Panel Laws

Tim Ganz · Aug 15, 2013

We have an AC drive that is 500 HP and it has 2 20,000 BTU ac units on the cabinet but it's still overheating as the 2 ac units need to be replaced / repaired because they are not cooling as they should.

The Maintenance manager wants to cut a a hole and fix flex duct into the side of the cabinet and connect it to the office AC system to help cool the drives. I would think this would be some type of major violation?

Am I correct?

iggy · Aug 15, 2013

He would be fired in our plant.

geniusintraining · Aug 15, 2013

iggy said:
He would be fired in our plant.

Why, I see nothing wrong with it as long as the return was not hooked up the the cabinet.... would he be fired because the office would be hot or because the machine would be running?

iggy · Aug 15, 2013

Safety, just how it is here. In no way shape or form could it be hooked up. Dont you know that trons can travel through ac duct...... Its just how they think here. Not my view's just how it is.

The Plc Kid · Aug 15, 2013

That would not fly here because it would be using the enclosure in a way it's not designed for but I don't know any specific regulation that would prohibit it.

leitmotif · Aug 15, 2013

geniusintraining said:
Why, I see nothing wrong with it as long as the return was not hooked up the the cabinet.... would he be fired because the office would be hot or because the machine would be running?

Hmm how novel -- take 40,000 BTU of waste heat and use to heat the office?

Some issues
Could work if cabinet can handle being at 85 F or maybe 90 (85 is minimum temp supply air going to office should be at)
Office has another heat source when machine shut down - machine should be considered as supplementary heat source.
Summer -- what are you going to do when office does not need heat and more than likely cooling? What are you going to dump waste heat to??
Filters are going to be needed to keep office dust (paper carpet and clothing fiber) out of cabinet.

Dan Bentler

rpoet · Aug 15, 2013

What happens when it's a cool day outside and the AC isn't running? I'll bet the drive will overheat.

What happens in the winter? Will you be "cooling" your cabinet with heated air?

How will you do humidity control? Granted, electronics and humans tend to like the same environmental conditions, but too wet or too dry could cause problems.

Panel AC units are essentially closed systems. They recirculate the air in the panel; little goes in or out. After changing the furnace filter in houses I've lived in, I can't imagine introducing that level of dust and shmoo into an electrical panel on purpose. I know it's an office and not a residence, but we humans are messy creatures with our hair and such

EDIT: I see that Dan types faster than me and covered the "dust" issue.

-rpoet

geniusintraining · Aug 15, 2013

What happens when it's a cool day outside and the AC isn't running?

Well if its cold you would not need them..

Not saying that its the best way or should be long term... but if I have a machine down because the cabinet is over heating I am going to get some flex and plum it up

It was 105 here a few years back... the cabinet was so hot you could not hold on to the doors, we had a about 50ft of flex and we did just that... about after one hour the drives cooled down and we were able to start back up, its just under 20k per hour for down time on that line, the cabinets were about 50ft long and they had a AC that could not keepup, this was enough to get them back to a normal range

It worked great and I would do it again, keep about 30 people working in that department and saved the company about 100k in down time

leitmotif · Aug 15, 2013

Hmmm 500 HP VFD

500 X .746 X 3412 = 1,272,676 BTU

so for every 1% inefficiency you need to dump 12,726.76 BTU
ASSUMING 95% efficiency (5% loss) that is about 64 K BTU

It just may be your heat pumps are undersized at 40 K. Get a HVAC guy out there to determine loading of units.

Once you know that then you can start getting yourself confused.

It appears to me that you have a lot of very large equipment. It may be best to consider a chill water system to cool machinery in plant. Heat from this can be used to heat other stuff ie offices hot water for restrooms, rinse tanks etc etc.

The big proviso and hurdle to this heat recovery and transfer idea is
The sink must always be greater in capacity than the supply.

Dan Bentler

James Mcquade · Aug 15, 2013

What about arc flash?

the energy from that alone can travel quiet a ways.
could even create a fire in the duct and at the closest vent.

regards,
james

shooter · Aug 15, 2013

The idea of a fan with some duct is oke, just make a heatexchanger on the outside of the cabinet. This way the hot heat is gone and the two units will cope with the rest. Even a simple fan inside does help, as it will use the panelsides and the door as heatexchanger.
Do not use fresh air, or any connection as it will get dirty as the air is not clean.

Tim Ganz · Aug 16, 2013

What about puttng another panel ac unit on the left fron door? This is a hoffman 2 door floor standing enclosure.

They are thinking of adding another hoffman ac unit to the door now.

dwoodlock · Aug 16, 2013

First if there is a problem with the existing cabinet air conditioners I would just get them fixed.

If it just plain exceeds their capacity, and this is something thats gonna be permanent, buy a window unit and modify to suit.

obviously if this is something thats costing tens of thousands in downtime costs, you have to consider function over fashion.

Mark Buskell · Aug 16, 2013

We had a couple of cabinets that size that have lost their AC. Our temporary solution is to open the door and place portable chiller fans blowing on the drive. I have seen other places use a hurricane fans to blow air in.

shooter · Aug 16, 2013

better is to put the fans in the cabinet and close the doors, a lot safer.

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