Large cabinet A/C

Hello all

This is the BIGGEST cabinet I have had the privilege to build. 600 amps

Fifteen Class "D" starters, seven VFD's, L30ER, two power supplies, 16 I/O cards, two "F" starters, two stand alone 24 volt dc ( 20 amp) power supplies, 12 inch HMI in the panel door. Dozens of smaller relays, three servo controllers, and some other stuff.

It's final resting place is mid Oklahoma, mid 90's most of the year with 75% humidity or better.

My question is should we use an A/C unit, or just a push/pull fan system.

Any and all opinions appreciated.

Here's a calculator tool from Hoffman/Pentair that might be of help.

If you're inclined to do some legwork, I made this spreadsheet a while ago for working out a similar thing. Basically, you have to work out how much heat load you've got in your panel. Servo's and VFD's are the main culprits, and most drive manuals etc should be able to tell you how much power dissipation via heat they generate. Then give yourself a bit of extra leeway for DC power supplies, PLC's, ethernet switches etc.

Punch all the values into the spreadsheet (you'll need to convert to degrees celcius, because, 'merica) and it'll tell you how much forced air cooling you need in cubic metres per hour.

Then check out your fan ratings (make sure you get the rating for fan/filter combo, not just unrestricted air flow) and work out how many/how big your fans need to be to achieve that. If the result looks ridiculous/impossible, go for an A/C unit!

If you DO need an A/C unit, then you can work out how many watts of cooling you need by subtracting the "Heat Dissipation Through Panel Surface" value from your total heat load value.

600121 BTU/hr................geeeze

I like the next line

There is a possibility that multiple units may be required. Contact Customer Service at 1-800-***-**** for more information.

Ok ASF

If forced air flow stays in the green then I can go with fans...............did I read that right. 5439.86 cubic meters per hour. That almost bigger than a 3/4 h squirrel cage blower.

Ill call the cabinet manufacturer for an A/C unit. hope its not bigger than the cabinet.

thank you all

The thing to be wary about cooling just the enclosure... What happens when you open the door?

It is quite possible to have every surface inside the panel go wet within seconds of opening the door if the conditions are right. Take care not to overcool it.

In extreme cases it may actually make sense to build a shed to get the panel out of the weather and cool the shed. Then at least you can work on it.

John Morris said:

If forced air flow stays in the green then I can go with fans...............did I read that right.

Click to expand...

In theory, yes. Although the size of the fan, as you say, might be somewhat ridiculous.

It goes red if fans physically can't lower the temperature of the cabinet, generally this will happen if your maximum ambient temperature exceeds your maximum internal temperature. A fan can't cool a cabinet if the air it's blowing in is hotter than the air it's trying to cool. I put that functionality in after a discussion that went something like this:

(the factory in question is in a sub-tropical climate where summer temperatures routinely hit 40 degrees C (100F), and this panel has close to 100kW of VSD's in it)
"So the panel is going on the inside wall, right?"
"Well, it was, but now we're going to put the panel on the outside wall because it'll be easier to get the cabling up the outside wall than up the inside wall."
"Riiiiight...whereabouts is this wall?"
"On the northern side of [building]".
"Uh huh...so will it be exposed to direct sunlight?"
"Only for a few hours a day. Maybe from 1pm to 5pm."
"So...you're talking an ambient temperature of 40 degrees C, in direct sunlight for four hours at the hottest part of the day?"
"Yeah. Obviously we'll need some cooling fans on the panel."
"Um. A cooling fan only works if the air outside is cooler than the air inside."
"Yeah?"
"Yeah. Your drives are rated to 40 degrees. Even if we put it on the inside wall where it's 20 degrees, we still need two 300mm fan/filter combo's just to deal with the heat generated by the drives. You want to put it in 40 degree ambient, in direct sunlight. That's not going to work."
"Oh. Could you use an air conditioner?"
"Sure. You're looking at around $10-$15k for an air conditioner that can handle those ambient conditions. How much easier is it going to be to do your cabling outside again?"
"...Let's put the panel inside."

thank you mellis, that is something to watch out for.

