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pressure in VFD room

pressure in VFD room

pressure in VFD room

(OP)
I am working on the design of HVAC system for a VFD room, which is a part of a modular building.
My main concern is to apply positive pressure inside the VFD room.
How do I achieve that and what is the recommended positive pressure?


VFD produces 15000cfm hot air.
Room Dimensions are 20'Lx15'Wx14'H
HVAC unit used = 6 tons

Thank you



 

RE: pressure in VFD room

Where does the 15,000 cfm come from?   Where does it go?

 

RE: pressure in VFD room

(OP)


The 15000cfm is produced from the VFD itself and is blown into the room where the vfd exists.
Thanks

RE: pressure in VFD room

You're going to have a wind tunnel for a room to keep it cool.  Forced draft (fan forcing air into the room) will keep a positive pressure on it.  I think 0.25-0.5 inWC is a typical positive room pressure but I'm no HVAC expert.  You might want to look for ways to use all this VFD heat.

RE: pressure in VFD room

(OP)
Yes, the 15000cfm will be used during winter in heating the VFD room,While during summer it has to be exhausted from the room.It can be also 50% exhausted and 50% blown into the room in certain times.

RE: pressure in VFD room

wow must be a monster drive, sure there is no extra zero or two in there

Take the "V" out of HVAC and you are left with a HAC(k) job.

RE: pressure in VFD room

7500 CFM would probably make a F1 votex in that little room

Take the "V" out of HVAC and you are left with a HAC(k) job.

RE: pressure in VFD room

let me know if I am just a wise guy with my foot in my mouth on this one, but the airflow sounds pretty high for a room that is only 4200 cubic feet

Take the "V" out of HVAC and you are left with a HAC(k) job.

RE: pressure in VFD room

(OP)
You are right,let me check this back with the supplier.I guess it has to be 15oo cfm(not 15000cfm)

RE: pressure in VFD room

(OP)

Well,I checked the specs. of the VDF --and it produces 15000cfm. I have to explain more ..the room has an external door of 4' x 9' and internal one of 4'x9'.The external temp. is ranging from -2C to 40C. There is another sourse of leakage which is the louvers of the intake fan.
Please tell me what other info might be helpful.
 

RE: pressure in VFD room

So the VFD produces air from nothing?  That's a neat trick.

Where is the air intake?  Where is the air discharge?

With 15,000 cfm to work with in a 4200 cubic foot room you will have no problems establishing a positive pressure - at least until the walls fall down.

RE: pressure in VFD room

(OP)
There are air blowers (intake fans) which are blowing external air to the room.
 The vfd has a rectifier and a transformer(this is the source of heat).
Exhaust louver to be used to discharge the air outside the room,and an intake grill to be used to recerculate it through the room.
 

RE: pressure in VFD room

Then, is your only issue determining, calculating and maintaining a positive pressure?

Since you are blowing air into the room you "should" have a small positive pressure.  If you need more you either need a higher pressure fan, smaller outlet louvers or to fix your leaks.

RE: pressure in VFD room

(OP)
First,I want to be sure about the recommended positive pressure for such a room?
Is their a formula to calculate?and how to maintain this.
Any other design or control options?
  

RE: pressure in VFD room

Generally, the purpose of positive pressure is to prevent dirt from entering the room under doors, and through other leaks in the envelope.

In your case, you are bringing in an AWFUL LOT of outside air via the drive's cooling fans.  Every cubic foot of this outside air has some amount of dust in it.  Is this outside air filtered?  To what degree?

RE: pressure in VFD room

(OP)
The air is filtered through built in filters in the VFD unit

RE: pressure in VFD room

Why do you need a positive room pressure?  

It sounds like your VFD is bringing in filtered air to cool itself and I would bet the VFD is designed to maintain its own positive internal pressure to prevent dust ingress.

RE: pressure in VFD room

At a certain point,during summer time, all the air blown by the intake fans will be exhausted. What is the effect on pressure in this case?

RE: pressure in VFD room

(OP)
Now,checking back my A/C unit capacity. Assuming exhausting all the 15000cfm from the VFD to outside.
Do you think 6 ton A/C unit will be good enough to cool the room.

RE: pressure in VFD room

I am on the electrical side.  I also think you (OP), have something amiss in either your units or your numbers.  A VFD, by itself cannot possibly produce 15000cfm of air. Maybe 15000 Btuh of heat? Even at that, it sounds like one giant drive.  What size and type of motor is this controlling?  What is the service voltage?  Something is missing in this picture.

Just an electrical observation.

RE: pressure in VFD room

This is a mess, take it back to basics.  Draw the room as a control volume and put arrows with values for all of the mass and energy that is entering and exiting the room.  Then it's simple math.

RE: pressure in VFD room

abeerkhayyat, Got the make, model #, etc on the drive?  or a link to the data sheet?
 

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