I'll ask the owner and see what he thinks...

 

[kwired]

Putting a NEMA 1 drive in a NEMA 1 box doesn't sound like you are gaining much other than physical protection, usually people are looking at NEMA 4 or higher as a necessity. If dust is the main concern NEMA 1 will not do much for you.

 

[milemaker13]

Talked it over with the boss. He wants everything in one box, so I will go ahead and install cooling fans.

But now that I have these fans too, my control xfmr won't provide enough 110v.

I have 6 size 0 starters, 5 dampers (drawing 7.5 va each) and 3 relays (@19ma each) to power with 110v. The fans draw about .1 amps, depending which we actually choose.

I need help finding the inrush and sealed current of the starters.

 

[Joethemechanic]

roughly 3HP worth of air compressor to run it! These companies do NOT make that anywhere near clear in their data sheets, they make you find out the hard way AFTER you buy it and install it (been there, done that).

OOPS

Looked like a good idea from a surface glance.

I guess when you look at the properties of air as a refrigerant gas,,,,,,,,,,,,,,,,,,,,,,

 

[milemaker13]

I have in stock a larger .3 kva control xfmr, and also a 1 kva xfmr that would hang outside the enclosure.

At least 5 of these starters will come in simultaniously. Do you think the .3 would hang in there?

 

[Jraef]

I have in stock a larger .3 kva control xfmr, and also a 1 kva xfmr that would hang outside the enclosure.

At least 5 of these starters will come in simultaniously. Do you think the .3 would hang in there?

You should be able to look up the coil data on whatever brand of starters you have in the manufacturer's catalog, there is no other way. Quick and dirty guesstimate on CPT sizing is total sealed VA x 1.25, + largest inrush VA.

 

[ptonsparky]

I have in stock a larger .3 kva control xfmr, and also a 1 kva xfmr that would hang outside the enclosure.

At least 5 of these starters will come in simultaniously. Do you think the .3 would hang in there?

I thought these were vfds. Depending on how you are working the control for these you may not need 120v.
You do not have to have the fans come on immediately. Put thermostat(s) on them.
.3 kva = 300 va. do your math and add your loads.

 

[milemaker13]

Well, its all part of a larger system. The VFD will run a large "2 speed" fan, while the starters will run 2 intake fans and 4 circulator fans. The starters will all be in their own boxes while the VFD and all relays, switches and xfmr will be in a common cabinet.
I cannot seem to find info on coil currents for either SD or CH in their catalogs. If someone can help?? Otherwise I gleened some info from another post reguarding sz 3 starters. If I use those values (678 va pull in, 47 sealed)and add it all up like Jraef suggests, I come up with 1100 va.

This is 1.1 kva? I do also have a 2 kva I could use. Maybe that is the best way to go.

 

[CONTROL FREQ]

I am installing a 5 hp fan using a VFD. The book says it will operate up to 131*F. Our plant is warm, around 80*. I want to mount this VFD inside a closed box to avoid dust, damage, ect. The VFD has cooling fins and a small fan.

Do you think this could raise the temp inside the box enough to be an issue? Would I need to ventilate the box? Or better to just mount the VFD to the wall, instead of inside a box?

THAT my dear sir/ma'am(? who knows now days), would MOST definitely and without question... depend on the size of the box! been awhile since I've been on here so I'll give this a shot. seems easy enough... HMMM. Use a vortex cooler as previously recommended (bosses ALWAYS say compressed air is expensive, but in reality when you use a snap switch to turn it 'on' or 'off' as needed they are very efficient.) AND if you've joined us in 2012 set timers in your PLC so that your "across the line" motor starters fire a few seconds apart, this will keep you from having a big load hit all at once... If this is not PLC controlled, simply throw in a couple timer relays (cheap). which ever way you go, you shouldn't need to worry about inrush. I'm not saying I know my way around YOUR facility, just saying I've never seen a scenario where all fans HAD to come on at precisely the same moment. :bye:

cheers and good luck to you friend!

 

[kwired]

(bosses ALWAYS say compressed air is expensive, but in reality when you use a snap switch to turn it 'on' or 'off' as needed they are very efficient.)

If the user never turns it off the snap switch was pointless, and there is no increased efficiency. Automatic, maybe via thermostat, control when it is needed is going to be most efficient.