I didn't explain correctly. It will be in a lights out automated factory. If I do my job correctly, the cabinet should never have to be opened. Right. I assume with out the presence of people they are not going to air condition the floor. so conditions could hit the upper 90's and a dew point of around 70-75% is usual for that area.

But with so much computing power at my disposal I can run a thermocouple inside the cabinet and switch power to the a/c only when needed, and just enough to keep it happy.

Hit that sweet spot between the left to right PLC connector cable. Just like being married............keep the PLC happy and very one is happy.

John Morris said:

But with so much computing power at my disposal I can run a thermocouple inside the cabinet and switch power to the a/c only when needed, and just enough to keep it happy.

Click to expand...

Most panel A/C units will have a built in thermostat and cut in and out automatically.

That's quite a story ASF,

Now that I know I need an A/C, I'll start with the cabinet companies (Hoffman, Saginaw, Rittal) see what they recommend/offer, then move to other vendors, check everybody's info, keep them honest, and get the price down.

But at least now i know...............Thank you all

I have a project going to south Texas. Calculations proved that we need a modest A/C unit. Customer (in MI) said to drop the A/C and just use a fan to save cost on his project going to Texas.

I said we really need the A/C. No, just use a fan. A/C units are too expensive.

OK, sign this release... He said this is a gentleman's discussion and no need to sign anything.

I said OK.

Emails are a wonderful thing

John Morris said:

That's quite a story ASF,

Now that I know I need an A/C, I'll start with the cabinet companies (Hoffman, Saginaw, Rittal) see what they recommend/offer, then move to other vendors, check everybody's info, keep them honest, and get the price down.

But at least now i know...............Thank you all

Click to expand...

Call IceQube, and ask for Tom Churchel.

http://www.iceqube.com/

He's taken very good care of us on several recent projects; they built an AC unit for a project last summer in a remarkably short turnaround, and then built another even faster when the first one was smashed by the shipper.

For a more recent project, they built us two AC units that will be used outside on a cruise ship. Marine environments are unkind to AC units; the ones they build for us were all 316-stainless, with additional corrosion protection as well.

IceQube makes very good kit, and are helpful sizing and spec-ing as well. Their units are UL-listed too. They'll take good care of you.


-rpoet

If I could make a suggestion, it would be to put the PLC, I/O cards, and stand-alone power supplies in a separate cabinet.

Having everything in the same cabinet seems like a noise-fest waiting to happen. Been there, done that.

mellis said:

The thing to be wary about cooling just the enclosure... What happens when you open the door?

It is quite possible to have every surface inside the panel go wet within seconds of opening the door if the conditions are right. Take care not to overcool it.

Click to expand...

Good point well made.

In extreme cases it may actually make sense to build a shed to get the panel out of the weather and cool the shed. Then at least you can work on it.

Click to expand...

We routinely do this for installations that go to warm places (Asia, Africa, southern Europe). Our projects go to harsh environments (salty dust going everywhere). Most projects include a PC. Because of dust we usually spec a shed inside the factory hall, to hold both the main cabinet as well as the PC desk.

For moderate climates it is enough to get clean outside air with slight over pressure to keep the dust out. For the really hot places we usually spec an AC shed. Keeps the PC, electrical cabinet and the operator cool and in good working condition.

Mid 90s most of the year? I only wish. It was 33 degrees in Guymon when I left my hotel room this morning. We can have a month of highs over 100 most every summer. 115 wouldn't be a record in most Oklahoma cities. I have seen the temperature change so fast that the streets buckled up at intersections. 80 degree swings in a day do happen here.

I would recommend flange mount VFDs with air-over type enclosures so that most of the heat is outside the box.

Basically the enclosure has two backplates and the inside one is cut out for your drives, and the second one has a vent for heat to escape. We had some of these built for us for some recent projects and they turned out pretty nice. One of them is NEMA 4 mounted outdoors. Neither has had to survive Oklahoma summer yet, so I should probably have never talked about it...

But flange mount drives are definitely going to help you with your BTU requirements. It might make the calculation more complicated, because the part of the drive inside the main part of the box still produces heat...but how much?

I can put you in touch with the guy who did the design and procurement of our drive panels if you'd like. They came in with the cutouts done and drilled and tapped for our VFDs. Lead time was a little long, but not terrible.